Study On The Plastic Deformation Mechanism Of AZ31 Mg Alloy Sheet With Bimodal Non-basal Texture Under Uniaxial Tension At Room Temperature

In this paper,AZ31 magnesium alloy sheet with a bimodal non-basal texture is fabricated by equal channel angular rolling and continuous bending with subsequent annealing process(ECAR-CB-A).In order to investigate the tensile plastic deformation behaviors and mechanisms at room temperature,five samples with different initial loading directions are designed.The angle between loading direction and rolling direction(RD)is 0°?30°? 45°? 60° and 90°,respectively.Uniaxial tensile test at room temperature,electron backscattered diffraction(EBSD)technique and visco plastic self-consistent(VPSC)crystal plastic simulation,are employed to study the effect of different initial textures on microstructure evolution and mechanical behavior of AZ31 Mg alloy sheet during uniaxial tensile test along rolling direction(RD).The effect of loading directions on in-plane anisotropy of mechanical behavior and microstructure evolution of AZ31 Mg alloy sheet are analyzed.As for the bimodal non-basal texture sheet,the contribution of various deformation modes to uniaxial tensile plastic deformation behavior is investigated.The coressponding conclusions are as follows:(1)The influence of initial texture on the tensile plastic deformation behavior of AZ31 Mg alloy sheet at room temperature is studied:(1)As for the As-received sample with typical basal texture,dislocation slip is the dominant deformation mechanism,while in the bimodal non-basal texture sample prepared by ECAR-CB-A process,dislocation slip and extension twins(ETs)can both contribute to plastic deformation due to the c-axis of grains inclining about ±40° from normal direction(ND)to RD.(2)Basal texture of the Asreceived sample does not change,and the basal texture components rotate toward ND slightly after deformation.However,for the ECAR-CB-A sample,with the increase of the angle between the basal poles and ND,the number of activated ET variants in a single grain increases,which can contribute to rotating the texture toward ND and the formation of new transverse direction(TD)texture components.(3)For the ECAR-CB-A sample,the fracture to elongation(FE)increased by 10% compared with the As-received sample due to the activation of a large number of ETs during the deformation process;meanwhile,the softening effect of the bimodal non-basal texture can contribute to the activation of basal <a> slip during the deformation process,ultimately making the yield strength(YS)and YS / UTS decrease by about 50%.(2)The effect of loading direction on the room temperature plastic deformation behavior of AZ31 Mg alloy sheet with bimodal non-basal texture is studied:(1)with the angle between loading direction and RD gradually increasing from 0° to 90°,the volume fraction of ETs in the deformed microstructure gradually decreases,and the dislocation density gradually increases.(2)For the five samples with different orientations,a new TD texture component formed at the dormation degree of 12% and the bimodal texture gradually rotates toward ND during deformation process.However,with the increase of angle between loading direction and RD,the rotation tendency of bimodal texture to ND gradually decreases.(3)With the angle between the loading direction and RD increasing from 0° to 90°,the number of activated ET variants in a single grain decreases obviously,and the parallel ET variant pairs disappear gradually;when the angle between the basal poles and ND is less than 60°,the activated ET variants rotate texture toward TD;while when the angle between c-axis and ND is in the range of 60°-90°,the activated ET variants rotate the texture toward ND.(4)As the angle between loading direction and RD increasing from 0° to 90°,the bimodal non-basal texture AZ31 Mg alloy sheet exhibites obvious in-plane mechanical behavior anisotropy,which shows that the YS of the sheet increases gradually while the FE decreases gradually.(3)The uniaxial tensile plastic deformation mechanisms of bimodal non-basal texture sheet under different loading directions are studied:(1)Correct material parameters of the AZ31 Mg alloy thin sheet with bimodal non-basal texture are obtained by the minimum parameter approach;(2)As for 0° and 30° samples,basal <a> slip is the main deformation mechanism,prismatic <a> slip and {10-12} ETs are the secondary ones.There exhibites a transition effect for 45° sample,the relative activity of prismatic <a> slip begins to increase obviously.It can make a contribution to plastic deformation together with basal <a> slip and a small amount of {10-12} ETs.For 60° and 90° samples,prismatic <a> slip is the dominant deformation mechanism,basal <a> slip and a small amount of pyramidal <c+a> slip are the secondary ones contributing to plastic deformation.(3)As the angle between the loading direction and RD increasing from 0° to 90°,the sum of the relative activity of the basal <a> slip and the ET decreases gradually,resulting in the tendency of the bimodal texture to ND decreases gradually.