Microstructures,micro-segregation and solidification path of directionally solidified Ti-45Al-5Nb alloy  

作　　者：Liang-shun Luo Tong Liu Kun Li Yan-qing Su Jing-jie Guo Heng-zhi Fu 

机构地区：[1]National Key Laboratory for Precision Hot Processing of Metals,Harbin Institute of Technolory,Harbin 150001,China [2]China FA W Casting Company Limited,Changchun 130011,China [3]State Key Laboratory,of Advanced Welding and Joining,Harbin Institute of Technolory.Harbin 150001.China

出　　处：《China Foundry》2016年第2期107-113,共7页中国铸造（英文版）

基　　金：financially supported by the National Natural Science Foundation of China(Nos.51331005 and 51425402)

摘　　要：To investigate the effect of solidification parameters on the solidification path and microstructure evolution of Ti-45Al-5Nb(at.%) alloy, Bridgman-type directional solidification and thermodynamics calculations were performed on the alloy. The microstructures, micro-segregation and solidification path were investigated.The results show that the β phase is the primary phase of the alloy at growth rates of 5-20 μm·s^(-1) under the temperature gradients of 15-20 K·mm^(-1), and the primary phase is transformed into an α phase at relatively higher growth rates(V >20 μm·s^(-1)). The mainly S-segregation and β-segregation can be observed in Ti-45Al-5Nb alloy at a growth rate of 10 μm·s^(-1) under a temperature gradient of 15 K·mm^(-1). The increase of temperature gradient to 20 K·mm^(-1) can eliminate β-segregation, but has no obvious effect on S-segregation. The results also show that 5 at.% Nb addition can expand the β phase region, increase the melting point of the alloy and induce the solidification path to become complicated. The equilibrium solidification path of Ti-45Al-5Nb alloy can be described as L L→β L+β L+β→αα+β_R β→ααα→γα+γα→α_2+γγ_R+(α_2+γ), in which β_R and γ_R mean the residual β andTo investigate the effect of solidification parameters on the solidification path and microstructure evolution of Ti-45Al-5Nb（at.%） alloy, Bridgman-type directional solidification and thermodynamics calculations were performed on the alloy. The microstructures, micro-segregation and solidification path were investigated.The results show that the β phase is the primary phase of the alloy at growth rates of 5-20 μm·s^（-1） under the temperature gradients of 15-20 K·mm^（-1）, and the primary phase is transformed into an α phase at relatively higher growth rates（V 〉20 μm·s^（-1））. The mainly S-segregation and β-segregation can be observed in Ti-45Al-5Nb alloy at a growth rate of 10 μm·s^（-1） under a temperature gradient of 15 K·mm^（-1）. The increase of temperature gradient to 20 K·mm^（-1） can eliminate β-segregation, but has no obvious effect on S-segregation. The results also show that 5 at.% Nb addition can expand the β phase region, increase the melting point of the alloy and induce the solidification path to become complicated. The equilibrium solidification path of Ti-45Al-5Nb alloy can be described as L L→β L＋β L＋β→αα＋β_R β→ααα→γα＋γα→α_2＋γγ_R＋（α_2＋γ）, in which β_R and γ_R mean the residual β and γ

关 键 词：TiAl-Nb alloy directional solidification MICROSTRUCTURE MICRO-SEGREGATION solidification path 

分 类 号：TG146.23[一般工业技术—材料科学与工程]