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Microstructural evolution of ZK60 magnesium alloys, during twin roll cast (TRC) and hot compression (HC) with a strain rate of 0.1 s -1 at 350°C and subsequent annealing at temperatures of 250-400°C for 10 2 -5 9 10 5 s, has been observed by optical microscopy (OM), transmission electron microscopy (TEM) and electron backscatter diffraction (EBSD). The distribution of average grain size and recrystallized grain size at different annealing conditions were calculated. Activation energy and recrystallized volume fractions during annealing were discussed using analysis of static recrystallization (SRX) kinetics. Based on examination of microstructure evolution during annealing, it was found that several SRX mechanisms were co-activated. Subgrains with high misorientation angles to surrounding grains were formed by dislocation rearrangement, and they seemed to evolve into newly recrystallized grains.

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The flow stress of A7A1M (Mg-Al-Zn-Mn-Ca) and ZK 60 (Mg-Zn-Zr) wrought magnesium alloys under the deformation conditions of twin rolling casting and hot compression at different temperature and strain rates was studied. Deformation behavior and failure mechanism of them were discussed. Microstructure evolutions were analyzed by optical micro structure and electron backscatter diffraction technique. The results have indicated that AZ41M and ZK 60 have different strain-stress curve under the same conditions. Working hardening results in occurrence of cracks in or around the shear bands. The reoystallized, equiaxed, and fined grains in shear bands attribute to recovery and recrystallization, grains refinement causes local working hardening as well as decreases of crack tip driving forces. Stress concentrated in shear bands causes crack initiation and propagation. Nucleus of cracks due to casting defects is another failure mode. With the increase of strain, dislocation rearranged in subgrain level while the low angle grain boundaries continuously evolved into high angle grain boundaries.