摘要
采用热力学平衡模拟计算、差热分析(DTA)和等温凝固淬火试验(ISQ)相结合的方法对一种新型镍基高温合金K4750合金的凝固组织和主要元素的偏析行为进行研究。结果表明,实际K4750合金的固相线温度为1270℃,液相线温度为1350℃,MC型碳化物析出温度为1320℃;凝固顺序为L→γ(1350℃),L→γ+MC(1320℃)。K4750合金在凝固初期凝固速度较快,液相体积分数下降明显,凝固后期速度开始变慢,在1310~1290℃温度区间内枝晶间连通残余液相开始断开,同时会有大块状的MC相析出,进一步阻碍液相的连通,从而极易导致合金凝固疏松的形成。合金中W、Fe、Cr的溶质分配系数大于1,富集于枝晶干,为负偏析元素;Ti、Nb、C、Mo的溶质分配系数小于1,富集于枝晶间的液相中,为正偏析元素。
The solidification microstructures and elemental microsegregation behavior of a new Ni-base superalloy K4750 was comparatively investigated by differential thermal analysis (DTA),Thermo-Calc calculation and isothermal solidification quenching (ISQ) experiment.The results of ISQ indicate that the temperature of liquidus and solidus of K4750 alloy are 1350 ℃ and 1270 ℃,respectively,and the precipitated temperature of MC carbide is 1320 ℃.The temperature of liquidus obtained by DTA and Thermal-Calc is in close agreement with the result of ISQ,but the temperature of solidus obtained by DTA and Thermal-Calc are 1306 ℃ and 1296 ℃,respectively.In the initial stage of the solidification process,the volume fraction of residual liquid decreases sharply.In solidification process within the temperature range of 1310 ℃~1290 ℃,the residual liquid in the interdendritic region transforms from connected channels to isolated micro-liquid pools.In the last stage of solidification,these isolated micro-liquid pools are quite sluggish and result in the formation of porosity.The microsegregation coefficients of W,Fe and Cr are larger than 1,so they are considered to be negative segregation elements and segregate in solid.In contrast,the microsegregation coefficients of Ti,Nb,C and Mo are less than 1,and thus they are positive segregation elements and segregated in the liquid.
作者
于洵
王琳琳
欧美琼
马颖澈
辛啟斌
刘奎
Yu Xun;Wang Linlin;Ou Meiqiong;Ma Yingche;Xin Qibin;Liu Kui(Institute of Metal Research,Chinese Academy of Science,Shenyang 110016,China;Northeastern University,Shenyang 110819,China)
出处
《稀有金属材料与工程》
SCIE
EI
CAS
CSCD
北大核心
2019年第5期1488-1496,共9页
Rare Metal Materials and Engineering
