Hybrid reinforced aluminum matrix composites fabricated by selective laser melting

Abstract In this work, near full density and crack-free hybrid aluminum matrix composites (HAMCs) reinforced with Cr3C2 ceramic particles and Ni–Cr trace elements were successfully fabricated by selective laser melting (SLM). The phase structure, microstructure, mechanical properties and strengthening mechanism of HAMCs were investigated. The results show that various intermetallic compounds, such as Al13Cr2, Al11Cr2 and Al3Ni etc. are generated in HAMCs for the incorporation of trace elements Ni and Cr. These hard-intermetallic compounds provide significant precipitation strengthening effect. Moreover, additions of Cr exert a solid solution strengthening effect because of its good solubility in Al. For the Cr3C2 ceramic, the load transfer from matrix to the reinforcing particles plays an important role on strengthening metal matrix composites. And acicular Al4C3 is formed at the interface between Cr3C2 and the matrix, which improves the interface bonding strength. With various positive strengthening mechanisms, the microhardness of HAMCs increases by 32% and the compressive strength increase by 22%. HAMCs exhibit excellent compressive strength. However, a significant reduction (26%) in tensile properties was found because the crack in the ceramic particle is more sensitive to tensile stress than compressive stress. Micro-particles Cr3C2 are the source of fracture failure of the tensile sample.