Abstract:
A metal induction forming method includes providing a metal sheet, cold forming the metal sheet by applying shaping pressure to the metal sheet, heating the metal sheet while applying shaping pressure to the metal sheet and quenching the metal sheet.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation-in-part of U.S. Utility patent application Ser. No. 11/854,733, filed Sep. 13, 2007, now U.S. Pat. No. 8,017,059 and entitled COMPOSITE FABRICATION APPARATUS AND METHOD, which utility patent application is incorporated by reference herein in its entirety. 
    
    
     TECHNICAL FIELD 
     The disclosure relates to composite fabrication apparatus and methods. More particularly, the disclosure relates to an induction forming process which uses induction heating to allow rapid heating and cooling of aluminum and magnesium alloys in combination with the application of tool pressure to form and/or mold near net shaped parts at elevated temperatures with subsequent incorporation of an in-tool quenching step. 
     BACKGROUND 
     Processing techniques and facilities which enable widespread use of molded thermoplastic composite components at production rates and production costs and that allow significant weight savings scenarios may be desirable in some applications. The capability to rapidly heat, consolidate and cool in a controlled manner may be required for high production rates of composite components. Current processing techniques include the use of heated dies, and therefore, may not allow for the optimum controlled cool-down which may be required for optimum fabrication. Furthermore, current processing techniques may have limitations in forming the desired components since such techniques have limitations in the capability to hold the dimensions of the component accurately or maintain the composite in a fully consolidated state and may not optimize performance of the current resin systems. 
     Superplastic forming and hot forming methods for fabricating aluminum and to some extent magnesium components may be hampered by the inability to effectively integrate the superplastic forming process with the heat treatment requirements. The savings produced by the excellent formability at SPF temperatures may be nullified by the loss of dimensional control due to the need to solution-treat and quench the component after superplastic forming to produce competitive strength characteristics. 
     The lower strength of non-heat treatable alloys may be a significant contributing factor mainly as to why there has not been widespread implementation of the SPF of aluminum components in the aerospace industry. Moreover, the long cycles and low strength of characteristic of the current process may be deterrents to using the SPF of aluminum and magnesium in the automotive industry. 
     Therefore, an induction forming process is needed which uses induction heating to allow rapid heating and cooling of aluminum and magnesium alloys in combination with the application of tool pressure to form and/or mold near net shaped parts at elevated temperatures with subsequent incorporation of an in-tool quenching step. 
     SUMMARY 
     The disclosure is generally directed to a metal induction forming method. An illustrative embodiment of the metal induction forming method includes providing a metal sheet, cold forming the metal sheet by applying shaping pressure to the metal sheet, heating the metal sheet while applying shaping pressure to the metal sheet and quenching the metal sheet. 
     In some embodiments, the metal induction forming method may include providing an induction forming apparatus comprising a first tooling die and a second tooling die; placing a metal sheet between the first tooling die and the second tooling die; cold forming the metal sheet by applying the first tooling die and the second tooling die to the metal sheet; heating the first tooling die and the second tooling die while applying the first tooling die and the second tooling die to the metal sheet; quenching the metal sheet by cooling the first tooling die and the second tooling die; and removing the metal sheet from between the first tooling die and the second tooling die. 
     In some embodiments, the metal induction forming method may include providing an induction forming apparatus comprising a first tooling die and a second tooling die each having a plurality of laminated sheets; placing a metal sheet between the first tooling die and the second tooling die; cold forming the metal sheet by applying the first tooling die and the second tooling die to the metal sheet; heating the first tooling die and the second tooling die while applying the first tooling die and the second tooling die to the metal sheet; quenching the metal sheet by cooling the first tooling die and the second tooling die; and removing the metal sheet from between the first tooling die and the second tooling die. 
     In some embodiments, the metal induction forming method may include providing an induction forming apparatus comprising a first tooling die and a second tooling die each having a plurality of laminated sheets, a first contoured die surface on the first tooling die, a second contoured die surface on the second tooling die, a first die susceptor on the first contoured die surface and a second die susceptor on the second contoured die surface; placing a metal sheet selected from the group consisting of aluminum, aluminum alloy, magnesium and magnesium alloy between the first die susceptor and the second die susceptor; cold forming the metal sheet by applying the first die susceptor and the second die susceptor to the metal sheet; heating the first die susceptor and the second die susceptor while applying the first die susceptor and the second die susceptor to the metal sheet; quenching the metal sheet by spraying a quenching medium between the laminated sheets of the first tooling die and the second tooling die to cool the first die susceptor and the second die susceptor; and removing the metal sheet from between the first die susceptor and the second die susceptor. In some embodiments, the method may include some degree of hot die forming followed by pressurized gas forming. This may enable a die design that need not be as exacting but can also leverage the speed and thinning pattern attributed to hot matched die forming (opposite that of hot forming). 
