Effect of Al alloys on selective laser melting behaviour and microstructure of in situ formed particle reinforced composites

This work investigates the effects of various Al alloys (including Al, AlMg1SiCu, and AlSi10Mg), mixed with 15 wt% Fe2O3, on the selective laser melting (SLM) facilitated in situ reaction and formation of Al metal matrix composite (MMC) components. The results contribute to the development of medium/high strength Al composite parts which can be produced as complex net-shape products via the SLM process. Visual observation and computed tomography (CT) scanning reveal the best SLM consolidation performance and the lowest porosity for AlSi10Mg. SLM facilitated in situ reaction and subsequent rapid solidification introduce very fine particles (down to similar to 50-100 nm), reinforcing the microstructure of all Al (alloy) composites. The particles are Al-Fe intermetallics, Al oxides such as alpha-Al2O3, plus Si crystals (alone or in combination) depending on the alloy composition. Ultrafine/nanoscale dendritic feature appears in the reinforced matrix of AlSi10Mg/15 wt% Fe2O3, in contrast with featureless matrix of Al/15 wt% Fe2O3. The in situ particle reinforced Al (alloy) composites are significantly harder than corresponding conventionally manufactured (e. g. casting) Al alloys without Fe2O3, due to superior microstructural characteristics such as featureless or very fine dendritic matrix, ultrafine/nanoscale particles, and also enhanced solid solubility of the SLM products. (C) 2012 Elsevier B. V. All rights reserved.