纵向静磁场下单晶高温合金定向凝固籽晶回熔界面杂晶的形成与演化  

Formation and Evolution of Stray Grains on Remelted Interface in the Seed Crystal During the Directional Solidification of Single-Crystal Superalloys Assisted by Vertical Static Magnetic Field

作　　者：苏震奇 张丛江 袁笑坦 胡兴金 芦可可 任维丽[1,2] 丁彪 郑天祥[1,2] 沈喆[1,2] 钟云波 王晖[3] 王秋良[3] SU Zhenqi;ZHANG Congjiang;YUAN Xiaotan;HU Xingjin;LU Keke;REN Weili;DING Biao;ZHENG Tianxiang;SHEN Zhe;ZHONG Yunbo;WANG Hui;WANG Qiuliang(School of Materials Science and Engineering,Shanghai University,Shanghai 200444,China;State Key Laboratory of Advanced Special Steel,Shanghai University,Shanghai 200444,China;Institute of Electrical Engineering,Chinese Academy of Sciences,Beijing 100190,China)

机构地区：[1]上海大学材料科学与工程学院,上海200444 [2]上海大学省部共建高品质特殊钢冶金与制备国家重点实验室,上海200444 [3]中国科学院电工研究所,北京100190

出　　处：《金属学报》2023年第12期1568-1580,共13页Acta Metallurgica Sinica

基　　金：国家自然科学基金项目No.51871142;省部共建高品质特殊钢冶金与制备国家重点实验室;上海市钢铁冶金新技术开发应用重点实验室自主研发项目No.SKLASS 2021-Z08;上海市科学技术委员会项目No.19DZ2270200

摘　　要：通过对单晶高温合金定向凝固生长过程中显微组织的考察,研究了磁场下杂晶在籽晶回熔区附近的产生及其在生长过程中的演变机制。磁场使得定向凝固籽晶重熔区界面上出现大取向杂晶和大角度晶界,其多分布于样品边缘,磁场强度和抽拉速率的增大均增加了杂晶数量和大角度晶界长度。凝固起始阶段形成的大取向杂晶和大角度晶界以较快速率被淘汰,演化成小取向枝晶和小角度晶界;随着凝固继续进行,枝晶取向和晶界角度进一步减小,但是演化速率急剧降低,拉速的增大强化了此演变过程。重熔区界面上杂晶的形成是由于热电磁力对枝晶的扭断,而宏观尺度上的热电磁环流在凝固过程挟制着扭断碎晶,使得碎晶演化成较多分布于样品边缘的杂晶。Nickel-based superalloys,especially single-crystal(SC)ones,have long been recognized as important materials for turbine blades used in aerospace and gas engines.Static magnetic fields are effective at controlling the material forming.The use of static magnetic fields during solidification has evolved as a sophisticated approach for efficiently controlling the microstructures and mechanical performance of metallic materials.In recent years,studies have shown that static magnetic fields have a complex effect on dendrites in SC superalloys.However,the mechanism of static magnetic fields regulating stray grains on remelted interface needs to be investigated further.This work studied the generation of stray grains near the seed remelted zone and the evolution mechanism during the directional solidification of the SC superalloy assisted by a magnetic field by tracing the solidification microstructure.The stray grains of large orientation that deviated from the<001>direction appeared on the remelted zone interface of the solidification microstructure when the magnetic field was applied,accompanied by the formation of a large-angle grain boundary(LAGB).Most of the stray grains were distributed at the sample edge.The increase in magnetic field intensity and pulling speed increased the number of stray grains and the length of the LAGB.As the solidification progressed,the large-orientation stray grains and the LAGBs were eliminated at a fast speed and evolved into small-orientation dendrites.During the following solidification,the orientation of the dendrites became even smaller and the evolution speed decreased sharply.The increase in withdrawal speed intensified the evolution process.The stray grains formed in the remelted zone can be attributed to the twisting dendrite by the thermoelectric magnetic force.The distribution of more stray grains around the sample was caused by the circulation from thermoelectric magnetic convection at the macroscopic scale.

关 键 词：单晶高温合金 纵向静磁场 定向凝固 杂晶 

分 类 号：TG132.3[一般工业技术—材料科学与工程]