The Effect Of Pre-strain On The Dynamic Compression Properties Of AZ31 Magnesium Alloy

Magnesium alloy has been widely used in aerospace,electronics,automobile,and many other industries due to its characteristics of lightweight.In order to further understand the characteristics of the deformation of the magnesium alloy under high strain rates,enrich magnesium alloy plasticity theory system,Split Hopkinson Pressure Bar(SHPB)tests are conducted on rolled direction.Prior dynamic deformation the samples are pre-strained in a certain amount of strain by tensile and compression along rolling direction,the dynamic compression deformation are conducted at room temperature.The microstructure and properties of AZ31 magnesium alloy after pre deformation along the rolling directions,the dynamic compression deformation are conducted at room temperature.The microstructure and properties of AZ31 magnesium alloy after pre deformation along the rolling direction are analyzed in details.The macro textures are observed by X-ray.The microstructures are observed by optical microscope(OM).The fractures are observed by scanning electron microscope(SEM).Through Matlab software and Origin drawing software,the true stress and stain curves are acquired.The dynamic failure and deformation mechanisms of magnesium alloys are discussed based on the microstructure evolution.The results show that the basal texture in the rolled AZ31 sheet causes the anisotropy of dynamic mechanical properties.After the tensile deformation,the strength of the material slightly increases.A small amount of compression twinning activate during the pre-tension,and along with non-basal.The number of twinning increases with the increasing of the deformation degree at first,and then it decreases.After dynamic compression deformation,the stress-strain curve does not show obvious improve for plastic,but strength is improved slightly.A large number of tensile twinning activates during loading the sample,and there are a large number of the pre-microstructure.After the pre-compression deformation,the strength of the material reduces greatly.During pre-compression twinning take plane,the number of twinning in organization as decreases first with the increasing of the deformation.There is no improvement after dynamic compression deformation in plastic,and the strength is greatly reduced.In both cases the fracture morphology shows the tongue shape patterns,there are many cleavage steps and show the cleavage fracture mode.The experimental data that obtained by dynamic compression deformation after the pre-tension or pre-compression deformation is used to fit the constitutive equation,in order to calculate the C value under different amount of result.The simulation result is consistent with the experimental result,namely the dynamic compression stress-strain curves of AZ31 magnesium alloy after pre deformation shows that the strength increases with the increase of strain rate,in a word,that shows the strengthening effect of strain rate.