Thermal Deformation Behavior And Microstructure Evolution Of Mg-Gd-Y-Zn-Zr Alloy

Rare earth magnesium alloy has excellent mechanical properties at high temperature and room temperature.It is widely used in aerospace,aviation,weaponry and other industries.It has a wide range of applications.In this paper,the as-cast and homogenized Mg-Gd-Y-Zn-Zr alloys are taken as the research objects.According to the data obtained from the hot tensile test,the flow stress characteristics at different temperatures and different strain rates are analyzed,and the flow stress constitutive model and recrystallization theory model are established by analyzing the flow curve data.Combined with metallographic observation,EBSD technology and fracture scanning,the influence of deformation conditions on the microstructure,recrystallization and fracture mode of the alloy is analyzed.The theory of hot deformation of Mg-Gd-Y-Zn-Zr alloy is improved,which is of great significance to practical application.In this paper,the as-cast and homogenized Mg-Gd-Y-Zn-Zr alloys were deformed at a temperature range of 360°C-480°C and a gradient of 40°C and strain rates of 0.1/s,0.01/s,0.001/s and 0.0001/s.The flow stress curves under different deformation conditions were obtained,and the flow curves were dynamic recrystallization.The Arrhenius constitutive equation was established by data fitting to predict the mechanical properties of the alloy.The theoretical model of dynamic recrystallization was constructed by analyzing the relationship between work hardening rate θ and critical stress and critical strain.The main research contents are as follows:(1)High temperature uniaxial tensile tests were carried out on Mg-Gd-Y-Zn Zr alloy at different temperatures and strain rates.The flow stress curve was obtained,the flow stress characteristics were analyzed,and the Arrhenius type constitutive equation of Mg-Gd-Y-Zn Zr alloy was constructed to predict the mechanical properties of the material.(2)By means of work hardening rate θ Analyze the relationship between critical stress and critical strain,construct a dynamic recrystallization critical condition model and a dynamic recrystallization grain size model.The constructed constitutive model and dynamic recrystallization prediction model were embedded into Deform simulation software to simulate the hot stretching process.(3)Through metallographic observation,EBSD analysis,and fracture scanning,the influence of different deformation conditions on the microstructure evolution of the alloy was analyzed.The dynamic recrystallization mechanism and fracture mechanism were analyzed,and compared with numerical simulation results to verify the accuracy of the dynamic recrystallization model.