Densification and microstructural evolution during laser sintering of A356/SiC composite powders

This article reports experimental results on laser sintering of A356 aluminum alloy and A356/SiC composite powders. Effects of scan rate, sintering atmosphere, hatch spacing, and SiC volume fraction (up to 20%), and particle size (7 and 17 m) on the densification were studied. The phase formation and microstructural development were analyzed by X-ray diffraction (XRD) and scanning electron microscopy (SEM) coupled with energy-dispersive X-ray spectroscopy (EDS). Laser sintering under argon atmosphere exhibited higher densification compared to nitrogen. A faster sintering kinetics was observed as the scan rate decreased. Except at a low SiC content (5 vol%), the composite powders exhibited lower densification kinetics. The densification was improved when finer SiC particles were utilized. Microstructural studies revealed directional solidification of aluminum melt to form columnar grains with inter-columnar silicon precipitates. In the presence of SiC particles, aluminum melt reacted with the ceramic particles to form Al4SiC4 plates.