Microstructure And Mechanical Properties Of AZ80 Magnesium By Extrusion

Magnesium(Mg)alloys are most promising structural metallic materials in the 21^stcentury due to their low density,and researches whom aim to expand its application in transportation sectors are gradually attracting world widely attention.The wrought magnesium alloy showed better mechanical properties than the cast magnesium counterpart and exhibited a wider range of applications.However,compared with other metals,the strength of magnesium alloys is still low,and how to improve its mechanical properties has been widely concerned.Therefore,the preparation of magnesium alloys with low cost and high performance would extend market prospects.In this study,AZ80 alloy was selected.After introduced pre-extrusion(PE),the secondary forming behavior of AZ80 alloy(including extrusion and caliber rolling)was investigated and the effects of PE process on the microstructure and mechanical properties was analyzed in detail.Moreover,the influence of the solution heat treatment(T4)before extrusion and caliber rolling on the microstructure and mechanical properties of the alloy was also studied.Based on this,the high performance AZ80 wrought magnesium alloy was successfully prepared,and the yield strength,tensile strength and elongation at break were 249 MPa,440 MPa and 15.1%,respectively.In addition,the hot deformation behavior of pre-extruded AZ80 alloy was studied by hot compression deformation test in the temperature range of 200-400?and strain rate of 0.001-10s^-1.The results reveal that the true stress-strain curve of PE alloy exhibits obvious dynamic recrystallization(DRX)characteristics and the thermal constitutive equation is established based on the Arrhenius type hyperbolic sine equation.Moreover,the processing maps corresponding to different true strains are also constructed.It was found that the true strain plays a significant role in processing window of studied alloy,and we determine the optimal processing parameters of PE alloy based on the processing map and microstructure analysis.Grains are remarkably refined due to DRX during the extrusion and caliber rolling processes,a strong base texture was formed,and the second phase broken and distributed along the deformation direction.The PE process increases the strength and elongation of both extruded and rolled alloys.For the extrusion deformation,the AZ80 alloy extruded after PE process shows the stronger texture and solid solution strengthening than that of AZ80 alloy extruded without PE.In case of rolling deformation,PE process greatly improves the plastic working behavior of as-cast alloys and the enhancement in strength and ductility is attributed mainly to the nano-scale second phase precipitated during rolling process.In addition,the AZ80 alloy extruded or rolled after T4 exhibits a higher yield strength than that of AZ80 alloy extruded or rolled without heat treatment.This is because the intense super-saturation of?-Mg matrix,which enhances the solid solution strengthening effect in the extruded alloy,and promotes the dynamic precipitation of the nano-second particles in the rolling process.