Strain Rate Sensitivity Of An Mg Alloy At Room Temperature

Magnesium alloys and other metals have low strain rate sensitivity at room temperature.Strain rate sensitivity(SRS)is a material characteristic,which depends on the material itself,temperature,loading conditions,and may change with strain.AZ31 magnesium alloy is selected in this project.The following work is carried out through tensile and compression experiments,Optical Microscope(OM),Electron Backscattered Diffraction(EBSD)and VPSC model.Firstly,the experimental samples of tension and compression were obtained by annealing heat treatment.Then the tensile and compression experiments were carried out at room temperature in different strain rates.The stress-strain curves of deformation at different strain rates were obtained and corrected.The deformation microstructure was characterized and analyzed by OM and EBSD.The results show that the form of stress-strain curves of AZ31 magnesium alloy under tension or compression varies greatly in different directions,which is related to the main deformation modes of AZ31 magnesium alloy during deformation.When AZ31 magnesium alloy is deformed,its flow stress increases with the increase of strain rate,and with the increase of strain rate,the sample breaks at lower strain.The twin volume fraction increases with the increase of strain,while the twin volume fraction increases slightly with the increase of strain rate.Finally,the deformation behavior of AZ31 magnesium alloy was simulated by VPSC under the same experimental conditions.The simulation results were compared with the experimental results.The stress-strain curves of AZ31 magnesium alloy were in good agreement with the experimental ones,and the accuracy of the parameters was verified.Then the deformation behavior of AZ31 magnesium alloy with different strain rate sensitivity exponent n is simulated by VPSC.It is found that the selection of n has an important effect on flow stress.With the decrease of n value,flow stress decreases significantly.However,when the {10(?)2} twin are compressed along RD direction,the simulated flow stress decreases significantly with the increase of n.n affect the simulated flow stress depended by material and loading direction.The strain rate affects the twin volume fraction,and twin volume fraction increases with the increase of strain rate.The selection of n has an important effect on strain anisotropy and simulated texture evolution: n has a significant effect on R value,and the decrease of n increasesthe isotropy,that is,r value is closer to 1.The effect of n on texture strength is greater.The lower n is,the weaker the texture strength is.The maximum texture strength increases with the increase of n.