(1. 東北大學 材料與冶金學院，沈陽 110004； 2. 中國科學院 金屬研究所，沈陽 110016； 3. 沈陽理工大學 機械工程學院，沈陽 110168)
摘 要: 采用組織分析和差熱分析相結合的方法系統(tǒng)研究GH742y合金的凝固偏析行為和鑄態(tài)組織形成規(guī)律。GH742y合金枝晶偏析嚴重，組織析出復雜：Cr、Co、W、V和Al偏析于枝晶干，而Nb、Ti和Mo等元素在枝晶間的富集導致一次和二次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的偏析導致Ni5Ce相和富氧硫稀土相的枝晶間析出。相分計算表明，嚴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合金的凝固順序為：γ基體、MC碳化物、一次γ′相、(γ+ γ′)共晶、Laves相、Ni5Ce相和M6C碳化物。
關鍵字: 鎳基高溫合金；偏析；鑄態(tài)組織；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
