Effect Of Sn And Sr Addition On Microstructure And Mechanical Properties Of Mg-4Al-0.4Mn Magnesium Alloy

At present,alloying is a common and simple method to improve the properties of magnesium alloys.After a lot of research by scholars,it is found that add ing a small amount of rare earth to magnesium alloys can effectively improve their high temperature properties,which makes magnesium alloys have a certain application in the field of high temperature.However,due to the rare and expensive rare earth elements,resulting in the production of rare earth magnesium alloy required high cost,so that its scope of use is limited.In this paper,Mg-4Al-0.4Mn ternary magnesium alloy was selected as the basic alloy,and Sn and Sr elements were used as alloying elements.Mg-4Al-0.4Mn-xSn-ySr（x=0,0.4,0.8,1.2,1.6;y=0,0.2,0.4,0.6,0.8 wt.%）magnesium alloy containing a certain proportion of Sn and Sr elements were prepared by melting and casting method.The effects of Sn and Sr co-addition on the microstructure and mechanical properties of as-cast,heat-treated and extruded Mg-4Al-0.4Mn magnesium alloy were analyzed.On this basis,the effects of different contents of Sn and Sr on the texture of Mg-4Al-0.4Mn magnesium alloy after hot deformation were analyzed.The results show that the microstructure of as-cast Mg-4Al-0.4Mn-xSn-ySr magnesium alloy mainly composed ofα-Mg phase,β-Mg₁₇Al₁₂ phase,Al₆Mn phase,Mg₂Sn phase and Al₄Sr phase.With the addition of Sn,Sr elements increasing,the grains of the alloy are refined first and then coarsened.The mechanical properties at room temperature and high temperature are increased first and then decreased.When the content of Sn and Sr elements is 1.2 wt.%and 0.6 wt.%,respectively,the tensile strength at room temperature is 195 MPa,the yield strength is 88 MPa,and the elongation is 8.32%.In order to improve some defects in the as-cast alloy,the as-cast alloys of each component were heat treated under the corresponding optimum process parameters,and it was found that the distribution of the second phase in the alloy was more uniform.The alloy after solution treatment was subjected to forward extrusion with an extrusion ratio of 16,and the second phase in the alloy was crushed to become fine,so that the structure was refined.The combined addition of Sn and Sr elements can improve the thermal stability of the alloy to a certain extent,thereby improving its high temperature performance.Finally,the effect of Sn and Sr addition on the texture of Mg-4Al-0.4Mn magnesium alloy after forward extrusion hot deformation was analyzed by EBSD technique.It was found that the composite addition of Sn and Sr elements did not change the hard orientation and silk texture of most grains of Mg-4Al-0.4Mn magnesium alloy after forward extrusion hot deformation.The activation ability of{1-100}prismatic slip system in the alloy is higher than that of{0001}basal slip system,and the proper addition of Sn and Sr elements can weaken the{0001}basal texture of Mg-4Al-0.4Mn magnesium alloy after forward extrusion hot deformation and promote the activation of basal slip system.