Subgrain-assisted spontaneous grain refinement in rapid solidification of undercooled melts  

作　　者：Jianbao Zhang Dongpeng Hua Dexu Cui Xin Li Ke Hua Yixuan He Haifeng Wang Yuhong Zhao 

机构地区：[1]State Key Laboratory of Solidification Processing,Center of Advanced Lubrication and Seal Materials,Northwestern Polytechnical University,Xi’an 710072,China [2]School of Materials Science and Engineering,North University of China,Taiyuan 030051,China

出　　处：《Journal of Materials Science & Technology》2024年第7期234-248,共15页材料科学技术（英文版）

基　　金：supported by the Natural Science Foundation of China(No.51975474);the Research Fund of the State Key Laboratory of Solidification Processing(NPU),China(No.2023-BJ-02);the Project funded by China Postdoctoral Science Founda-tion(No.2023M732871);the Fundamental Research Funds for the Central Universities(No.3102019JC001).

摘　　要：The grain refinement mechanism for rapid solidification of undercooled melts is still an open problem even after 60 years of on-going studies.In this work,rapid solidification of undercooled Ni and equi-atomic FeCoNiPd melts was studied and spontaneous grain refinement was found at both low and high undercooling.After a detailed electron backscattered diffraction analysis,subgrain-induced grain orien-tation scattering and splitting were found to occur along with the transition from coarse dendrites to fine equiaxed grains at low and high undercooling,respectively,indicating that subgrains play an im-portant role during the formation of fine equiaxed grains.On this basis,a compromise mechanism of subgrain-assisted spontaneous grain refinement was proposed.Because the dendrite re-melting induced thermo-mechanical process and fluid flow induced dendrite deformation occur simultaneously during the post-recalescence stage,stress accumulation would be maximum at both low and high undercooling,thus inducing dynamic recrystallization,during which the formation and rotation of subgrains make the grain orientations scattering and even splitting.Furthermore,the grain/subgrain size of undercooled FeCoNiPd ascribing to its unique co-segregation behavior keeps almost invariable from low to high undercooling,indicating that the co-segregation strategy would be effective to inhibit grain growth after rapid solidifi-cation and would be useful in practice.

关 键 词：Rapid solidification UNDERCOOLING Spontaneous grain refinement Grain growth High entropy alloy 

分 类 号：TG146.23[一般工业技术—材料科学与工程]