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The effect of heat treatment on the microstructure evolution of a high Nb containing TiAI alloy has been studied.The results indicate thatβ-segregation,α-segregation and S-segregation in the as-cast and as-forged alloys can be effectively eliminated at the temperature above T_α(1350-1400℃) for long holding time (12-24 h) and the full lamellar (FL) microstructure is gained.For the two alloys,the lamellar colony sizes are 120μm and 2000μm,respectively after heat treatment at 1400℃for 12 h.Meanwhile,the sizes are 210μm and 3000μm,respec- tively at 1350℃for 24 h.To get a free homogenous microstructure,the primary as-cast alloy is first subjected to preheat treatment for eliminating the segregations.After the preheat treatment,the alloy is processed by the multi-step canned forging to attain the microstructure with fine grain size.
The effect of heat treatment on the microstructure evolution of a high Nb containing TiAl alloy has been studied. The results indicate that β-segregation, α-segregation and S-segregation in the as-cast and as-forged alloys can be substantial eliminated at the For the two alloys, the lamellar colony sizes are 120 μm and 2000 μm, respectively, after heat treatment at 1400 (1350-1400 ° C.) for long holding time (12-24 h) and the full lamellar ℃ for 12 h.Meanwhile, the sizes are 210 μm and 3000 μm, respec- tively at 1350 ° C for 24 h.To get a free homogenous microstructure, the primary as-cast alloy is first subjected to preheat treatment for eliminating the segregations. After the preheat treatment, the alloy is processed by the multi-step canned forging to attain the microstructure with fine grain size.