Abstract:
A method for manufacturing a three-dimensional part. The method includes: performing partial densification processing on loose machining powder, to form a densified and sealed enclosure, where there is still loose machining powder accommodated inside the enclosure; and performing overall densification processing on the enclosure and the machining powder inside the enclosure, so as to implement metallurgical bonding between the machining powder inside the enclosure and the enclosure during the densification, thereby forming a target three-dimensional part.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims benefit of priority under 35 USC 119 to earlier-filed China Patent Application 201410065130.3, filed Feb. 25, 2014, which is hereby incorporated by reference. 
       TECHNICAL FIELD 
       [0002]    Embodiments of the technology relate generally to manufacturing methods, and in particular, to a three-dimensional object manufacturing method using powder products. 
       BACKGROUND 
       [0003]    For the production of complex and high performance articles, powder metallurgical processing has been used and often provides significant advantages over other casting and wrought processing routes. Multiple techniques have been developed to process powder or particulate materials into bulk essentially fully dense articles including pressing and sintering, canning and densification, and additive manufacturing. In each of these techniques, the complexity and production cost of the processing must be considered in defining effective routes for production of articles. Cost of the raw material and amount of machining or shaping processing after densification can also significantly affect the selection of optimized processing routes. Processing route may also affect the resulting physical, microstructural, and mechanical properties of the article and so article performance level also may be considered in defining the process route. In order to produce complex and high performance articles, several typical techniques are known in the art. 
         [0004]    For complex shaped articles, additive manufacturing processes have been used which have the capability of producing net or near net shapes directly. Electron beam melting (EBM) and direct metal laser melting (DMLM) are examples of types of additive manufacturing for three dimensional articles, especially for metal objects. They are often classified as rapid manufacturing methods because they also have the advantage of being able to produce a part from an electronic definition without the need to produce specialized tooling which can often lead to long lead times for production of articles by other processing routes. Many of the additive processing technologies including EBM and DMLM technologies manufacture three-dimensional objects by melting powder layer by layer with a laser beam or an electron beam in a high vacuum chamber in the case of EBM, and in a chamber, typically under inert gas for DMLM. For example, an EBM or DMLM machine reads data from a three-dimensional model and lays down successive layers of powdered material according to the three-dimensional model. These layers of powdered material are melted together by utilizing a computer controlled electron or laser beam. In this way it builds up the three-dimensional object to be manufactured. The process takes place under vacuum for EBM, while DMLM may be performed under vacuum or inert gas, such as Argon, which makes it suited to manufacture three-dimensional objects of reactive materials with a high affinity for oxygen, e.g. titanium. These techniques are particularly well suited for producing limited numbers of parts at low or intermediate volumes due to the typical deposition rates used. However, when the number of the three-dimensional objects to be manufactured is quite large, the whole manufacturing process may take much more time. This will require more EBM and/or DMLM machines to be used to meet the throughput which will increase the investment. 
         [0005]    For more simple shaped and larger articles, canning and densification processing of powders is also used. With these powder metallurgical processes, materials are typically placed into a can that isolates the materials from the surrounding environment and provides a transfer medium for further processes, such as hot isostatic pressing (HIP) and pneumatic isostatic forging (PIF). Cans are typically fabricated from sheet materials and welded into the shape of interest to make an article. Cans are oversized versus the desired final product size and shape in order to account for shrinkage than occurs during densification. Cans can be filled with loose powder or may be used to encapsulate pressed or semi porous powder preforms. Cans provide a manner in which the powder materials may be mechanically pressed into a porous or semi-porous object which is suitable for handling, transfer, and consolidation or densification into a target object. However, the use of the can requires several extra steps and leads to higher yield loss (due in part to interaction between the materials and the can material), thus reducing efficiency and increasing cost. Can cost and complexity can contribute significantly to the overall cost and time needed to produce powder articles or objects. 
         [0006]    Whether processed by additive manufacturing processes or by canning of loose partially densified compacts, powder derived materials are frequently subjected to densification processes that utilize elevated temperature, pressures, or both, in order to fully densify the structure. Some examples of such processing include sintering, hot pressing, and hot isostatic pressing (HIP). Additionally, U.S. Pat. No. 5,816,090 discloses a process for the consolidation of powder objects using pneumatic isostatic forging (PIF). Rather than applying heat and pressure simultaneously over a longer period of time, as in the typical HIP process, the &#39;090 patent relies on high temperatures and higher pressures over a short period of time in a pneumatic isostatic forging process. The &#39;090 patent describes only partially sealing the outer surface of the workpiece, or coating the workpiece with a potentially reactive material, prior to the “pre-sintering” step disclosed therein. The &#39;090 patent therefore discloses solutions that apply only to the process described therein and relies on extra steps not used in typical HIP processes. 
         [0007]    Pressing and sintering processes are also used whereby powders are put into a die and pressed into a shape, released from the die and then sintered at high temperatures in order to densify by diffusion. In this processing route, higher part volumes may be feasible but resulting articles are typically limited in geometry and ultimate density level and may be inferior to other powder metallurgical processing routes. 
