Contribution of grain boundary sliding in low-temperature superplasticity of ultrafine-grained aluminum alloys

摘要

Ultrafine-grained (0.6 mum) Al-Mg-Sc alloy with predominant high-angle boundaries was produced by friction stir processing. A superplastic elongation of 210 percent was obtained at 175 deg C, and the optimum strain rate and maximum elongation increased with increasing temperature. Marker lines were scratched on the polished specimen surfaces using a nano-indenter to measure grain boundary sliding (GBS) offsets during deformation, which indicated that the GBS contribution to the strain exceeded 50 percent at 175 deg C and increased with increases in strain and temperature.