Accelerating and decelerating effects of Gd content and peak-aging treatment on the grain growth of magnesium

Abstract

This short communication concerns the dependence of thermal stability of fine grains in Mg alloy on the Gd content. The enhanced thermal stability via increasing Gd content can be reflected by the SRX mechanism and corresponding boundary migration ability. In the low Gd-alloyed Mg, continuous SRX dominates the annealing process via dislocation re-arrangement. The grain boundaries composed by dislocations can easily migrate, since the uniform Gd solute distribution provides limited delaying effect. In the high Gd-alloyed Mg, discontinuous SRX dominates the annealing process via consuming dislocations for grain nucleation. The grain boundaries can hardly migrate due to the strong delaying effect provided by the Gd-segregation along grain boundaries. But unexpectedly, peak-aging can deteriorate the decelerated effect of high Gd-alloying owing to the absent Gd-segregation. Consequently, an accelerated grain growth rate is attained, even faster than that in the low Gd-alloyed Mg.