     The disclosure is further generally directed to a thixoforming method. An illustrative embodiment of the method includes providing at least one thixotropic block, loading the thixotropic block into a cold die, rapidly heating the die and the thixotropic block, forming a structure from the thixotropic block, cooling the die and the structure and removing the structure from the die. 
    
    
     
       BRIEF DESCRIPTION OF THE ILLUSTRATIONS 
         FIG. 1  is a sectional view of a pair of tooling dies of a stacked tooling apparatus, with molding compounds positioned between the tooling dies. 
         FIG. 2  is a sectional view of a pair of tooling dies, with the molding compounds enclosed between a pair of die susceptors provided on the tooling dies. 
         FIG. 3  is a sectional view of the tooling dies, with the tooling dies applying pressure to form and consolidate a composite sheet. 
         FIG. 4  is a sectional view of the tooling dies, with the tooling dies closed against the die susceptors and composite sheet and a cooling system engaged to cool the tooling dies. 
         FIG. 5  is a sectional view of the tooling dies, with the tooling dies and die susceptors released from the composite sheet after forming and cooling of the composite sheet. 
         FIG. 6  is a schematic view of a tooling die, more particularly illustrating a die susceptor and die liner provided on the engaging surface of the tooling die and multiple induction coils extending through the tooling die. 
         FIG. 7  is a front sectional view of a tooling die, more particularly illustrating multiple induction coils and multiple thermal expansion slots provided in the metal sheet. 
         FIG. 8  is a flow diagram which illustrates an exemplary composite fabrication method. 
         FIG. 9  is a flow diagram of an aircraft production and service methodology. 
         FIG. 10  is a block diagram of an aircraft. 
         FIG. 11  is a sectional view of a pair of tooling dies of an induction forming apparatus, with a metal sheet positioned between the tooling dies. 
         FIG. 12  is a sectional view of a pair of tooling dies of the induction forming apparatus, with the metal sheet enclosed between a pair of die susceptors provided on the tooling dies and the tooling dies applying pressure to form a shaped metal panel. 
         FIG. 13  is a sectional view of the tooling dies of the induction forming apparatus, with the tooling dies closed against the die susceptors and metal sheet and a cooling system engaged to cool the tooling dies and quench the shaped metal panel. 
         FIG. 14  is a sectional view of the tooling dies of the induction forming apparatus, with the tooling dies and die susceptors released from the shaped metal panel after forming and cooling of the metal sheet. 
         FIG. 15  is an end view of a tooling die of the induction forming apparatus, more particularly illustrating multiple induction coils extending through the tooling die. 
         FIG. 16  is a graph which illustrates the effect of susceptor thickness on quenching rates of the shaped metal panel. 
         FIG. 17  is a graph which illustrates the required cooling rates needed to meet full alloy strength potentials. 
         FIG. 18  is a flow diagram of a metal induction forming method. 
         FIG. 19  is a flow diagram of a thixoforming method. 
     
    
    
     DETAILED DESCRIPTION 
     Referring initially to  FIGS. 1-7  of the drawings, a stacked tooling apparatus which is suitable for implementation of the composite fabrication method is generally indicated by reference numeral  1 . The stacked tooling apparatus  1  may include a first die frame  2  and a second die frame  8 . A first tooling die  3  may be provided on the first die frame  2 , and a second tooling die  9  may be provided on the second die frame  8 . The first tooling die and the second tooling die  9  may be hydraulically-actuated to facilitate movement of the first tooling die  3  and the second tooling die  9  toward and away from each other. The first tooling die  3  may have a first contoured die surface  4 , whereas the second tooling die  9  may have a second contoured die surface  10  which is complementary to the first contoured die surface  4  of the first tooling die  3 . 
