Selective laser melting of in-situ formed nano SiC-reinforced AlSi10Mg composite: Microstructural and mechanical properties

Abstract

In this work, a chemical reduction method was developed to produce AlSi10Mg powders uniformly coated with a graphene-oxide-derived carbon layer (rGO/AlSi10Mg powders, where rGO denotes partially reduced graphene oxide). The composite (designated as SiC-AlSi10Mg) was then fabricated using selective laser melting (SLM). The microstructure of the as-built composite is remarkably refined, its average grain size decreases to approximately 5.1 μm, compared with the heterogeneous, coarser-grain structure of the SLM AlSi10Mg alloy (featuring coarse grains reaching 15–20 μm). During SLM, combined evidence from XRD, Raman spectroscopy, EDS and HRTEM suggests the possible in-situ formation of minor nanoscale SiC, with carbon originating from partially reduced graphene oxide and silicon from the AlSi10Mg alloy. These potentially in-situ formed SiC particles tend to segregate at grain boundaries, correlating with increased dislocation density. The SLM SiC-AlSi10Mg alloy delivers a superior combination of mechanical properties: its tensile strength (ultimate tensile strength ~467 MPa, yield strength ~383 MPa) and microhardness (161.2 HV0.1) significantly exceed those of the SLM AlSi10Mg alloy (~401 MPa, ~275 MPa, and ~116.9 HV0.1, respectively). Notably, such property improvement is not achieved at the expense of ductility; instead, the elongation increase from 8.6% to 16.1%. The concurrent enhancement of strength and ductility arises from the combined contributions of dislocation generation, grain refinement, the potential formation of trace SiC, and residual graphene‑derived phases.