WO2019140048A1

WO2019140048A1 - Methods for making titanium aluminide materials

Info

Publication number: WO2019140048A1
Application number: PCT/US2019/012988
Authority: WO
Inventors: Dongjian Li; John E. Barnes
Original assignee: Arconic Inc.
Priority date: 2018-01-12
Filing date: 2019-01-10
Publication date: 2019-07-18

Abstract

The present disclosure relates to methods for cryogenically milling titanium aluminide materials. The methods generally include crushing titanium aluminide scrap thereby producing titanium aluminide pieces that are separated into a first portion of titanium aluminide pieces (e.g., small, not greater than 13 mm) and a second portion of titanium aluminide pieces (e.g., large, at least 13 mm). The first portion of titanium aluminide pieces are then cryogenically milled into a titanium aluminide powder comprised of titanium aluminide particles having an average size of not greater than 265 microns, and where the net relative reduction from the titanium aluminide pieces to titanium aluminide powder is at least 80%.

Description

METHODS FOR MAKING TITANIUM ALUMINIDE MATERIALS

FIELD OF THE INVENTION

[0001] Broadly, the present application relates to various methods for recycling titanium aluminide scrap (e.g., forming scrap into a powder product). More specifically, the present patent application relates to various embodiments of methods for cryogenically milling titanium aluminide materials.

BACKGROUND

[0002] Titanium aluminides are materials comprised of at least one of the phases of g- TiAl, a2-ThAl, and Ti Al·,. In general, titanium aluminide materials have low density and a high resistance to oxidation, and are able to withstand elevated temperatures.

SUMMARY OF THE DISCLOSURE

[0003] Broadly, the present disclosure relates to methods for cryogenically milling titanium aluminide materials. In this regard, the methods for cryogenically milling titanium aluminide materials generally include crushing titanium aluminide scrap, thereby producing a first portion and second portion of titanium aluminide pieces, separating the titanium aluminide pieces into a first portion and a second portion, and then cryogenically milling the first portion of titanium aluminide pieces into a titanium aluminide powder comprised of particles having an average size of not greater than 265 microns. In some embodiments, the titanium aluminide scrap may be crushed until titanium aluminide pieces suitable for cryogenic milling are realized.

[0004] Due to the methods for cryogenically milling the titanium aluminide materials, the resultant titanium aluminide powder may be used to produce titanium aluminide products, such as, via additive manufacturing methods or powder metallurgy methods, among others. In this regard, the cryogenic milling may facilitate production of titanium aluminide powders having an acceptable oxygen content (e.g., not greater than 0.30 wt. % O) for producing and/or using titanium aluminide products. Furthermore, cryogenic milling may facilitate an increase in productivity of titanium aluminide production processes (e.g., producing ingot) by utilizing waste streams (i.e., the titanium aluminide scrap).

BRIEF DESCRIPTION OF THE DRAWINGS

[0005] FIG. 1 is an embodiment illustrating a method for cryogenically milling titanium aluminide scrap into titanium aluminide powder. [0006] FIG. 2 is an optical micrograph depicting a representative image of titanium aluminide Ti-48Al-2Cr-2Nb scrap.

[0007] FIG. 3 is an optical micrograph depicting a representative image of a titanium aluminide particle having no grain boundaries therein.

[0008] FIG. 4 is an illustration of an embodiment of a stirred-ball type cryogenic mill, which can be utilized in accordance with one or more of the embodiments described herein.

