Microstructure and microsegregation of directionally solidified Ti–45Al–8Nb alloy with different solidification rates  

作　　者：Xiang-Jun Xu Lin Song Xiao-Ou Jin Dong-Dong Han Xin Wang Jun-Pin Lin 

机构地区：[1]Materials and Chemistry School,Zhongyuan University of Technology [2]State Key Laboratory for Advanced Metals and Materials,University of Science and Technology Beijing [3]School of Architecture and Engineering,Heilongjiang University

出　　处：《Rare Metals》2016年第1期70-76,共7页稀有金属（英文版）

基　　金：financially supported by the National Natural Science Foundation of China(Nos.U1204508 and 51271016);the National Basic Research Program of China(No.2011CB605501)

摘　　要：Microstructure and microsegregation of directionally solidified Ti-45Al-8Nb alloy were investigated by scanning electron microscopy（SEM）,transmission electron microscopy（TEM） and electron probe microanalyzer（EPMA）.For the alloy solidified at the solidification rates（v） ranging from 10 to 400 μm·s^（-1）,the microstructure of the mushy zone exhibits a cellular-dendritic structure at lower growth rate（v=10-50 μm·s^（-1）） and a typical dendritic morphology at higher growth rate（v = 100-400 μm·s^（-1））.The relationship between primary dendrite arm spacing（λ_1）and v is λ_1=1.08×10~3v^（-0.35）.Al and Nb elements segregate at interdendritic zone and in the dendritic core,respectively.In solid of mushy zone,a relatively flat concentration profile is observed for the typical dendrite structure,and Nb enriches in B2 phase induced by β→α＋βtransformation.The content of B2 phase is hardly affected by v.The extent of microsegregation in steady-state zone decreases at a lower growth rate because holding the samples at higher temperature after solidification for a long time can homogenize the solid effectively.Microstructure and microsegregation of directionally solidified Ti-45Al-8Nb alloy were investigated by scanning electron microscopy（SEM）,transmission electron microscopy（TEM） and electron probe microanalyzer（EPMA）.For the alloy solidified at the solidification rates（v） ranging from 10 to 400 μm·s^（-1）,the microstructure of the mushy zone exhibits a cellular-dendritic structure at lower growth rate（v=10-50 μm·s^（-1）） and a typical dendritic morphology at higher growth rate（v = 100-400 μm·s^（-1））.The relationship between primary dendrite arm spacing（λ_1）and v is λ_1=1.08×10~3v^（-0.35）.Al and Nb elements segregate at interdendritic zone and in the dendritic core,respectively.In solid of mushy zone,a relatively flat concentration profile is observed for the typical dendrite structure,and Nb enriches in B2 phase induced by β→α＋βtransformation.The content of B2 phase is hardly affected by v.The extent of microsegregation in steady-state zone decreases at a lower growth rate because holding the samples at higher temperature after solidification for a long time can homogenize the solid effectively.

关 键 词：Nb-containing TiAl alloy Solidification MICROSTRUCTURE MICROSEGREGATION 

分 类 号：TG146.23[一般工业技术—材料科学与工程]