Microstructural analysis of fine-grained magnesium after cyclic tension–tension fatigue testing at 0 °C

Abstract

Microstructures were characterized for the fine-grained magnesium samples that experienced tension–tension fatigue testing and quasi-static tensile testing at 0 °C. Three fatigue cases were selected based on the relation between the maximum loading stress (σmax) of fatigue testing and the material's yield strength (σy). σmax was lower than σy for the first case, about equal to σy for the second case, and higher than σy for the third case. No tensile twinning was observed in the tested samples. With the increase of σmax experienced by the material, the number of small grains decreased and the number of large grains increased in the tested samples. Average grain size became larger for the samples after testing, and it increased linearly with the increase of σmax. Grain growth began with the merging of the blocks of small grains and continued with the merging of small grains to the neighboring large grains through grain rotation when σmax was increased.