Hierarchical ultrafine-grained network mediated high strength and large plasticity in an Al-based alloy

An in-situ ultrafine-grained/nanocrystalline Al-based bulk alloy with ultrahigh strength and large compressive plasticity has been produced by copper mold casting. According to the microstructural investigations, hierarchical ultrafine-grained/nanocrystalline eutectic colonies consisting of α-Al and Y₃Al₂ with homogeneously embedded Ag₂Al nano-particles have been observed, besides few submicron-sized Al ₉Co₂. The macroscopic and microscopic structural heterogeneities are able to achieve ultrahigh strength of ~1.5 GPa and large plasticity of ~28%, which are considered to be attributed to the hierarchical network of strengthening intermetallic phases combining with deformable α-Al solid solution suppressing the propagation of microcracks or shear bands. This may promote another perspective on designing and obtaining ductile ultrahigh-strength Al-based alloys.