TiAl-BASED ALLOY AND METHOD FOR PRODUCING THE SAME

A method for producing a TiAl-based alloy, wherein the TiAl-based alloy is held at a first temperature for a predetermined period of time in an (α+γ) two-phase region, an α single-phase region, a (β+α) two-phase region, or a (β+α+γ) three-phase region, then the TiAl-based alloy is quenched at a cooling rate equal to or higher than air cooling, and the quenched TiAl-based alloy is held at a second temperature for a predetermined period of time in a (β+γ) two-phase region, a (β+α2+γ) three-phase region, or an (α2+γ) two-phase region to form a metal structure comprising (α2/γ) lamellar grains and a cellular structure or a secondary lamellar structure precipitated at (α2/γ) lamellar grain boundaries, and wherein

• the second temperature and a holding time at the second temperature are controlled so that the cellular structure is a (β/γ) cellular structure or an (α2/γ/β) cellular structure;
• the secondary lamellar structure has (α2/γ) lamellar grains finer than the (α2/γ) lamellar grains;
• and
• a volume fraction of the cellular structure or the secondary lamellar structure is 1 vol % or more and 50 vol % or less, the TiAl-based alloy containing, in atomic percent, Al:
• 45% to 49%, β-stabilizing elements:
• 3% to 11%, Ni:
• ≤1.0%, C:
• ≤0.6%, Si:
• ≤0.5%, O:
• ≤1.5%, the balance being Ti and inevitable impurities, the β-stabilizing elements being any of Cr, Nb, V, Mn and Mo or a combination thereof.