Selective laser melting of in-situ Al4SiC4 + SiC hybrid reinforced Al matrix composites: Influence of starting SiC particle size

Selective laser melting (SLM) additive manufacturing of the SiC/AlSi10Mg composite powder systems with different starting SiC particle sizes was performed to produce in-situ Al4SiC4 + SiC hybrid reinforced Al matrix composites. The influence of starting SiC particle size on the constitutional phases, microstructural features, and mechanical properties of the SLM-processed composite parts was studied. As the SiC particle size decreased, the extent of in-situ reaction between aluminum melt and SiC particles was enhanced, leading to the elevated formation of Al4SiC4 reinforcing phase. With the fine SiC particles (D50 = 5 μm) used, the residual SiC particles with a reduced size of 3 μm were dispersed homogeneously throughout the matrix, thereby enhancing the microstructural homogeneity of the part. With the enhancement of in-situ reaction, the formation of plate-like and particle-structured Al4SiC4 reinforcement was significantly accelerated, favoring the formation of (Al4SiC4 + SiC)/Al hybrid reinforced composites after SLM. Using fine SiC particles, the reinforcement/matrix wettability was improved, leading to a nearly full densification level of 97.2% theoretical density of SLM-processed part. The microhardness of 218.5 HV0.1 showed at least 50% improvement upon SLM-processed unreinforced AlSi10Mg. The fine SiC particles also reduced the coefficient of friction (COF) by 19% and the wear rate by 66% compared to the SLM part processed with coarse SiC particles.