| 摘要 |
PROBLEM TO BE SOLVED: To provide a TiAl-based casting alloy material which is subjected to micronization of crystal grains of a TiAl-based casting alloy material, without dependence upon foreign matter and is excellent in high-temperature creep strength owing to a heat treatment under appropriate conditions and also good in ductility and toughness at ordinary temperature.SOLUTION: A TiAl-based casting alloy comprises 42-44 atomic% of Al, 6.0-9.0 atomic% of Nb, 0-3.5 atomic% of Cr, 0.3-1.0 atomic% of Si, 0.3-1.0 atomic% of C and remaining Ti and unavoidable impurities, and the alloy element index P, determined by the following expression, is -0.9 to 1.5. The TiAl-based casting alloy has a fine structure in which lamellar particles of an average particle size of 30-200 μm composed of an α2 phase and a γ phase, laminated together, and arranged densely, but a &bgr; phase is not present. Expression: P=(41-Al)/3+0.25 Nb+0.8Cr-0.8Si-1.7C. |
