Synergistic enhancement of strength and ductility in novel solid-stir continuous extrusion: Influence of heterogeneous microstructure and alloy chemistry

Abstract

Friction stir-derived solid-state processes leverage the synergistic effect of frictional heating and intense shear deformation to achieve localized microstructural modification for the improvement of mechanical properties. In the present work, a novel processing route called solid-stir extrusion (SSE) has been explored for continuous, high-rate extrusion of a high strength non-age-hardenable-AlMgSc alloy. In the current study, loss of strength associated with frictional heating during the process is mitigated as elevated strength is observed in as-extruded condition, thereby eliminating the need for post process heat treatment. The effect of process attributes on mechanical property and microstructure evolution was investigated. The SSE process caused extensive grain refinement and fragmentation of thermally stable Al3Sc intermetallic periodically at shear bands, which contributes to the elevated mechanical strength. The spatial variation in mechanical properties and microstructural heterogeneity was characterized using nanoindentation and microstructural correlation. The current findings indicate the significance of the process-specific alloy design approach to increase performance of material in as-processed condition.