Study On Microstructure And Properties Of AZ31 Magnesium Alloy By Friction Stir Processing

Magnesium alloys are the lightest metal structure material,which have high specific strength,good electromagnetic shielding performance as well as damping property.Due to the less symmetrical crystal structure,magnesium alloys always show poor formability,which restricts their wider industrial application.Previous research work shows that grain refinement could improve the ductility and strength simultaneously for magnesium alloys.Friction stir processing(FSP),as one of severe plastic deformation method,would significantly refine the grain size.Thus in the present work,the microstructure evolution during Friction stir process was investigated for AZ31 magnesium alloy,as well as the plastic behavior during ambient tensile test.Hot rolling was also conducted for the FSPed sheet.TEM and SEM-EBSD technique was employed to analyze the twinning,dynamic recrystallization(DRX)during hot-rolling process.The experimental results showed that FSP refined the original grain size effectively,which increased the tensile strength and ductility simultaneously.However the yield strength was reduced.During hot-rolling process,? twinning played an important role at early strain stage.On furtherstaining,DRX started to initiate at original grain boundaries,which produced a neck-lace like structure at higher strain range.Moreover,low angle sub-grains were formed in matrix.Micro-texture results show that the formation of such sub-grains followed the orientation gradient from matrix while the DRX grains did not.