DETAILED DESCRIPTION

[0009] With reference to FIG. 1, an embodiment of a method for cryogenically milling a titanium aluminide material (100) is illustrated. First, titanium aluminide scrap (101) is crushed (102), and then separated (e.g., by sieving) (103) into a first portion and second portion. In this regard, a first portion of small titanium aluminide pieces (e.g., not greater than 13 mm (“millimeters”) in size) (103) may be separated from a second portion of large titanium aluminide pieces (e.g., at least 13 mm in size) to be cryogenically milled (104). A second portion of large pieces (e.g., at least 13 mm in size) may be iteratively returned to be crushed (102), until crushed into small pieces. Alternatively, the titanium aluminide scrap (101) may be crushed until small titanium aluminide pieces suitable for cryogenic milling (e.g., less than 13 mm in size) are realized. Regardless, following the crushing (102), the small titanium aluminide pieces may then be cryogenically milled (104). In this regard, the cryogenic milling (104) may include providing an amount of energy to the cryogenic mill sufficient to realize plastic deformation (106) of the small titanium aluminide pieces. In this regard, the amount of energy generally is sufficient to mechanically deform and fragment the titanium aluminide material into smaller pieces. The resultant titanium aluminide powder may comprise particles having an average size of not greater than 265 microns (107). The resultant powder (107) may be used subsequently in a number of methods for producing titanium aluminide products, including additive manufacturing methods (111) and powder metallurgy methods (112).

[0010] As used herein,“titanium aluminide scrap” means titanium aluminide material left over from a prior operation. For instance, titanium aluminide scrap may be produced as a part of conventional production of titanium aluminide ingot and/or billet. Conventional processing of titanium aluminide ingot/billet may include scalping, machining, and/or rolling that may produce the titanium aluminide scrap. [0011] As used herein,“titanium aluminide” means a metal alloy having titanium and aluminum as the predominant alloying elements, wherein the amount of aluminum is at least 10 wt. % Al, and wherein the metal alloy includes at least one of the phases of g-TiAl, a ₂- Ti₃Al, and TiAl_3.

[0012] As used herein,“g-TίAG means a phase having an equal stoichiometric ratio of titanium to aluminum and a Llo structure.

[0013] As used herein, “o^-TbAl” means a phase having a stoichiometric ratio of titanium to aluminum of 3 : 1 and a DO 19 structure.

[0014] As used herein,“TiAl₃” means a phase having a stoichiometric ratio of aluminum to titanium of 3 : 1 and a Ll₂ or DO22 structure.

[0015] As used herein,“milling” means mechanically deforming a material to fragment the material into smaller pieces. Some nondimiting examples of milling include ball milling, jet milling, impact milling, vibratory ball milling, attritor milling (e.g., stirred ball- type), rod milling, hammer milling, and planetary milling, among others.

[0016] As used herein,“cryogenic milling” means milling that is performed in a milling fluid at a temperature sufficient to keep the milling fluid in the liquid phase. For instance, cryogenic milling may be performed using liquid nitrogen (N2) (Boiling Point = 77 K), or liquid argon (Ar) (Boiling Point = 87 K), among others.

[0017] As used herein,“powder” means a material comprising a plurality of particles. Powders may be used to produce components using additive manufacturing and powder metallurgy techniques. For instance, titanium aluminide powder may be utilized in an additive manufacturing apparatus to produce additively manufactured components.

[0018] As used herein,“particle” means a minute fragment of matter having a size suitable for use in additive manufacturing apparatuses and/or powder metallurgy apparatuses. For instance, a suitable size for additive manufacturing powders may be from 10 microns to 150 microns. Further, a suitable size for use in powder metallurgy may be from 10 microns to 220 microns.

[0019] Prior to the crushing (102), the titanium aluminide scrap generally has an initial average grain size of not greater than 600 pm. In one embodiment, the titanium aluminide scrap has an initial average grain size of not greater than 500 pm. In another embodiment, the titanium aluminide scrap has an initial average grain size of not greater than 400 pm. In one embodiment, the titanium aluminide scrap has an initial average grain size of at least 10 mih. In another embodiment, the titanium aluminide scrap has an initial average grain size of at least 25 pm. In yet another embodiment, the titanium aluminide scrap has an initial average grain size of at least 50 pm. In one embodiment, the titanium aluminide scrap has an initial average grain size of from 50 to 400 pm. For instance, FIG. 2 shows an optical micrograph of titanium aluminide Ti-48Al-2Cr-2Nb (nominal composition, in at. %) scrap. Furthermore, the micrograph shown in FIG. 2 demonstrates the microstructure of equiaxed g-TiAl (200) and lamellar g-TiAl (210) grains, where the grains range in size from about 50 pm to 400 pm.

