Patent Publication Number: US-11020815-B2

Title: Single-piece extended laminar flow inlet lipskin

Description:
CROSS-REFERENCE 
     
         
         
           
             This application is a Continuation-in-Part of U.S. Ser. No. 15/603,899, now U.S. Pat. No. 10,766,626, filed May 24, 2017, the entirety of which is incorporated by reference herein as if made a part of this application. 
           
         
       
    
    
    
     TECHNOLOGICAL FIELD 
     The present disclosure relates generally to the field of fabricating metal structures. More specifically, the present disclosure relates to manufacturing a metal structure or component comprising shaping the metal structure or component while in specified heat-treatment conditions, and introducing a friction stir weld into the metal structure or component with the friction stir weld being maintained in the finished component. Still more specifically, the present disclosure relates to the manufacture of components and assemblies used to make lipskins for aircraft engine nacelles. 
     BACKGROUND 
     Laminar flow is the smooth, uninterrupted flow of air over the contour of wings, fuselages, or other parts of an aircraft in flight. Laminar flow is most often found at the front of a streamlined body. If the smooth flow of air is interrupted, turbulence is created, which can result in drag acting on the body. Increases in deviation away from optimal laminar flow at aircraft surfaces can result in an increase in fuel consumption, and therefore a commensurate increase in cost of operation. 
     Many known aircraft engines, for example jet engines and turbofan jet engines are surrounded by an annular, barrel-shaped nacelle. At least some known nacelles include a lipskin at the leading edge, or inlet, of the nacelle. While some large structures have been formed in a unitary fashion to reduce transverse weld lines or other couplings that could impact laminar flow, such unitary forming processes (e.g. spin-forming, etc.) are time-consuming, expensive and difficult or impractical in terms of size limitations for producing spin-formed lipskins of a desired, large size. Further, spin-formed lipskins can exhibit undesirable waves or ripples that could adversely affect laminar flow, leading to undesirable turbulence, increased fuel consumption, and/or increased cost of operation. 
     In attempts to solve the potential restrictiveness of spin-forming or other processes, some known methods for lipskin construction for aircraft engine nacelles have included the introduction of friction stir welds during lipskin construction, followed by removal of the welds during shaping, finishing, and other manufacturing processes, and further followed by the introduction of additional coupling components and parts (e.g. doublers). However, additional processing steps are often time-consuming, and the addition of parts in an aircraft assembly is often undesirable due to the commensurate increase in weight, assembly complexity, manufacturing time, additional inspections, etc., and can increase the overall cost of operating and maintaining the aircraft. 
     SUMMARY 
     Aspects of the present disclosure are directed to methods for forming metal lipskins for engine nacelles and the lipskins and nacelles so formed, as well as structures comprising the nacelles that comprise the lipskins, where the introduction of at least one “fly away” weld (including without limitation, one friction stir weld), and forming processes of a metal lipskin occurs in specified conditions of the metal such that the “fly away” weld is maintained in the finished lipskin. 
     An aspect of the present disclosure is directed to a method for making a heat-treated structure formed of metal, the method comprising performing a first heat-treating process on a roughly-shaped metal workpiece in an annealed condition, to transition the roughly-shaped metal workpiece from an annealed condition to a first-hardened condition, with the roughly-shaped metal workpiece comprising at least one friction stir weld; forming the roughly-shaped metal workpiece into a shaped metal workpiece while the roughly-shaped metal workpiece is in the first-hardened condition, with the shaped metal workpiece comprising one of a near finally-shaped metal workpiece or a finally-shaped metal workpiece; and performing a second heat-treating process on the shaped workpiece to transition the shaped metal workpiece from the first-hardened condition to a second-hardened condition. 
     In another aspect, the step of forming the roughly-shaped metal workpiece into a shaped metal workpiece comprises using at least one forming process to shape the roughly-shaped metal workpiece into the shaped metal workpiece. 
     In a further aspect, the shaped metal workpiece is a near-finally-shaped metal workpiece, with a method further comprising forming the near-finally-shaped metal workpiece into the finally-shaped metal workpiece while the near-finally-shaped metal workpiece is in the second-hardened condition. 
     In another aspect, the shaped metal workpiece comprises a finally-shaped metal workpiece, with a method further comprising using a plurality of forming processes to shape the roughly-shaped metal workpiece into the finally-shaped metal workpiece. 
     In another aspect, the forming process includes a stretch forming process; a form-die forming process; an explosion forming process and combinations thereof. 
     Another aspect of the disclosure is directed to a method for making a heat-treated structure formed of metal, the method comprising performing a first heat-treating process on a roughly-shaped metal workpiece to transition the roughly-shaped metal workpiece into a first hardened condition to produce a first-hardened metal workpiece, the roughly-shaped metal workpiece being in an annealed condition and comprising at least one friction stir weld; performing a second heat-treating process on the first-hardened metal workpiece to transition the first-hardened metal workpiece to a second-hardened condition to produce a second-hardened metal workpiece; forming the second-hardened metal workpiece into a shaped metal workpiece, said shaped metal workpiece being in one of a near-finally-shaped metal workpiece or a finally-shaped metal workpiece. 
     In a further aspect, the steps of performing the first heat-treating process and second heat-treating process further comprise performing at least one age-hardening process on the roughly-shaped metal workpiece in the first-hardened condition; and performing at least one age-hardening process on the shaped metal workpiece in the second-hardened condition, wherein the first-hardened condition comprises a first age-hardened condition and the second-hardened condition comprises a second age-hardened condition. 
     In another aspect, the shaped metal workpiece comprises a friction stir weld. 
     In a further aspect, the shaped metal workpiece comprises a near finally-shaped workpiece, the method further comprising forming the near finally-shaped metal workpiece into a finally-shaped metal workpiece while the near finally-shaped metal workpiece is in the second-hardened condition. 
     In a further aspect, the shaped metal workpiece comprises a near finally-shaped metal workpiece the method further comprises the step of using a plurality of forming processes to shape the near finally-shaped metal workpiece into the finally-shaped workpiece while the near finally-shaped metal workpiece is in the second-hardened condition. 
     In another aspect, the shaped metal workpiece comprises a near finally-shaped metal workpiece and further comprising the step of using at least one explosion forming process to shape the near finally-shaped metal workpiece into the finally-shaped workpiece while the near finally-shaped metal workpiece is in the second-hardened condition. 
     In a further aspect, before the step of performing a first heat-treating process on a roughly-shaped metal workpiece, further comprising forming a metal sheet into the roughly-shaped metal workpiece while the metal sheet is in the annealed condition. 
     In another aspect, the step of forming a metal sheet further comprises rolling the metal sheet into the roughly-shaped metal workpiece. 
     In another aspect, the step of forming a metal sheet further comprises forming the metal sheet, while the metal sheet is in the annealed condition; and using at least one forming process forming process to form the metal sheet, with the forming process including a stretch forming process; a form-die forming process; an explosion forming process or combinations thereof. 
     In a further method, the step of forming a metal sheet into the roughly-shaped metal workpiece while the metal sheet is in the annealed condition further comprises forming the sheet into a conical or frusto-conical metal workpiece. 
     In a further aspect, the steps of performing the first heat-treating process and second heat-treating process further comprise performing at least one age-hardening process on the roughly-shaped metal workpiece in the first-hardened condition; and performing at least one age-hardening process on the on the shaped metal workpiece in the second-hardened condition; wherein the first-hardened condition comprises a first age-hardened condition, and the second-hardened condition comprises a second age-hardened condition. 
     In another aspect, the step of performing a first heat-treating process comprises performing a natural aging process on the roughly-shaped metal workpiece. 
     In a further aspect, the step of performing a first heat-treating process comprises solution heat-treating the metal and natural aging the roughly-shaped metal workpiece. 
     In another aspect, the step of performing a first heat-treating process, further comprising performing a T-4 heat-treating process on the roughly-shaped metal workpiece. 
     In another aspect, performing a second heat-treating process comprises performing an artificial aging process on the shaped metal workpiece. 
     In a further aspect, performing a second heat-treating process comprises performing a solution heat-treating process on the shaped metal workpiece; and performing an artificial aging process on the shaped metal workpiece. 
     In a further aspect, performing a second heat-treating process comprises performing a T-6 heat-treating process. 
