Microstructure instability of fully lamellar TiAl alloy containing high content of Nb after long-term thermal cycling  

全片层高Nb含量TiAl合金长期热循环后的显微组织不稳定性(英文)

作　　者：方璐[1] 丁贤飞[2] 何建平[1] 张来启[1] 林志[1] 林均品[1] 

机构地区：[1]北京科技大学 新金属材料国家重点实验室,北京100083 [2]北京科技大学 国家材料服役安全科学中心,北京100083

出　　处：《Transactions of Nonferrous Metals Society of China》2014年第10期3095-3102,共8页中国有色金属学报（英文版）

基　　金：Project(2011CB605500)supported by National Basic Research Program of China;Project(51171015)supported by National Natural Science Foundation of China;Project(2012M520166)supported by China Postdoctoral Science Foundation;Project(2012Z-06)supported by State Key Laboratory for Advanced Metals and Materials,University of Science and Technology Beijing,China;Project(FRF-TP-12-164A)supported by Fundamental Research Funds for the Central Universities of China

摘　　要：Microstructure instabilities of the fully lamellar Ti-45Al-8.5Nb-（W,B,Y） alloy were investigated by SEM and TEM after long-term thermal cycling（500 and 1000 thermal cycles） at 900 °C. Two major categories of microstructure instability were produced in the alloy after the thermal cycling： 1） The discontinuous coarsening implies that grain boundary migrations are inclined to occur in the Al-segregation region after the long-term thermal cycling, especially after 1000 thermal cycles. Al-segregation can be reduced during the process of long-term thermal cycling as a result of element diffusion; 2） The α2 lamellae become thinner and are broken after 1000 thermal cycles caused by the dissolution of α2 lamellae through phase transformation of α2→γ. The γ grains nucleate within the α2 lamellae or（α2＋γ） lamellae in a random direction.对全片层Ti-45Al-8.5Nb-(W,B,Y)合金在900℃下进行长期热循环(500次和1000次)实验,采用扫描电镜(SEM)及透射电镜(TEM)研究该合金长期热循环后的显微组织不稳定性。结果表明:合金经热循环后主要产生两种类型的组织不稳定性:1)长期热循环特别是1000次热循环后,在Al偏析处易产生因晶界迁移引起的不连续粗化,随着循环次数的增加,元素扩散致使Al偏析逐渐减少;2)1000次热循环后,α2片层变细且发生断裂,这是由α2→γ相变导致的α2片层溶解所致。同时,γ晶粒在α2片层或(α2+γ)片层内部以任意方向形核。

关 键 词：TiAl alloys thermal cycling thermal stability discontinuous coarsening 

分 类 号：TG146.23[一般工业技术—材料科学与工程]