         [0008]    Frequently powder metallurgical processing is used in order to produce high performance materials with properties that are difficult or impossible to achieve using standard casting and wrought processing methods. Processing routes that involve solid state processing (press and sinter, or can and densify, for example) may be advantageous over fusion based additive processing routes in that fine scale microstructural features may be maintained through processing and no solidification type structures may be produced during processing. Such constraints can also make optimum processing difficult for complex high performance materials. 
         [0009]    For these and other reasons, there is a need for increasing efficiency and saving cost in the rapid manufacturing field, and in particular, in densification processes involving powder metallurgy processing and subsequent densification by processes such as HIP and/or PIF. 
       SUMMARY 
       [0010]    One or more aspects are summarized in the present invention to facilitate a basic understanding of the present invention, where the induction of the present invention do not extend the overview, and is neither intended to identify certain elements of the present invention, nor intended to draw out of its range. On the contrary, the main purpose of the induction is to present some concepts of the present invention in a simplified form before more detailed descriptions are presented below. 
         [0011]    An aspect of the present invention is to provide a method for manufacturing a three-dimensional part. The method includes: performing partial densification processing on loose machining powder, to form a densified and sealed enclosure, where there is still loose machining powder accommodated inside the enclosure; and performing overall densification processing on the enclosure and the machining powder inside the enclosure, so as to implement metallurgical bonding between the machining powder inside the enclosure and the enclosure during the densification, thereby forming a target three-dimensional part. 
         [0012]    Another aspect of the present invention is to provide another method for manufacturing a three-dimensional part. The method includes: performing partial densification processing on loose machining powder by using an EBM technology, to form a densified and sealed vacuum enclosure, where there is still loose machining powder accommodated inside the enclosure; repeating the foregoing step until a predetermined number of the enclosures that accommodate the loose machining powder are machined; and performing overall densification processing simultaneously on the predetermined number of the enclosures that accommodate the loose machining powder, so as to implement metallurgical bonding between the machining powder inside the several enclosures and a corresponding enclosure during the densification, thereby simultaneously forming the predetermined number of target three-dimensional parts. 
         [0013]    Yet another aspect of the present invention is to provide another method for manufacturing a three-dimensional part. The method includes: performing partial densification processing on loose machining powder by using an additive manufacturing technology, to form a densified enclosure with an airway tube, where there is still loose machining powder accommodated inside the enclosure; connecting the airway tube to an air-extracting apparatus to discharge gas from the enclosure; performing sealing processing on the enclosure after a vacuum degree inside the enclosure reaches a predetermined value; repeating the foregoing step until a predetermined number of sealed vacuum enclosures that accommodate the loose machining powder are machined; and performing overall densification processing simultaneously on the predetermined number of the enclosures that accommodate the loose machining powder, so as to implement metallurgical bonding between the machining powder inside the several enclosures and a corresponding enclosure during the densification, thereby simultaneously forming the predetermined number of target three-dimensional parts. 
         [0014]    Yet another aspect of the present invention is to provide another method for manufacturing a three-dimensional part. The method includes: performing first densification processing on loose machining powder, to form a permeable porous half-finished part having a first density level; performing second densification processing on an outer surface area of the half-finished part, to form the outer surface area into a sealed enclosure having a second density level; and performing overall densification processing on the outer surface area having the second density level and an inner area having the first density level, to form a target three-dimensional part. 
         [0015]    Compared with the prior art, in the present invention, a three-dimensional part is manufactured and machined in steps. First, selective enclosure machining is performed on loose machining powder by using, for example, an additive manufacturing technology. In this way, in a situation in which a large quantity of target parts are to be machined, efficiency is significantly improved and energy consumption is significantly reduced because only an enclosure section, which occupies a very small portion of the entire part, is machined in the step. Then, in a subsequent step of an HIP or PIF technology, overall densification processing is performed simultaneously on the foregoing numerous enclosures that are finished machining and accommodate machining powder, so as to machine numerous target three-dimensional parts at once. Because numerous half-finished parts are machined simultaneously at once in the step, efficiency is also improved, and energy consumption is also reduced. In addition, metallurgical bonding between the enclosure and the machining powder inside the enclosure is implemented in the step without applying a conventional can to aid the machining. In this way, a manufacturing technique is significantly simplified. 
