On the Breakdown of SiC during the Selective Laser Melting of Aluminum Matrix Composites

Selective laser melting (SLM) is used to produce a SiC reinforced aluminum metal matrix composite (AMMC, Al–12Si plus 10 vol% SiC) with laser energy densities ( ) between 20 and 80 J mm −3 . Microstructural analysis shows that at lower energies, SiC is present in the Al–12Si matrix; however, at higher energies there is a distinct lack of SiC particles and the extensive formation of Al 4 C 3 needles and primary Si particles. XRD analysis confirms a decrease in the volume of SiC and an increase in the amount of Al 4 C 3 and primary Si with increasing . This indicates that a reaction occurs between the Al and SiC during SLM. The underlying mechanism is attributed to the selective absorption of laser energy into the SiC particles, causing regions of extremely high temperatures. The formation of the reaction products cause errors in the theoretical density calculations. Therefore, X‐ray micro tomography (XMT) is used to independently measure the relative density of the samples with a peak relative density ≈97.4%, which is much higher than that (relative density ≈93%) measured using the Archimedes method.