     As shown in  FIG. 6 , multiple induction coils  26  may extend through each of the first tooling die  3  (and the second tooling die  9 , not shown) to facilitate selective heating of the first tooling die  3  and the second tooling die  9 . A thermal control system  27  may be connected to the induction coils  26 . A first die susceptor  20  may be thermally coupled to the induction coils  26  of the first tooling die  3 . A second die susceptor  21  may be thermally coupled to the induction coils  26  of the second tooling die  9 . Each of the first die susceptor  20  and the second die susceptor  21  may be a thermally-conductive material such as, but not limited to, a ferromagnetic material, cobalt, nickel, or compounds thereof. In some embodiments, each of the first die susceptor  20  and the second die susceptor  21  may be made of alloys including one or more of the ferromagnetic elements Iron, Nickel and Cobalt plus other elements of lesser fractions such as Molybdenum, Chromium, Vanadium and Manganese, for example and without limitation. As shown in  FIGS. 1-5 , the first die susceptor  20  may generally conform to the first contoured die surface  4  and the second die susceptor  21  may generally conform to the second contoured die surface  10 . 
     As shown in  FIG. 6 , an electrically and thermally insulative coating  30  may be provided on the first contoured die surface  4  of the first tooling die  3 , as shown, and on the second contoured die surface  10  of the second tooling die  9  (not shown). The electrically and thermally insulative coating  30  may be, for example, alumina or silicon carbide. The first die susceptor  20  may be provided on the electrically and thermally insulative coating of the first tooling die  3 , as shown, and the second die susceptor  21  may be provided on the electrically and thermally insulative coating  30  of the second tooling die  9  (not shown). 
     As shown in  FIGS. 1-5 , a cooling system  14  may be provided in each of the first tooling die  3  and the second tooling die  9 . The cooling system  14  may include, for example, coolant conduits  15  which have a selected distribution throughout each of the first tooling die  3  and the second tooling die  9 . As shown in  FIG. 4 , the coolant conduit  15  may be adapted to discharge a cooling medium  17  into the first tooling die  3  or the second tooling die  9 . The cooling medium  17  may be a liquid, gas or gas/liquid mixture which may be applied as a mist or aerosol, for example. 
     Each of the first tooling die  3  and the second tooling die  9  may each include multiple stacked metal sheets  28  such as stainless steel which are trimmed to the appropriate dimensions for the induction coils  26 . This is shown in  FIGS. 6 and 7 . The stacked metal sheets  28  may be oriented in generally perpendicular relationship with respect to the first contoured die surface  4  and the second contoured die surface  10 . Each metal sheet  28  may have a thickness of from about 1/16″ to about ½″, for example and preferably ⅛″. An air gap  29  may be provided between adjacent stacked metal sheets  28  to facilitate cooling of the first tooling die  3  and the second tooling die  9  (not shown). The stacked metal sheets  28  may be attached to each other using clamps (not shown), fasteners (not shown) and/or other suitable technique known to those skilled in the art. The stacked metal sheets  28  may be selected based on their electrical and thermal properties and may be transparent to the magnetic field. An electrically insulating coating (not shown) may, optionally, be provided on each side of each stacked sheet  28  to prevent flow of electrical current between the stacked metal sheets  28 . The insulating coating may be a material such as ceramic, for example, or other high temperature resistant materials. However, if an air gap exists inbetween the stacked sheets, then no coating would be necessary. Multiple thermal expansion slots  40  may be provided in each stacked sheet  28 , as shown in  FIG. 6 , to facilitate thermal expansion and contraction of the stacked tooling apparatus  1 . 
     In typical implementation of the composite fabrication method, molding compounds  24  are initially positioned between the first tooling die  3  and the second tooling die  9  of the stacked tooling apparatus  1 , as shown in  FIG. 1 . The first tooling die  3  and the second tooling die  9  are next moved toward each other, as shown in  FIG. 2 , as the induction coils  26  ( FIG. 6 ) heat the first tooling die  3  and the second tooling die  9  as well as the first die susceptor  20  and the second die susceptor  21 . Therefore, as the first tooling die  3  and the second tooling die  9  close toward each other, the first die susceptor  20  and the second die susceptor  21  rapidly heat the molding compounds  24 . Thus, the molding compounds  24  which may be thermally molded as the first tooling die  3  and the second tooling die  9  continue to approach and then close against the molding compounds  24 , as shown in  FIG. 2 , forming the molding compounds  24  to the configuration of a composite sheet  25  (shown in  FIGS. 3-5 ) which may be defined by the first contoured surface  4  of the first tooling die  3  and the second contoured surface  10  of the second tooling die  9 . 