[0020] As used herein, the word“grain” takes on the meaning defined in ASTM El 12

§3.2.2, i.e.,“the area within the confines of the original (primary) boundary observed on the two-dimensional plane of-polish or that volume enclosed by the original (primary) boundary in the three-dimensional object”. Grain dimensions are determined in two-dimensional space, in accordance with the“Heyn Lineal Intercept Procedure” method described in ASTM standard El 12-13, entitled,“Standard Test Methods for Determining Average Grain Size”.

[0021] As used herein“average grain size” means the average size of a plurality of grains as determined in accordance with the“Heyn Lineal Intercept Procedure” method described in ASTM standard El 12-13, entitled,“Standard Test Methods for Determining Average Grain Size”.

[0022] As noted above, the methods for cryogenically milling titanium aluminide materials generally include crushing titanium aluminide scrap (defined above). In this regard, the crushing may be accomplished by a variety of crushing apparatuses, such as a jaw crusher, gyratory crusher, roll crusher, cone crusher, an impact crusher, and combinations thereof. In one embodiment, the crushing comprises using a jaw crusher apparatus. In another embodiment, the crushing comprises using a gyratory crusher. In yet another embodiment, the crushing comprises using a roll crusher. In another embodiment, the crushing comprises using a cone crusher. In another embodiment, the crushing comprises using an impact crusher. As noted above, the crushing generally produces titanium aluminide pieces comprised of a first portion and a second portion. In this regard, the first portion may generally realize a size of not greater than 13 mm (“small pieces”), whereas the second portion may generally realize a size of at least 13 mm (“large pieces”). The large pieces (second portion) may be returned to the crusher until they are crushed into small pieces. As noted above, in some embodiments the titanium aluminide scrap may be crushed titanium aluminide pieces suitable for cryogenic milling are realized (e.g., without a separation step). Following crushing, the small titanium aluminide pieces may then be cryogenically milled.

[0023] The cryogenic milling (104) may be accomplished via a suitable cryogenic milling apparatus. For instance, a ball mill, impact mill, vibratory ball mill, attritor mill (e.g., stirred ball-type mill), rod mill, hammer mill, planetary mill, and combinations thereof may be used. In one embodiment, the cryogenic milling comprises using a ball mill. In another embodiment, the cryogenic milling comprises using a stirred ball-type mill (see FIG. 4). Regardless of the milling apparatus used for the cryogenic milling, the milling apparatus may be supplied with a cryogenic milling fluid (108). In some embodiments, the cryogenic milling fluid is generally non-reactive with the milling media (e.g., balls, arms, etc.) and/or titanium aluminide material. As a non-limiting example, the milling fluid may be comprised of an inert substance or inert substances (e.g., nitrogen, noble gases, and combinations thereof). For instance, a cryogenic milling apparatus may be supplied with at least one of nitrogen (N₂), helium (He), argon (Ar), krypton (Kr), and xenon (Xe). In one embodiment, a cryogenic milling fluid (108) comprises nitrogen (N₂). In another embodiment, a cryogenic milling fluid (108) comprises argon (Ar). Generally, the cryogenic milling fluid is a liquid during operation of the cryogenic mill. However, the cryogenic milling fluid may also be a gas-liquid mixture or gas. Thus, in some embodiments, the temperature of the milling fluid is less than the boiling point of the fluid. Low temperatures (e.g., less than 130 K) utilized during the cryogenic milling may facilitate plastic deformation and fragmentation of the titanium aluminide material during milling, thereby producing a titanium aluminide powder from the small titanium aluminide pieces. Thus, in one embodiment, cryogenically milling comprises providing an amount of energy sufficient to realize plastic deformation of the titanium aluminide pieces, wherein the amount of energy is sufficient to mechanically deform and fragment the titanium aluminide material into smaller pieces.

