WO2020086263A1

WO2020086263A1 - New titanium aluminide alloys and methods for making the same

Info

Publication number: WO2020086263A1
Application number: PCT/US2019/055245
Authority: WO
Inventors: Alojz Kajinic; Xuan Nguyen-Dinh
Original assignee: Arconic Inc.
Priority date: 2018-10-22
Filing date: 2019-10-08
Publication date: 2020-04-30

Abstract

The present patent application relates to Ti-48Al-2Cr-2Nb alloys (titanium aluminide style), having at least 0.12 at. % boron and at least 0.10 at. % Si. In some embodiments, the alloy includes 0.12-0.93 at. % B. In some embodiments, the alloy includes an amount of boron from Bmin to Bmax, wherein Bmin is (in at. %) = ((4.0*Al + 3.0*Cr - 6.4*Nb + 39.6*Si -156.6) / 306.9), and wherein Bmax is (in at. %) = ((971.3 - 17.3*Al - 10.2*Cr - 11.0*Nb - 18.8*Si) / 127.1).

Description

NEW TITANIUM ALUMINIDE ALLOYS AND METHODS FOR MAKING THE

SAME

BACKGROUND

[001] Titanium aluminide alloys having 48 at. % aluminum, 2 at. % Cr and 2 at. % Nb, the balance being titanium and impurities (a.k.a.“Ti-48Al-2Cr-2Nb”) appear to have been the subject of U.S. Patent Number 4,879,092, entitled“Titanium aluminum alloys modified by chromium and niobium and method of preparation.” The use of electron beam melting (EBM) to additively manufacture the Ti-48Al-2Cr-2Nb alloy is described in“Electron beam melting of Ti-48Al-2Cr-2Nb alloy: Microstructure and mechanical properties investigation” by S. Biamino et. al., Intermetallics, Vol. 19 (2011), pp. 776-781. However, EBM has several significant drawbacks, such as a requirement for high vacuum and a relatively short lifespan of the filament (the source of electrons for melting). This short lifespan of the filament negatively impacts the productivity and it also increases the scrap rate when the filament bums out during the AM process. Attempts to use other conventional additive manufacturing processes to make crack-free / acceptable Ti-48Al-2Cr-2Nb alloy products have failed.

SUMMARY

[002] Broadly, the present patent application relates to the use of boron and silicon in Ti- 48Al-2Cr-2Nb alloys (e.g., for use in facilitating additive manufacturing of such alloys). In one embodiment, a new Ti-48Al-2Cr-2Nb alloy includes a sufficient amount of boron and silicon such that (a) a crack-free additively manufactured product is produced and/or (b) crack- free repairs of existing titanium aluminide alloy products can be made (e.g., crack-free repairs of existing Ti-48Al-2Cr-2Nb alloy products).

i. Composition

[003] In one embodiment, a new Ti-48Al-2Cr-2Nb alloy includes at least 0.12 at. % boron and at least 0.10 at. % Si. In one embodiment, a new Ti-48Al-2Cr-2Nb alloy includes not greater than 0.93 at. % B. In one embodiment, a new Ti-48Al-2Cr-2Nb alloy includes not greater than 0.75 at. % Si. In one embodiment, a new Ti-48Al-2Cr-2Nb alloy comprises 0.12- 0.93 at. % B and 0.10-0.75 at. % Si. In one embodiment, a new titanium aluminide alloy includes an amount of boron from B_minto B_max, wherein B_min is (in at. %) = ((4.0*Al + 3.0*Cr - 6.4*Nb + 39.6*Si -156.6) / 306.9), and wherein B_max is (in at. %) = ((971.3 - 17.3*A1 - l0.2*Cr - l l .0*Nb - l8.8*Si) / 127.1). For the B_min and B_max formulae, Al, Cr, Nb, and Si are given in atomic percentages (at. %). In one embodiment, a new titanium aluminide alloy includes an amount of silicon from Si_minto Si_max, wherein Si_min is at least 0.10 at. % and wherein Simax is (in at. %) = ((6. l l*Al + 3.8l*Cr - 6.56*Nb -245.68) / 56.825). For the Simax formula, Al, Cr, and Nb are given in atomic percentages (at. %)

