工程科学学报，第40卷，第11期：1332-1341,2018年11月 Chinese Joural of Engineering,Vol.40,No.11:1332-1341,November 2018 DOI:10.13374/j.issn2095-9389.2018.11.007;http://journals.ustb.edu.cn K424高温合金凝固特征及冷却速度对其影响规律 赵 展，董建新四，张麦仓，姚志浩，江河 北京科技大学材料科学与工程学院，北京100083 区通信作者，E-mail:jxdong(@usth.cdu.cn 摘要采用等温凝固实验、差示扫描量热仪(DSC)研究了K424合金的凝固行为以及冷却速度对其影响.利用光学显微镜、 扫描电镜以及能谱分析仪分析了合金在不同温度等温凝固、不同冷却速度下的微观组织以及凝固后期的元素的偏析行为，确 定K424合金的固相线、液相线和主要相的析出温度等凝固特性以及冷却速度对Y相、MC碳化物以及共晶组织的影响规律. 研究结果表明：K424合金的凝固顺序为：1345℃，Y相从液相析出，随后在1308℃析出MC型碳化物，在非平衡凝固条件下， 共晶组织在1260℃析出，1237℃，凝固结束：共晶组织的形成与凝固末期A1、T元素的偏析行为以及冷却速度密切相关：随着 冷却速度的增加，MC和共晶组织尺寸及数量均呈现先增大后减小的趋势：γ相形貌从花瓣形状向规则立方及球形转变，尺寸 也从2μm减小至60nm. 关键词K424高温合金；凝固特性；冷却速率；(Y+Y)共晶组织 分类号TG132.3 Solidification characteristics and microstructures evolution of Ni-based superalloy K424 with different solidification cooling rates ZHAO Zhan,DONG Jian-xin,ZHANG Mai-cang,YAO Zhi-hao,JIANG He School of Materials Science and Engineering,University of Science and Technology Beijing,Beijing 100083,China Corresponding author,E-mail:jxdong@ustb.edu.cn ABSTRACT The solidification behavior and microstructures evolution of cast Ni-based superalloy K424 under different cooling rates were investigated by isothermal solidification quenching experiments and differential scanning calorimetry(DSC).The microstructures and segregation characteristics of K424 were analyzed at different isothermal temperatures and cooling rates using optical microscopy, scanning electron microscopy,and energy-dispersive spectrometry (EDS).The isothermal solidification,microstructure,and distribu- tion characteristics of elements at the final solidification stage were also investigated,and the liquidus,solidus,and the formation tem- peratures of the main phases were evaluated.Furthermore,the influence of cooling rate on the morphology and size of MC carbides,(y +y')eutectic,and precipitated y'phase were discussed.The results show that the solidification of the K424 alloy follows the se- quence:(1)LL +y at 1345 C:the solidification begins with the formation of primary y,and the liquidus temperature is 1345 ℃；(2)L→L+y+MC at 1.308℃：as the solidification continues,Ti and Nb are enriched in the liquid interdendrite,which re- sults in the formation of MC carbides at 1.308℃；(3)L→y+(y+y')atl260℃：the precipitation of the(y+y')eutectic oc- curs at about 1260C because of non-equilibrium solidification.Finally,the solidification ends with a solidus temperature of 1237C. Furthermore,it is found that the precipitation of (y+)eutectic at the interdendtitic regions is closely related to the cooling rate and the severe segregation behavior of Al and Ti into the residual liquid at the final solidification stage.With the increase of cooling rate,the quantity and size of MC carbides and eutectic first increase and then decrease.Moreover,with increasing cooling rate,y' shapes transform from irregular petal-like structure to near cuboidal and spherical patterns,and the size scale of y'precipitates decrea- ses from 2 um to 60 nm. 收稿日期：2017-11-15工程科学学报,第 40 卷,第 11 期:1332鄄鄄1341,2018 年 11 月 Chinese Journal of Engineering, Vol. 40, No. 11: 1332鄄鄄1341, November 2018 DOI: 10. 