Tailoring strain delocalization in particle-reinforced metal matrix composites toward strength-ductility synergy through core-shell heterostructured metallic building blocks

Abstract

Particle-reinforced metal matrix composites (PRMMCs) suffer from severe strain localization stemming from the mechanical incompatibility between hard reinforcements and soft metallic matrices. To overcome this challenge, SiC-nanoparticle-decorated aluminum powder was subjected to low-energy ball milling to produce core-shell heterostructured building blocks composed of ultrafine-grained (UFG) shells surrounding coarse-grained (CG) cores. Upon consolidation with micro-SiC particles, these building blocks induce a bulk composite featuring a dual core-shell architecture of CG-UFG matrix and SiC-UFG particles. Mechanistically, the UFG shells served distinct and complementary functions: Those around the CG in the matrix provided a hetero-deformation-induced strengthening contribution of ∼68 MPa (∼14% of yield strength) via long-range back stresses arising from hetero-interfaces; concurrently, those around micro-SiC particles suppressed strain localization at particle-matrix interfaces and promoted macroscale uniform deformation. As a result, an exceptional tensile strength of ∼685 ± 26 MPa combined with > 8% elongation was achieved. Therefore, the featured dual core-shell architecture induced by CG-UFG metallic building blocks offers a robust design route for achieving strength-ductility synergy in PRMMCs.