     As shown in  FIG. 4 , the cooling system  14  is next operated to apply the cooling medium  17  to the first tooling die  3  and the second tooling die  9  and to the first die susceptor  20  and the second die susceptor  21 . Therefore, the cooling medium  17  actively and rapidly cools the first tooling die  3  and the second tooling die  9  as well as the first die susceptor  20  and the second die susceptor  21 , also cooling the composite sheet  25  sandwiched between the first die susceptor  20  and the second die susceptor  21 . The composite sheet  25  remains sandwiched between the first tooling die  3  and the second tooling die  9  for a predetermined period of time until complete cooling of the composite sheet  25  has occurred. This allows the molded and consolidated composite sheet  25  to retain the structural shape which is defined by the first contoured surface  4  and the second contoured surface  10  after the first tooling die  3  and the second tooling die  9  are opened, as shown in  FIG. 5 . The formed and cooled composite sheet  25  is removed from the stacked tooling apparatus  1  without loss of dimensional accuracy or delamination of the composite sheet  25  when it is cooled at an appropriate property-enhancing rate. 
     Referring next to  FIG. 8 , a block diagram  800  which illustrates an exemplary composite fabrication method is shown. In block  802 , a stacked tooling apparatus comprising a first tooling die and a second tooling die may be provided. In block  804 , molding compounds may be placed between the first tooling die and the second tooling die. In block  806 , the first tooling die and the second tooling die may be heated. In block  808 , the first tooling die and the second tooling die may be moved into contact with the molding compounds. In block  810 , the first tooling die and the second tooling die may be cooled. In block  812 , a molded composite sheet is removed from between the first tooling die and the second tooling die. 
     Referring next to  FIGS. 9 and 10 , embodiments of the disclosure may be used in the context of an aircraft manufacturing and service method  78  as shown in  FIG. 9  and an aircraft  94  as shown in  FIG. 10 . During pre-production, exemplary method  78  may include specification and design  80  of the aircraft  94  and material procurement  82 . During production, component and subassembly manufacturing  84  and system integration  86  of the aircraft  94  takes place. Thereafter, the aircraft  94  may go through certification and delivery  88  in order to be placed in service  90 . While in service by a customer, the aircraft  94  is scheduled for routine maintenance and service  90  (which may also include modification, reconfiguration, refurbishment, and so on). 
     Each of the processes of method  78  may be performed or carried out by a system integrator, a third party, and/or an operator (e.g., a customer). For the purposes of this description, a system integrator may include without limitation any number of aircraft manufacturers and major-system subcontractors; a third party may include without limitation any number of vendors, subcontractors, and suppliers; and an operator may be an airline, leasing company, military entity, service organization, and so on. 
     As shown in  FIG. 10 , the aircraft  94  produced by exemplary method  78  may include an airframe  98  with a plurality of systems  96  and an interior  100 . Examples of high-level systems  96  include one or more of a propulsion system  102 , an electrical system  104 , a hydraulic system  106 , and an environmental system  108 . Any number of other systems may be included. Although an aerospace example is shown, the principles of the invention may be applied to other industries, such as the automotive industry. 
     The apparatus embodied herein may be employed during any one or more of the stages of the production and service method  78 . For example, components or subassemblies corresponding to production process  84  may be fabricated or manufactured in a manner similar to components or subassemblies produced while the aircraft  94  is in service. Also, one or more apparatus embodiments may be utilized during the production stages  84  and  86 , for example, by substantially expediting assembly of or reducing the cost of an aircraft  94 . Similarly, one or more apparatus embodiments may be utilized while the aircraft  94  is in service, for example and without limitation, to maintenance and service  92 . 
     Referring next to  FIGS. 11-15  of the drawings, an induction forming apparatus which is suitable for implementation of the metal induction forming method is generally indicated by reference numeral  101 . The apparatus  101  may include a first die frame  102  and a second die frame  108 . A first tooling die  103  may be provided on the first die frame  102 , and a second tooling die  109  may be provided on the second die frame  108 . The first tooling die  103  and the second tooling die  109  may be hydraulically-actuated to facilitate movement of the first tooling die  103  and the second tooling die  109  toward and away from each other. The first tooling die  103  may have a first contoured die surface  104 , whereas the second tooling die  109  may have a second contoured die surface  110  which is complementary to the first contoured die surface  104  of the first tooling die  103 . 