[004] Any suitable amounts of aluminum, chromium, and niobium may be used in the new titanium aluminide alloys. In one approach, a new Ti-48Al-2Cr-2Nb alloy comprises 45-50 at. % Al. In one embodiment, a new Ti-48Al-2Cr-2Nb alloy comprises at least 45.5 at. % Al. In another embodiment, a new Ti-48Al-2Cr-2Nb alloy comprises at least 46.0 at. % Al. In one embodiment, a new Ti-48Al-2Cr-2Nb alloy comprises not greater than 49.5 at. % Al. In another embodiment, a new Ti-48Al-2Cr-2Nb alloy comprises not greater than 49.0 at. % Al. In yet another embodiment, a new Ti-48Al-2Cr-2Nb alloy comprises not greater than 48.75 at. % Al. In one embodiment, a new Ti-48Al-2Cr-2Nb alloy comprises 46.0-48.75 at. % Al.

[005] In one approach, a new Ti-48Al-2Cr-2Nb alloy comprises 1.0-3.0 at. % Cr. In one embodiment, a new Ti-48Al-2Cr-2Nb alloy comprises at least 1.25 at. % Cr. In another embodiment, a new Ti-48Al-2Cr-2Nb alloy comprises at least 1.5 at. % Cr. In one embodiment, a new Ti-48Al-2Cr-2Nb alloy comprises not greater than 2.75 at. % Cr. In another embodiment, a new Ti-48Al-2Cr-2Nb alloy comprises not greater than 2.5. at. % Cr. In one embodiment, a new Ti-48Al-2Cr-2Nb alloy comprises 1.5-2.5 at. % Cr.

[006] In one approach, a new Ti-48Al-2Cr-2Nb alloy comprises 1.0-3.0 at. % Nb. In one embodiment, a new Ti-48Al-2Cr-2Nb alloy comprises at least 1.25 at. % Nb. In another embodiment, a new Ti-48Al-2Cr-2Nb alloy comprises at least 1.5 at. % Nb. In one embodiment, a new Ti-48Al-2Cr-2Nb alloy comprises not greater than 2.75 at. % Nb. In another embodiment, a new Ti-48Al-2Cr-2Nb alloy comprises not greater than 2.5. at. % Nb. In one embodiment, a new Ti-48Al-2Cr-2Nb alloy comprises 1.5-2.5 at. % Nb.

[007] In one specific approach, a new Ti-48Al-2Cr-2Nb alloy includes 46.0-48.75 at. % Al, 1.5-2.5 at. % Cr, 1.5-2.5 at. % Nb, 0.12-0.93 at. % B, and 0.10-0.75 at. % Si, the balance being titanium, optional incidental elements, and impurities. Optional incidental elements may include elements or materials that are known to be added to titanium aluminides during production. Incidental elements may be present in minor amounts, or may be present in significant amounts, and may add desirable or other characteristics on their own without departing from the alloy described herein, so long as the alloy retains the desirable characteristics described herein. It is to be understood, however, that the scope of this disclosure should not/cannot be avoided through the mere addition of an element or elements in quantities that would not otherwise impact the combinations of properties desired and attained herein. [008] While this section (i) has generally been described relative to the use of niobium in the new Ti-48Al-2Cr-2Nb alloys, tantalum (Ta) may be used in lieu of, or as a partial substitute for niobium (Nb). Thus, all of the ranges and amounts recited in the above paragraphs relating to niobium also apply equally to titanium aluminide alloys having tantalum (i.e., Ti-48Al-2Cr- 2Ta alloys), or both of tantalum and niobium (i.e., Ti-48Al-2Cr-2(Ta,Nb) alloys).