     
    
     
       BRIEF DESCRIPTION 
         [0016]    These and other features, aspects, and advantages of the present technology will become better understood when the following detailed description is read with reference to the accompanying drawings in which like characters represent like parts throughout the drawings, wherein: 
           [0017]      FIG. 1  is a schematic view of an exemplary EBM machine for manufacturing a shell containing powder of a target object; 
           [0018]      FIG. 2A ,  FIG. 2B ,  FIG. 2C , and  FIG. 2D  are schematic views of different manufacturing statuses of the shell of the target object manufactured by the EBM machine of  FIG. 1 ; 
           [0019]      FIG. 3A ,  FIG. 3B ,  FIG. 3C ,  FIG. 3D ,  FIG. 3E , and  FIG. 3F  are schematic views of different manufacturing statuses of the shell of the target object manufactured by the EBM machine of  FIG. 1  in another aspect; 
           [0020]      FIG. 4  is a schematic view of an exemplary HIP machine for manufacturing the shell containing powder of the target object manufactured by the EBM machine of  FIG. 1  in a beginning status; 
           [0021]      FIG. 5  is a schematic view of an exemplary HIP machine for manufacturing the shell containing powder of the target object manufactured by the EBM machine of  FIG. 1  in a finished status; 
           [0022]      FIG. 6  is a flowchart of a method for manufacturing a three-dimensional object, according to one embodiment; 
           [0023]      FIG. 7  is a schematic view of an original three-dimensional model and a compensated three-dimensional model according to an implementation manner of the invention; 
           [0024]      FIG. 8A ,  FIG. 8B ,  FIG. 8C , and  FIG. 8D , and  FIG. 9A ,  FIG. 9B , and  FIG. 9C  are two schematic views of different manufacturing statuses of a shell containing powder of a target object manufactured by an SLM method according to an implementation manner of the invention; 
           [0025]      FIG. 10  is a schematic view of an exemplary HIP machine for manufacturing the shell containing powder of the target three-dimensional object manufactured by the Selective Laser Melting (SLM) method of  FIGS. 8A-8D  and  9 A- 9 C in a beginning status; 
           [0026]      FIG. 11  is a schematic view of a process to cut a duct part from a target object according to an implementation manner of the invention; 
           [0027]      FIG. 12  is a schematic view of a shell containing powder of a target object, according to another embodiment; 
           [0028]      FIG. 13  is a flowchart of a method for manufacturing a target object, according to another embodiment; 
           [0029]      FIG. 14  is a schematic view of a shell containing powder of a target object, according to yet another embodiment; 
           [0030]      FIG. 15  is a schematic view of a shell containing powder of a target object, according to yet another embodiment; 
           [0031]      FIG. 16  is a schematic view of a shell containing powder of a target object, according to yet another embodiment; 
           [0032]      FIG. 17  shows several stages of a method for forming a target object; and 
           [0033]      FIG. 18  shows several stages of an alternative embodiment of a method for forming a target object. 
       
    
    
     DETAILED DESCRIPTION 
       [0034]    Embodiments of the present disclosure will be described with reference to the accompanying drawings. In the subsequent description, well-known functions or constructions are not described in detail to avoid obscuring the disclosure in unnecessary detail. 
         [0035]    Unless defined otherwise, technical and scientific terms used herein have the same meaning as is commonly understood by one of ordinary skill in the art to which this invention belongs. The terms “first”, “second”, and the like, as used herein do not denote any order, quantity, or importance, but rather are used to distinguish one element from another. Also, the terms “a” and “an” do not denote a limitation of quantity, but rather denote the presence of at least one of the referenced items, and terms such as “front”, “back”, “bottom”, and/or “top”, unless otherwise noted, are merely used for convenience of description, and are not limited to any one position or spatial orientation. Moreover, the terms “coupled” and “connected” are not intended to distinguish between a direct or indirect coupling/connection between two components. Rather, such components may be directly or indirectly coupled/connected unless otherwise indicated. 
         [0036]    Referring to  FIG. 1 , an exemplary EBM machine  10  for manufacturing three-dimensional objects is shown. For ease of explanation, only certain parts of the EBM machine  10  are shown in  FIG. 1 . As an example, the EBM machine  10  includes an electron beam gun  11 , a vacuum chamber  12 , a building table  13 , a powder container  14 , and a controller  15 . In other embodiments, the EBM machine  10  may have other different configurations. Moreover, rather than utilizing an EBM machine, alternative embodiments may utilize any possible manner of emitting energy or heat, including, but not limited to, direct metal laser melting, laser sintering, and infrared. 
         [0037]    The electron beam gun  11  is used to generate an electron beam  112  to melt powder  142  located on the building table  13  layer by layer according to a three-dimensional model stored in the controller  15 , to build a target three-dimensional object which has the same shape as the three-dimensional model. The powder container  14  is used to contain the powder  142  and deliver the powder  142  onto the building table  13  layer by layer according to control signals from the controller  15 . The controller  15  controls the electron beam gun  11 , the vacuum chamber  12 , the building table  13 , and the powder container  14  according to predetermined control programs, and the whole manufacturing process is under vacuum environment in the vacuum chamber  12 . It is understood that the EBM machine  10  may include other additive parts, such as power supplies, communication interfaces, etc. 
         [0038]    Referring to  FIGS. 1 ,  2  and  3  together, some different manufacturing statuses of a shell  24  containing the powder  142  of a target object  20  manufactured by the EBM machine  10  is shown. For ease of explanation, a target object  20  shown in  FIG. 5  is a columnar solid element. In other embodiments, the shape of the target object  20  may vary according to different requirements. The target object  20  shown in  FIGS. 2 and 3  is an unfinished target object  20 . In  FIGS. 2 and 3 , the shell  24  of the target object  20  is not exactly columnar-shape because the shell  24  needs to be compensated in this EBM manufacturing process before the subsequent HIP manufacturing process. After HIPping the shell  24  containing powder  142  manufactured by the EBM machine  10 , the target object  20  may be manufactured to the expected columnar-shape, which will be described in the following paragraphs. 
