Abstract
Mg alloys need to be deformed at high temperatures to develop structural vehicles caused by crystal structure of Mg alloy. In this study, the effects of grain size on the deformation strength of Mg alloys under high-temperature deformation were examined in order to understand the deformation properties of Mg alloys at high temperatures. In this present study, external parameters, namely, the mechanical properties and strain rate, and an internal parameter, namely, the grain size, of the Mg alloy were investigated. Tensile tests were conducted at 623 K on three types of AZ31Mg alloys with different grain sizes at initial strain rates of 1x10^-1 to 1x10^-4 s^-1. It was found that the relationship between deformation stress and grain size is given by σ∝d^b ; this relationship serves as a model of the grain-boundary sliding. It was found that deformation stress was affected by the deformation mechanism. The magnitude of the reduction in the strength increased as the grain-boundary sliding became more dominant, and the internal stress caused by the grain-boundary sliding increased as the grain size decreased.