     In another aspect, forming the roughly-shaped metal workpiece into a shaped workpiece comprises using at least one forming process selected from the group consisting of a stretch forming process; a form-die forming process; and an explosion forming process to shape the roughly-shaped metal workpiece into the shaped workpiece. 
     In a further aspect, the shaped workpiece is a near-finally-shaped metal workpiece, the method further comprising forming the near-finally-shaped metal workpiece into a finally-shaped metal workpiece while the near-finally-shaped metal workpiece is in the second-hardened condition. 
     In a further aspect, the shaped metal workpiece is a finally-shaped metal workpiece and further comprising forming the roughly-shaped metal workpiece into a finally-shaped metal workpiece using at least one forming process including a stretch forming process; a form-die forming process; an explosion forming process and combinations thereof. 
     A further aspect of the present disclosure is directed to a metal structure formed according to any of the aforementioned methods. 
     In another aspect, a method is disclosed for making a heat-treated structure formed of metal, with the method including forming a first hardened metal workpiece into a shaped first-hardened metal workpiece, with the first-hardened metal workpiece in a first-hardened condition, and with the shaped first-hardened metal workpiece comprising at least one friction stir weld, said first-hardened metal workpiece in a first-hardened T3 condition. The method further includes performing a first heat-treating process on the shaped first-hardened metal workpiece in the first-hardened condition to transition the shaped first-hardened metal workpiece from the first-hardened condition to a shaped second-hardened metal workpiece in a second-hardened condition, with the shaped second-hardened metal workpiece in a second-hardened T8 condition; and wherein the shaped second-hardened metal workpiece in the second-hardened T8 condition comprises at least one friction stir weld. 
     In another aspect. the method further includes using at least one forming process to form the first-hardened metal workpiece into the shaped first-hardened metal workpiece. 
     In another aspect, the at least one forming process comprises at least one of: a stretch forming process; a form-die forming process; an explosion forming process; and combinations thereof. 
     In a further aspect, before the step of forming a first-hardened metal workpiece into a shaped first-hardened metal workpiece, the method further includes forming a metal sheet into the shaped first-hardened metal workpiece while the metal sheet is in the first-hardened T3 condition. 
     In another aspect, the step of forming a metal sheet further includes rolling the metal sheet into the shaped first-hardened metal workpiece. 
     In another aspect, the method further includes performing at least one age-hardening process on the shaped first-hardened metal workpiece in the T3 condition to form the second-hardened metal workpiece into the T8 condition. 
     In a further aspect, the method further includes performing an artificial aging process on the shaped first-hardened metal workpiece in the T3 condition to form the second-hardened metal workpiece in the T8 condition. 
     In another aspect, a method is disclosed for making a heat-treated metal structure, with the method including forming a metal workpiece in a first-hardened condition into a shaped first-hardened metal workpiece, said shaped first-hardened metal workpiece comprising at least one friction stir weld, with the first-hardened metal workpiece in a T3 condition, and performing a heat-treating process on the shaped first-hardened metal workpiece in the first-hardened condition to transition the shaped first-hardened metal workpiece from the first-hardened condition to a shaped second-hardened metal workpiece in a second-hardened condition, with the shaped second-hardened metal workpiece in a T8 condition. The method further includes using at least one forming process to form the metal workpiece in the first-hardened condition into the shaped first-hardened metal workpiece in the T3 condition, and using at least one forming process to form the shaped second-hardened metal workpiece in the T8 condition, wherein the at least one forming process comprises at least one of: a stretch forming process; a form-die forming process; an explosion forming process; and combinations thereof. 
     In another aspect, before the step of forming a first-hardened metal workpiece into a shaped first-hardened metal workpiece, the method further includes forming a metal sheet into the shaped first-hardened metal workpiece while the metal sheet is in the first-hardened T3 condition. 
     In another aspect, the method further includes performing an artificial aging process on the shaped first-hardened metal workpiece in the T3 condition to form the shaped second-hardened metal workpiece in the T8 condition. 
     In another aspect, a metal structure formed according to the aforementioned methods includes aluminum or an aluminum alloy. 
     In another aspect, the metal structure is a lipskin for use in an engine nacelle assembly. 
     In a further aspect, a nacelle assembly for use on an aircraft is disclosed, with the nacelle assembly including a lipskin made from a metal that has been heat-treated according to the method including forming a first hardened metal workpiece into a shaped first-hardened metal workpiece, with the first-hardened metal workpiece in a first-hardened condition, and with the shaped first-hardened metal workpiece comprising at least one friction stir weld, said first-hardened metal workpiece in a first-hardened T3 condition. The method further includes performing a first heat-treating process on the shaped first-hardened metal workpiece in the first-hardened condition to transition the shaped first-hardened metal workpiece from the first-hardened condition to a shaped second-hardened metal workpiece in a second-hardened condition, with the shaped second-hardened metal workpiece in a second-hardened T8 condition; and wherein the shaped second-hardened metal workpiece in the second-hardened T8 condition comprises at least one friction stir weld, with the lipskin comprising at least one friction stir weld. 
     In another aspect, the nacelle assembly includes a lipskin, with the lipskin comprising at least one of aluminum and aluminum alloy, and with the lipskin further comprising at least one fiction stir weld. 
     In another aspect, a nacelle assembly is disclosed with the nacelle assembly includes a metal structure made from a metal including at least one of aluminum and aluminum alloy in the T8 condition. 
     In another aspect, the metal structure is annularly-shaped. 
     In a further aspect, the metal structure is a lipskin for use in an engine nacelle assembly. 
     In another aspect, the metal structure is a heat-treated structure in the second-hardened condition. 
     According to another aspect, the present disclosure is further directed to a metal structure for use on an aircraft comprising a metal that has been heat-treated, with the metal structure comprising at least one friction stir weld. 
     A further aspect of the present disclosure is directed to a nacelle assembly for use on an aircraft, the assembly comprising a lipskin made from a metal that has been heat-treated, with the lipskin comprising at least one friction stir weld. 
     A further aspect of the present application is directed to structures comprising the lipskin made from a metal that has been heat-treated, with the lipskin comprising at least one friction stir weld, the structures including, without limitation, manned and unmanned aircraft, manned and unmanned rotorcraft, manned and unmanned spacecraft, manned and unmanned terrestrial vehicles, manned and unmanned surface water borne vehicles, manned and unmanned sub-surface waterborne vehicles, rockets, missiles, etc. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Having thus described variations of the disclosure in general terms, reference will now be made to the accompanying drawings, which are not necessarily drawn to scale, and wherein: 
         FIG. 1  is a flowchart illustrating an exemplary forming method of the present disclosure; 
         FIG. 2  is a flowchart illustrating an exemplary method of the present disclosure; 
         FIG. 3  is a flowchart illustrating an exemplary method of the present disclosure; 
         FIG. 4  is a flowchart illustrating an exemplary method of the present disclosure; 
         FIG. 5  is a flowchart illustrating an exemplary method of the present disclosure; 
         FIG. 6  is a flowchart illustrating an exemplary method of the present disclosure; 
         FIG. 7  is a flowchart illustrating an exemplary method of the present disclosure; 
         FIGS. 8A, 8B and 8C  are cross-sectional side-views of a workpiece progressing through stages of a forming process from a rough-shaped metal workpiece into a shaped, near-finally shaped and finally-shaped metal workpiece, according to aspects of the present disclosure; 
         FIG. 9  is a perspective view of a roughly-shaped metal workpiece in a frusto-conical orientation; 
         FIG. 10  is a perspective view of a roughly-shaped metal workpiece being oriented into a forming block of a forming process, according to aspects of the present disclosure; 
         FIGS. 11A, 11B, 11C, 11D, and 11E  are cross sectional side views of forming blocks in a forming process used to transform a roughly-shaped metal workpiece into a near-finally-shaped and finally-shaped metal workpiece; 
         FIG. 12  is a perspective view of a final-shaped metal workpiece as lipskin for a nacelle made according to aspects of the present disclosure; 
         FIG. 13  is a perspective view of an aircraft comprising an engine nacelle. 
