Beta-Type Titanium Alloy

Abstract

Disclosed is a β-titanium alloy consisting of, in weight percent, 5-15% of V, 0.5-2.5% of Fe, 0.5-6% of Mo, 0.5-5% of Cr, 1.5-5% of Al, and the balance of Ti and impurities. When the weight % of V content is expressed as X_V, the weight % of Fe content is expressed as X_Fe, the weight % of Mo content is expressed as X_Mo, and the weight % of Cr content is expressed as X_Cr; the value of X_V+2.95X_Fe+1.5X_Mo+1.65 X_Cr is 15-23%. Such a β-titanium alloy has excellent cold workability, while having higher strength than Ti-20V-4Al-1Sn β-titanium alloy.

Description

FIELD OF THE INVENTION [0001] The present invention relates to a β-type titanium alloy and a method for heat treatment thereof. BACKGROUND OF THE INVENTION [0002] Titanium alloys are light in weight and high in strength, and of them, there exist titanium alloys called as β-type titanium alloys that comprise only the β-phase, many of which are excellent in cold workability compared with titanium alloys that comprise mainly the α-phase, and many being able to be increased in strength by an aging treatment. [0003] Examples of the known β-type titanium alloys include Ti-20V-4Al-1Sn (Patent Reference 1), Ti-15V-3Cr-3Al-3Sn, Ti-22V-4Al (Patent Reference 2), Ti-15V-6Cr-4Al (Patent Reference 3), Ti-13V-9Cr-3Al, Ti-15Mo-5Zr-3Al, Ti-3Al-8V-6Cr-4Mo-4Zr, Ti-13V-11Cr-3Al, and Ti-4.5Fe-6.8Mo-1.5Al. [0004] Of them, Ti-15V-6Cr-4Al, Ti-13V-9Cr-3Al, Ti-15Mo-5Zr-3Al, Ti-3Al-8V-6Cr-4Mo-4Zr and Ti-13V-11Cr-3Al are high in strength, but have a high deformation resistance in cold working and hot working, ...

AI Technical Summary

Benefits of technology

[0014] According to the present invention, it is possible to provide a titanium alloy that is more excellent in strength than the Ti-20V-4Al-1Sn β-type titanium alloy due to the solid solution hardening action, while having excellent cold workability as compared with a Ti-20V-4Al-1Snβ-type titanium alloy, by containing Fe, Mo and Cr in addition to the V, and specifically containing, by mass %, V: 5 to 15%, Fe: 0.5 to 2.5%, Mo: 0.5 to 6%, and Cr: 0.5 to 5%, wherein the value of XV+2.95XFe+1.5XMo+1.65XCr is from 15 to 23%, in which XV represents the mass % of the V, XFe represents the mass % of the Fe, XMo represents the mass % of the Mo and XCr represents the mass % of the Cr.

[0015] Now, the description will be made for the reason for determining the content of each element in a titanium alloy of this embodiment.

[0016] The titanium alloy of this embodiment contains, by mass %, V: 5 to 15%, Fe: 0.5 to 2.5%, Cr: 0.5 to 5% and Al: 1.5 to 5%, and Ti and impurities, in which the Ti and the impurities constitute the residue.

[0017] It is possible to provide a β-type titanium alloy, which has excellent cold workability, by melting a titanium alloy of these elements and rapidly cooling the same.

[0018] Then, the β-type titanium alloy is processed into a desired shape and then is subjected to a heat treatment which is called as an aging treatment to have the α-phase, which has a higher strength than the β-phase, precipitated in the β-type titanium alloy and thereby can be increased in strength.

[0019] V is contained, by mass %, within a range from 5 to 15% because when the content of V is less than 5%, the cold workability of a β-type titanium alloy is deteriorated and thus excellent cold workability is not obtainable; and when the content of V exceeds 15%, the precipitation of the α-phase in the aging treatment is inhibited and hence more excellent strength than Ti-20V-4Al-1Sn is not obtainable.

Problems solved by technology

Of them, Ti-15V-6Cr-4Al, Ti-13V-9Cr-3Al, Ti-15Mo-5Zr-3Al, Ti-3Al-8V-6Cr-4Mo-4Zr and Ti-13V-11Cr-3Al are high in strength, but have a high deformation resistance in cold working and hot working, deteriorating the workability thereof, and thus are limited in application to special fields.

However, no β-type titanium alloys that have excellent cold workability and a higher strength than Ti-20V-4Al-1Sn have been found through the studies made up to the present, and therefore the above demands have not yet been satisfied.