Deformation mechanisms of Al alloys containing shearable/non-shearable L12 precipitates: A comparative study under varied slip system activations

Although the shearing and bypassing mechanisms have been extensively studied in precipitation-hardened alloys, the effects of shearable and non-shearable precipitates under multiple slip system activation remain not fully understood. This study explores the influence of shearable and non-shearable Al₃(Sc, Zr) precipitates on the deformation behavior of Al–Mg–Sc–Zr alloy through micropillar compression tests under three distinct crystallographic orientations: single-slip, coplanar double-slip and non-coplanar double-slip. In single-slip micropillars, shearable precipitates allow dislocations to cut through, resulting in low dislocation storage. In contrast, non-shearable precipitates cause dislocations to bypass via Orowan looping, promoting secondary slip activation and increasing dislocation storage and strain hardening. In coplanar double-slip micropillars, the effect of precipitate type is diminished. Coplanar dislocation reactions forming quadrilateral dislocation structures that suppress secondary slip activation with non-shearable precipitates and increase dislocation storage in those with shearable precipitates, resulting in similar hardening behavior. However, in non-coplanar double-slip micropillars, the effect of precipitate type is drastically pronounced. In micropillars with non-shearable precipitates, complex dislocation interactions (between primary/secondary slip systems and non-coplanar reactive dislocations) lead to cellular dislocation structures and enhanced strain hardening. This work highlights the critical roles of precipitates and slip system activation in governing the underlying deformation mechanisms.