Titanium alloy having high ductility, fatigue strength and rigidity and method of manufacturing same

Abstract

A titanium alloy is provided wherein metal boride is uniformly crystallized and / or precipitated in the matrix. The heating temperature in the finishing hot working is set smaller than the beta transus temperature by not less than 10° C., thereby causing the matrix to include an equiaxial alpha structure in a rate of not less than 40 vol %. This titanium alloy has excellent properties, i.e., high rigidity, ductility and fatigue strength, which are all required for structural components, and therefore can be widely applied to a mechanical component such as an engine of an automobile, a structural component in an aircraft as well as a component for a high speed rail vehicle.

Description

[0001] The present invention relates to a titanium alloy having a high ductility, fatigue strength and rigidity, which alloy is used in a mechanical component requiring excellent mechanical properties and a light weight as well, for instance, a connecting rod, valve, camshaft, crankshaft and push rod in an engine of an automobile or a structural component in an aircraft, a high-speed rail vehicle or the like. The present invention also relates to a method of manufacturing such a titanium alloy.[0002] A titanium alloy has excellent properties for the corrosion resistance and the heat resistance, along with a high mechanical strength and a lightweight property, so that an application of the alloy to various mechanical components in an automobile, an aircraft and a high-speed rail vehicle is now widely extending. However, titanium alloy has a relatively small Young's modulus, i.e., about half of that in iron or steel materials. Accordingly, buckling and bending must be taken into accou...

AI Technical Summary

Benefits of technology

[0007] On the other hand, it is required that the structural elements may be used in a much severer environment and the manufacturing cost may also be reduced, along with an excellent hot workability and mechanical strength. For instance, a high hot workability, a high rigidity, an excellent ductility and fatigue strength are all required for a connecting rod of an automobile, although it can be used in such a sever environment and the manufacturing cost is further reduced. Nevertheless, any titanium alloy having such properties has not developed yet.

[0041] Elements V, Mo, Cr, Fe, Nb, Ni or W may be used as a .beta. phase stabilizing element. The .beta. phase stabilizing element included in the alloy decreases the .beta. transus temperature and improves the hot workability. These elements are solved in the matrix and suppress an excessive generation of metallic compound (Ti.sub.3Al), thereby enabling a greater content of Al to be solved. However, an excessive content of these elements causes the Young's modulus to be markedly reduced. Accordingly, one or more than two of these elements should be added to the alloy within a range not more than 10% in the v equivalent given by the below equation (a), and more preferably not more than 5% in the V equivalent: 2 V equivalent = V + 15 10 Mo + 15 6.3 Cr + 15 4.0 Fe + 15 36 Nb + 15 9 Ni + 15 25 W ( a )

Problems solved by technology

As described above, there is a problem that titanium alloy has a relatively higher mechanical strength, but a smaller Young's modulus, compared with the iron or steel materials.

However, no improvement has been succeeded yet to obtain a high hot workability and a high ductility.

Nevertheless, any titanium alloy having such properties has not developed yet.

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