         [0039]    In a beginning status  FIG. 2A , a first layer of the powder  142  is delivered onto a building platform  132  of the building table  13 , for example by using a roller  134  to smoothly push the powder  142  onto the building platform  132 . After the first layer of the powder  142  is laid on the building platform  132  evenly, a bottom surface  21  of the shell  24  is manufactured by using the electron beam  112  to melt the corresponding part of the first layer of the powder  142  according to the three-dimensional model, as shown in the status of  FIG. 2B , and also shown in the status of  FIG. 3A . 
         [0040]    After the bottom surface  21  of the shell  24  is finished, a side surface  22  of the shell  24  is manufactured by using the electron beam  112  to melt the corresponding part of subsequent powder  142  layer by layer according to the three-dimensional model. As shown in the status of  FIG. 3B , a second layer of the powder  142  is put onto the building platform  132 , and a first layer of the side surface  22  is manufactured by using the electron beam  112  to melt the corresponding part of the second layer of the powder  142  according to the three-dimensional model as shown in the status of  FIG. 3C . The remaining layers of the side surface  22  are formed by the same manufacturing method as the first layer, and are not described in any further detail. The status of  FIG. 2C  and the status of  FIG. 3D  both show an intermediate status which is to manufacture one layer of the side surface  22 . 
         [0041]    After the side surface  22  is finished, a top surface  23  of the shell  24  is manufactured by using the electron beam  112  to melt the corresponding part of last layer of the powder  142  according to the three-dimensional model. As shown in the status of  FIG. 2D  and the status of  FIG. 3E , the last layer of the powder  142  is laid onto the building platform  132  and then the top surface  23  is manufactured by using the electron beam  112  to melt the corresponding part of the last layer of the powder  142  according to the three-dimensional model. Finally, a whole shell  24  is finished and it also contains loose powder  142 , or a mixture of loose powder and rapidly sintered supported patterns inside, as described in more detail below. In other words, after the EBM manufacturing, the target object  20  including the shell  24  and the powder  142  inside of the shell  24  as shown in the status of  FIG. 3F  is finished. The loose powder  142  may also be sintered using a faster scanning speed to below a predetermined density, for example 80%. The shell  24  is thus formed as a vacuum sealed three-dimensional shell having a predetermined internal porosity. 
         [0042]    Compared to the target object  20 , the shell  24  is not finished yet and has at least one unfinished part containing loose powder  142  or a mixture of loose powder and rapidly sintered supporting patterns which will be manufactured by a further manufacturing method. Here, the target object  20  is further manufactured by HIPping as described below. However, in other embodiments, the treatment and densification process may be other than HIP. For example, PIF or another densification process may be utilized. 
         [0043]    Referring to  FIG. 4 , the shell  24  is put into a high pressure containment vessel  42  of a HIP machine  40 . The HIP machine  40  may further include a controller  44  used to control temperature and pressure inside of the vessel  42 , which can provide a HIPping force to the shell  24  full of powder  142  and any supporting patterns that may be present. It is understood that the HIP machine  40  may include other additive parts, such as power supplies, communication interfaces, etc. 
         [0044]    In a beginning status shown in  FIG. 4 , the shape of the shell  24  still maintains the compensated shape, which is bigger than the expected shape of the target object  20 . According to predetermined program, the controller  44  will control the temperature and pressure in the vessel  42 , to provide a HIP treatment to the shell  24 . During the HIP treatment process, the shell  24  will press the loose powder  142  and any supporting patterns present to make it solid and metallurgically bond with the shell  24 . After finishing the HIP treatment, a solid target object  20  is manufactured as shown in  FIG. 5 . In  FIG. 5 , the powder  142  has become the same or nearly the same density as the shell  24 , which means the shell  24  and the loose powder  142  and any supporting patterns become one target object  20  to be manufactured, and the shape of the target object  20  becomes the expected columnar-shape as an example. 
         [0045]    Referring to  FIG. 6 , a flowchart of a method  60  for manufacturing the target three-dimensional object  20 , according to one embodiment is shown. The method  60  begins in step  61 , an original three-dimensional model is input/stored preferably into the controller of an EBM machine. The original three-dimensional model is the same as the target object  20 . For example,  FIG. 7  shows an original three-dimensional model X 1  which is columnar-shaped. In some embodiments, the three-dimensional model is a three-dimensional computer aided design (CAD) model. 
         [0046]    In step  62 , the original three-dimensional model X 1  is analyzed to determine what the shrinkage/distortion change  29  would be after a shell  28  containing loose powder having the same shape as the original three-dimensional model X 1  is treated by the HIP process. It is understood that the analysis of the shrinkage change of the shell containing powder can be simulated and analyzed based on appropriate algorithms, such as by using a finite element method (FEM) tool of ANSYS software. The detailed analysis process is not disclosed here. 
         [0047]    In step  63 , according to above shrinkage change analysis result, a compensated three-dimensional model is calculated based on appropriate algorithms, such as also by using the ANSYS software. For example,  FIG. 7  shows a compensated three-dimensional model X 2  which is bigger than the columnar-shaped original three-dimensional model X 1 . 