     As shown in  FIG. 15 , at least one set of induction coils  126  may extend through each of the first tooling die  103  (and the second tooling die  9 , not shown) to facilitate selective heating of the first tooling die  103  and the second tooling die  109 . In some embodiments, the induction coils  126  may be solenoid-shaped. A thermal control system  127  may be connected to the induction coils  126 . A first die susceptor  120  may be thermally coupled to the induction coils  126  of the first tooling die  103 . A second die susceptor  121  may be thermally coupled to the induction coils  126  of the second tooling die  109 . Each of the first die susceptor  120  and the second die susceptor  121  may be a thermally-conductive material such as, but not limited to, a ferromagnetic material, cobalt, nickel, or compounds thereof. In some embodiments, each of the first die susceptor  120  and the second die susceptor  121  may be made of alloys including one or more of the ferromagnetic elements Iron, Nickel and Cobalt plus other elements of lesser fractions such as Molybdenum, Chromium, Vanadium and Manganese, for example and without limitation. As shown in  FIGS. 11-14 , the first die susceptor  120  may generally conform to the first contoured die surface  104  and the second die susceptor  121  may generally conform to the second contoured die surface  110 . 
     As shown in  FIGS. 11-14 , a cooling system  114  may be provided in each of the first tooling die  103  and the second tooling die  109 . The cooling system  114  may include, for example, coolant conduits  115  which have a selected distribution throughout each of the first tooling die  103  and the second tooling die  109 . As shown in  FIG. 13 , the coolant conduit  115  may be adapted to discharge a quenching medium  117  into the first tooling die  103  or the second tooling die  109 . The quenching medium  117  may be a liquid, gas or gas/liquid mixture which may be applied as a mist or aerosol, for example. In some applications, the quenching medium  117  may be water. 
     Each of the first tooling die  103  and the second tooling die  109  may each include multiple laminated metal sheets  128  such as stainless steel which are trimmed to the appropriate dimensions for the induction coils  126 . The stacked metal sheets  128  may be oriented in generally perpendicular relationship with respect to the induction coils  126 . An air gap (not shown) may be provided between adjacent stacked metal sheets  128  to facilitate cooling of the first tooling die  103  and the second tooling die  109  (not shown). The laminated metal sheets  128  may be attached to each other using clamps (not shown), fasteners (not shown) and/or other suitable technique known to those skilled in the art. The laminated metal sheets  28  may be selected based on their electrical and thermal properties and may be transparent to the magnetic field. An electrically insulating coating (not shown) may, optionally, be provided on each side of each laminated sheet  128  to prevent flow of electrical current between the laminated metal sheets  128 . The insulating coating may be a material such as ceramic, for example, or other high temperature resistant materials. However, if an air gap exists in between the stacked sheets, then no coating may be necessary. Multiple thermal expansion slots (not shown) may be provided in each stacked sheet  128  to facilitate thermal expansion and contraction of the apparatus  101 . 
     In typical implementation of the metal induction forming method, a metal plate  124  is initially positioned between the first tooling die  103  and the second tooling die  109  of the stacked tooling apparatus  101 , as shown in  FIG. 11 . In some applications, the metal plate  124  may be aluminum, magnesium or alloys thereof, for example and without limitation. The first tooling die  103  and the second tooling die  109  are next moved toward each other, as shown in  FIG. 12 , until the metal plate  124  is initially partially formed between the first die susceptor  120  and the second die susceptor  121 . Once the cold forming limit of the metal plate  124  is reached, the induction coils  126  are energized to heat the first die susceptor  120  and the second die susceptor  121  to the induction forming temperature. In aluminum alloy applications, the induction forming temperature may be between about 900˜1000 degrees F. Accordingly, the induction coils  126  heat the first die susceptor  120  and the second die susceptor  121 , which form or shape the metal sheet  124  to the contour of the first contoured die surface  104  and the second contoured die surface  110 . This step may also include the stamping/flow (molding) of material for thickness changes in portions of the metal sheet  124  in which thickness reducing and thickness increases are needed. 
