Bulk nanostructured Al-Si alloy with remarkable improvement in strength and ductility

Abstract

Refinement of microstructure for metallic materials alloyed by low-soluble elements has always been a difficult task. Here we propose a novel two-step route to achieve this goal, which has been successfully applied to a hypoeutectic Al-Si alloy. Al-Si single-phase alloy first prepared by solution treatment under ultra-high isostatic pressure was then subjected to high-pressure torsion, obtaining a bulk nanostructured hypoeutectic Al-Si alloy for the first time. The ultrafine Al grains, Si nano-particles, concentrated Si solutes and dislocations greatly contributed to the yield strength. Meanwhile, the brittle fracture of micrometer-sized Si phase in common Al-Si alloys was avoided by refining Si to nanoscale, and the ductility was significantly enhanced. Consequently, the nanostructured Al-Si alloy exhibited a high yield strength of 403 MPa and a large total elongation of 32%. This work provides a promising approach for realizing bulk nanostructured alloys with low-soluble components.