ii. Processing

[009] The new Ti-48Al-2Cr-2Nb alloys may be produced using a variety of methods, such as by conventional methods (e.g., cast-and-wrought methods), powder metallurgy methods, and additive manufacturing, among others. For instance, the new Ti-48Al-2Cr-2Nb alloys may be cast as ingot and/or formed into billet and further processed to new Ti-48Al-2Cr-2Nb alloy products using conventional thermomechanical (e.g., cast-and-wrought) methods. The new Ti- 48Al-2Cr-2Nb alloys may also be cast as shape cast products. For instance, the new TΪ-48A1- 2Cr-2Nb alloys may be cast into a near-net shape (e.g., via investment casting). Further, the new Ti-48Al-2Cr-2Nb alloys may be produced as powder, and the powder may be processed into a product by powder metallurgy and additive manufacturing methods (e.g., by selective laser melting or electron beam melting). The new Ti-48Al-2Cr-2Nb alloys may also be produced as any applicable additive manufacturing feedstock, for instance, such as a powder, a wire, and combinations thereof. In one embodiment, a new Ti-48Al-2Cr-2Nb alloy is a powder. In one embodiment, a Ti-48Al-2Cr-2Nb alloy is a wire. In one embodiment, a new Ti-48Al-2Cr-2Nb alloy powder is used to produce an additively manufactured product. Furthermore, the new Ti-48Al-2Cr-2Nb alloy products may be produced by hybrid processing methods, such as methods that couple additive manufacturing with deformation (e.g., hot-die forging, non-isothermal forging, among others). In one embodiment, the new Ti-48Al-2Cr- 2Nb alloys may be both additively manufactured and hot worked (e.g., in a manner consistent with the methods described in commonly owned U.S. Patent Publication No. 2015/013144).

[0010] 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”. The new Ti-48Al-2Cr-2Nb products may be manufactured 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. Non-limiting examples of additive manufacturing processes useful in producing new crack-free Ti-48Al-2Cr-2Nb alloy products include, for instance, DMLS (direct metal laser sintering), SLM (selective laser melting), SLS (selective laser sintering), and EBM (electron beam melting), among others. Any suitable feedstocks may be used, including one or more powders, one or more wires, and combinations thereof. In some embodiments the additive manufacturing feedstock is comprised of one or more powders. Shavings are types of particles. In some embodiments, the additive manufacturing feedstock is comprised of one or more wires. A ribbon is a type of wire.

[0011] As noted above, the new Ti-48Al-2Cr-2Nb alloys may be additively manufactured using a variety of additive manufacturing techniques. In particular, the compositions of the new Ti-48Al-2Cr-2Nb alloys described above may enable additive manufacturing of new crack-free Ti-48Al-2Cr-2Nb alloy products without the use of an electron beam. In one embodiment, a new crack-free Ti-48Al-2Cr-2Nb alloy product is additively manufactured via a laser-based additive manufacturing process (e.g., DMLS, SLM, SLS).

[0012] In some embodiments, a new Ti-48Al-2Cr-2Nb alloy product is a crack-free product. In some embodiments,“crack-free” means that the product is sufficiently free of cracks such that it can be used for its intended, end-use purpose. The determination of whether a product is“crack-free” may be made by any suitable method, such as, by visual inspection, dye penetrant inspection, and/or by non-destructive test methods. In some embodiments, the non destructive test method is an ultrasonic inspection. In some embodiments, the non-destructive test method is a computed topography scan (“CT scan”) inspection (e.g., by measuring density differences within the product). In one embodiment, a new Ti-48Al-2Cr-2Nb alloy product is determined to be crack-free by visual inspection. In another embodiment, a new Ti-48Al-2Cr- 2Nb alloy product is determined to be crack-free by dye penetrant inspection. In yet another embodiment, a new Ti-48Al-2Cr-2Nb alloy product is determined to be crack-free by CT scan inspection, as evaluated in accordance with ASTM E1441. In another embodiment, a new Ti- 48Al-2Cr-2Nb alloy product is determined to be crack-free during an additive manufacturing process, wherein in situ monitoring of the additively manufactured build is employed. iii. Properties

