Effects Of Heat Treatment On Microstructure And Service Properties Of AQ80M Magnesium Alloy Die Forging

AQ80M magnesium alloy,with excellent comprehensive mechanical properties and low cost,has a good application prospect in aerospace field.In this article,an AQ80 M magnesium alloy casing prepared by isothermal die forging process is studied.The microstructure and service properties of AQ80 M magnesium alloy die forging in different regions were systematically studied and the effects of heat treatment on microstructure and service properties of AQ80 M magnesium alloy die forging were analyzed using optical microscopy,scanning electron microscopy,X-ray diffraction,electron backscatter diffraction,transmission electron microscopy,tensile test and creep test.The results provide theoretical basis and process guidance for the processing and comprehensive properties regulation of magnesium alloy die forgings,and provide service evaluation data for the application of magnesium alloy die forgings in aerospace field.The main conclusions are as follows:1.The inhomogeneous deformation of isothermal die forging resulted in the inhomogeneous microstructure of die forging,and the second phase distribution,average grain size,texture characteristics and dynamic recrystallization degree are different in each region.The texture strengthening effect is the most significant in the middle region,and the yield strength is the highest.The outer region has the smallest average grain size and the highest plastic and ultimate tensile strength.The bimodal texture in the middle region leads to mechanical anisotropy,and prismatic slip contributes more to deformation along the RD,resulting in higher yield strength.2.Static recrystallization and grain growth occurred during solution treatment,which had little effect on the texture of die forging.Discontinuous precipitates and continuous precipitates were formed during aging treatment,and the area fraction of discontinuous precipitates in T5 sample is higher than that in T6 sample due to the difference of precipitation behavior.3.At room temperature,discontinuous precipitates exhibit more significant precipitation hardening and are the main nucleation sites of microcracks.Therefore,the strength of die forging is higher and the plastic decreases more after T5 treatment.However,discontinuous precipitates show worse resistance to high temperature softening,leading to lower tensile strength and creep resistance of T5 sample than that of T6 sample at elevated temperature,contrary to the results at room temperature.The findings provide new insights for optimizing the heat treatment process of AZ series magnesium alloys at different service temperatures.