         FIG. 14  is a flowchart illustrating an exemplary method of the present disclosure; 
         FIG. 15  is a flowchart illustrating an exemplary method of the present disclosure; 
         FIG. 16  is a flowchart illustrating an exemplary method of the present disclosure; and 
         FIG. 17  is a flowchart illustrating an exemplary method of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     Methods for constructing unitary, or single-piece, aircraft engine lipskins that can provide improved laminar flow are disclosed herein. The methods and apparatuses disclosed herein provide a lightweight, efficient, reproducible and high-performance engine nacelle lipskin made from a heat-treatable metal that has been shaped and tempered according to specified protocols that facilitate unitary formation of a large contoured metal structure without requiring introduction of additional components to structurally reinforce areas of the unitary structure where welds occur. That is, in the structures and methods according to aspects of the present application, the welds made in the structures are retained in the finished structure. 
     Retention of the welds in structures used in aircraft (e.g. lipskins on aircraft nacelle assemblies) allows such welds to be so-called “fly away” welds that are retained in the finished structure. Without being bound to any particular theory, and according to certain present aspects, the shaping of the metals used to make the lipskins, according to aspects of the present disclosure, is predominantly conducted and accomplished while the metal is in the annealed condition. The order of shaping in the annealed condition can allow for weld retention in a finished product due to internal metal stresses being managed in a predetermined way that obviates the need to remove such welds and introduce additional reinforcing components that would complicate the manufacturing process and add weight to a structure comprising the lipskin. 
     For the purposes of the present disclosure, “heat-treatable metals” refer to heat-treatable metals that include aluminum and the 2000-, 6000-, and 7000-series aluminum alloys. 
     According to certain aspects of the present disclosure, a metal workpiece in the annealed state can be formed into a roughly-shaped metal workpiece by being subjected to at least one forming process. For the purpose of the present disclosure, stretch forming processes, form-die processes, and explosive-forming processes are examples of a forming process and can be equivalently and interchangeably referred to as “forming processes”. 
     According to present aspects, stretch forming and stretch forming processes refer to processes characterized by a solid material (that can be, for example, in sheet form, etc.) and a tension state of stress. Typically, the workpiece can be clamped and stretched (typically stretched over or otherwise in contact with a shaping tool, mandrel, die, etc.) to a shape that can be a final shape or near-final shape. Stretch forming of metals (including, for example, metals in sheet form) can shape metals into large parts, components, assemblies, sub-assemblies etc., with the parts having varying curvatures such as, for example, skin panels, door frames, etc., and a variety of stretch-forming machines can be used to produce the stretch forming contemplated according to present aspects. 
     According to further present aspects, explosive-forming processes can be equivalently and interchangeably referred to as “explosion-molding”, “explosive molding”, “explosion-forming” or “high-energy hydroforming” (HEHF) processes. An explosive-forming process is a metalworking process where an explosive charge is used to supply the compressive force (e.g. a shockwave) to a metal workpiece against a form (e.g. a mold) otherwise referred to as a “die”. Explosive-forming is typically conducted on materials and structures of a size too large for forming such structures using a punch or press to accomplish the required compressive force. According to one explosive-forming approach, a metal workpiece, up to several inches thick, is placed over or proximate to a die, with the intervening space, or cavity, optionally evacuated by a vacuum pump. The entire apparatus is submerged into an underwater basin or tank, with a charge having a predetermined force potential detonated at a predetermined distance from the metal workpiece to generate a predetermined shockwave in the water. The water then exerts a predetermined dynamic pressure on the workpiece against the die at a rate on the order of milliseconds. The die can be made from any material of suitable strength to withstand the force of the detonated charge such as, for example, concrete, ductile iron, etc. The tooling should have higher yield strength than the metal workpiece being formed. 
     Explosive forming processes are sometimes divided into two groups, depending upon the position of the explosive charge relative to the workpiece. According to the “stand off” method, a workpiece is placed over a die with the intervening space evacuated by a vacuum, with the entire assembly immersed under water, preferably in a basin or tank. The explosive material is then placed at a predetermined distance from the assembly and detonated. According to the “contact method”, an explosive charge is placed in direct contact with the workpiece and the detonation produces interface pressures on the workpiece surface up to several million pounds per square inch (psi). 
     Friction stir welding (FSW) refers to a process for the solid-state joining of two workpieces using a non-consumable tool without melting the material of the workpiece(s). Heat is generated by friction between a rotating tool and the workpiece, resulting in a softened region proximate to the FSW tool. As the FSW tool proceeds along a desired joining line, the tool mechanically intermixes the material of the workpieces to be joined. In this way, hot and softened metal of the workpieces is forged by the mechanical pressure that is applied by the FSW tool, resulting in a solid state deformation of dynamic recrystallization of the workpiece materials without melting the workpieces. While aspects of the present disclosure describe producing and retaining friction stir welds in the metals used, the present disclosure contemplates, without limitation, any type of welds can be “fly-away welds”. As explained above, “fly-away welds” refer to welds in components and parts that remain in the part or component as used in flight. In other words, “fly-away welds” are retained in the finished structures as opposed to being removed from the structures before use. 
     According to the present disclosure, a heat-treated structure is a structure, preferably a metal structure, that is exposed to heat-treating. Heat-treating for metals (especially metal alloys) manipulates the properties of the metal by controlling rates of diffusion and the rate of cooling within a metal&#39;s microstructure. Heat-treating predictably alters the mechanical properties of a metal, manipulating properties including hardness, strength, ductility, elasticity, etc. The present specification discloses first heat-treating processes and second heat-treating processes to achieve metal workpieces having a particular “state” or heat-treatment “condition”. According to certain aspects of the present disclosure, for aluminum alloys, the heat-treatment conditions include an annealed condition, a first hardened condition, and a second-hardened condition. 
     According to certain aspects, for aluminum alloys, the annealed condition is used to describe alloys used for workpieces made by some shaping processes. The annealed condition is the lowest strength condition for a metal alloy workpiece. Annealing is a heat treatment that alters the physical properties of a material to increase stability and reduce hardness, making the material more “workable”. In annealing atoms migrate in a material&#39;s crystalline lattice, with the number of dislocations decreasing, leading to a change in ductility and hardness. A dislocation refers to the primarily linear defects present throughout a material&#39;s crystalline structure and the internal stresses caused thereby. Annealing conditions for aluminum alloys vary according to individual aluminum alloys, but generally require exposing the aluminum alloy to a temperature of from about 650° F. (343.3° C.) to about 770° F. (410° C.) for 2 to 3 hours, followed by slow cooling to about 500° F. (260° C.) followed by uncontrolled cooling rates to room temperature. Specific temperatures, times, cooling rates, etc. can differ from the examples above, depending upon which metal (e.g., aluminum alloy) is being treated. 
     The “T” temper designation for heat-treated (e.g., heat-treatable) aluminum and aluminum alloys includes a number that indicates a basic type of treatment. of particular interest for certain present aspects are the T4 and T6 conditions. As used herein the T4 condition is an example of a “first hardened-condition”. A T4 condition indicates that the T4 treated alloy has incurred a heat treatment and has naturally aged to a stable condition. As used herein, the T6 condition is an example of a “second-hardened condition”. A T6 condition indicates that the T6 treated alloy has been solution heat treated and, without any significant cold working, and has been artificially aged to achieve additional precipitation hardening to become stable metallurgically. 
     According to further present aspects, a T3 condition indicates a condition where the T3 treated alloy has incurred a solution heat treatment and is naturally aged and cold worked to become metallurgically stable. For present purposes and according to certain present aspects, a metal workpiece in the T3 condition is used as a starting condition (and as a starting material) in a first-hardened condition, with a metal workpiece in a T3 condition used as a starting material/starting condition when the “final” shaped workpiece is desired to be in the T8 condition. The T8 condition is achieved by starting with a workpiece (that can be a shaped workpiece) in the T3 condition, and the T3 workpiece is then heat-treated at about 350° F. (176.67° C.) for about 18 hours and is artificially aged to achieve the “second-hardened” T8 condition workpiece. In the protocol where the shaped metal workpiece progresses as a T3 starting material (from the first-hardened T3 condition) to the T8 second-hardened condition, the T8 condition is said to be the first heat-treated condition. In the T3 to T8 protocol presently disclosed, the shaping of the metal workpiece can occur in the T3 condition alone, or shaping of the metal workpiece can occur in both the T3 condition and the T8 condition. 
