Microstructure of cast γ-TiAl based alloy solidified from β phase region
β相区凝固的铸造γ-TiAl基合金的微观组织(英文)作者机构：中南大学粉末冶金国家重点实验室长沙410083 中南大学材料科学与工程学院长沙410083
出 版 物：《Transactions of Nonferrous Metals Society of China》 (中国有色金属学报（英文版）)
年 卷 期：2011年第21卷第2期
页 面：215-222页
核心收录：
学科分类：080503[工学-材料加工工程] 08[工学] 0805[工学-材料科学与工程（可授工学、理学学位）] 0802[工学-机械工程] 080201[工学-机械制造及其自动化]
基 金：Project (14) supported by Postdoctoral Science Foundation of Central South University, China Project (2008AA03A233) supported by the High-tech Research and Development Program of China
主 题：γ-TiAl based alloy microstructure phase transformation β phase solidification heat treatment
摘 要：The microstructures and phase transformation of Ti-43Al-4Nb alloy in as-cast and heat-treated states were investigated by using optical microscopy, scanning and transmission electron microscopy as well as differential scanning calorimetry. The results show that a fine microstructure of the as-cast alloy can be obtained by solidifying through the β phase. γ grains can nucleate directly from the β phase. The coexistence of β phase and γ phase along primary α grain boundaries contributes to the decrease in the grain size of the as-cast alloy. The phase transformation sequence during solidification of the Ti-43Al-4Nb alloy is suggested as L→L＋β→β→α＋β→α＋βr→α＋γ＋βr→lamellae（α2＋γ）＋γ＋βr. The microstructure of the alloy after heat treatment at 1 250 ℃ for 16 h exhibits a certain coarsening compared with that of the as-cast state. The remnant β phase can be removed by the heat treatment process due to the diffusion of Nb and the non-equilibrium state of β phase.
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