Effect Of Solution And Pre-aging Treatment On Thermal Tensile Behavior And Microstructure Of Extruded AZ80 Magnesium Alloy

Magnesium alloys have excellent properties and potential application,and meet the new requirements for the sustainable and lightweight development of materials in the 21st century.In recent years,the exploration and development of high strength wrought magnesium alloy is a trend at home and abroad.AZ80 magnesium alloy,as a higher strength alloy in the traditional Mg-Al-Zn magnesium alloys,has obvious aging strengthening effect.In this paper,the AZ80 magnesium alloy was treated with solution and pre-aging heat treatment.Combined with thermal tensile test,numerical simulation and other testing methods,deformed condition and the effect of pre-precipitatedβ-Mg₁₇Al₁₂ phase on the thermal deformation behavior and microstructure of solution and pre-aging AZ80 magnesium alloy was investigated.The main work and conclusions are as follows:The thermal tensile stress-strain curves of the solution and pre-aging AZ80magnesium alloy in the range of 150⁴00°C were basically the same,with the increase of temperature,the maximum flow stress decreased and the elongation increased that shows a typical dynamic recrystallization（DRX）process.However,the DRX volume fraction of pre-aging specimens was significantly higher than the solid solution samples at the same temperature,and the temperature of the recrystallization of the pre-aging specimens was about 50°C earlier.Temperature and deformation has a significant effect on the microstructure of solution and pre-aging AZ80 magnesium alloy after hot tensile deformation,and the temperature was one of the main factors.In lower temperature（<300°C）,with the increase of temperature and deformation,the volume fraction of DRX particles andβ-phase particles increased,and the grains was obviously refined.In higher temperature（≥300°C）,DRX process was completed and grains growed,the influence of temperature and deformation on the microstructure was weaker.The dynamic precipitation（DP）phenomenon occured in the thermal tensile process,andβ-phase particles are dynamically deposited along the equiaxed grain boundaries or the DRX grain boundaries.The pre-aging precipitates provide more nucleation cores for the alloy and play a significant role in grain refinement.Pre-aging precipitation had an important influence on the thermal tensile properties of AZ80 magnesium alloy.The pre-aging precipitation phase could greatly reduce the tensile strength and obviously improved the elongation at lower temperature（150³00°C）,which was beneficial to low-temperature plastic processing;the tensile strength was increased at above 300°C;250³00°C is the critical transition temperature range for the mechanical properties of solid solution and pre-aging alloy.The thermal tensile specimens of solution and pre-aging AZ80 magnesium alloy have ductile fractures.The fracture of non-precipitated sample was along the grain boundaries,and with precipitated phase fractured at the interface between the matrix and the precipitated phase.In addition,a numerical simulation of the thermal tensile deformation process of magnesium alloy was performed to analyze the stress and failure position evolution at different temperature in detail,simulation results were in good agreement with experimental results.