Effect Of Rolling Processes On Microstructure And Properties Of Mg-Ca-Mn-Sn Magnesium Alloy Sheets

Magnesium（Mg）alloy materials have a light structure and great application potential,especially in reducing weight and protecting the environment.Unfortunately,compared with traditional steel materials,such as titanium,aluminum,and their alloys,the strength of Mg and its alloys is low,and the number of anisotropic and slip systems at room temperature（RT）is limited,which leads to the strong plasticity of Mg alloys is far from satisfactory.Therefore,firstly,the Mg alloy material as-cast Mg-1.03Ca-0.47Mn-2.39Sn（TXM210）is taken as the research object,and the thermal deformation behavior of Mg alloy is systematically studied by Gleeble thermal simulation compression experiment;Then,taking the extruded Mg-1.03Ca-0.47Mn-2.39Sn Mg alloy sheet as the research object,the process combination of cold rolling,cold rolling+temperature controlled differential speed rolling（TCDSR）,hot rolling,hot rolling+TCDSR and annealing are used to comprehensively improve the mechanical properties of the alloy.This study systematically studied the change law of microstructure in the deformation process of Mg alloy sheets and tested the ability of Mg alloy sheets to resist plastic deformation and basic mechanical properties at RT through a tensile experiment.The results are as follows:（1）By constructing the flow stress-strain curve of as-cast TXM210 Mg alloy under thermal compression,the thermal deformation behavior of as-cast TXM210Mg alloy was analyzed,and the hot working map of the alloy was drawn;The machinable areas with power dissipation value greater than 30%are low temperature and low strain area(300～340℃,0.001～0.004s^-1)and high temperature and low strain area(380～450℃,0.001～0.23s^-1).The low temperature and low strain region have been successfully applied to the rolling deformation process,and the maximum single pass reduction of alloy hot rolling has reached 40%,which is mainly since many Ca Mg Sn second phase promotes the dynamic recrystallization at low temperature,and the recrystallized grains with low dislocation density with the second phase as the core are continuously formed,thus increasing the low-temperature Machinable region.The second phase is helpful to promote the dynamic recrystallization process of the alloy and effectively consumes the dislocations produced in the rolling deformation.（2）Cold rolling,cold rolling+TCDSR process significantly refined The average grain size of the rolled sheet is 18.4%of that of the extruded sheet is refined to 6.2μm、5.3μm respectively.Due to insufficient dynamic recrystallization in the alloy,the tensile strength of the sheet after rolling is only280MPa and 290MPa.In addition,many small-angle grain boundaries were found in the rolled Mg alloy sheet,and the dislocation density decreased.The basal texture is inclined,and the elongation of the Mg alloy sheet is greatly improved,from the original 7.5%to 14%and 17%respectively.（3）Under the hot rolling+TCDSR process,the alloy shows an excellent high-strength plastic matching,that is,the tensile strength and elongation are as high as 310 MPa and 22.0%respectively.After rolling,the texture tilts±30°along the TD direction,and the average grain size is refined to 4.5μm;In addition,in the rolling process,the second phase of Ca Mg Sn is further broken,then evenly distributed in the matrix,and gradually spheroidized after annealing,which significantly improves the strength and plasticity of the alloy.Due to the uniform microstructure,the results show that（～5.4μm）The precipitation of high-density strip Ca Mg Sn and spherical Mg₂Ca phase significantly improves the strength of Mg alloy.