Dynamic Responses Of AZ80 Magnesium Alloy In Tension And Compression

AZ80 magnesium alloy has the advantages of high specific strength,high specific stiffness and good mechanical properties,which is widely used in aerospace,transportation and other fields as a structural material.Structural components made of magnesium alloy may be subjected to impact loadings during service.Therefore,it is necessary to understand the tensile and compressive mechanical responses of AZ80 alloy at high strain rates.On the other hand,magnesium alloys maybe subjected to complex loading conditions in plastic processing and practical applications.Bauschinger effect exists when the strain path is changed,so it is also necessary to investigate the effect of pre-deformation on the tensile and compressive deformation behavior of AZ80 alloy under dynamic loadings.Quasi-static and dynamic uniaxial tension and uniaxial compression tests were conducted along extrusion direction and perpendicular to extrusion direction of AZ80 alloy bar.Experimental results show that the uniaxial tensile and compressive deformation behavior of AZ80 alloy is orientation-dependent and strain-rate dependent.Moreover,AZ80 alloy exhibits tension-compression asymmetry,which is also influenced by the loading strain-rate and orientation.Uniaxial tensile and compressive plastic deformation responses of AZ80 alloy at quasi-static and high strain rates were simulated using the visco-plastic self-consistent model.Numerical results indicate that the orientation-dependence and tensioncompression asymmetry of the uniaxial mechanical behavior of AZ80 alloy is related to {1012} tension twinning.The "S"-shaped hardening characteristic of the compression curve along the extrusion direction is the result of the dominant role of twinning and slip in different stages of loading.The activation of the deformation mechanism of AZ80 alloy is correlated with the loading strain rate,which leads to the strain-rate dependence of the tension-compression asymmetry of AZ80 alloy.The improved high strain-rate tension and compression testing systems were used to realize the dynamic loading-unloading experiments.Experiments on the effect of pre-tension deformation on the dynamic compressive behavior of AZ80 alloy were carried out,and the influences of strain-rate,orientation and pre-strain on the Bauschinger effect were also investigated.Experimental results show that Bauschinger effect of AZ80 alloy has strain-rate dependence under the strain path of pre-tensionunloading-reverse compression.Bauschinger effect at the high strain rate is weaker than that under quasi-static loading conditions.Increasing the pre-tension strain enhances the Bauschinger effect along extrusion direction,but weakens it in perpendicular to the extrusion direction.Moreover,Bauschinger effect of AZ80 alloy also exhibits orientation dependence,which is stonger in perpendicular to extrusion direction than that along extrusion direction,and such anisotropy is influenced by the loading strainrate and pre-strain.