| 摘要 |
PROBLEM TO BE SOLVED: To obtain a Ti2 AlX (titanium aluminide) type alloy increased in tensile strength and creep strength, usable at high temp., and having sufficient ductility at ordinary temp. by providing a composition which contains Ti, Al, Nb, Ta, and Mo and in which respective relative quantities of the above elements and Si are regulated to values in specific ranges, respectively. SOLUTION: This alloy has a composition consisting of 20-25% Al, 10-14% Nb, 1.4-5% Ta, 2-4% Mo, 0-0.5% Si, and Ti as the balance on the basis of 100%. The alloy with this composition is subjected to pressure extrusion treatment at a temp. suited to form a creep-resistant single-phase structure and then to annealing treatment at 800 to 920 deg.C for at least 4 hr, by which a stable two-phase structure ofβ0 +O2 capable of advantageously contributing to ductility is formed and transformation is carried out. In this case, prior to the pressure extrusion treatment, isothermal forging treatment can be performed at a temp. below theβ-transus temp. of the alloy. The alloy transformed in this way can be suitably used for turbomachinery parts.
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