Grain boundary mobility under a stored-energy driving force: a comparison to curvature-driven boundary migration

Grain boundary mobility has been measured in high-purity aluminum alloyed with 0.03 wt.% Zr using energy stored during plastic deformation as a driving force. In general, the dependence of mobility on grain boundary character was similar to that observed by previous authors with a maximum in mobility in the vicinity of the Sigma 7 type (38 degrees < 111 >). The exact location of the mobility maximum varied, however, with temperature in a manner similar to that observed for curvature-driven mobility measurements. Although < 111 > tilt boundaries exhibit high mobilities in general, the single peak at the Sigma 7 position at low temperatures changes to a double peak at high temperatures with a local minimum at Sigma 7. The combination of mobility variation and the thermal activation analysis of the results points to a compensation temperature effect. All these results suggest that grain boundary mobility is a true material property.