Abstract
The present work was performed on two composites: Al-15vol.% B4C and experimental 6063/15% B4C. Additions of 0.45% Ti + 0.25% Zr were made to both composites melts. The composites were cast from the respective melts at 730? using two metallic molds to produce tensile as well as impact test samples. All samples were solution heat treated for 24h at 540? for both composites, followed by aging at 200? for 10h. Samples for microstructure and fractography were examined using field emission scanning electron microscopy. The results show that the powder injection technique used in this study produces composites with B4C uniformly distributed throughout the matrix. The strength and impact toughness of the two composites are controlled by the simultaneous precipitation of Al3Zr and Mg2Si phase particles depending on the matrix type. Hardening caused by precipitation of Mg2Si is more pronounced than that caused by Al3Zr phase precipitation. No B4C particle debonding was observed due to the presence of Zr-/Ti-rich layers surrounding the B4C particles. The cracks mainly propagate through the B4C reinforcement particles.