(1. 东北大学 材料与冶金学院，沈阳 110004； 2. 中国科学院 金属研究所，沈阳 110016； 3. 沈阳理工大学 机械工程学院，沈阳 110168)
摘 要: 采用组织分析和差热分析相结合的方法系统研究GH742y合金的凝固偏析行为和铸态组织形成规律。GH742y合金枝晶偏析严重，组织析出复杂：Cr、Co、W、V和Al偏析于枝晶干，而Nb、Ti和Mo等元素在枝晶间的富集导致一次和二次γ′相、(γ+ γ′)共晶、MC碳化物、M6C碳化物、Laves相和δ相的析出；稀土元素La和Ce的偏析导致Ni5Ce相和富氧硫稀土相的枝晶间析出。相分计算表明，严重的元素偏析以及大量富Nb和Ti相的析出是σ相和μ相等有害TCP相析出的主要原因。GH742y合金的凝固顺序为：γ基体、MC碳化物、一次γ′相、(γ+ γ′)共晶、Laves相、Ni5Ce相和M6C碳化物。
关键字: 镍基高温合金；偏析；铸态组织；凝固
（1. School of Material & Metallurgy, Northeastern University, Shenyang 110004, China; 2. Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016, China; 3. School of Mechanical Engineering, Shenyang University of Science and Technology, Shenyang 110168, China）
Abstract:The solidification, segregation and microstructure of GH742y alloy were systematically investigated by microstructure characterization and differential thermal analysis. The as-cast GH742y alloy exhibits severe dendritic segregation and complicated precipitation. Cr, Co, W, V and Al are segregated to the dendritic arm. The primary and secondary γ′ phases, (γ+ γ′) eutectic, MC carbide, M6C carbide, Laves phase and δ phase are precipitated due to the enrichment of Nb, Ti and Mo in the interdendritic region. The Ni5Ce phase and RE-O-S phase are precipitated in the interdendritic region due to the segregation of La and Ce. The phase calculation indicates that the severe segregation and precipitates containing Nb and Ti are the main reasons for the precipitation of TCP phases such as σ phase and μ phase. The solidification sequence of GH742y alloy is as follows: γ matrix, MC carbide, primary γ′, (γ+ γ′) eutectic, Laves phase, Ni5Ce phase and M6C carbide.
Key words: Ni-base superalloy; segregation; as-cast microstructure; solidification