[0024] As noted above, the methods used herein may generally utilize an inert cryogenic milling fluid and/or low temperatures. Such cryogenic milling conditions may suppress the reaction of oxygen with the titanium aluminide material during milling. In this regard, oxygen is generally deleterious to the properties of titanium aluminide products (e.g., strength, ductility, among others). Thus, a reduction in oxygen uptake may allow for production of titanium aluminide powders within suitable specifications for producing and/or using titanium aluminide products. In one embodiment, the titanium aluminide powder comprises not greater than 0.30 wt. % O (i.e., 3000 ppm O). In another embodiment, the titanium aluminide powder comprises not greater than 0.20 wt. % O. In yet another embodiment, the titanium aluminide powder comprises not greater than 0.15 wt. % O. In another embodiment, the titanium aluminide powder comprises not greater than 0.10 wt. % O. In yet another embodiment, the titanium aluminide powder comprises not greater than 0.075 wt. % O.

[0025] As noted above, the titanium aluminide powder produced by cryogenically milling comprises particles having an average size of not greater than 265 microns. In one embodiment, the titanium aluminide powder comprises particles having an average size of not greater than 230 microns. In another embodiment, the titanium aluminide powder comprises particles having an average size of not greater than 190 microns. In yet another embodiment, the titanium aluminide powder comprises particles having an average size of not greater than 165 microns. In another embodiment, the titanium aluminide powder comprises particles having an average size of not greater than 140 microns. In yet another embodiment, the titanium aluminide powder comprises particles having an average size of not greater than 100 microns. In another embodiment, the titanium aluminide powder comprises particles having an average size of not greater than 50 microns. In yet another embodiment, the titanium aluminide powder comprises particles having an average size of not greater than 25 microns. In another embodiment, the titanium aluminide powder comprises particles having an average size of not greater than 10 microns.

[0026] In another aspect of the invention, the titanium aluminide pieces may be cryogenically milled to a net relative reduction of at least 80%. The net relative reduction is calculated by the following equation: [(Si-S₂)/Si]*l00%, where Si is the average size of the titanium aluminide pieces and where S₂ is the average size of the titanium aluminide particles after cryogenic milling. In one embodiment, the net relative reduction is at least 85%. In another embodiment, the net relative reduction is at least 90%. In yet another embodiment, the net relative reduction is at least 95%. In another embodiment, the net relative reduction is at least 97%. In yet another embodiment, the net relative reduction is at least 98%. In another embodiment, the net relative reduction is at least 98.5%. In yet another embodiment, the net relative reduction is at least 99%. In another embodiment, the net relative reduction is at least 99.3%. In yet another embodiment, the net relative reduction is at least 99.6%. In another embodiment, the net relative reduction is at least 99.9%. [0027] Due to the cryogenic milling processes described herein, the resultant titanium aluminide powder may also possess unique microstructural characteristics. For instance, due to the cryogenic milling processes described herein, in some embodiments at least 75% of the titanium aluminide particles are free of cold-welded grain boundaries. In this regard, the fragmentation of the titanium aluminide scrap occurs generally along grain boundaries and without cold welding between particles, resulting in particles having a size and shape substantially corresponding to the initial grains in the titanium aluminide scrap. In other words, at least 75% or more of the resultant particles are free of cold-welded grain boundaries, and due to the low level of cold welding, the particles generally retain their size and shape from the initial grains. In this aspect of the invention, the prevention of cold welding may be measured by the amount of particles free of cold-welded grain boundaries. For instance, cold welding of two titanium aluminide particles would result in the formation of at least one grain boundary. In this regard, preventing cold welding of the titanium aluminide material allows for the production of particles suitable for use in additive manufacturing and/or powder metallurgy production processes. As an example, a titanium aluminide particle of approximately 70 pm having no is shown in FIG. 3. As illustrated, the micrograph shows a microstructure predominately comprised of lamellar g-TΐAI (300). In this regard, grain boundaries between lamellar g-TiAl (300) grains can be seen. However, no cold-welded grain boundaries can be seen. Thus, in one embodiment, at least 85% of the titanium aluminide particles are free of cold-welded grain boundaries. In another embodiment, at least 95% of the titanium aluminide particles are free of cold-welded grain boundaries. In yet another embodiment, at least 98% of the titanium aluminide particles are free of cold-welded grain boundaries. In another embodiment, at least 99% of the titanium aluminide particles are free of cold-welded grain boundaries. In yet another embodiment, at least 99.9% of the titanium aluminide particles are free of cold-welded grain boundaries.

