Characterisation of microstructure, microhardness and tribological properties of Al matrix hybrid nanocomposites reinforced with B4C and in-situ GNSs

With the increasing demands of automobile and aerospace industries, it is necessary to develop novel wear-resistant Al matrix composites (AMCs). Graphene is commonly used as an additive in self-lubricating AMCs due to its high strengthening efficiency and 2D structure. Considering the high cost of graphene and reinforcing the Al matrix by multiple reinforcements, novel Al matrix hybrid nanocomposites reinforced with B4C and in-situ GNSs were developed in this study. Al-10 vol% (x1 B4C-x2 graphite) composites (x1: x2 = 10:0, 9:1, 7:3, 5:5) were prepared by powder metallurgy. Vickers hardness tests and ball-on-disc wear tests were used to assess the mechanical and tribological properties of the composites. It is found that in-situ GNSs can be formed in Al-9 vol% B4C-1 vol% graphite (Al–9B-1G) and Al-7 vol% B4C-3 vol% graphite (Al–7B-3G) composites, thereby significantly increasing the Vickers hardness. Benefiting from the strengthening effects of B4C and in-situ GNSs, as well as the lubricating effect of the GNSs, the wear resistance of Al–9B-1G and Al–7B-3G is improved remarkably. Al–7B-3G has the best wear resistance with the least wear rate of 1.41 × 10−3 mm3/Nm, which is 87.4% and 76.7% lower than that of Al and Al–10B, respectively.