     According to other aspects of the present disclosure, an aluminum alloy can be provided in the annealed condition as a sheet of material (i.e., the “O” condition) with either partial or full anneal cycles intermittently conducted on the aluminum alloy. The annealed aluminum alloy is brought to the first-hardened condition, such as the T4 condition, via a solution heat treatment, and bringing the aluminum alloy sheet to a temperature above 900° F. (482.2° C.) for a time that is dependent on the particular alloy and the thickness of the sheet) followed by quenching in water or glycol. The aluminum alloys selected are precipitation age-hardenable, allowing the alloys to naturally age at room temperature. If desired, the aging in the T4 condition can be tailored by placing the alloy in the T4 condition in dry ice or in a freezer. The alloy sheet in the first-hardened condition (e.g., the T4 condition) can then be formed into a roughly-shaped metal workpiece that includes introducing at least one friction stir weld introduced in the annealed condition to shape the metal workpiece as desired. According to a contemplated aspect, in the case of forming lipskins for aircraft engine nacelles, the alloy in the annealed condition is shaped and friction stir welded to a roughly-shaped metal workpiece, and then the alloy in the first-hardened condition is shaped or formed to a near-finally-shaped metal workpiece or finally-shaped workpiece. 
     According to certain aspects of the present disclosure, during the first-hardened process, the alloy is subjected to at least one forming process that includes, for example, an explosive forming process, to create the near-finally-shaped metal workpiece or the finally-shaped metal workpiece. According to contemplated aspects, most of the forming of the aluminum alloy into the near-finally-shaped metal workpiece is conducted with the alloy in the first-hardened condition (e.g., the T4 condition). The near-finally-shaped metal workpiece is then brought to a second-hardened condition (i.e. T6 condition) by artificially aging the metal workpiece. For example, for aluminum alloy Al-2219, the cycle time and temperature is 375° F. (190.5° C.) for 36 hours. 
       FIGS. 1-7  are flowcharts describing certain aspects of the present disclosure. Consistent with particular aspects of the present disclosure,  FIG. 1  is directed to a method  10  for making a heat-treated structure formed of metal. The method  10  includes forming  12  a metal sheet into a roughly-shaped metal workpiece having a friction stir weld while the metal sheet is in an annealed condition. One example of the roughly-shaped metal workpiece is the metal workpiece  90  having at least one friction stir weld  92  as shown in  FIG. 9 , which is described in more detail below. 
     Method  10  includes step  12  performed in a manner consistent with aspects of the present disclosure using forming processes such as rolling or other physical shaping means suitable to physically transform and shape a metal from a first, or initial, orientation to a subsequent orientation. Further forming processes to transform metal to a roughly-shaped metal workpiece, as contemplated by aspects of the present disclosure, can take place in step  12  including subjecting the metal sheet to stretch forming, form-die processes, explosive-forming processes, and combinations thereof. The roughly-shaped state of the metal workpiece, according to aspects of the present disclosure, therefore contemplates the state of the metal work-piece between the initial form of a metal (e.g., a metal sheet that can be substantially planar) and a shaped (i.e., near-finally-shaped, or finally-shaped) metal workpiece that has been subjected to subsequent forming processes after attaining the roughly-shaped metal workpiece. 
     The method  10  further includes performing  14  a first heating-treating process on the roughly-shaped metal workpiece to transition the roughly-shaped metal workpiece from an annealed condition to a first-hardened condition. The roughly-shaped metal workpiece includes the at least one friction stir weld (e.g. friction stir weld  92  shown in  FIG. 9 ). When the metal workpiece is aluminum or an aluminum alloy, the first-hardened condition is the T4 condition. The method  10  includes forming  16  the roughly-shaped metal workpiece into a shaped metal workpiece while the roughly-shaped metal workpiece is in the first-hardened condition. An example of the shaped metal workpiece is the metal workpiece  114   b ,  114   c ,  114   d ,  114   e  and  120  as shown in  FIG. 9  and  FIGS. 11B, 11C, 11D, 11E  and  FIG. 12 , which is described in more detail below. According to aspects of the present disclosure, the shaped metal workpiece retain and includes the friction stir weld  92  introduced to the roughly-shaped metal workpiece as shown in  FIG. 9 . The shaped metal workpiece comprises one of a near finally-shaped metal workpiece or a finally-shaped metal workpiece. 
     According to aspects of the present disclosure, method  10  includes forming  16  processes used to transform a roughly-shaped metal workpiece into the shaped (i.e. near-finally-shaped or finally-shaped) metal workpieces include subjecting the metal sheet to stretch forming, form-die processes, explosive-forming processes, and combinations thereof. When an explosive-forming process is used in step  16 , the explosive-forming process also includes the quenching step of the first heat-treating process. 
     Aspects of the method  10  include performing  18  a second heat-treating process on the shaped workpiece to transition the shaped metal workpiece from the first-hardened condition to produce a second-hardened condition. When the metal workpiece is aluminum or an aluminum alloy, the second-hardened condition is a T6 condition. At least one forming process can be performed while the metal is in the second-hardened condition. However, the forming processes on the roughly-shaped workpiece (e.g., forming the roughly-shaped metal workpiece into the shaped metal workpiece) can be completed while the metal is in the first-hardened condition. 
     Consistent with certain aspects of the present disclosure,  FIG. 2  is directed to a method  20  for making a heat-treated structure formed of metal. The method described in  FIG. 2  is similar to the method outlined in  FIG. 1 , except the method  20  contemplates starting with a roughly-shaped metal workpiece rather than, for example, a flat sheet of metal. The method  20  includes performing  22  a first heat-treating process on a roughly-shaped metal workpiece in an annealed condition to transition the roughly-shaped metal workpiece from an annealed condition to a first-hardened condition, with the roughly-shaped metal workpiece comprising at least one friction stir weld introduced to the metal workpiece in the annealed condition. One example of the roughly-shaped metal workpiece is the metal workpiece  90  having at least one friction stir weld  92  as shown in  FIG. 9 , which is described in more detail below. The first-hardened condition of the metal is in the T4 condition when the metal workpiece is aluminum or an aluminum alloy. 
     The method  20  further includes forming  24  the roughly-shaped metal workpiece into a shaped metal workpiece while the roughly-shaped metal workpiece is in the first-hardened condition, with the shaped metal workpiece being one of a near finally-shaped metal workpiece or a finally-shaped metal workpiece. According to aspects of the present disclosure, the forming process(es) in step  24  used to transform a roughly-shaped metal workpiece into the shaped (i.e., near-finally-shaped or finally-shaped) metal workpiece includes subjecting the roughly-shaped metal workpiece to at least one forming process that includes stretch forming processes, form-die processes, explosive-forming processes, and combinations thereof. An example of the shaped metal workpiece is the metal workpiece  114   b ,  114   c ,  114   d ,  114   e  and  120 , as shown in  FIGS. 11B, 11C, 11D, 11E  and  FIG. 12 , and which is described in more detail below. According to aspects of the present disclosure, the shaped metal workpiece retains and includes the friction stir weld  92  introduced to the roughly-shaped metal workpiece as shown in  FIG. 9 . When an explosive-forming process is used in step  24 , the explosive-forming process also includes the quenching step of the first heat-treating process. 
     The method  20  further includes performing  26  a second heat-treating process on the shaped workpiece to transition the shaped metal workpiece from the first-hardened condition to produce a second-hardened condition. When the metal workpiece is aluminum or an aluminum alloy, the second-hardened condition is the T6 condition. At least one forming process can be performed while the metal is in the second-hardened condition. However, as contemplated by method  20 , the forming processes on the roughly shaped metal workpiece (e.g. forming the roughly-shaped metal workpiece into the shaped metal workpiece) can be completed while the metal is in the first-hardened condition. 
     Consistent with certain aspects of the present disclosure,  FIG. 3  is directed to a method  30  for making a heat-treated structure formed of metal. Whereas  FIGS. 1 and 2  outline methods,  10  and  20  respectively, where the roughly-shaped metal workpiece is formed into a shaped metal workpiece in the first-hardened condition, as shown in  FIG. 3 , a method  30  is further defined such that at least some forming of the metal workpiece into the shaped metal workpiece occurs after the metal workpiece is in the second-hardened condition. The method  30  includes performing  32  a first heat-treating process on a roughly-shaped metal workpiece in an annealed condition (with the workpiece in an annealed condition including at least one friction stir weld) to transition the roughly-shaped metal workpiece into a first-hardened condition to produce a first-hardened metal workpiece. One example of the roughly-shaped metal workpiece is the metal workpiece  90  having at least one friction stir weld  92  as shown in  FIG. 9 , which is described in more detail below. The first-hardened condition of the metal is the T4 condition when the metal workpiece is aluminum or an aluminum alloy. 
