Preparation of ultra-high ductility and high strength Mg-Sn-Zn-Zr alloy by differential thermal ECAP(DT-ECAP)induced heterogeneous structure  

作　　者：Tianshui Zhou Bing Wang Yaqin Li Shiwen Hu Xiaoqiang Li Dexue Liu 

机构地区：[1]State Key Laboratory of Advanced Processing and Recycling of Non-ferrous Metals,Lanzhou University of Technology,Lanzhou 730050,China [2]School of Materials Science and Engineering,Lanzhou University of Technology,Lanzhou 730050,China

出　　处：《Journal of Materials Science & Technology》2024年第32期222-245,共24页材料科学技术(英文版)

基　　金：supported by the National Natu-ral Science Foundation of China(No.12162023);The Key Talent Projects of Gansu Province,Gansu Basic Research Innovation Group Project(No.23JRRA757);Incubation Program of Excellent Doc-toral Dissertation-Lanzhou University of Technology.

摘　　要：Developing high-ductility magnesium(Mg)alloys has become an imminent issue for their wide appli-cation.In this work,a new Mg-Sn-Zn-Zr alloy with ultra-high ductility(elongation,El.over 40%)and high ultimate tensile strength(UTS,~309-354 MPa)was prepared by a novel differential thermal equal-channel angular pressing(DT-ECAP).Heterogeneous structures,including bimodal grain structures and in-homogeneous distribution of second phases composed of banded structure and particle free zone(PFZ),were induced by DT-ECAP process.Based on the results of electron backscatter diffraction(EBSD),trans-mission electron microscopy(TEM),high-resolution TEM(HRTEM),and selected area electron diffraction(SAED),the bimodal grain structure originated from incomplete dynamic recrystallization(DRX)domi-nated by Zener pinning,strain-induced grain boundary migration(SIBM)and the limitation of polycrys-tallization due to lower dislocation density.Meanwhile,the bimodal distribution of second phases was highly associated with the defect density and initial structure.More importantly,the enhanced strength of DT-ECAPed alloys can be primarily attributed to hetero-deformation induced(HDI)strengthening,grain boundary strengthening,and precipitation strengthening.Moreover,HDI hardening,texture weakening or randomizing activation of non-basal slip,high density of dislocations in sub-structures,and twining in-duced superior work-hardening effect,which was highly responsible for the ultra-high ductility in sixth pass(6P)alloy.The current work provides a novel DT-ECAP process for inducing heterogeneous structure and offers beneficial insight into the development of ultra-high ductility and high strength for rare-earth-free Mg alloys via a combination of HDI strengthening and hardening and other vital mechanisms.

关 键 词：DT-ECAP process Heterogeneous structures HDI strengthening and hardening Mechanical properties Mg-Sn-Zn-Zr alloy 

分 类 号：TG1[金属学及工艺—金属学]