Titanium tungsten alloys produced by additions of tungsten nanopowder

Abstract

Disclosed herein are titanium-tungsten alloys and composites wherein the tungsten comprises 0.5% to 40% by weight of the alloy. Also disclosed is a method of making such alloys and composites using powders of tungsten less then 3 μm in size, such as 1 μm or less. Also disclosed is a method of making the titanium alloy by powder metallurgy, and products made from such alloys or billets that may be cast, forged, or extruded. These methods of production can be used to make titanium alloys comprising other slow-diffusing beta stabilizers, such as but not limited to V, Nb, Mo, and Ta.

Description

[0001] This application claims the benefit of domestic priority to U.S. Provisional Patent Application Ser. No. 60 / 563,009, filed Apr. 19, 2004, which is herein incorporated by reference in its entirety.[0002] Disclosed herein are titanium-tungsten alloys and composites. Also disclosed is a method of making such alloys and composites using nanopowders of tungsten and optionally comprising slow-diffusing beta stabilizers, such as but not limited to V, Nb, Mo, and Ta. [0003] While Ti alloys strengthened by W are generally desirable because they are strong wear resistant alloys, such alloys are difficult, if not impossible, to prepare by typical techniques. For example, in a casting process, W generally completely dissolves in the molten Ti during the melting step. As the resulting ingot solidifies beta-rich large, elongated islands form between the dendrites of the solidified casting. These resulting defects lead to poor mechanical properties in the final product. [0004] Until the pre...

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Benefits of technology

[0005] Literature that does describe Ti based alloys comprising W describes W being added to form a particulate dispersion. For example, M. Frary, S. M. Abkowitz, and D. C. Dunand, “Microstructure and Mechanical Properties of Ti / W and Ti-6Al-4V / W Composites Fabricated by Powder-Metallurgy,” Materials Science and Engineering A344 (2003) 103-112, which is herein incorporated by reference, shows that partially diffused W dispersions in Ti powder (Commercially Pure “CP” Ti) and Ti-based alloys (Ti-6Al-4V) increases strength with an acceptable loss in ductility. The alloys described in Frary et al. comprise 3 μm to 10 μm tungsten powders that are too large to completely diffuse. SUMMARY OF THE INVENTION

[0011] Disclosed herein is a method of making an alloy having a uniform dispersion of beta phase islands within a Ti matrix. According to this aspect, this uniform dispersion of beta phase islands can be controlled within the Ti matrix by adjusting the P / M sintering time and / or by manipulating the W powder size to a range from 8 angstroms to less then 3 μm, such as less than 1 μm. The beta phase island dispersion results in improved room and elevated temperature properties.

Problems solved by technology

While Ti alloys strengthened by W are generally desirable because they are strong wear resistant alloys, such alloys are difficult, if not impossible, to prepare by typical techniques.

These resulting defects lead to poor mechanical properties in the final product.

Until the present disclosure, the preparation of Ti—W by powder metallurgy (P / M), was not commercially viable because of the high melting point and slow diffusivity associated with W that causes it to remain segregated as discrete or undissolved particles.

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