Manufacturability and microstructure of AlSi10Mg/SiC composites with different volume fractions of SiC using laser powder bed fusion

In the present study commercially available AlSi10Mg and SiC powders were mixed in a tumble mixer with resulting compositions of 5, 15 and 25 vol% SiC and processed using laser powder bed fusion. Different process parameters were used to manufacture samples which were characterized by various properties, such as porosity, microstructure and occurring phases to evaluate the manufacturability of the powder mixtures. The samples showed increasing porosity with lowered volumetric energy density and increasing SiC content. Relative densities of about 93.0% (25 vol% SiC), 94.5% (15 vol% SiC) and 98.5% (5 vol% SiC) respectively could be achieved. In addition, the correlation between the used energy density and the retained SiC particles in the samples was investigated. The quantity of retained SiC particles correlates negatively with the achievable density for all compositions, making compromises between these two properties necessary depending on the desired application. It is shown that SiC can get dissolved due to the high absorption of the laser energy resulting in the formation of primary silicon crystals as well as Al$_4$C$_3$ and Al$_4$SiC$_4$ phases. ... mehrMicrostructure characterizations using AFM revealed the influence of the SiC fraction on the eutectic structure and the formation of the new phases. Finally, EDS and TOF-SIMS analysis showed that the formed Al$_4$C$_3$ phase can react with the humidity of ambient air at the surface, leading to localized cracks due to AlOOH formation.