Effect of heat treatment and laser surface remelting on AlSi10Mg alloy fabricated by selective laser melting

Abstract

The selective laser melting (SLM) of aluminium alloys is of interest to researchers because of these alloys’ potential applications in the aerospace and automotive domains. Post-processing is generally required in order to enhance the mechanical properties of devices that involve moving parts, where surface mechanical properties are significant factors. This paper describes a preliminary study that was conducted to investigate the effect of post-processing on the microstructure and mechanical properties of SLM fabricated AlSi10Mg alloy, with an emphasis on the laser surface remelting (LSR) process. The experimental results demonstrate that the heat treatment degraded tensile strength while improving ductility by achieving grain growth and residual stress release. The yield strength obtained in the experiment was reduced from 200 to 100 MPa, whereas the elongation increased from 6 to 22%. The LSR process was found to contribute to an improvement in surface finish. The surface roughness indicator Ra was determined to be 0.93 μm in the LSR post-processed sample, compared to a fairly high value of 19.3 μm in the as-fabricated samples. The LSR process also enhanced the microhardness by refining the microstructure; the Si eutectic dendritic structure that formed was found to be finer than that of the as-fabricated samples. Compared to the as-fabricated samples, the LSR process contributed to a 19.5% increase in microhardness. The findings suggest that the microstructure and mechanical properties of SLM-fabricated AlSi10Mg parts could be tailored by suitable post-processing such as heat treatment and LSR. The significance of this research is its proposal of a novel technique to enhance surface hardness using LSR, which is a significant step towards the combination of SLM and LSR processes to manufacture customised aluminium components for the automotive and aerospace sectors.