Influence Of Extrusion Deformation On The Microstructure And Mechanical Properties Of Mg-Nd-Zn-Zr Alloy

In recent years,magnesium rare earth alloys have attracted much attention due to their excellent mechanical properties.Magnesium rare earth alloys represented by Mg-Gd series have been praised for their excellent aging hardening properties and good heat resistance.But at the same time,the high price of Mg-Gd series Mg-RE alloy greatly increases the cost of the alloy,so this paper chooses Mg-Nd series alloy with excellent aging hardening characteristics to reduce the cost,so as to achieve high strength and low cost Mg-RE alloy.The Mg-2.5Nd-0.8Zn-0.4Zr alloy was selected as the original alloy and Ca,Cu and Ni elements less than 1wt%were added respectively,and the performance of the alloy was optimized again through microalloying treatment.The microstructure and mechanical properties of the modified Mg-2.5Nd-0.8Zn-0.4Zr-X alloy were investigated by means of optical microscope,scanning electron microscope,X-ray diffraction analysis and hardness test.The influences of the addition of three trace elements on the microstructure and mechanical properties of Mg-2.5Nd-0.8Zn-0.4Zr-0.8Ca were investigated,and the optimal alloying composition was obtained as Mg-2.5Nd-0.8Zn-0.4Zr-0.8 Ca.The heat treatment of Mg-2.5Nd-0.8Zn-0.4Zr-0.8Ca alloy was studied to explore the effect of solid solution treatment on the microstructure of the as-cast alloy,and the optimal microstructure of the alloy was obtained when the solid solution treatment of Mg-2.5Nd-0.8Zr-0.4Zr-0.8Ca alloy was performed for 10h at525?.On this basis,the positive extrusion deformation was used to treat the solid solution alloy,and the change rule of the microstructure and mechanical properties of Mg-2.5Nd-0.8Zn-0.4Zr-0.8Ca alloy under different extrusion ratios was explored.The aging treatment of the extruded alloy was carried out and the aging hardening characteristics of the alloy were analyzed.The results show that the hardness of the alloy reaches its peak value after aging treatment at 200°C for 16h,and its value is 88.34 HV.On this basis,the transmission electron microscope(tem)analysis of extruded and peak aged alloys has been carried out.The results show that the fine Mg₁₂Nd and Ca₂Mg₆Zn₃phases are precipitated in the alloy after aging treatment,which has a good effect on improving the properties of the alloy.The hot tensile test of the extruded alloy was carried out and the hot tensile data of the alloy were analyzed.It was found that the alloy reached superplasticity and elongation reached 310%at 400?and the tensile rate was 10^-4s^-1.On this basis,the constitutive equation of Mg-2.5Nd-0.8Zn-0.4Zr-0.8Ca alloy was established.