Effects of Manufacturing Processes on Microstructure and Properties of Al/A356-B4C Composites

Liquid and semi-solid stir casting processes were applied to fabricate B4C particles-reinforced aluminum-matrix composites. The effects of manufacturing processes on particle distribution, particle/matrix interface, and mechanical properties of the prepared composites were studied. The results show that particle distribution can be significantly improved by using K2TiF6-flux and Ti powders in the liquid stir casting process, whereas in the semi-solid stir casting process it could be improved by decreasing the temperature of the slurry. With additions of Ti, the decomposition of B4C was prevented, and the interfacial bonding strength was significantly improved due to the fact that a TiB2 layer formed at the particle/matrix interface. Compared to the matrix, the hardness and tensile strength of the Al-B4C composite fabricated by the liquid stir casting process were increased by 89.6% and 128.8%, respectively; those of the A356-B4C composite fabricated by the semi-solid stir casting process had no significant improvement due to the weak particle/matrix interface and the presence of particle porosity clusters.