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 R a 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.

Effect of process parameters on the microstructure and mechanical properties of AA2024 fabricated using selective laser melting

“…A slower cooling rate allows more grain growth, increasing the coarse-grained microstructure formation [32]. It has previously been observed that thermal gradients, which are created by using different hatch spacing parameters, can result in the formation of these different microstructures and that both fine-grained and coarse-grained microstructures can be found around the HAZ in a single sample [33]. Owing to these thermal gradients, columnar grains can form during the solidification process, which then grow from the top to the bottom of the melt pool [17].…”

Additive manufacturing of high-strength crack-free Ni-based Hastelloy X superalloy

“…In addition, the cost of the extra post-processing reduces the economic attractiveness of metal LPBF. Therefore, this type of posttreatment hence does not represent an ideal alternative in order to mitigate hot cracking defects and limit their effect on the mechanical behaviour of nickel-based superalloys [22][23] [24]. Sanchez-Mata et al [25] investigated the microstructure of LPBF-fabricated HX, and cracks were not observed under their optical microscopy examination, however the detailed process parameters that were employed were not disclosed.…”

Gold, Silver, and Electrum Electroless Plating on Additively Manufactured Laser Powder-Bed Fusion AlSi10Mg Parts: A Review

“…Understanding the influence of main LPBF processing parameters on the surface roughness of AM components can be used for additional process optimization [11]. Surface post-processing techniques, such as heat treatment, shot peening, polishing, sand blasting, and coatings [12], and the resulting part qualities for the AlSi10Mg alloy have been discussed before [13][14][15]. Yet, surface post-processing techniques increase the production time and cost [12].…”