         [0048]    In step  64 , the compensated three-dimensional model X 2  is analyzed to determine if a shell containing powder having the same shape of the compensated three-dimensional model X 2  will be changed to the same shape as the original three-dimensional model X 1  after being treated by the HIP process. If yes, the process goes to next step  65 . If no, the process goes back the previous step  63 . It is also understood that this analysis can be simulated based on appropriate algorithms, such as by using the FEM tool of ANSYS software, which are not described here. It is also understood that, in this and other embodiments, the powder size distribution is a key factor affecting packing density and subsequent shrinkage. Preferably the analysis in steps  61 - 64  are incorporated into the controller of the EBM machine. Alternately the analysis in steps  61 - 64  may be performed in a separate system then the output transferred to the controller for the subsequent steps  65  and on. 
         [0049]    In step  65 , a shell  24  full of loose powder  142  and any additional supporting patterns is manufactured by using the EBM method based on the compensated three-dimensional model X 2 , which has been described above. 
         [0050]    In step  66 , the shell  24  containing the loose powder  142  and any supporting patterns is formed into the target three-dimensional object  20  by using the HIP method, which also has been described above. 
         [0051]    According to above method  60 , a target object  20  (for example shown in  FIG. 5 ) is manufactured by combining the EBM method and the HIP process. As only the shell  24  is manufactured by the EBM process, and not the whole target object  20 , the power used by the electron beam  112  is reduced and time may be saved as well. If several target objects  20  need to be manufactured, those corresponding shells  24  with the loose powder  142  and any supporting patterns can be HIP treated in the vessel  42  at the same time, which can increase efficiency. Furthermore, the shell  24  will become one part of the target object  20  through metallurgical bonding with the powder  142  after the HIP treatment, which can further simplify the manufacturing process. 
         [0052]    In other embodiments, instead of using the EBM method, the shell  24  together with loose powder  142  and any supporting patterns can be manufactured by other rapid manufacturing methods, such as selective laser melting (SLM) and direct metal laser melting (DMLM) methods under the non-vacuum condition, which are respectively performed in a SLM machine and a DMLM machine. Notably, however, both SLM and DMLM can also be performed under vacuum. 
         [0053]    Referring to  FIG. 8A-8D  and  FIG. 9A-9C , two schematic views for showing different manufacturing statuses of the shell  24  manufactured by the SLM method is shown. Compared with the EBM method shown in  FIG. 2A-FIG .  2 D, the SLM method of  FIG. 8A ,  FIG. 8B ,  FIG. 8C , and  FIG. 8D  may be performed in non-vacuum condition. Furthermore, the SLM method may further manufacture a duct  25  that may extend from the top surface  23 . In other embodiments, the duct  25  may extend from the side surface  22 . 
         [0054]    Referring to  FIG. 9A ,  FIG. 9B , and  FIG. 9C , after the shell  24  including the duct  25  and containing the loose powder  142  and any supporting patterns is finished, an air pump (not shown) is used to pump air and/or remnant inert gas from the shell  24  through a pipe  90  communicated with the duct  25 , which make the inside space of the shell  24  is vacuum (see  FIG. 9A ). In some embodiments, the duct  25  is quite long or the pipe  90  is quite long along the vertical direction, thus the loose powder  142  cannot be removed out from the shell  24 . In some embodiments, the shell  24  can be placed in a big vessel having an outlet (not shown), then the air pump is used to pump air from the big vessel through the outlet, thus the air inside of the shell  24  is indirectly pumped out without removing the loose powder  142 . The air inside of the shell  24  can also be pumped out according to other modes. 
         [0055]    When a vacuum level of the inside space of the shell  24  is satisfied according to a predetermined value, for example when the vacuum level is lower than about 0.01 Pascal, the extended duct  25  is sealed through appropriated methods, such as by an appropriated welding method (see  FIG. 9B ). Namely, the inside space of the shell  24  is sealed by a weld part  29 . Then, the weld part  29  is cut through appropriated cutting methods (see  FIG. 9C ), which makes the shell  24  be vacuum, like the shell  24  shown in  FIG. 4 . Note, the pipe may be locally heated and crimped shut, thus ensuring the vacuum is maintained inside the shell  24 . The pipe may be cut above the line of the crimp. 
         [0056]    Referring to  FIG. 10 , the sealed shell  24  full of loose powder  142  and any supporting patterns is treated by the HIP machine  40  to form the target object  20 . The manufacturing process is similar to that shown in  FIG. 4 , and thus the process is not described again. 
         [0057]    Referring to  FIG. 11 , after the HIP process, a solid target object  20  is formed, but a duct part  26 , due to the duct  25 , is an additional part on the target object  20 . The duct part  26  can be cut by appropriate cutting methods, for example a hydraulic cutting method, etc. After cutting the duct part  26 , the target object  20  is finished. Similar to the EBM method combining the HIP method, the SLM method combining the HIP method also can achieve a target object  20  which metallurgically bonds the shell  24  and the powder  142 . For clarity the deposition processes such as DMLM, SLM, and EBM can be practiced with or without the duct within the scope of this invention. 
