Microstructure and mechanical properties of Al – 3Mg – 0.25 Sc alloy sheets produced by cryorolling

Abstract

Al-3Mg-0.25Sc alloy with 50% and 75% rolling reductions from the initial thickness at room and cryogenic temperatures resulted in a higher dislocation density, enhanced lattice strain and reduced crystallite size for the cryorolled (CR) sample with 75% reduction (CR 75). A hierarchical grain size distribution was noted in CR samples through electron backscattered diffraction studies that led to a combination of 490 MPa of strength and 27% of ductility in CR 75. Also, due to hierarchical grain distribution, during the tensile test, deformation was expected to follow a complex strain distribution rather than localised necking, which had resulted in higher elongation. Further, a low mechanical anisotropy and a proportional decrement in texture index with a higher fraction of Cube texture enhanced the ductility of CR 75 among the rolled samples. Higher work hardening rate was reported by the CR samples than that of room temperature rolled (RTR) ones due to the influence of cryorolling and the existence of Al3Sc precipitates. Among the rolled samples, the CR 75 sample reported a higher necking percentage of 24% based on the stress based necking limit and fracture limit diagram, which indicated its ability to withstand higher strain before failure was consistent with the mechanical properties reported.