时效热处理对α挤压态TiAl合金显微组织的影响

Effect of aged-heat treatment on microstructure of α extruded TiAl alloy

研究了不同时效热处理后挤压态γ-TiAl合金在高温期间显微组织的稳定性。结果表明:在1330℃将Ti-47Al-2Cr-2Nb-0.15B合金挤压得到近片层组织,将α单相区热处理后得到全片层组织,在700～1000℃停留不同时间后进行时效处理,从平行挤压方向上观察,在全片层晶界处出现细小γ晶粒,随着时效时间的延长,γ晶粒增大,其体积分数增加;全片层晶粒晶界处的非连续界面处首先发生不连续粗化,最终转变为拉长的γ晶粒,然后层片晶团内部各片层之间的连续界面处发生连续粗化,具有小曲率的薄α_2片层开始以逐步变薄的方式断开和溶解,γ片层得到粗化。

The stability of the microstructure of extruded γ-TiAI alloy in high temperature was studied after different aged-heat treatment. The results show that Ti-47Al-2Cr-2Nb-0.15B alloy is extruded in 1 330℃ and the deformed near full lamellar （NFL） microstructure is obtained. Full lamellar （FL） microstructure forms after single a phase is heat treated. Observing from parallel extruding direction, the fine y grain appears in FL grain boundary after being held at 700- 1 000℃ for different times. As the aged-time prolongs, the y grain grows up and the volume fraction of γ grain increases. Discontinuous coarsening happens in the discontinuous boundary of FL grains firstly, which transforms the extended grain eventually, and then the continuous interface thickens continuously among lamellars in inner grain, the thin and small curvature α2 lamellar starts to disconnect and melt and the γ lameUar is thickened.