[0013] Products made by the new Ti-48Al-2Cr-2Nb alloys described herein may realize an improved combination of properties. In one embodiment, a new Ti-48Al-2Cr-2Nb alloy product realizes:

(i) a hot crack susceptibility index of from 2158 to 10545 °C, wherein the hot crack susceptibility index (in °C) is calculated as -170.3 Al + 6200.1 Cr + 1262.8 Nb - 1330.6

Si - 1015.6 B (all elements given in at. %); or (ii) a non-equilibrium freezing range of from 52 to 142 °C, wherein the non-equilibrium freezing range (in °C) is calculated as 0.3 Al + 41.4 Cr + 13.4 Nb - 41.0 Si - 28.1 B (all elements given in at. %); or

(iii) both (i) and (ii). iv. Products and Product Applications

[0014] In one embodiment, a new Ti-48Al-2Cr-2Nb alloy is in the form of a crack-free additively manufactured product. In another embodiment, a new Ti-48Al-2Cr-2Nb alloy is in the form of a crack-free repair region on an existing titanium aluminide alloy product. In another embodiment, a new Ti-48Al-2Cr-2Nb alloy is in the form of an additive manufacturing feedstock (e.g., a powder or a wire). In one embodiment, the additive manufacturing and/or repairing comprises a powder-based method of additive manufacturing and/or repairing (e.g., selective laser melting). In another embodiment, the additive manufacturing and/or repairing comprises a wire-based method of additive manufacturing and/or repairing.

[0015] Due to their improved combination of properties, the new Ti-48Al-2Cr-2Nb alloy products described herein may be used in a variety of product applications. In one embodiment, a new Ti-48Al-2Cr-2Nb alloy product is utilized in an elevated temperature application, such as in an aerospace or automotive vehicle. In one embodiment, a new Ti-48Al-2Cr-2Nb alloy product is utilized as an engine component in an aerospace vehicle (e.g., in the form of compressor blades, disks, blisks, casings, and vanes). In another embodiment, a new TΪ-48A1- 2Cr-2Nb alloy product is used as a heat exchanger for the engine of an aerospace vehicle. The aerospace vehicle including the engine component / heat exchanger may subsequently be operated. In one embodiment, a new Ti-48Al-2Cr-2Nb alloy product is an automotive engine component (e.g., a turbo charger component; an automotive valve). The automotive vehicle, including the engine component, may subsequently be operated. For instance, a new TΪ-48A1- 2Cr-2Nb alloy product may be used as a turbo charger component (e.g., a compressor wheel of a turbo charger, where elevated temperatures may be realized due to recycling engine exhaust back through the turbo charger), and the automotive vehicle including the turbo charger component may be operated. In another embodiment, a new Ti-48Al-2Cr-2Nb alloy product may be used as a blade in a land based (stationary) turbine for electrical power generation, and the land based turbine included the new Ti-48Al-2Cr-2Nb alloy product may be operated to facilitate electrical power generation.

[0016] In one embodiment, a new Ti-48Al-2Cr-2Nb alloy product is utilized as a structural component of an aerospace vehicle. For instance, the new Ti-48Al-2Cr-2Nb alloy products may be formed into various components for use in the aerospace industry, such as floor beams, seat rails, pylons, and fuselage framing, among others. In some embodiments, a new TΪ-48A1- 2Cr-2Nb alloy product is utilized in a defense application, such as in body armor, and armed vehicles (e.g., armor plating).

[0017] Aside from the applications described above, the new Ti-48Al-2Cr-2Nb alloy products of the present disclosure may also be utilized in a variety of consumer products, such as any consumer electronic products, including laptops, cell phones, cameras, mobile music players, handheld devices, computers, televisions, microwave, cookware, washer/dryer, refrigerator, sporting goods, or any other consumer electronic product requiring durability and selective visual appearance. In one embodiment, the visual appearance of the consumer electronic product meets consumer acceptance standards.