         [0058]    In above mentioned embodiments, only the outside shell  24  is finished during the EBM or SLM process. However, in other embodiments, some of the powder  142  inside of the shell  24  also can be melted or sintered into different density levels. In that regard, referring to  FIG. 12 , a shell  24  of a target object  20  containing loose powder or partially consolidated powder  142  according to another embodiment is shown. Compared with the shell  24  shown in  FIG. 4 , the shell  24  of  FIG. 12  is not a uniform solid shell but includes at least two different density level layers. As an exemplary embodiment shown in  FIG. 12 , the illustrated shell  24  includes three different density level layers  241 ,  242 , and  243  from outside to inside. The density level from layer  241  to  243  is gradually reduced. For example, the density level of the first layer  241  is about 100%, the density level of the target object, the second layer  242  is about 90%, and the density level of the third layer  243  is about 80%. In other embodiments, the number of the density level layers, the density level of each layer, the thickness of each layer can be adjusted based on appropriate algorithms, such as by using the FEM tool of ANSYS software, which are not described here. 
         [0059]    Referring to  FIG. 13 , a flowchart of a method  70  for manufacturing a three-dimensional object, according to another embodiment is shown. Compared with the method  60 , the steps  71 - 73  of the method  70  are the same as the steps  61 - 63  of the method  60 . Thus, the steps  71 - 73  are not described here. 
         [0060]    In step  74 , based on the compensated three-dimensional model, the shell  24  is calculated to determine the number of the density level layers (like the layers  241 ,  242 ,  243 ) of the shell  24 , the density level of each layer, and the thickness of each layer. As mentioned above, those parameters can be calculated based on appropriate algorithms, such as by using the FEM tool of ANSYS software, which are not described here. 
         [0061]    In step  75 , the compensated three-dimensional model is analyzed to determine if a shell containing powder and any supporting patterns having the same shape of the compensated three-dimensional model will be changed to the same shape as the original three-dimensional model after being treated by the HIP process. If yes, the process goes to next step  76 . If no, the process goes back the previous step  73 . This step  75  is similar to the step  64  mentioned above. 
         [0062]    In step  76 , the shell  24  containing loose powder  142  and any supporting patterns is manufactured by using the EBM method. As the shell  24  includes at least two different density level layers, the electron beam  112  will melt the different density level layers by using different power levels of electron beams according to above calculated parameters of the shell  24 . Even though the shell  24  shown in  FIG. 12  is thicker than the shell  24  shown in  FIG. 4 , the power used by the electron beam  112  is still reduced and can save time compared with the conventional EBM methods. 
         [0063]    In step  77 , the shell  24  containing loose powder  142  and any supporting patterns is manufactured by using the HIP method. After the HIP process, a target solid object  20  (like the object  20  shown in  FIG. 5 ) is finished. Because the shell  24  is manufactured to several different density level layers during the EBM process, the HIP process may more easily and effectively achieve the target solid object  20  compared with the method  60 . 
         [0064]    In other embodiments, the shape of the object  20  may be not regular, such as a tear drop shape.  FIG. 14  shows a target object  20  as an example. In the EBM process, the object  20  of  FIG. 14  can be manufactured from a shell like the shell  24  shown in  FIG. 4 , i.e. from a shell of a single density. It should be appreciated that the target object  20  of  FIG. 14  can also be manufactured from a shell having several different density level layers, such as  241 ,  242 ,  243 , and  244  shown in  FIG. 14 . The detailed parameters can be calculated based on appropriate algorithms, such as by using the FEM tool of ANSYS software, which are not described here. 
         [0065]    In other embodiments, when the shell  24  is designed to include several different density level layers, each layer may also include different density level parts based on the material of the shell  24 , the HIP process, and other related parameters.  FIG. 15  shows an exemplary embodiment of a target object  20  manufactured by the EBM process. The shell  24  of the target object  20  of  FIG. 15  includes three layers  241 ,  242 , and  243 . The density level of the first layer  241  is about 100%. The second layer  242  include two density level parts  2421  and  2422 , the first part  2421  is in the middle of each side of the second layer  242 . As an example, the density level of the first part  2421  is about 100%; the density level of the second part  2422  is about 90%. Namely, the density level of the first part  2421  is greater than the second part  2422 . Similarly, the third layer  243  may include a first part  2431  with about 90% density level, and a second part  2432  with about 80% density level. The above parameters&#39; arrangement is calculated in the step  74  of the method  70  as mentioned above. 
         [0066]    In other embodiments, compared with the embodiment shown in  FIG. 16 , the shell  24  may further include some support ribs  27  extended from inside surfaces to opposite insides surfaces of the shell  24 . These support ribs  27  may also be manufactured by using the electron beam  112  to melt the corresponding part of the powder  142  according to a three-dimensional model having support ribs. In other embodiments, the shell  24  containing powder  142  may be designed in different types according to related parameters, but not limited as in the embodiments disclosed above. 
