Effects of processing parameters and heat treatment on thermal conductivity of additively manufactured AlSi10Mg by selective laser melting

This work investigates the thermal conductivity of parts which have been additively manufactured using the aluminium alloy AlSi10Mg by selective laser melting, a laser-based powder bed fusion technique. Thermal conductivity characterisation is of particular importance to thermal engineers wishing to make use of additive manufacturing in next generation thermal management solutions. A number of processing parameters and scanning strategies were employed to fabricate samples for experimental characterisation. While the porosity of produced parts had a significant impact on thermal conductivity, after an anneal heat treatment post-processing step, thermal conductivity increased by 18–41% without any measurable change in porosity. Even though the parts produced with the “points” strategy have higher levels of porosity compared to the “contour-hatch” strategy, it has been found that after the heat treatment step, its thermal conductivity can be increased up to the “contour-hatch” strategy. Analysis of the resulting microstructures using scanning electron microscope and energy-dispersive X-ray showed precipitation and coalescence of Si with increasing heat treatment temperature, with dwell time having a lower impact. While there is a desire for additively manufactured parts with little to no porosity, it has been shown in this study that it is possible to reduce laser energy density requirements by approximately one order of magnitude and still produce parts with acceptable levels of thermal conductivity which could be used for components that are not subjected to strenuous loading conditions, such as heat sinks.