Initial-grain-size dependency of high-temperature deformation behavior and microstructural change of AZ80Mg alloys
AZ80Mg alloys with having different initial grain sizes from 0.53μm to 16 μm were prepared in advance by means of multi-directional forging. They were deformed in compression at various testing conditions of true strain rates from 5.0 × 10-4 s-1 to 5.0 × 10-1 s-1 and temperatures between 423 K and 673 K. The coarser-grained samples showed large anisotropy of high-temperature deformation behavior and less significant dependency on temperature and strain rate, whereas those of finer-grained ones exhibited opposite behaviors. Change in the microstructure was also strongly depended on the initial grain size. While twinning and kinking as well as dynamic recrystallization contributed to microstructural changes in the coarser grain-sized samples, only simple grain coarsening appeared in the finer-grain sized ones. These grain-sized dependent deformation behaviors are precisely discussed from the differences in evolution of deformation-induced microstructures, thermal stability and grain-boundary sliding.
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