Achieving a heterogeneous lamella-structured aluminum alloy with excellent synergy of strength and ductility by powder thixoforming

A lamella structured aluminum alloy with multiple heterogeneities of grain size and composition was prepared by a previously unidentified casting method, powder thixoforming, through mixing harder and softer component alloy powders together. The lamella structure with multiple heterogeneities enabled the resultant alloy to possess an ultimate tensile strength of 346 MPa and a uniform elongation of 16.2%, which represented an increase of 9.5% in comparison with the strength of harder component alloy and an enhancement of 20% compared to the ductility of softer component alloy, exhibiting an excellent strength-ductility synergy. A strong effect of strain partitioning was clearly evidenced in such a structure by in-situ scanning electron microscope observation, through which the underlying mechanisms for strengthening and toughening were clarified. The results obtained in this work would provide a simple promising approach to fabricate lamella structured metallic materials with high tensile performance. • Powder thixoforming was used to produce heterogeneous lamella structure with relatively low cost and good formability. • Multiple heterogeneities of grain size and grain composition were coupled in the lamella structure (LS&M structure). • The LS&M structured alloy exhibited an excellent strength-ductility synergy. • The superior ductility was ascribed to large strain partitioning from the LS&M structure. • The high strength resulted mainly from geometrically necessary dislocation strengthening due to obvious strain partitioning.