| Mg-Gd-Y-Zn-Zr magnesium alloy will form LPSO phase during heat treatment,deformation and aging process,making it have ultra-high toughness mechanical properties and heat resistance,and magnesium alloys are required in more and more fields The higher strength and high temperature resistance make this series of alloys receive more and more attention.Therefore,the research on the strength and toughness of Mg-Gd-Y-Zn-Zr magnesium alloy is of great significance for its wide application.In this paper,the Mg-9.2Gd-1.9Y-1.8Zn-0.5Zr magnesium alloy provided by Shanxi Yinguang Magnesium Co.,Ltd.was used as the research object.The experimental alloy was subjected to solution aging heat treatment at different temperatures and different times.The microstructure was observed and analyzed by electron microscopy.The phase was analyzed using XRD diffractometer.The effect of heat treatment process on the microstructure evolution and mechanical properties of the extruded alloy was investigated.And through Minitab software based on the central composite design method for the experimental alloy heat treatment process model construction and response optimization,to determine the best heat treatment program and test verification.Research indicates:(1)The main phase of ?-Mg matrix and LPSO phase in Mg-9.2Gd-1.9Y-1.8Zn-0.5Zr magnesium alloy extruded alloy,the main phase in the test alloy after solid solution has not changed.In the low-temperature solid solution process,solid solution strengthening and grain coarsening work together on the hardness of the alloy.When solid solution strengthening plays a major role,the alloy hardness increases,and when grain coarsening dominates,the alloy hardness decreases.In the process of high temperature solid solution,solid solution strengthening,second phase strengthening and grain coarsening work together.The second phase strengthening plays a major role.(2)The main phases of Mg-9.2Gd-1.9Y-1.8Zn-0.5Zr magnesium alloy aging alloy are?-Mg matrix and LPSO phase and Mg5(Gd,Y,Zn)precipitated after aging.In the agingprocess,precipitation strengthening and grain coarsening jointly determine the hardness value of the alloy.When precipitation strengthening dominates,the hardness increases,and when grain coarsening dominates the hardness,the hardness decreases.When the aging time is 24 h and the temperature is 225 ?,the hardness value is the highest.(3)The optimal heat treatment process of Mg-9.2Gd-1.9Y-1.8Zn-0.5Zr magnesium alloy after optimized response is: solution temperature is 491 ?,solution time is 13.9h,aging temperature is 229 ?,aging time For 24.3h,the corresponding predicted response variables should be elongation 10.5958%,yield strength 270.2504 MPa,tensile strength 363.0084 MPa.After the heat treatment using the predicted best process,it was found that the tensile mechanical properties of the materials were within the prediction interval,proving that the model's prediction is effective and accurate.(4)Mg-9.2Gd-1.9Y-1.8Zn-0.5Zr magnesium alloy undergoes homogenization treatment at 510 ? × 18 h,the true deformation is 2.097 after extrusion deformation,and then undergoes a solution temperature of 491 ? and a solution time After 13.9h,aging temperature of 229 ? and aging time of 24.3h,the mechanical properties have been improved from tensile strength of 187 MPa and elongation of 3.9% to tensile strength of 370 MPa and elongation of 10.8%.. |
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