[0018] In some embodiments, the new Ti-48Al-2Cr-2Nb alloy products of the present disclosure may be utilized in a variety of products including non-consumer products including the likes of medical devices, transportation systems and security systems, to name a few. In other embodiments, the new Ti-48Al-2Cr-2Nb alloy products may be incorporated in goods including the likes of car panels, media players, bottles and cans, office supplies, packages and containers, among others.

[0019] While various embodiments of the present disclosure have been described in detail, it is apparent that modifications and adaptations of those embodiments will occur to those skilled in the art. However, it is to be expressly understood that such modifications and adaptations are within the spirit and scope of the present disclosure.

Claims

CLAIMS What is claimed is:

1. A Ti-48Al-2Cr-2Nb alloy, wherein the Ti-48Al-2Cr-2Nb alloy includes at least 0.12 at. % boron and at least 0.10 at. % Si.

2. The Ti-48Al-2Cr-2Nb alloy of claim 1, wherein the alloy includes 0.12-0.93 at. % B.

3. The Ti-48Al-2Cr-2Nb alloy of any of the preceding claims, wherein the alloy includes 0.10-0.75 at. % B.

4. The Ti-48Al-2Cr-2Nb alloy of any of the preceding claims, wherein the alloy includes an amount of boron from B_minto B_max, wherein B_min is (in at. %) = ((4.0*Al + 3.0*Cr - 6.4*Nb + 39.6*Si -156.6) / 306.9), and wherein B_max is (in at. %) = ((971.3 - 17.3*A1 - l0.2*Cr - 1 l .0*Nb - l8.8*Si) / 127.1).

5. The Ti-48Al-2Cr-2Nb alloy of any of the preceding claims, wherein the alloy includes an amount of silicon from Si_minto Si_max, wherein Si_min is at least 0.10 at. % and wherein Si_max is (in at. %) = ((6.1 l *Al + 3.8l *Cr - 6.56*Nb -245.68) / 56.825).

6. The Ti-48Al-2Cr-2Nb alloy of any of the preceding claims, wherein the alloy includes 45-50 at. % Al.

7. The Ti-48Al-2Cr-2Nb alloy of any of the preceding claims, wherein the alloy includes In one embodiment, a new Ti-48Al-2Cr-2Nb alloy comprises 46.0-48.75 at. % Al.

8. The Ti-48Al-2Cr-2Nb alloy of any of the preceding claims, wherein the alloy includes 1.0-3.0 at. % Cr.

9. The Ti-48Al-2Cr-2Nb alloy of any of the preceding claims, wherein the alloy includes 1.5 -2.5 at. % Cr.

10. The Ti-48Al-2Cr-2Nb alloy of any of the preceding claims, wherein the alloy includes 1.0-3.0 at. % Nb.

11. The Ti-48Al-2Cr-2Nb alloy of any of the preceding claims, wherein the alloy includes 1.5-2.5 at. % Nb.

12. An additively manufactured product made from the Ti-48Al-2Cr-2Nb alloy of any of the preceding claims, wherein the additively manufactured product is crack-free.

13. The additively manufactured product of claim 12, wherein the additively manufactured product realizes one of:

(i) a hot crack susceptibility index of from 2158 to 10545 °C, wherein the hot crack susceptibility index (in °C) is calculated as -170.3 Al + 6200.1 Cr + 1262.8 Nb - 1330.6 Si - 1015.6 B (all elements given in at. %); or (ii) a non-equilibrium freezing range of from 52 to 142 °C, wherein the non-equilibrium freezing range (in °C) is calculated as 0.3 Al + 41.4 Cr + 13.4 Nb - 41.0 Si - 28.1 B (all elements given in at. %); or

(iii) both (i) and (ii).

14. The additively manufactured product of claim 12 or 13, wherein the additively manufactured product is a crack-free automotive or aerospace component .

15. The additively manufactured product of claim 14, wherein the additively manufactured product is an engine component.