Effects Of Hot Rolling Processes On The Microstructure And Mechanical Properties Of AZ31 Magnesium Alloy

In this work, the effects of three different hot rolling processes, i.e. accumulate rolling bonding(ARB), large strain hot rolling(LSHR) and homogeneous hot rolling(HR), on the microstructure and mechanical properties of AZ31 Mg alloy were studied. The asreceived AZ31 Mg alloy was annealed at 400℃ for 3 hours. Then the material was deformed at 400℃ with a rolling speed of 0.44m/s to different strains by three processing. The as-processed materials were then annealed at series of temperatures from room temperature to 400 oC. After rolling process and annealing treatment, the mechanical properties of each sample was measured by tensile test. Optic microscopy, SEM-EBSD and TEM were used to characterize the microstructures and textures of samples after deformation and annealing. The plastic forming ability of the alloy was discussed, the structural and textural evolutions of AZ31 Mg alloys during annealing were analyzed in details and deformation mechanism was discussed. The following conclusions can be drawn:(1)All three kinds of rolling processe can refine the grain size of AZ31 alloy. ARB and LSHR is more effective to refine the grain size than HR does.(2)Bimodal lamella structure were produced in AZ31 by ARB and LSHR.(3)After rolling, the texture of AZ31 Mg alloy is(0002) basal texture. Annealing of AZ31 Mg alloy sheet can hardly modify the texture.(4)The samples after plastic deformation and low temperature annealing has excellent mechanical properties. The strengthes of these samples are slightly lower than the deformed sample while the ductilities are similar to fully annealed sample the or even better. After 2-cycle ARB and 250 ℃ annealing, the yield strength and enlongation of ARBed samples are 203 MPa and 26%, repectively. After LSHT to 75% and 180℃annealing. The yield strength and enlongation of LSHRed samples are 230 MPa and 27%, respectively.(5)The ARBed samples after annealing at low temperature derive their high ductility from their high work-hardening rate. The good ductility of ARBed samples may be contributed by the bimodal lamella structure, grain size and non-basal slip.