     The method  30  further includes performing  34  a second heat-treating process on the first-hardened metal workpiece to transition the first-hardened workpiece a second-hardened condition to produce a second-hardened metal workpiece. When the metal workpiece is aluminum or an aluminum alloy, the second-hardened condition is the T6 condition. 
     The method  30  further includes forming  36  the second-hardened metal workpiece into a shaped metal workpiece, with the shaped metal workpiece being in one of a near-finally-shaped metal workpiece or a finally-shaped workpiece. An example of the shaped metal workpiece is the metal workpiece  114   b ,  114   c ,  114   d ,  114   e  and  120  as shown in  FIGS. 11B, 11C, 11D, 11E  and  FIG. 12 , which is described in more detail below. According to aspects of the present disclosure, the shaped metal workpiece retains and includes the friction stir weld  92  introduced to the roughly-shaped metal workpiece as shown in  FIG. 9 . According to aspects of the present disclosure, in method  30 , forming processes  36  used to transform a roughly-shaped metal workpiece into the shaped (i.e. near-finally-shaped or finally-shaped) metal workpiece includes subjecting the metal workpiece to stretch forming, form-die processes, explosive-forming processes, and combinations thereof. As contemplated by method  30 , the forming processes on the roughly shaped metal workpiece (e.g. forming the roughly-shaped metal workpiece into the shaped metal workpiece) can be completed while the metal is in the second-hardened condition. 
     Consistent with certain aspects of the present disclosure,  FIG. 4  is directed to a method  40  for making a heat-treated structure formed of metal. Whereas  FIGS. 1 and 2  outline methods,  10  and  20  respectively, where the roughly-shaped metal workpiece is formed into a shaped metal workpiece in the first-hardened condition, as shown in  FIG. 4 , a method  40  is further defined such that at least some forming of the metal workpiece into the shaped metal workpiece occurs after the metal workpiece is in the second-hardened condition. Further, as compared with the method  30  outlined in  FIG. 3 , in  FIG. 4  the metal workpiece is formed into a near-finally-shaped and finally-shaped metal workpiece while the metal workpiece is in the second-hardened condition. The method  40  includes performing  32  a first heat-treating process on a roughly-shaped metal workpiece (with the workpiece in an annealed condition including at least one friction stir weld) to transition the roughly-shaped metal workpiece into a first-hardened condition to produce a first-hardened metal workpiece. One example of the roughly-shaped metal workpiece is the metal workpiece  90  having at least one friction stir weld  92  as shown in  FIG. 9 , which is described in more detail below. The first-hardened condition of the metal is the T4 condition when the metal workpiece is aluminum or an aluminum alloy. 
     The method  40  further includes performing  34  a second heat-treating process on the first-hardened metal workpiece to transition the first-hardened workpiece to a second-hardened condition to produce a second-hardened metal workpiece. When the metal workpiece is aluminum or an aluminum alloy, the second-hardened condition is the T6 condition. 
     The method  40  further includes forming  37  the second-hardened metal workpiece into a near-finally-shaped metal workpiece. An example of a near-finally-shaped metal workpiece is the metal workpiece  114   d  as shown in  FIG. 11D , which is described in more detail below. According to aspects of the present disclosure, the shaped metal workpiece retains and includes the friction stir weld  92  introduced to the roughly-shaped metal workpiece as shown in  FIG. 9 . According to aspects of the present disclosure, the method  40 , in step  37  the forming processes used to transform a roughly-shaped metal workpiece into the near-finally-shaped metal workpiece includes subjecting the metal sheet to stretch forming, form-die processes, explosive-forming processes, and combinations thereof. 
     The method  40  further includes forming  42  the near-finally shaped metal workpiece into the finally-shaped metal workpiece while the near-finally-shaped metal workpiece is in the second-hardened condition. According to aspects of the present disclosure, the method  40 , forming processes  42  used to transform a roughly-shaped metal workpiece into the shaped (i.e. near-finally-shaped or finally-shaped) metal workpiece including subjecting the metal sheet to stretch forming, form-die processes, explosive-forming processes, and combinations thereof. An example of the finally-shaped metal workpiece is the metal workpiece  114   e  and  120  as shown in  FIG. 11E  and  FIG. 12 , which is described in more detail below. As contemplated by method  40 , the forming processes on the roughly shaped metal workpiece (e.g. forming the roughly-shaped metal workpiece into the near-finally-shaped metal workpiece and the finally-shaped metal workpiece) can be completed while the metal is in the second-hardened condition 
     Consistent with certain aspects of the present disclosure,  FIG. 5  is directed to a method  50  for making a heat-treated structure formed of metal.  FIGS. 1 and 2  outline methods,  10  and  20  respectively, where the roughly-shaped metal workpiece is formed into a shaped metal workpiece in the first-hardened condition. Further, as compared with the method  30  outlined in  FIG. 3 , in  FIG. 4  (method  30 ) and  FIG. 5  (method  50 ) the metal workpiece is formed into a shaped ( FIG. 5 ) or near-finally-shaped ( FIG. 4 ) metal workpiece while the metal workpiece is in the second-hardened condition.  FIG. 5  further specifies, in step  52 , using a plurality of forming processes to form the shaped metal workpiece into a finally-shaped metal workpiece while in the second-hardened condition. The method  50  includes performing  32  a first heat-treating process on a roughly-shaped metal workpiece in an annealed condition (with the workpiece in an annealed condition including at least one friction stir weld) to transition the roughly-shaped metal workpiece into a first-hardened condition to produce a first-hardened metal workpiece. One example of the roughly-shaped metal workpiece is the metal workpiece  90  having at least one friction stir weld  92  as shown in  FIG. 9 , which is described in more detail below. The first-hardened condition of the metal is the T4 condition when the metal workpiece is aluminum or an aluminum alloy. 
     The method  50  further includes performing  34  a second heat-treating process on the first-hardened metal workpiece to transition the first-hardened workpiece to a second-hardened condition to produce a second-hardened metal workpiece. When the metal workpiece is aluminum or an aluminum alloy, the second-hardened condition is the T6 condition. 
     The method  50  further includes forming  36  the second-hardened metal workpiece into a shaped metal workpiece, with the shaped metal workpiece being in one of a near-finally-shaped metal workpiece or a finally-shaped workpiece. An example of the shaped metal workpiece is the metal workpiece  114   b ,  114   c ,  114   d ,  114   e  and  120  as shown in  FIGS. 11B, 11C, 11D, 11E  and  FIG. 12 , which is described in more detail below. According to aspects of the present disclosure, in method  50 , forming processes  36  used to transform a roughly-shaped metal workpiece into the shaped (i.e., near-finally-shaped or finally-shaped) metal workpiece includes subjecting the metal workpiece to stretch forming, form-die processes, explosive-forming processes, and combinations thereof. As contemplated by method  50 , the forming processes on the roughly shaped metal workpiece (e.g., forming the roughly-shaped metal workpiece into the shaped metal workpiece) can be completed while the metal is in the second-hardened condition. 
     The method  50  further includes using  52  a plurality of forming processes to form the shaped metal workpiece into the finally-shaped metal workpiece while the shaped metal workpiece is in the second-hardened condition, with the forming processes set forth above for use in step  36  also contemplated as available forming methods in step  52 . An example of the finally-shaped metal workpiece is the metal workpiece  114   e  and  120  as shown in  FIG. 11E  and  FIG. 12 , which is described in more detail below. 
     Consistent with certain aspects of the present disclosure,  FIG. 6  is directed to a method  60  for making a heat-treated structure formed of metal. Method  60  is similar to method  50  outlined in  FIG. 50 , but includes forming  62  a metal sheet into a roughly-shaped metal workpiece including a friction stir weld, while the metal sheet is in the annealed condition. One example of the roughly-shaped metal workpiece is the metal workpiece  90  having at least one friction stir weld  92  as shown in  FIG. 9 , which is described in more detail below. The roughly-shaped state of the metal workpiece, according to aspects of the present disclosure, therefore contemplates the state of the metal work-piece between the initial form of a metal (e.g. a metal sheet that can be substantially planar) and a shaped (i.e. near-finally-shaped, or finally-shaped) metal workpiece that has been subjected to subsequent forming processes after attaining the roughly-shaped metal workpiece. 
