Fabrication of high strength yet light and low cost composite materials with good mechanical properties at room and elevated temperatures is a challenge that metallurgy and materials science communities are facing for many years. The primary goal of this study was to fabricate, characterize, and to carry out tensile tests on Al-based composite materials with commercially-available hexagonal BN particles as a reinforcement agent. The composites were fabricated by combination of high-energy ball milling and spark plasma sintering techniques.
The structures of powder mixtures and composite materials, as well as their fracture surfaces, were studied by scanning and transmission electron microscopy. The influence of BNNPs content (0.5, 1.5, 3, 4.5, 6, 7.5 and 10 wt.%) on the tensile strength was investigated. A maximum increase in strength was observed for the composites with 3.0 wt.% of BNNPs. This sample demonstrated a tensile strength of 500 MPa which is 500% higher than the strength of pristine Al. In addition, the tensile tests performed at 500o C revealed that the tensile strength of produced Al-based composite was 180 MPa, whereas the strength of pure Al at the same temperature was less than 30 MPa. X-ray and EDX analysis demonstrated that BNNPs had reacted with Al forming AlB2 and AlN nano-phases during high-energy ball milling and sintering processes. These inclusions have a positive effect on the composite mechanical properties. SEM and TEM investigations revealed a peculiar nanoscaled structure of synthesized composites.