Titanium-Based Alloy

Abstract

The titanium-based alloy consists of aluminum, vanadium, molybdenum, iron, and oxygen in the following weight percent ratio: aluminum 3.5-4.4, vanadium 2.0-4.0, molybdenum 0.1-0.8, iron maximum 0.4, oxygen maximum 0.25, the balance titanium. The technical objective is to provide a versatile alloy to be used for making large forgings and die forgings, rolled sheet products and foil having sufficient strength, ductility and structure.

Description

BACKGROUND OF THE INVENTION[0001]1. Field of the Invention[0002]The invention relates to the field of metallurgy and particularly to the field of developing state-of-the-art titanium alloys used for making high-strength and high-workability articles including large articles, i.e., alloys of high versatility.[0003]Titanium alloys are widely used as aerospace materials, e.g., in air-planes and rockets, since the alloys are mechanically tough and are comparatively light.[0004]2. Background Information[0005]The most widely used titanium alloy is Ti6Al4V (B. A. Kalachyov, I. S. Polkin and V. D. Talalayev. Titanium Alloys of Different Countries. Reference Book. Moscow: VILS, 2000, p. 58-59-[1]). This alloy was developed in the USA during the 1950s. It is characterized by medium strength of 850 up to 1000 MPa and high workability. It is a good material to work by forming: forging, die forging, and extruding. It is widely used in aeronautical and aerospace engineering, shipbuilding, the aut...

AI Technical Summary

Benefits of technology

[0011]It is an object of the invention to provide a versatile titanium alloy having minimal manufacturing costs and capable of being made into a wide variety of products, such as large forgings and die forgings, as well as rolled sheet products and foil having sufficient strength, plastic properties and structure.SUMMARY OF THE INVENTION

[0015]Aluminum is an α-stabilizer for the α+β-titanium alloys, which contributes to increased mechanical strength. However, if the aluminum content is below 3.5%, strength sufficient to meet the invention goal cannot be obtained; whereas if the aluminum content exceeds 4.4%, resistance to hot deformation is increased and ductility at lower temperatures is decreased, which leads to lower productivity.

[0016]Vanadium is added to titanium as a β-stabilizer for the α+β-titanium alloys, increasing mechanical strength without forming brittle intermetallic compounds with titanium. The presence of vanadium in the alloy impedes formation of α2-superstructure in the α-phase as the β-phase stabilizes, and increases both strength and ductility. If the vanadium content is below 2%, strength sufficient to meet the invention goal cannot be obtained; whereas if the vanadium content exceeds 4.0%, the superplastic elongation is decreased by lowering of the beta transus. Vanadium content within the range of 2.0-4.0% in this alloy has the benefit that scrap of the most-used Ti6Al4V can be utilized.

[0018]Iron added to the alloy up to 0.4% increases the volume ratio of the β-phase, decreasing resistance to deformation in hot working of this alloy, thus evading the generation of such defects as cracking. An iron content exceeding 0.4% generates a segregation phase with beta-flecks upon melting and solidifying the alloy, which leads to heterogeneity of mechanical properties, especially ductility.

[0019]Oxygen enhances mechanical strength by constituting a solid solution, mainly in the α-phase. If the oxygen content exceeds 0.25%, the alloy ductility may deteriorate.

Problems solved by technology

The disadvantage of Ti6Al4V is its insufficient versatility.

It is difficult to make rolled sheet products, foil, and tubes thereof since the alloy possesses relatively high resistance to deformation, which, at deformation temperatures below 800° C., leads to the generation of defects such as cracks and shortens the life of working tools, or necessitates costly tools.

The disadvantage of this alloy also is its low versatility since it requires stress relieving in making large structural parts thereof.

The disadvantage of this alloy is that it is rich in Fe and Mo and, therefore, is prone to segregation.