     The method  60  further includes performing  32  a first heat-treating process on the roughly-shaped metal workpiece in an annealed condition (with the workpiece in an annealed condition comprising at least one friction stir weld) to transition the roughly-shaped metal workpiece into a first-hardened condition to produce a first-hardened metal workpiece. The first-hardened condition of the metal is the T4 condition when the metal workpiece is aluminum or an aluminum alloy. 
     The method  60  further includes performing  34  a second heat-treating process on the first-hardened metal workpiece to transition the first-hardened workpiece a second-hardened condition to produce a second-hardened metal workpiece. When the metal workpiece is aluminum or an aluminum alloy, the second-hardened condition is the T6 condition. 
     The method  60  further includes forming  36  the second-hardened metal workpiece into a shaped metal workpiece, with the shaped metal workpiece being in one of a near-finally-shaped metal workpiece or a finally-shaped workpiece. An example of the shaped metal workpiece is the metal workpiece  114   b ,  114   c ,  114   d ,  114   e  and  120  as shown in  FIGS. 11B, 11C, 11D, 11E  and  FIG. 12 , which is described in more detail below. According to aspects of the present disclosure, the forming processes in the method  60  used to transform a roughly-shaped metal workpiece into the shaped (i.e. near-finally-shaped or finally-shaped) metal workpiece includes subjecting the metal sheet to stretch forming, form-die processes, explosive-forming processes, and combinations thereof. 
     Method  60  further includes using  52  a plurality of forming processes to form the near-finally shaped metal workpiece into the finally-shaped metal workpiece while the near-finally-shaped metal workpiece is in the second-hardened condition, with the forming processes set forth above for use in step  36  also contemplated as available forming methods in step  52 . An example of the finally-shaped metal workpiece is the metal workpiece  114   e  and  120  as shown in  FIG. 11E  and  FIG. 12 , which is described in more detail below. 
     Consistent with certain aspects of the present disclosure,  FIG. 7  is directed to a method  70  for making a heat-treated structure formed of metal. The method  70  described in  FIG. 7  is similar to the method outlined in  FIG. 1 , except the method  70  contemplates performing  72  at least one age-hardening process on the roughly-shaped metal workpiece in the first-hardened condition, and performing  74  at least one age-hardening process on the shaped metal workpiece in the second-hardened condition. Method  70  therefore includes forming  12  a metal sheet into a roughly-shaped metal workpiece having a friction stir weld while the metal sheet is in an annealed condition. Step  12  is performed in a manner consistent with aspects of the present disclosure using forming processes including forming processes such as rolling or other physical shaping means suitable to physically transform and shape a metal from a first, or initial, orientation to a subsequent orientation. Further forming processes to transform metal to a roughly-shaped metal workpiece, as contemplated by aspects of the present disclosure, can take place in step  12  including subjecting the metal sheet to stretch forming, form-die processes, explosive-forming processes, and combinations thereof. One example of the roughly-shaped metal workpiece is the metal workpiece  90  having at least one friction stir weld  92  as shown in  FIG. 9 , which is described in more detail below. The roughly-shaped state of the metal workpiece, according to aspects of the present disclosure, therefore contemplates the state of the metal workpiece between the initial form of a metal (e.g., a metal sheet that can be substantially planar) and a shaped (i.e. near-finally-shaped, or finally-shaped) metal workpiece that has been subjected to subsequent forming processes after attaining the roughly-shaped metal workpiece. 
     Method  70  further includes performing  14  a first heat-treating process on the roughly-shaped metal workpiece to transition the roughly-shaped metal workpiece from an annealed condition comprising at least one friction stir weld to produce a first-hardened condition, with the roughly-shaped metal workpiece comprising at least one friction stir weld. When the metal workpiece is aluminum or an aluminum alloy, the first-hardened condition is the T4 condition. 
     The method  70  further includes performing  72  at least one age-hardening process on the roughly-shaped metal workpiece in the first-hardened condition. When the metal workpiece is aluminum or an aluminum alloy and the first-hardened condition is the T4 condition, the age-hardening process can be a natural aging process to age the metal workpiece to a stable condition. 
     The method  70  further includes forming  16  the roughly-shaped metal workpiece into a shaped metal workpiece while the roughly-shaped metal workpiece is in the first-hardened condition. The shaped metal workpiece is one of a near finally-shaped metal workpiece or a finally-shaped metal workpiece. An example of the shaped metal workpiece is the metal workpiece  114   b ,  114   c ,  114   d ,  114   e  and  120  as shown in  FIGS. 11B, 11C, 11D, 11E  and  FIG. 12 , which is described in more detail below. According to aspects of the present disclosure, in step  16  the forming processes used to transform a roughly-shaped metal workpiece into the shaped (i.e. near-finally-shaped or finally-shaped) metal workpiece includes subjecting the metal sheet to stretch forming, form-die processes, explosive-forming processes, and combinations thereof. 
     Method  70  further includes performing  18  a second heat-treating process on the shaped workpiece to transition the shaped metal workpiece from the first-hardened condition to produce a second-hardened condition. When the metal workpiece is aluminum or an aluminum alloy, the second-hardened condition is the T6 condition. 
     The method  70  further includes performing  74  at least one age-hardening process on the shaped metal workpiece in the second-hardened hardened condition. When the metal workpiece is aluminum or an aluminum alloy and the second-hardened condition is the T6 condition, the age-hardening process can be an artificial aging process to age the metal workpiece to achieve precipitation hardening. 
     At least one forming process can be performed while the metal is in the second-hardened condition. However, the forming processes on the roughly-shaped workpiece (e.g. forming the roughly-shaped metal workpiece into the shaped metal workpiece) can be completed while the metal is in the first-hardened condition. 
       FIGS. 8A, 8B and 8C  show a series in progression of exemplary drawings illustrating how a workpiece can be formed during an explosive forming process that can be used in the forming processes shown in steps  16 ,  24 ,  36 ,  37 ,  42 , and  52 . According to explosive forming assembly  80   a , a tank  82  contains an amount of water  83 . A die  84  defines a cavity  85  and a vacuum line  87  extends from the cavity  85  through the die  84  to a vacuum (not shown). Workpiece  86   a  is held in position in the die  84  via a hold-down ring or other retaining device (not shown). An explosive charge  88  is shown suspended in the water  83  via a charge detonation line  89 , with charge detonation line  19   a  connected to a detonator (not shown). As shown in  FIG. 8B , the charge  88  (shown in  FIG. 8A ) has been detonated in explosive forming assembly  80   b  creating a shock wave “A” emanating from a gas bubble “B”, with the shock wave “A” causing the deformation of the workpiece  86   b  into cavity  85  until the workpiece  86   c  is driven against (e.g., immediately proximate to and in contact with) the inner surface of die  84  as shown in  FIG. 8C . 
     Consistent with particular aspects of the present disclosure,  FIG. 9  is a perspective drawing of a metal workpiece  90  in an annealed condition and, for the purpose of the present disclosure, in a roughly-shaped condition or state. As shown in  FIG. 9 , workpiece  90  has been shaped into a substantially frusto-conical shape. Friction stir welds  92  are shown in workpiece  90 , and are introduced into the metal workpiece before, after and/or during the forming of the metal workpiece into the roughly-shaped condition. While friction stir welds are shown, the present disclosure contemplates any welds that collectively can be referred to as “fly away” welds as described herein. As shown, workpiece  90  is a metal workpiece that is preferably made from aluminum or an aluminum alloy or alloys. Workpiece  90  can be shaped into the frusto-conical orientation by forming processes, including forming processes such as rolling or other physical shaping means suitable to physically transform and shape a metal from a first, or initial, orientation (e.g. a metal sheet) to a subsequent roughly-shaped orientation, such as shown in  FIG. 9 . 
     Consistent with particular aspects of the present disclosure,  FIG. 10  is a perspective view of a forming station  100 . As shown in  FIG. 10 , workpiece  90  is introduced into forming block  102  that has a forming block cavity  104 . The forming station  100  is non-specific as to any particular forming process that can be used to shape metal workpieces. Representative forming processes include forming processes used to transform a roughly-shaped metal workpiece into the shaped (i.e. near-finally-shaped or finally-shaped) metal workpiece such as stretch forming, form-die processes, explosive-forming processes (such as the process shown in  FIGS. 8A-8C ), and combinations thereof, and include a forming block or die against which, by a force, a metal workpiece can be driven to achieve a predetermined shape. 
