Research Of Low Cycle Fatigue Of ZM61 Wrought Magnesium Alloy

As the lightest metal structure material,magnesium alloys has been widely used in the aerospace,automotive and electronics and other fields,which have excellent properties such as high specific strength,high specific stiffness and good recyclability.For Mg alloys employed as load-bearing structural components,it is of great importance to understand the cyclic deformation mechanisms and fatigue properties of Mg alloys so that the reliability and durability of the products can be ensured and fatigue failure can be prevented by applying appropriate fatigue design principles.Based on magnesium alloy Mg-6Zn-1Mn extrusion bar(ZM61)as the research object,the current work investigated the cyclic deformation and low cycle fatigue properties of extruded ZM61 alloy under different strain amplitude control of tension and compression strain fatigue test.Subsequently,double-aged treatment was performed on the extruded ZM61 alloy to study the effect of grain size on cyclic deformation behavior and low-cycle fatigue properties of extruded ZM61 alloy.In this study,the fatigue property and static mechanical properties of extruded and double-aged ZM61 alloys were tested by electro-hydraulic servo fatigue testing machine(MTS)and electronic universal test machine,respectively.Based on the results of optical microstructure(OM),X-ray diffraction(XRD),scanning electron microscopic and electron backscatter diffraction(EBSD)techniques,the fatigue property and the deformation mechanism of extruded and double-aged ZM61 magnesium alloys under different strain amplitude.The Coffin-Manson formula was used to analyze the fatigue life,and its plasticity and elastic strain life equation and ZM61 magnesium alloy fatigue life equation were investigated respectively.The difference in the microstructure between the as-extruded alloy and the double-aged alloy results in a higher fatigue life in the as-extruded state than in the aging state.Microstructure has a significant effect on the fatigue performance of magnesium alloysThe stress-strain hysteresis loops exhibit an asymmetric shape in both as-extruded and double-aged alloys,which is mainly due to the twins participating in the cyclic deformation.During the tension and compression fatigue cycling,dislocation slip and detwinning dominate deformation in tension,while mechanical twinning dominates deformation in compression.The as-extruded and double-aged ZM61 alloys exhibit significant tension-compression asymmetry,twinning and detwinning phenomenon.For ZM61 magnesium alloys of different states,the plastic strain equations and elastic strain equations can be represented by the Coffin-Manson and Basquin equations respectively,and the total fatigue strain equation can be obtained.