13374 / j. issn2095鄄鄄9389. 2018. 11. 007; http: / / journals. ustb. edu. cn K424 高温合金凝固特征及冷却速度对其影响规律 赵 展, 董建新苣 , 张麦仓, 姚志浩, 江 河 北京科技大学材料科学与工程学院, 北京 100083 苣 通信作者, E鄄mail: jxdong@ ustb. edu. cn 摘 要 采用等温凝固实验、差示扫描量热仪(DSC)研究了 K424 合金的凝固行为以及冷却速度对其影响. 利用光学显微镜、 扫描电镜以及能谱分析仪分析了合金在不同温度等温凝固、不同冷却速度下的微观组织以及凝固后期的元素的偏析行为,确 定 K424 合金的固相线、液相线和主要相的析出温度等凝固特性以及冷却速度对 酌忆相、MC 碳化物以及共晶组织的影响规律. 研究结果表明:K424 合金的凝固顺序为: 1345 益 ,酌 相从液相析出,随后在 1308 益 析出 MC 型碳化物,在非平衡凝固条件下, 共晶组织在 1260 益析出,1237 益 ,凝固结束;共晶组织的形成与凝固末期 Al、Ti 元素的偏析行为以及冷却速度密切相关;随着 冷却速度的增加,MC 和共晶组织尺寸及数量均呈现先增大后减小的趋势;酌忆相形貌从花瓣形状向规则立方及球形转变,尺寸 也从 2 滋m 减小至 60 nm. 关键词 K424 高温合金; 凝固特性; 冷却速率; (酌 + 酌忆)共晶组织 分类号 TG132郾 3 收稿日期: 2017鄄鄄11鄄鄄15 Solidification characteristics and microstructures evolution of Ni鄄based superalloy K424 with different solidification cooling rates ZHAO Zhan, DONG Jian鄄xin 苣 , ZHANG Mai鄄cang, YAO Zhi鄄hao, JIANG He School of Materials Science and Engineering, University of Science and Technology Beijing, Beijing 100083, China 苣 Corresponding author, E鄄mail: jxdong@ ustb. edu. cn ABSTRACT The solidification behavior and microstructures evolution of cast Ni鄄based superalloy K424 under different cooling rates were investigated by isothermal solidification quenching experiments and differential scanning calorimetry (DSC). The microstructures and segregation characteristics of K424 were analyzed at different isothermal temperatures and cooling rates using optical microscopy, scanning electron microscopy, and energy鄄dispersive spectrometry (EDS). The isothermal solidification, microstructure, and distribu鄄 tion characteristics of elements at the final solidification stage were also investigated, and the liquidus, solidus, and the formation tem鄄 peratures of the main phases were evaluated. Furthermore, the influence of cooling rate on the morphology and size of MC carbides, (酌 + 酌忆) eutectic, and precipitated 酌忆 phase were discussed. The results show that the solidification of the K424 alloy follows the se鄄 quence: (1) L 寅 L + 酌 at 1345 益 : the solidification begins with the formation of primary 酌, and the liquidus temperature is 1345 益 ; (2) L 寅 L + 酌 + MC at 1308 益 : as the solidification continues, Ti and Nb are enriched in the liquid interdendrite, which re鄄 sults in the formation of MC carbides at 1308 益 ; (3) L 寅 酌 + (酌 + 酌忆) at 1260 益 : the precipitation of the (酌 + 酌忆) eutectic oc鄄 curs at about 1260 益 because of non鄄equilibrium solidification. Finally, the solidification ends with a solidus temperature of 1237 益 . Furthermore, it is found that the precipitation of (酌 + 酌忆) eutectic at the interdendtitic regions is closely related to the cooling rate and the severe segregation behavior of Al and Ti into the residual liquid at the final solidification stage. With the increase of cooling rate, the quantity and size of MC carbides and eutectic first increase and then decrease. Moreover, with increasing cooling rate, 酌忆 shapes transform from irregular petal鄄like structure to near cuboidal and spherical patterns, and the size scale of 酌忆 precipitates decrea鄄 ses from 2 滋m to 60 nm