         [0067]    With respect to  FIG. 17 , in another embodiment, method for manufacturing a target object includes forming a porous object  300  from a loose powder to have a first density level, which may be at least approximately 30% and may be more than approximately 50% in other embodiments. In the embodiment shown, the density level of the porous object  300  is approximately 70%. In order to form the porous, or “pre-compacted” object  300 , an amount of loose powder may be directed into a constriction die (not shown) and densified to the first density level. The loose powder may be an elemental, blended elemental that may contain master alloy, or alloy powder metallurgical product. In a preferred embodiment, an outer surface region  302  of the porous object has a surface porosity having finely distributed pores. The pores may have sizes between approximately 10 micrometers and approximately 100 micrometers, which, as understood in the art, depends on the size of the powder metallurgical products and the density level of the object. In order to increase the density level of a portion of object, the porous object  300  is treated to thereby define a treated region  304  having a second density level. More specifically, an outer surface region  302  is treated to have the second density level. As described herein, “outer surface region” is meant to describe a region of the object beginning at the outer surface and traversing inward of the body of the object toward an imaginary axis thereof. Moreover, when referring to “outer surface region” herein, such a term encompasses the whole of the outer surface region  302  as disclosed above or, alternatively, only a portion thereof. Therefore, in one embodiment, the treated region  304  may encompass all or part of the outer surface region  302 . Alternatively, the treated region  304  may be located at other parts of the object  300 . 
         [0068]    In at least one embodiment, once the outer surface region  302  is treated, the density level of the treated region  304 , or the second density level, is at least about 95% such that the pores that existed prior to the treatment are substantially eliminated. With a density level of at least about 95% and a thickness between approximately 0.025 mm and approximately 1 mm, the treated region  304  essentially acts as a hermetic seal to the inner portion  306 , which still has the first density level. The thickness of the treated region  304  is sufficient such that a seal can be formed and that sufficient strength is present to maintain the seal through further transportation, treatment, and processing, such as by HIP or PIF, or any other treatment processes or methods by which an object may be densified or consolidated. Once the porous object  300  is treated, the object  300  is densified or consolidated to form the target object  308  having at least about 95% density level and preferably about 100% density. Notably, the shrinkage of the target object  308  after the HIP or PIF process will be taken into account in a same or similar manner as described above with respect to the other embodiment. It will be appreciated that the size and shape difference that the target object  308  may possess relative to the porous object  300  after HIP or PIF treatment, but before shrinkage occurs, is not shown. It will also be appreciated that while the inner, untreated region  306  may include the first density level and the treated region  304  may include the second density level, there may not be an exact point of delineation between the first and second densities. Rather, there may be a gradual change, or density gradient, from the second density level to the first density level. 
         [0069]    Such an approach of essentially sealing the porous object  300  prevents environmental and contaminant sources from infiltrating the porous object  300  prior to consolidation or densification of the object  300  to a target object shape and size. Moreover, the approach as disclosed herein allows for the use of lower packing density level materials. It will be appreciated that the treated region  304  is essentially an in situ can that likely does not require the use of a can described herein, as is a typical practice in the art. Finally, since no can is required, machining the target object  308  after densification to remove the excess material (caused by the interaction between the object and the can) is unnecessary, thereby saving time and reducing yield loss. Further cost savings are realized when it is considered that rather than replacing well-known processes with new processes to create densified target objects, the disclosure herein teaches an approach that is supplemental to existing powder metallurgy processes such as HIP or PIF. 
         [0070]    In one embodiment, treating the porous object  300  includes utilizing a material fusion process. In order to effectuate treatment of the outer surface region  302 , a penetration of the fusion process is limited to a certain depth such that only the outer surface region  302  is treated. Such material fusion processes may include, but are not limited to, microwave, laser melting, electron beam (EB) melting, TIG melting, infrared heating, and other weld-overlay type processes involving a rastered scan of the surface that produce overlapping fusion zones and a high quality surface layer. The local fusion layer may also be formed by processes including, but not limited to, transient liquid phase sintering and induction melting. 
         [0071]    In another embodiment, treating the porous object  300  involves solid state processing by sintering and diffusion in the outer surface region  302 . Such processes include, but are not limited to, microwave sintering, induction sintering, and controlled laser sintering. In yet another embodiment, treating the porous object  300  includes formation of a local fusion layer at the outer surface region  302 . 
         [0072]    In yet another embodiment, treating the porous object  300  includes selectively mechanically and plastically deforming the outer surface region  302 . The deformation may be accomplished by processes including, but not limited to peening, burnishing, cold extrusion, warm extrusion, or other deformation processes whereby the outer surface portion  302  is deformed such that the density level thereof is at least about 95%. 
         [0073]    In yet another embodiment, treating the porous object  300  includes coating the outer surface region  302  with a coating layer. Preferably, the coating layer is non-reactive with the materials from which the porous object  300  is made. Such a non-reactive material may include glass or aluminum. Alternatively, a material that reacts with the surface to form a stable coating layer that is capable of transferring a load at temperatures of approximately ½ of the melting temperature of the material from which the porous object is made or higher when it diffuses into or with the base material, may be used. The coating layer may coat the entire outer surface region  302  or, alternatively, only a portion thereof. 
