Thermoplastic Deformation And Microstructure Evolution Of AZ31 Magnesium Alloy

Magnesium alloys have been widely used in the fields of aerospace,transportation and home electronics in recent years due to their excellent characteristics of weight reduction,energy saving and easy recovery.Therefore,the study on twin and slip mechanism of magnesium alloy in thermoplastic deformation process can not only enrich the basic knowledge of deformation of magnesium alloy,but also provide theoretical guidance for the expanded application of magnesium alloy,so it has important research significance.In this paper,the thermoplastic deformation behavior and microstructure evolution of AZ31 magnesium alloy were studied by Gleeble-3800 thermal simulation test machine.Deformation temperature set at 100? to 400?,the strain rate were set to 0.001s-1,0.1s-1,10s-1.The effect of deformation temperature and strain rate on the thermal deformation behavior of AZ31 magnesium alloy was studied and the microstructure evolution and fracture morphology of AZ31 magnesium alloy during thermal deformation were analyzed under the condition that the compression deformation was 50%.The results show that the peak stress of AZ31 magnesium alloy increases with the increase of strain rate and decreases with the increase of deformation temperature.The microstructure in the temperature of 100? andstrain rate of 0.001s-1,the organization is not uniform,by the fine grained and coarse grain and some of twin.To increase the temperature to 200?,most of the microstructure grain size is very small,the dynamic recrystallization happens more completely.Continue to raise the temperature to 300? and 400?,grain coarsening of the trend.As the strain rate increases to 0.1s-1 and 10s-1,the dynamic recrystallization happens entirely will be done at temperature of 300 ?.According to the true stress-strain curve in the process of thermoplastic deformation,the constitutive equation of AZ31 magnesium alloy is determined as follows:=4.6977 ×109×[sinh(0.0085327?)6.0808×exp(-104.236/RT)In order to investigate the effect of deformation amount on twinning behavior and microstructure evolution,the annealed AZ31 magnesium alloy was compressed to 2%,4%,6%,8%and 100%at the temperature of 250? and strain rate of 0.1s-1.The results show that{1012} extension twinning dominates the primary stage of thermoplastic deformation of rolled AZ31 magnesium alloy(?<40%).Only one{1012}twin variant or variant pair is formed in most of the grains,and the twin structure is paralled to each other,and the grain is divided into lamellar structure.When the deformation amount is increased to 4%-8%,the{1011} compression twins appear in the microstructure.At this time,the twins in the microstructure are intercepted with each other.When the deformation amount is exceed?>10%,then twins is saturated and dislocation slip becomes the main deformation mechanism of AZ31 magnesium alloy.