Bimodal grain structure formation and strengthening mechanisms in Mg-Mn-Al-Ca extrusion alloys  

作　　者：Jianyue Zhang Peng Peng Qingshan Yang Alan A.Luo 

机构地区：[1]Department of Materials Science and Engineering,The Ohio State University,Columbus,OH 43210,USA [2]School of Metallurgy and Material Engineering,Chongqing University of Science and Technology,Chongqing,401331,China [3]Department of Integrated Systems Engineering,The Ohio State University,Columbus,Ohio 43210,USA

出　　处：《Journal of Magnesium and Alloys》2023年第12期4407-4419,共13页镁合金学报（英文）

基　　金：funded by the National Natural Science Foundation of China (Project 52271092);the Chongqing Science and Technology Commission (cstc2021jcyj-msxm X0814,CSTB2022NSCQ-MSX0891);the Chongqing Municipal Education Commission (KJQN202101523);the support from The Ohio State University。

摘　　要：The effects of small additions of calcium (0.1%and 0.5%~1) on the dynamic recrystallization behavior and mechanical properties of asextruded Mg-1Mn-0.5Al alloys were investigated.Calcium microalloying led to the formation of Al_(2)Ca in as-cast Mg-1Mn-0.5Al-0.1Ca alloy and both Mg_(2)Ca and Al_(2)Ca phases in Mg-1Mn-0.5Al-0.5Ca alloy.The formed Al_(2)Ca particles were fractured during extrusion process and distributed at grain boundary along extrusion direction (ED).The Mg_(2)Ca phase was dynamically precipitated during extrusion process,hindering dislocation movement and reducing dislocation accumulation in low angle grain boundaries (LAGBs) and hindering the transformation of high density of LAGBs into high angle grain boundaries (HAGBs).Therefore,a bimodal structure composed of fine dynamically recrystallized (DRXed) grains and coarse un DRXed regions was formed in Ca-microalloyed Mg-1Mn-0.5Al alloys.The bimodal structure resulted in effective hetero-deformation-induced (HDI) strengthening.Additionally,the fine grains in DRXed regions and the coarse grains in un DRXed regions and the dynamically precipitated Mg_(2)Ca phase significantly enhanced the tensile yield strength from 224 MPa in Mg-1Mn-0.5Al to335 MPa and 352 MPa in Mg-1Mn-0.5Al-0.1Ca and Mg-1Mn-0.5Al-0.5Ca,respectively.Finally,a yield point phenomenon was observed in as-extruded Mg-1Mn-0.5Al-x Ca alloys,more profound with 0.5%Ca addition,which was due to the formation of (■) extension twins in un DRXed regions.

关 键 词：Magnesium alloys EXTRUSION Dynamic precipitation Dynamic recrystallization Bimodal grain structure Mechanical properties 

分 类 号：TG379[金属学及工艺—金属压力加工]