     As shown in  FIG. 13 , the cooling system  114  is next operated to apply the quenching medium  117  between the laminated sheets  128  of the first tooling die  103  and the second tooling die  109  and directly against the first die susceptor  120  and the second die susceptor  121 . Therefore, the quenching medium  117  may impinge directly against the first die susceptor  120  and the second die susceptor  121  and actively and rapidly cool the first tooling die  3  and the second tooling die  109  as well as the first die susceptor  120  and the second die susceptor  121 . In turn, the first die susceptor  120  and the second die susceptor  121  quench the formed metal panel  132  sandwiched between the first die susceptor  120  and the second die susceptor  121 . The formed metal panel  132  may remain sandwiched between the first tooling die  103  and the second tooling die  10  for a predetermined period of time until complete cooling or quenching of the formed metal panel  132  has occurred. This may allow the formed metal panel  132  to retain the structural shape which is defined by the first contoured surface  104  and the second contoured surface  110  after the first tooling die  103  and the second tooling die  109  are opened, as shown in  FIG. 14 . Once cooled to room temperature, the formed metal panel  132  may be removed from the apparatus  101  without loss of dimensional accuracy or stability of the formed metal panel  132  when it is cooled at an appropriate property-enhancing rate. The formed metal panel  132  may be subsequently aged to achieve maximum strength by any number of heating methods known to those skilled in the art. The first tooling die  103  and the second tooling die  109  may be made dimensionally thin and capable of being cooled at rates that enable the formed metal panel  132  to be solution treated. 
     The method may have the capability to form complex components in addition to performing the solution treatment of these components in the same rapid thermal cycle. The process may use induction heating with smart susceptors in conjunction with laminate tooling designs to create a forming tool that exhibits very little thermal inertia and heats rapidly and exactly to optimum forming/solution-treatment temperatures for the various aluminum alloys (between 900 F and 1000 F). This same process may be used to form and heat-treat magnesium alloys. These components may have very complex geometries as enabled by the ability to use gas forming and also molded in changes in thickness due to the ability to mold in changes in materials thicknesses. Therefore, high quality, complex, lightweight aluminum and magnesium near net shaped solution treated components may be fabricated rapidly and the needed dimensional control may still be achieved. 
     A graph  136  which illustrates the effect of susceptor thickness on quenching rates of the shaped metal panel is shown in  FIG. 16 . The elapsed time after quenching water is turned on (in seconds) is plotted along the X-axis  137 . The temperature of the metal sheet mid-plane (degrees C.) is plotted along the Y-axis  138 . 
     A graph  142  which illustrates the required cooling rates needed to meet full alloy strength potentials is shown in  FIG. 17 . Typical heat treatment response of standard aluminum alloys given quenching rates shows that for thinner susceptors, adequate quenching for most alloys is attainable. 
     Referring next to  FIG. 18 , a block diagram  1800  which illustrates an exemplary metal forming induction method is shown. In block  1802 , an induction forming apparatus comprising a first tooling die and a second tooling die may be provided. In block  1804 , a metal sheet may be placed between the first tooling die and the second tooling die. In some applications, the metal sheet may be aluminum, magnesium or alloys thereof. In block  1806 , the first tooling die and the second tooling die may be moved into contact with the metal sheet. In block  1808 , the first tooling die and the second tooling die may be heated once the cold forming limit of the first tooling die and the second tooling die has been reached. In block  1810 , forming or shaping of the metal sheet may be completed. In block  1812 , the resulting formed metal panel may be quenched by cooling the first tooling die and the second tooling die. The first tooling die and the second tooling die may be cooled by spraying a quenching medium against the first tooling die and the second tooling die. In some applications, the quenching medium may be water. In block  1814 , the formed metal panel is removed from between the first tooling die and the second tooling die. In block  1816 , in some embodiments the panel may be subjected to pressurized gas forming which follows hot die forming. This may enable a die design that need not be as exacting but can also leverage the speed and thinning pattern attributed to hot matched die forming (opposite that of hot forming). 
     Referring next to  FIG. 19 , a flow diagram  1900  which illustrates an exemplary thixoforming process is shown. The process  1900  may be suitable for large thixoforming operations using thoxitropic blocks as the starting material. The process  1900  may be particularly suitable for magnesium due to the difficulty in producing sheet materials with magnesium. In block  1902 , a thixotropic bar of aluminum or magnesium may be loaded into a cold die. In block  1904 , the tooling surface and the thixotropic bar workpiece may be rapidly heated to facilitate flowing of the workpiece and enable formation of a large thin structure in block  1906 . In block  1908 , the tooling surface and the structure may be cooled. In block  1910 , the formed structure may be removed from the die. 
     Although the embodiments of this disclosure have been described with respect to certain exemplary embodiments, it is to be understood that the specific embodiments are for purposes of illustration and not limitation, as other variations will occur to those of skill in the art.