[0028] As used herein,“cold welding” means the fusion of at least two materials at a temperature below the liquidus temperature of the materials.

[0029] As used herein, a“cold-welded grain boundary” means a grain boundary formed by cold welding that excludes grain boundaries between lamellar g-TiAl grains, grain boundaries between equiaxed g-TiAl grains, and grain boundaries between lamellar g-TiAl grains and equiaxed g-TiAl grains. Cold-welded grain boundaries are determined using the “Particle Grain Boundary Analysis Procedure” given below. [0030] As used herein,“% of titanium aluminide particles free of cold-welded grain boundaries” means the amount of particles having no cold-welded grain boundaries in a population of particles as determined by the, “Cold-Welded Grain Boundary Analysis Procedure” given below.

[0031] The Cold-Welded Grain Boundary Analysis Procedure is as follows:

Cold-Welded Grain Boundary Analysis Procedure

1. A titanium aluminide powder is prepared for analysis as follows:

(i) mounting the titanium aluminide powder in a EPOMET® G Powder mounting material, or a suitable equivalent mounting material;

(ii) polishing the mounted titanium aluminide powder; and

(iii) etching the polished and mounted titanium aluminide powder using Kroll’s reagent;

2. A number of micrographs is then created using an optical microscope, and in accordance with the following requirements:

(i) the optical microscope is operated at a magnification of at least 500x magnification; and

(ii) the number of micrographs created must be sufficient analyze at least 200 individual titanium aluminide particles from the titanium aluminide powder prepared in step 1 ;

3. Each individual titanium aluminide particle from the micrographs created in step 2 is then analyzed by:

(i) counting the number of titanium aluminide particles having no cold- welded grain boundaries (N_zero); and

(ii) counting the number of titanium aluminide particles having at least one cold-welded grain boundary (N_one+);

4. Lastly, the “% of titanium aluminide particles free of cold-welded grain boundaries” is calculated using the following equation: [N zero / (N zero + None+)] * 100%.

[0032] In one embodiment, and with continued reference to FIG. 1, the apparatus used to cryogenically mill the small pieces of titanium aluminide may comprise milling balls (109), arms and shafts (110), such as a stirred ball-type mill. In this regard, and now with reference to FIG. 4, a stirred-ball type mill (400) is illustrated. As illustrated, the stirred-ball type mill (400) is comprised of a shaft (401), arms (402) connected to the shaft (401), a motor (405) connected to the shaft (401), and milling balls (403). As illustrated, the arms (402) and milling balls (403) are confined within a containment tank (404). Further, the motor (405) is fixed to the shaft (401) outside the containment tank (404). As illustrated, the motor (405) supplies energy to the shaft (401), thereby rotating the arms (402). Rotation of the arms (402) supplies energy to the milling balls (403), thereby fragmenting the titanium aluminide pieces (not illustrated) into a titanium aluminide powder.

[0033] In some embodiments, the milling media (e.g., milling balls) (403) are comprised of at least one of tungsten carbide, stainless steel, ceramics, titanium, titanium alloy, and combinations thereof. Furthermore, the cryogenic milling apparatus may be filled with an appropriate ratio of milling balls to titanium aluminide pieces. For instance, in one embodiment, the ratio of the mass of milling balls to the mass of titanium aluminide pieces is at least 2: 1. In one embodiment, the ratio of the mass of milling balls to the mass of titanium aluminide pieces is at least 3: 1. In another embodiment, the ratio of the mass of milling balls to the mass of titanium aluminide pieces is at least 5: 1. In yet another embodiment, the ratio of the mass of milling balls to the mass of titanium aluminide pieces is at least 8: 1. In another embodiment, the ratio of the mass of milling balls to the mass of titanium aluminide pieces is at least 10: 1.

