Novel Aluminum Based Composites by Selective Laser Melting (SLM) Additive Manufacturing (AM): Tailored Formation of Multiple Reinforcing Phases and its Mechanisms

Abstract

Selective laser melting (SLM) of the SiC/AlSi10Mg composites was performed to prepare the Al-based composites with the multiple reinforcing phases. The influence of the SLM processing parameters on the constitutional phases, microstructural features, and mechanical performance of the SLM-processed Al-based composites was studied. The reinforcing phases in the SLM-processed Al-based composites included the unmelted micron-sized SiC particles, the in situ formed micron-sized Al4SiC4 strips, and the in situ produced submicron Al4SiC4 particles. As the input “linear laser energy density” (LED) increased, the extent of the in situ reaction between the SiC particles and the Al matrix increased, resulting in a larger degree of formation of Al4SiC4 reinforcement. The densification rate of the SLM-processed Al-based composite parts increased as the applied LED increased. A sufficiently high density (~ 96 % theoretical density) was achieved for LED larger than 1000 J/m. Due to the generation of the multiple reinforcing phases, elevated mechanical properties were obtained for the SLM-processed Al-based composites, showing a high microhardness of 214 HV0.1, a considerably low coefficient of friction (COF) of 0.39, and a reduced wear rate of 1.56 × 10−5mm3N−1m−1. At an excessive laser energy input, the grain size of the in situ formed Al4SiC4 reinforcing phase, both the strip- and particle-structured Al4SiC4, increased markedly. The significant grain coarsening and formation of the interfacial microscopic shrinkage porosity lowered the mechanical properties of the SLM-processed Al-based composites.