Investigation of the microstructure and mechanical properties of NbB2 particle reinforced aluminum matrix composites

Abstract A mixture of Nb powder and boron salt (KBF4) was added to aluminum alloy melt to prepare particle reinforced aluminum matrix composites at 850 °C. Microstructure, fracture morphology, and the chemical composition of the composite were characterized using scanning electron microscopy, energy dispersive X-ray spectroscopy and X-ray diffraction. The average size of NbB2 in the studied composites is found to be about 0.3 μm under optimal process parameters. The size of primary silicon particles is refined from 60–100 μm to 30–50 μm. Tensile testing results reveal that the reinforced composite exhibits higher microhardness, tensile strength, yield strength and poorer ductility than those of the matrix alloy. The fracture mode is found to be brittle fracture, which is mainly dominated by silicon particle cracking and NbB2 particle–matrix debonding.