Effect Of Heat Treatment On Thermal Conductivity And Mechanical Properties Of Mg-5Sn-Mn(Zn) Alloy

Magnesium alloy is known as "green engineering metal structure material in twenty-first Century",which has the advantages of light weight,high specific strength,high rigidity and easy processing.In recent years,with the further research on the mechanical properties of magnesium alloys,the excellent physical properties of magnesium and magnesium alloys have attracted people's attention.Because of the high thermal conductivity,the thermal conductivity of magnesium alloy has become a hot issue.Thermal conductivity is the most important factor to measure the thermal conductivity of materials,so it is very important to improve the thermal conductivity of magnesium alloy,it is an effective method to improve the thermal conductivity of magnesium alloy by heat treatment.In this paper,as-cast Mg-5Sn-Mn,Mg-5Sn-Zn of the two kinds of alloy as the research object,using optical microscopy,scanning electron microscopy,X-ray diffraction,Energy Disperse Spectroscopy and tensile machine and other equipments,studied the effects of solution and aging treatment on the microstructure,thermal conductivity and mechanical properties of Mg-5Sn-Mn and Mg-5Sn-Zn alloys.Draw the following conclusions:The microstructure of Mg-5Sn-Mn alloy is composed of ?-Mg matrix,Mg2 Sn phase and Mn element.After 12 h soluted treatment at 440?,the Mg2 Sn phase disappear,solid solution treatment is best,and the Mn element is always present;in the solution process,with the increase of solution time,the thermal conductivity decreased from 81.65 W·m-1·K-1 to 72.3 W·m-1·K-1;the tensile strength increased first and then decreased,in the solution of 16 h,,the tensile strength reaches a peak 145.39 MPa,elongation has been rising,Brinell hardness values decreased first and then increased,in the solution of 16 h,reached the peak 50 HB,then gradually decreased.After aging treatment,with the increasing aging time,the precipitation of Mg2 Sn increased;the thermal conductivity first rose to the maximum value of 103.5 W·m-1·K-1 then decreased;tensile strength increased first and then decreased,and reached the peak of 161 MPa in aging120 h,and the elongation has been decreased;the Brinell hardness value increased after the first drop,reached a peak of 61.2HB in aging 120 h.The as-cast microstructure of Mg-5Sn-Zn alloy is composed of ?-Mg matrix,Mg2 Sn phase and Mg Zn phase;After solution treatment,Mg2 Sn and MgZn are dissolved into the matrix of ?-Mg,solid solution treatment is best.With the solution time increases,the thermal conductivity decreased gradually;the tensile strength increased first and then decreased,in the solution of 12 h,reached the peak 192.57 MPa,elongation has been increased;Brinell hardness increased first and then decreased,and reached the peak 61.5HB in solution 12 h.After aging treatment,with the increase in the aging time,the amount of Mg2 Sn phase and MgZn phase are more,in the aging 168 h,the second phases are gather and grow.thermal conductivity gradually increased,in aging 144 h reached the maximum 123.3W·m-1·K-1;the tensile strength increased first and then decreased,and reached the peak 200.17 MPa at 144 h,elongation has been decreased,Brinell hardness first increase and then decrease,reached the peak64.8HB at aging 144 h.