[0034] The resultant titanium aluminide powder may be spheroidized, such as by methods described in U.S. Patent Pub. No. 2007/0221635 Al. Spheroidizing the resultant titanium aluminide powder may, for instance, produce a higher quality powder (e.g., for use in additive manufacturing). Thus, in some embodiments, the method further comprises spheroidizing the titanium aluminide powder.

[0035] As noted above, and now referring back to FIG. 1, the resultant titanium aluminide powder may be utilized by additive manufacturing (111) methods to produce titanium aluminide products. As used herein,“additive manufacturing” means,“a process of joining materials to make objects from 3D model data, usually layer upon layer, as opposed to subtractive manufacturing methodologies”, as defined in ASTM F2792-l2a entitled “Standard Terminology for Additively Manufacturing Technologies”. Titanium aluminide products may be manufactured using the titanium aluminide powders described herein, and via any appropriate additive manufacturing technique described in this ASTM standard, such as binder jetting, directed energy deposition, material extrusion, material jetting, powder bed fusion, or sheet lamination, among others.

[0036] As noted above, the resultant titanium aluminide powder may be utilized by powder metallurgy (112) methods to produce titanium aluminide products. In this regard, titanium aluminide powders may be compacted into final or near-final product form by a variety of suitable methods. For instance, the powder may be compacted via low pressure methods such as, loose powder sintering, slip casting, slurry casting, tape casting, or vibratory compaction. In another aspect, pressure may be used to realize the compaction by methods such as, for instance, die compaction, cold/hot isostatic pressing, and/or sintering.

[0037] Any suitable titanium aluminide (defined above) material may be used in the cryogenic milling methods described herein. For instance, some suitable titanium aluminide materials may include the following (nominal composition, in at. %): Ti-48Al-2Cr-2Nb,Ti- 47.3A1-0.70-0.7B, Ti-47Al-2Nb-2Mn, Ti-47Al-2Nb-0.5W-0.5Mo-lMn-0.2Si, TΪ-45.8A1- 0.7W-l.4Cr-0.45Si-0.25B, Ti-46Al-4Nb-lW, Ti-43Al-4Nb-lMo-0.lB, Ti-28.6Al-9.3Nb- 2.4Mo, among many others.

[0038] The figures constitute a part of this specification and include illustrative embodiments of the present disclosure and illustrate various objects and features thereof. In addition, any measurements, specifications and the like shown in the figures are intended to be illustrative, and not restrictive. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a representative basis for teaching one skilled in the art to variously employ the present invention.

[0039] Among those benefits and improvements that have been disclosed, other objects and advantages of this invention will become apparent from the following description taken in conjunction with the accompanying figures. Detailed embodiments of the present invention are disclosed herein; however, it is to be understood that the disclosed embodiments are merely illustrative of the invention that may be embodied in various forms. In addition, each of the examples given in connection with the various embodiments of the invention is intended to be illustrative, and not restrictive.

[0040] Throughout the specification and claims, the following terms take the meanings explicitly associated herein, unless the context clearly dictates otherwise. The phrases“in one embodiment” and“in some embodiments” as used herein do not necessarily refer to the same embodiment s), though it may. Furthermore, the phrases“in another embodiment” and “in some other embodiments” as used herein do not necessarily refer to a different embodiment, although it may. Thus, as described below, various embodiments of the invention may be readily combined, without departing from the scope or spirit of the invention.

[0041] In addition, as used herein, the term "or" is an inclusive "or" operator, and is equivalent to the term "and/or," unless the context clearly dictates otherwise. The term "based on" is not exclusive and allows for being based on additional factors not described, unless the context clearly dictates otherwise. In addition, throughout the specification, the meaning of "a," "an," and "the" include plural references. The meaning of "in" includes "in" and "on".

