Anisotropy Of AZ31 Magnesium Alloy Under High Strain Rate Deformation

Magnesium and its alloys are widely studied and used in automobile,aerospace and many other industries due to their light weight.However,due to the low symmetry of HCP structure,slip systems in magnesium and its alloys can not supply sufficient independent slip systems so twinning plays a very important role during deformation,and leads to its low ductility.The anisotropic behavior is a common phenomenon owing to the strong initial texture.In order to study the anisotropic behavior during high speed deformation,Split Hopkinson Pressure Bar?SHPB?and Split Hopkinson Tension Bar?SHTB?were used to conduct the high strain rate deformation on AZ31 magnesium alloy rolling sheet.X-ray and electron backscatter diffraction were applied to obtain the texture of the materials,and optical microscope?OM?was used to observe the microstructure.The volume fraction of twinning after deformation was measured by quantitative analysis.The calculated Schmid factor?SF?combined with the observed microstructures were used to analysis the deformation modes and to study the effect of temperatures,strain rates and loading directions on anisotropy during high strain rates deformation.The main results were as follows:the high strain rates compression tests were conducted at the strain rate of 500s^-1?2200s^-11 and temperature at 20?350?along normal direction?ND?,transverse direction?TD?and rolling direction?RD?.The high strain rate tension tests were conducted at the strain rate of 600s^-1?2400s^-11 and at room temperature along rolling direction,45°direction and transverse direction.The compression results demonstrated that there were obvious anisotropy between ND and RD and TD samples,while the anisotropic phenomenon became weak gradually as the testing temperature increasing.The strain rate had no significant influence on the anisotropy.The tension results demonstrated that there was no anisotropy phenomenon was observed in AZ31 magnesium rolling sheet during the in-plane tension.The analysis results showed that the anisotropy phenomenon was obvious because of the different deformation modes resulted from the existence of strong texture during high strain rate deformation in AZ31 magnesium rolling sheet.The dominant deformation mode was{10-12}extension twinning when RD and TD samples were under compression,while for ND samples compression the dominant deformation modes were pyramidal?c+a?slip and{10-11}contraction twinning.In contrast,in the high strain rate tension event,the dominant deformation modes of all samples were{10-11}contraction twinning,prismatic and pyramidal?c+a?slip,the similar deformation mode of samples due to the similar grain orientions lead to the isotropic phenomenon during in-plane tension in AZ31 magnesium rolling sheet.In magnesium alloys,the variation trend of Schmid factor of different deformation system was different.The combination of SF with the critical resovled shear stress?CRSS?can be used to interpret the deformation mechanism and anisotropic phenomenon caused by strong texture in the present study.