一种Ni-Fe-Cr基合金的凝固特征和偏析行为  

Solidification Characteristics and Segregation Behavior of a Ni-Fe-Cr Based Alloy

作　　者：王常帅[1] 苏海军[2] 郭永安[1] 郭建亭[1] 周兰章[1] Wang Changshuai;Su Haijun;Guo Yongan;Guo Jianting;Zhou Lanzhang(Institute of Metal Research,Chinese Academy of Sciences,Shenyang 110006,China;State Key Laboratory of Solidification Processing,Northwestern Polytechnical University,Xi'an 710072,China)

机构地区：[1]中国科学院金属研究所,辽宁沈阳110016 [2]西北工业大学凝固技术国家重点实验室,陕西西安710072

出　　处：《稀有金属材料与工程》2018年第12期3816-3823,共8页Rare Metal Materials and Engineering

基　　金：国家重点研发计划(2017YFB0305204);国家能源局项目(NY20150102);国家自然科学基金(51301171);西北工业大学凝固技术国家重点实验室开放课题(SKLSP201512);四川省科技计划(2016JZ0036);德阳中科先进制造创新育成专项(YC-2015-QY01)

摘　　要：采用定向凝固技术结合液淬法研究了一种Ni-Fe-Cr基合金平界面和枝晶生长条件下的凝固特征和溶质偏析行为。结果表明,合金的组成相为γ基体、MC型碳化物和γ′沉淀强化相,凝固顺序为L→L+γ→L+γ+MC→γ+γ′+MC。平界面生长条件下淬火界面两侧溶质含量测定结果表明,Ti、Nb和Mo元素富集于液相,溶质分配系数小于1。Fe元素富集于固相,溶质分配系数大于1。Al和Cr元素在液固两相中浓度差别较小,溶质分配系数接近1。此外,固/液界面前沿存在溶质边界层,边界层内溶质原子通过扩散传输,边界层外主要借助流动传输。枝晶与平界面生长的溶质偏析行为基本一致,然而,枝晶生长时糊状区残余液相中溶质浓度与平界面生长时固/液界面前沿溶质浓度存在显著差别。枝晶生长条件下糊状区溶质偏析程度显著高于稳态生长区,固相反扩散和MC型碳化物的析出显著降低枝晶偏析程度。The solidification characteristics and segregation behavior of a Ni-Fe-Cr based alloy with planar interface and dendritic growth, which was obtained through quenching experiments during directional solidification, were investigated. Results show that the major precipitates are γ, γ′ and MC. The phase transition route is determined as follows: L→L+γ→L+γ+MC→γ+γ′+MC. The solution distribution coefficients of Ti, Nb and Mo are less than unity. The solution distribution coefficients of Fe is greater than unity, and Al and Cr are close to 1. The solute boundary layer forms ahead of the liquid/solid interface when the steady-state growth begins. The solute is carried away mainly by diffusion in the solute boundary layer, but carried away mainly by flow out of the solute boundary layer. The solut e distribution in solid phase with dendritic growth is similar to that with planar interface growth. However, the solute concentration in the quenche d liquid in the interdendritic area is obviously higher than that ahead of the liquid/solid interface. The solidification segre gation of the mushy zone is more serious than that of the solid region. It indicates that the back-diffusion in solid phase and the precipitation of MC carbide would reduce the solidification segregation during the dendritic growth.

关 键 词：Ni-Fe-Cr基合金 凝固组织 凝固路径 溶质分配系数 枝晶偏析 

分 类 号：TG146.15[一般工业技术—材料科学与工程]