[0042] While a number of embodiments of the present invention have been described, it is understood that these embodiments are illustrative only, and not restrictive, and that many modifications may become apparent to those of ordinary skill in the art. Further still, unless the context clearly indicates otherwise, the various steps may be carried out in any desired order (and any desired steps may be added and/or any desired steps may be eliminated).

Claims

CLAIMS What is claimed is:

1. A method comprising:

(a) crushing titanium aluminide scrap;

(i) wherein the crushing comprises producing titanium aluminide pieces;

(b) separating the titanium aluminide pieces into a first portion and a second portion;

(c) cryogenically milling the first portion of the titanium aluminide pieces into a titanium aluminide powder;

(i) wherein the titanium aluminide powder comprises titanium aluminide particles having an average size of not greater than 265 microns; and

(ii) wherein a net relative reduction of the titanium aluminide pieces to titanium aluminide powder is at least 80%.

2. The method of claim 1, wherein the titanium aluminide scrap has an average grain size of not greater than 600 pm, or 500 pm, or 400 pm.

3. The method of any of the preceding claims, wherein the titanium aluminide scrap has an average grain size of at least 10 pm, or 25 pm, or 50 pm.

4. The method of any of the preceding claims, wherein at least 75%, or 85%, or 95%, or 98%, or 99%, or 99.9% of the titanium aluminide particles are free of cold-welded grain boundaries.

5. The method of any of the preceding claims, wherein the first portion comprises titanium aluminide pieces of not greater than 13 mm in size.

6. The method of any of the preceding claims, wherein the net relative reduction of the titanium aluminide pieces to titanium aluminide particles is at least 85%, or 90%, or 95%, or 97%, or 98%, or 98.5%, or 99%, or 99.3%, or 99.6%, or 99.9%.

7. The method of any of the preceding claims, wherein the crushing comprises using at least one of a jaw crusher, gyratory crusher, roll crusher, cone crusher, an impact crusher, and combinations thereof.

8. The method of any of the preceding claims, wherein the cryogenically milling comprises using at least one of a ball mill, impact mill, vibratory ball mill, attritor mill, rod mill, hammer mill, a planetary mill, and combinations thereof.

9. The method of claim 8, wherein the attritor mill is a stirred ball-type mill.

10. The method of any of the preceding claims, wherein the cryogenically milling comprises a cryogenic milling fluid.

11. The method of claim 10, wherein the cryogenic milling fluid comprises at least one of nitrogen (N₂), helium (He), argon (Ar), krypton (Kr), and xenon (Xe).

12. The method of claim 10 or 11, wherein a temperature of the cryogenic milling fluid is less than the boiling point of the cryogenic milling fluid.

13. The method of any of the preceding claims, wherein the cryogenically milling includes providing an amount of energy sufficient to realize plastic deformation of the titanium aluminide pieces, wherein the amount of energy is sufficient to mechanically deform and fragment the titanium aluminide material into smaller pieces.

14. The method of any of the preceding claims, wherein the titanium aluminide powder comprises not greater than 0.30 wt. % O, or 0.20 wt. % O, or 0.15 wt. % O, or 0.10 wt. % O, or 0.075 wt. % O.

15. The method of any of the preceding claims, wherein the titanium aluminide powder comprises particles having an average size of not greater than 265 microns, or 230 microns, or 190 microns, or 165 microns, or 140 microns, or 100 microns, or 50 microns, or 25 microns, or 10 microns.

16. The method of any of the preceding claims, wherein the cryogenically milling comprises utilizing milling balls.

17. The method of claim 16, wherein the milling balls are comprised of at least one of tungsten carbide, stainless steel, ceramic, titanium, and titanium alloy.

18. The method of claim 16 or 17, wherein the milling balls comprise a mass of milling balls, and wherein the titanium aluminide pieces comprise a mass of titanium aluminide pieces, wherein a ratio of (the mass of milling balls) to the (mass of titanium aluminide pieces) is at least 2: 1, or 3: 1, or 5: 1, or 8: 1, or 10: 1.

19. The method of any of the preceding claims, further comprising spheroidizing the titanium aluminide powder.