The Study On Microstructure And Texture Evolution Of Mg-Sn-Based Alloys During Hot Deformation

It is easy to form strong deformation texture in the process of low-temperature deformation for the Mg-Sn-based alloys with HCP lattice structure,which seriously damages the ductility and stretch formability of the material.Therefore,controlling the microstructure and texture of Mg-based alloys is of paramount importance aimed at improving their mechanical performances to an acceptable level required for automotive and aerospace applications.Three kinds of alloys,Mg-8Sn-1Al-1Zn,Mg-1Sn-1Al-1Zn,and Mg-0.5Sn-0.5Al-0.5Zn with decreasing the dynamic precipitation capacity were prepared by traditional metal mold casting method,respectively.In addition,twinning deformation plays a key role in the low-temperature deformation process of magnesium alloys.Thus,all the studied alloys were compressed at relatively high strain rates in order to induce the occurrence of twinning.The effects of twinning and dynamic precipitation on texture evolution in the Mg-8Sn-1Al-1Zn alloy were investigated during the hot compression test at200°C up to a true strain of 0.7 with strain rates ranging from 0.1 to 10 s^-1.The results indicate that the types and intensities of the texture strongly depend on the strain rates during hot compression.Texture evolution was thoroughly investigated in terms of type/fraction of twins,and twinning-induced dynamic recrystallized grains.Moreover,the hindering effect of dynamically precipitated Mg₂Sn phases on the matrix lattice rotation was studied in detail,and the influence of this effect on the peak intensity of the(10-10)prismatic texture is summarized.Texture evolution of an extruded dilute Mg-1Sn-1Al-1Zn alloy was thoroughly investigated based on the twinning and dynamic recrystallization(DRX)behavior via hot compression at a strain rate of 10 s^-1and temperature of225°C.It was found that the types and intensities of the texture are strongly dependent on the fraction of twins and DRX modes as well as regions where sub-grain boundaries(sub-GBs)are intensively accumulated.At the initial stage of deformation,the formation of compression direction(CD)-tilted basal texture was mainly determined by the occurrence of{10-12}extension twins.As the strain increases,the variation in the texture intensity was greatly dominated by the DRX modes but the type of main texture remained unchanged.Microstructure evolution and texture tailoring of an extruded ultra dilute Mg-0.5Sn-0.5Al-0.5Zn alloy were studied by uniaxial compression at temperatures ranging from 125°C to 200°C with a high strain rate of 10 s^-1.The results indicate that{10-11}-{10-12}double twinning dominated the deformation,and the corresponding size(including twin thickness and aspect ratio)was strongly dependent on the deformation temperature during hot compression.Texture evolution was thoroughly investigated in terms of type/fraction of twins and dynamic recrystallized grains.Moreover,the effect of{10-11}-{10-12}double twin size on texture evolution under different compression temperatures was investigated systematically.The above-mentioned research results of this study provide new insights into controlling the texture during the fabrication of wrought Mg alloys,which is critical for producing alloys suitable for high-performance applications.At the same time,it has great reference significance for the design of microstructure and control of deformation condition of Mg-Sn-based alloys,which is conductive to the optimization of primary plastic deformation and multiple plastic deformation process parameters.