Pre-existing orthorhombic embryos-induced hexagonal-orthorhombic martensitic transformation in MnNiSi_(1-x)(CoNiGe)_x alloy  

作　　者：张婷婷 龚元元 鲁子骞 徐锋 Ting-Ting Zhang;Yuan-Yuan Gong;Zi-Qian Lu;Feng Xu†(MIIT Key Laboratory of Advanced Metallic and Intermetallic Materials Technology,School of Materials Science and Engineering,Nanjing University of Science and Technology,Nanjing 210094,China)

机构地区：[1]MIIT Key Laboratory of Advanced Metallic and Intermetallic Materials Technology,School of Materials Science and Engineering,Nanjing University of Science and Technology,Nanjing 210094,China

出　　处：《Chinese Physics B》2024年第4期691-699,共9页中国物理B（英文版）

基　　金：Project supported by the National Natural Science Foundation of China (Grant No.11974184)。

摘　　要：The thermal-elastic martensitic transformation from high-temperature Ni_(2)In-type hexagonal structure to low-temperature TiNiSi-type orthorhombic structure has been widely studied in MnMX(M=Ni or Co,and X=Ge or Si)alloys.However,the answer to how the orthorhombic martensite nucleates and grows within the hexagonal parent is still unclear.In this work,the hexagonal-orthorhombic martensitic transformation in a Co and Ge co-substituted MnNiSi is investigated.One can find some orthorhombic laths embedded in the hexagonal parent at a temperature above the martensitic transformation start temperature(M_(s)).With the the sample cooing to M_(s),the laths turn broader,indicating that the martensitic transformation starts from these pre-existing orthorhombic laths.Microstructure observation suggests that these pre-existing orthorhombic laths do not originate from the hexagonal-orthorhombic martensitic transformation because of the difference between atomic occupations of doping elements in the hexagonal parent and those in the preexisting orthorhombic laths.The phenomenological crystallographic theory and experimental investigations prove that the pre-existing orthorhombic lath and generated orthorhombic martensite have the same crystallography relationship to the hexagonal parent.Therefore,the orthorhombic martensite can take these pre-existing laths as embryos and grow up.This work implies that the martensitic transformation in MnNiSi_(1-x)(CoNiGe)_(x) alloy is initiated by orthorhombic embryos.

关 键 词：martensitic transformation MnMX alloy orthorhombic embryo crystallography relationship 

分 类 号：TG139[一般工业技术—材料科学与工程]