     Consistent with particular aspects of the present disclosure,  FIGS. 11A, 11B, 11C, 11D and 11E  are cross-sectional side views showing a section of a workpiece within forming blocks, and showing the progressive forming and shaping of a workpiece from a roughly-shaped workpiece  90  as shown in  FIGS. 9 and 10  into a near-finally and/or finally-shaped workpiece. 
       FIG. 11A  shows a cross-sectional side view of forming block  102  taken across line “A” of forming block  102  as shown in  FIG. 10 .  FIG. 11A , in step  110   a , shows cross-section of roughly-shaped metal workpiece  90  resting within the cavity of forming block  112   a  (a cross-section of forming block  102  taken along line “A” as shown in  FIG. 10 ). After workpiece  90  has been exposed to at least one forming process,  FIG. 11B  shows step  110   b , wherein roughly-shaped metal workpiece  90  is now shown as  114   b  having been shaped such that the roughly-shaped metal workpiece rests substantially proximate to the wall  113   a  of cavity  115 . The roughly-shaped workpiece  90  is thus transformed into shaped metal workpiece  114   b . Shaped metal workpiece  114   c  is shown as having been further shaped as compared to the shaped metal workpiece  114   b  shown in  FIG. 11B . 
     As shown in  FIG. 11C , shaped metal workpiece  114   b  has been further shaped into metal workpiece  114   c  by trimming workpiece end  114   c′  of metal workpiece  114   c .  FIG. 11D  shows a second forming block  112   b  having a wall  113   b  with a contour that is different from the contour of wall  113   a  of forming block  112   a . The wall  113   b  defines a cavity of the second forming block  112   b . In this way, forming block  112   b  has a different cavity configuration as compared to the cavity of forming block  112   a . As shown in step  110   c , the metal workpiece  114   c  has now been subjected to a further forming process and further shaped into a workpiece configuration shown as metal workpiece  114   d .  FIG. 11E  shows step  110   e  wherein metal workpiece  114   d  has been further shaped by a further forming process followed by a trimming operation to shape metal workpiece end  114   e′  of metal workpiece  114   e . According to aspects of the present disclosure, metal workpieces  90 ,  114   b , and  114   c  can be a roughly-shaped workpiece, while metal workpieces  114   d  and  114   e  are shown to be a nearly-finally shaped workpiece. In further aspects, metal workpieces  114   d  and/or  114   e  can be considered to be finally-shaped workpieces, depending upon the desired and predetermined configuration of the workpiece according to the final workpiece configuration needed in use. According to further aspects (not shown) additional forming steps can be used, requiring additional forming blocks, if desired. 
       FIG. 12  is a perspective view of a nacelle lipskin according to an aspect of the present disclosure. As shown in  FIG. 12 , a lipskin  120  is fabricated according to methods disclosed herein, and ready for installation to an aircraft engine nacelle  132  on an aircraft  130  as shown in  FIG. 13 . 
     According to aspects of the present disclosure, the forming processes are conducted while the metal workpiece is in the first-hardened condition. The present disclosure further contemplates aspects where some of the forming processes can be conducted while the metal workpiece is in the second-hardened condition. However, such forming of the workpiece in the second-hardened condition will be finished forming and shaping; in some cases modifying the metal workpiece less than about 3% of the forming conducted on the metal workpiece as compared with the forming conducted on the workpiece when the workpiece is in conditions other than the second-hardened condition. According to certain present aspects, when a protocol contemplates using an annealed material as the starting material, the present disclosure therefore contemplates forming the metal workpiece via forming processes conducted: 1) in the annealed “O” and first-hardened T4 conditions; 2) in the annealed “O” and in either the first-hardened T4 or second-hardened T6 conditions; and 3) in the annealed “O” and both the first-hardened T4 and second-hardened T6 conditions. 
     According to further present aspects, the present disclosure further contemplates a protocol contemplating using a T3 conditioned material as the starting material, the present disclosure contemplates forming the metal workpiece via forming processes conducted: 1) in the T3 first-hardened starting condition; 2) in one of either the T3 first-hardened starting condition or second-hardened T8 conditions; and 3) in both the first-hardened T3 starting condition and second-hardened T8 conditions. 
       FIGS. 14, 15, 16, and 17  are flowcharts describing aspects of the present disclosure. Consistent with certain aspects of the present disclosure,  FIG. 14  is directed to a method  1400  for making a heat-treated structure formed of metal with a “fly away” weld that can be a friction stir weld introduced to the metal in a “starting condition”, with the “fly away” weld retained in the metal throughout the processing of the metal, and with the “fly away” weld further retained in the finished product that is obtained with the metal in the final processing state. The method  1400  includes forming  1402  a first-hardened metal workpiece (that can be, for example, in the form of a metal sheet) in a T3 starting condition into a shaped metal workpiece having a friction stir weld introduced while the metal is in the T3 condition. One example of the shaped metal workpiece is the metal workpiece  90  having at least one friction stir weld  92  as shown in  FIG. 9 , which is described in more detail below. 
     Method  1400  includes forming  1402  in a manner consistent with aspects of the present disclosure (e.g., using forming processes such as rolling or other physical shaping means suitable to physically transform and shape a first-hardened metal in a T3 condition from a first, or initial, orientation to a subsequent orientation) a first-hardened metal workpiece in a T3 condition into a shaped first-hardened metal workpiece in a T3 condition. Further forming processes to transform metal in the T3 condition to a shaped metal workpiece in the T3 condition, as contemplated by aspects of the present disclosure, can take place in step  1402  including subjecting the metal sheet to stretch forming processes, form-die processes, explosive-forming processes, and combinations thereof. The shaped state of the metal workpiece, according to aspects of the present disclosure, contemplates the state of the metal workpiece between the initial form of a metal in a T3 condition (e.g., a metal sheet that can be substantially planar) and a shaped (i.e., near-finally-shaped, or finally-shaped) metal workpiece also in a T3 condition that is subjected to physical forming processes. 
     The method  1400  further includes performing  1404  a first heat-treating process on the shaped metal workpiece in the T3 starting condition to transition the shaped metal workpiece in the first-hardened T3 (starting) condition from the T3 (starting) condition to a second-hardened T8 condition. According to the method  1400  and  1500 , as shown in  FIGS. 14 and 15 , only one heat-treating process has been conducted to transition a starting material (the T3 material) in a first metallurgical condition (T3) to a final or finished material (the T8 material) in a second metallurgical condition (T8). The shaped metal workpiece includes the at least one friction stir weld (e.g. friction stir weld  92  shown in  FIG. 9 ). According to aspects outlined in  FIGS. 14, 15, 16 and 17 , when the metal workpiece is aluminum or an aluminum alloy, the starting T3 condition is the first-hardened condition. An example of the shaped metal workpiece made according to the T3 to T8 protocol can be the metal workpiece  114   b ,  114   c ,  114   d ,  114   e  and  120  as shown in  FIG. 9  and  FIGS. 11B, 11C, 11D, 11E  and  FIG. 12 , which is described in more detail herein. According to aspects of the present disclosure, the shaped metal workpiece, according to method  1400  as shown in  FIG. 14  retains and includes the friction stir weld  92  introduced to the shaped metal workpiece as shown in  FIG. 9 . The shaped metal workpiece can comprise one of a near finally-shaped metal workpiece or a finally-shaped metal workpiece. 
     Aspects of the present disclosure contemplate shaping the metal workpiece (in a starting condition as a starting material) while the metal workpiece is in the first-hardened condition. Method  1400  further contemplates heat-treating the first-hardened shaped metal workpiece to produce a second-hardened metal workpiece in the T8 condition. When the metal workpiece is aluminum or an aluminum alloy, the second-hardened condition is a T8 condition. Further aspects contemplate performing at least one forming process while the metal is in the second-hardened T8 condition. However, most or all of the forming processes on the metal workpiece (e.g., forming the metal workpiece into a shaped metal workpiece) can be completed while the metal is in the first-hardened T3 condition. 