         [0074]    In yet another embodiment, treating the porous object  300  includes cladding-type processes. Such cladding-type processes include, but are not limited to, laser cladding, TIG overlay, braze foil cladding, cold spray, metal paint, etc. Optionally, once the cladding-type process takes place, the outer surface region  302  may be optionally thermally treated to diffuse together the powder metallurgy product with the cladding-type materials in a controlled fashion in order to form an alternative coating layer. In another embodiment, referring to  FIG. 18 , treating a porous object  400 , and specifically, treating a surface region  401  includes encapsulating the porous object  400  in a bag  402 , made out of rubber, silicone, elastomer, or other similar material. The porous object  400  and the bag  402  are evacuated whereby they are subjected to a vacuum process. The porous object  400  and the bag  402  are then heated to an elevated temperature for a period of time such that the bag  402  and the outer surface region  401  of the porous object  400  reach the elevated temperature, but the inner portion  403  of the porous object  400  is at a temperature below the elevated temperature (i.e., at room temperature). In one embodiment, the elevated temperature is between approximately 600° F. and approximately 700° F. Once the porous object  400  is heated as just described, the heated porous object  400  is subjected to a PIF process. Because the flow stress of the heated surface region  401  is lower than the flow stress of the cooler inner portion, the PIF process results in only densification of the surface region  401 . Similar to other embodiments, after the outer surface region  401  is treated, a shell  404  is formed. The density of the shell  404  is at least approximately 95% such that the shell  404  provides a hermetic seal for the inner, untreated region  406 , which has a density of at least approximately 30%. As before, there may be a density gradient between the treated region (shell  404 ) and the untreated inner region  406 . Once the outer surface region  401  is treated, such that a shell  404  is formed, essentially forming an in situ can, the object  400  may be densified according to processes such as HIP, PIF, or other processes. For example, in a PIF process, the object  400  may be heated up to an elevated temperature which is a function of the melting point of the material(s) of which the object is composed. The object  400  is then removed from the source of heat and subjected to pressure between approximately 5,000 psi and 60,000 psi to densify the porous object  400  to a density of at least approximately 95%, and preferably 100% density, such that a target object  408  is formed. 
         [0075]    In any of the embodiments described herein, HIP processing may be performed at pressures in the range of up to about 45 ksi and at temperatures above about one half of the melting temperature but below the solidus of the material being subjected to HIP. Other material-specific considerations may also further limit the range of HIP temperatures used and therefore the HIP processing is not limited to the pressures and temperatures described herein. PIF conditions may be in the range of about 10 ksi to up to about 60 ksi pressure and preheat temperatures above about one half of the melting temperature but below the solidus of the material being subjected to the PIF process. Similar material-specific considerations may also further limit the range of PIF temperatures used and therefore the pressures and preheat temperatures described herein with respect to PIF are not meant to be limiting. 
         [0076]    The disclosure described herein may be used in combination with other processing techniques including those disclosed in U.S. Pat. Nos. 6,737,017, 7,329,381, and 7,897,103, which are incorporated herein by reference, in their entireties. The disclosure as described herein is particularly useful for the consolidation of high quality titanium alloy materials but is also applicable to other material systems including Al, Fe, Ni, Co, Mg, and other combinations of materials. The process as disclosed herein, which essentially creates a seal on the outer surface region  302  of a porous object  300 , (also referred to herein as a “precompacted shape”) of loose powder material (elemental, blended elemental that may contain master alloy, or alloy) that maintains its own shape on all sides without the use of a container such as a can. The precompacted shape may be any shape including a cylinder, rectangular prism, hexagonal cylinder, or other three-dimensional shape that is appropriate for downstream consolidation and use. The process can be applied to mill products (bars, billets, plate, sheets, tube, pipe, etc.) that can be further processed into components or to net or near net shape components directly. Components of interest include turbine engine parts such as disks, rings, blisks, shafts, blades, vanes, cases, tubes, and other components; automotive components including engine and body parts; industrial components; biomedical articles; sporting goods; and other applications. These embodiments of the invention, however, are not limited to specific applications. 
         [0077]    In each of the embodiments, the shell may be selected to be either thin or thick, have an abrupt interface with the material internal to the shell or have a graded density interface, may be made from the same material as the powder being consolidated or made from a differing material, the shell may be maintained in the final industrial part or may be removed by conventional machining or other dissolution or etching processes. Furthermore, the shell may contain an integral duct which can be used to evacuate the internal cavity of the initial object and then sealed off prior to densification processing in order to enable removal of undesirable gaseous species from the internal portions of the bulk material prior to densification. Additionally densified articles produced by this method can be net shape, near net shape, or may require significant additional processing by forging, machining and/or other processing routes prior to use. Preferably the article is formed of a metallic material and more preferably of a metallic alloy material but the scope of this disclosure is not so limited. 
         [0078]    While the technology has been described with reference to exemplary embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the claimed inventions. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the disclosure without departing from the scope of the claimed invention. Therefore, it is intended that the claimed inventions not be limited to the particular embodiments disclosed, but that the claimed inventions include all embodiments falling within the scope of the appended claims. 
         [0079]    It is to be understood that not necessarily all such objects or advantages described above may be achieved in accordance with any particular embodiment. Thus, for example, those skilled in the art will recognize that the systems and techniques described herein may be embodied or carried out in a manner that achieves or optimizes one advantage or group of advantages as taught herein without necessarily achieving other objects or advantages as may be taught or suggested herein.