Study On Microstructure And Hot-deformation Behavior Of AZ80+0.4% Ce Magnesium Alloy

The high-temperature mechanical behavior of AZ80+0.4% Ce magnesium alloy sheet at extrusion direction were tested using Gleeble-3500. Then,a constitutive model for the thermal deformation and thermal processing maps were established. The effects of different deforma-tion conditions on flow stress, microstructure evolution and critical point of dynamic recrysta-llization were analyzed.lt explains the reason why the defects of the structure happened and macroscopic morphology of the sample showed the ellipse. The effect of grain orientation on the properties of heat treatment was compared. The main conclusions are as follows:(1) The true stress-strain curves of AZ80+0.4%Ce magnesium alloy at a temperature of 300-420℃ and strain rate of 0.0005-0.5s-1 were showed the rheological characteristics of dy-namic recrystallization. The flow stress increases with the decrease of temperature and the in-crease of strain rate.Both the critical stress and the critical strain increase with the decrease of temperature and the increase of strain rate, the critical strain are within the range of 60 to 80% of peak strain, namely εc= (0.6～0.8) εp.(2) The hyperbolic sine Arrhenius model can accurately describe the relationship betw-een the flow stress σ, temperature T and strain rate ε. The activation energy Q was 163.287KJ /mol, The constitutive model of flow stress of AZ80+0.4%Ce magnesium alloy are as follow:(3) There are more Al11Ce3 phase and a small amount of Al-Mn phase in AZ80+0.4% Ce magnesium alloy, the Al11Ce3 phase became fragmentation chain during deformation. Dy- namic recrystallization grain size increased with the increase of the deformation temperature, but first decreased and then increased with the increase of the strain rate. The number of twins at low temperature and the volume fraction of dynamic recrystallization at high temperature increased with the increase of the strain. The nucleation of Dynamic recrystallization were at twin boundaries and original grain boundaries.(4) At low temperatures (300-340℃) and high strain rate (0.05-0.5s-1) localized deformation and cracks were found. The crack appears in four forms:wedge shape; holes; strip; crack along the massive development of rare earth ph- ase. Dynamic precipitation occurred in the microstructure at temperatures 300℃ and 340℃, The size and distribution of the precipitates are affected by the strain rate and deformation temperature.(5) The high power dissipation region and the unstable region in the extrusion direction (ED) are larger than normal direction (ND). Selection of 360-420℃,0.0025-0.0005s-1 as the AZ80+0.4%Ce magnesium alloy the best deformation parameters at extrusion direction (ED).