     Method  1500  includes forming  1402  in a manner consistent with aspects of the present disclosure (e.g., using forming processes such as rolling or other physical shaping means suitable to physically transform and shape a first-hardened metal in a T3 condition from a first, or initial, orientation to a subsequent orientation) a first-hardened metal workpiece in a T3 condition into a shaped first-hardened metal workpiece in a T3 condition. Further forming processes to transform metal in the T3 condition to a shaped metal workpiece in the T3 condition, as contemplated by aspects of the present disclosure, can take place in step  1402  including subjecting the metal sheet to stretch forming, form-die processes, explosive-forming processes, and combinations thereof. The shaped state of the metal workpiece, according to aspects of the present disclosure, contemplates the state of the metal workpiece between the initial form of a metal in a T3 condition (e.g., a metal sheet that can be substantially planar) and a shaped (i.e., near-finally-shaped, or finally-shaped) metal workpiece also in a T3 condition that is subjected to physical forming processes. 
     Consistent with additional present aspects,  FIG. 15  is directed to a method  1500  for making a heat-treated structure formed of metal. The method described in  FIG. 15  is similar to the method outlined in  FIG. 14 , except the method  1500  contemplates using  1501  at least one forming process to shape the first hardened metal workpiece in the T3 starting condition to form the shaped metal workpiece in the T3 condition. The method  1500  further includes performing  1404  a first heat-treating process on the shaped metal workpiece in the T3 starting condition to transition the shaped metal workpiece in the first-hardened T3 (starting) condition from the T3 (starting) condition to a second-hardened T8 condition. According to the method  1400  and  1500 , as shown in  FIGS. 14 and 15 , only one heat-treating process has been conducted to transition a starting material (the T3 material) in a first metallurgical condition (T3) to a final or finished material (the T8 material) in a second metallurgical condition (T8). The shaped metal workpiece includes the at least one friction stir weld (e.g. friction stir weld  92  shown in  FIG. 9 ). 
     The method  1600 , as shown in  FIG. 16 , includes forming  1402  a first-hardened metal workpiece (that can be, for example, in the form of a metal sheet) in a T3 starting condition into a shaped metal workpiece having a friction stir weld introduced while the metal is in the T3 condition. One example of the shaped metal workpiece is the metal workpiece  90  having at least one friction stir weld  92  as shown in  FIG. 9 , which is described in more detail below. 
     Method  1600  as shown in  FIG. 16  includes forming  1402  in a manner consistent with aspects of the present disclosure (e.g., using forming processes such as rolling or other physical shaping means suitable to physically transform and shape a first-hardened metal in a T3 condition from a first, or initial, orientation to a subsequent orientation) a first-hardened metal workpiece in a T3 condition into a shaped first-hardened metal workpiece in a T3 condition. Further forming processes to transform metal in the T3 condition to a shaped metal workpiece in the T3 condition, as contemplated by aspects of the present disclosure, can take place in step  1402  including subjecting the metal sheet to stretch forming, form-die processes, explosive-forming processes, and combinations thereof. The shaped state of the metal workpiece, according to aspects of the present disclosure, contemplates the state of the metal workpiece between the initial form of a metal in a T3 condition (e.g., a metal sheet that can be substantially planar) and a shaped (i.e., near-finally-shaped, or finally-shaped) metal workpiece also in a T3 condition that is subjected to physical forming processes. 
     The method  1600  further includes performing  1404  a first heat-treating process on the shaped metal workpiece in the T3 starting condition to transition the shaped metal workpiece in the first-hardened T3 (starting) condition from the T3 (starting) condition to a second-hardened T8 condition. According to the method  1400  and  1500 , as shown in  FIGS. 14 and 15 , only one heat-treating process has been conducted to transition a starting material (the T3 material) in a first metallurgical condition (T3) to a final or finished material (the T8 material) in a second metallurgical condition (T8). The shaped metal workpiece includes the at least one friction stir weld (e.g. friction stir weld  92  shown in  FIG. 9 ). According to aspects outlined in  FIGS. 14, 15, 16 and 17 , when the metal workpiece is aluminum or an aluminum alloy, the starting T3 condition is the first-hardened condition. An example of the shaped metal workpiece made according to the T3 to T8 protocol can be the metal workpiece  114   b ,  114   c ,  114   d ,  114   e  and  120  as shown in  FIG. 9  and  FIGS. 11B, 11C, 11D, 11E  and  FIG. 12 , which is described in more detail herein. According to aspects of the present disclosure, the shaped metal workpiece, according to method  1600  as shown in  FIG. 16  retains and includes the friction stir weld  92  introduced to the shaped metal workpiece as shown in  FIG. 9 . The shaped metal workpiece can comprise one of a near finally-shaped metal workpiece or a finally-shaped metal workpiece. 
     Method  1600 , as shown in  FIG. 16  further includes performing,  1601  at least one artificial age-hardening process on the shaped first-heat-treated metal workpiece in the to form the aged T8 condition. According to aspects of the present disclosure, the shaped metal workpiece in the T8 condition retains and includes the friction stir weld  92  introduced to the roughly-shaped metal workpiece as shown in  FIG. 9 . 
     Method  1700  as shown in  FIG. 17  includes forming  1402  in a manner consistent with aspects of the present disclosure (e.g., using forming processes such as rolling or other physical shaping means suitable to physically transform and shape a first-hardened metal in a T3 condition from a first, or initial, orientation to a subsequent orientation) a first-hardened metal workpiece in a T3 condition into a shaped first-hardened metal workpiece in a T3 condition. Further forming processes to transform metal in the T3 condition to a shaped metal workpiece in the T3 condition, as contemplated by aspects of the present disclosure, can take place in step  1402  including subjecting the metal sheet to stretch forming, form-die processes, explosive-forming processes, and combinations thereof. The shaped state of the metal workpiece, according to aspects of the present disclosure, contemplates the state of the metal workpiece between the initial form of a metal in a T3 condition (e.g., a metal sheet that can be substantially planar) and a shaped (i.e., near-finally-shaped, or finally-shaped) metal workpiece also in a T3 condition that is subjected to physical forming processes. 
     The method described in  FIG. 17  is similar to the method outlined in  FIG. 15 , except the method  1500  contemplates using  1501  at least one forming process to shape the first hardened metal workpiece in the T3 starting condition to form the shaped metal workpiece in the T3 condition. The method  1700  further includes performing  1404  a first heat-treating process on the shaped metal workpiece in the T3 starting condition to transition the shaped metal workpiece in the first-hardened T3 (starting) condition from the T3 (starting) condition to a second-hardened T8 condition. According to the method  1600  and  1700 , as shown in  FIGS. 16 and 17 , only one heat-treating process has been conducted to transition a starting material (the T3 material) in a first metallurgical condition (T3) to a final or finished material (the T8 material) in a second metallurgical condition (T8). The shaped metal workpiece includes the at least one friction stir weld (e.g. friction stir weld  92  shown in  FIG. 9 ). According to aspects outlined in  FIGS. 14, 15, 16 and 17 , when the metal workpiece is aluminum or an aluminum alloy, the starting T3 condition is the first-hardened condition. An example of the shaped metal workpiece made according to the T3 to T8 protocol can be the metal workpiece  114   b ,  114   c ,  114   d ,  114   e  and  120  as shown in  FIG. 9  and  FIGS. 11B, 11C, 11D, 11E  and  FIG. 12 , which is described in more detail herein. The method  1700  described in  FIG. 17  is similar to the method outlined in  FIG. 15 , except the method  1700  contemplates using  1701  at least one forming process to shape the second-hardened metal workpiece into the shaped second-hardened metal workpiece in the T8 condition. According to aspects of the present disclosure, the shaped metal workpiece in the T8 condition retains and includes the friction stir weld  92  introduced to the roughly-shaped metal workpiece as shown in  FIG. 9 . 
     According to aspects of the present disclosure, friction stir welds that are incurred in the metal workpieces produced according to the methods presented herein are retained in the near-finally-shaped and/or finally-shaped metal workpieces. In other words, the friction stir weld(s) made in the metal workpieces are not removed in finishing steps. As a result, the need for couplers or other reinforcing component parts (e.g. rivets, fasteners, etc.) is obviated according to aspects of the present disclosure. 
     Aspects of the present disclosure can of course, be carried out in other ways than those specifically set forth herein without departing from essential characteristics of the aspects presented herein. The present aspects are to be considered in all respects as illustrative and not restrictive, and all changes coming within the meaning and equivalency range of the appended claims are intended to be embraced therein.