Preparation of super-high strength nanostructured B4C reinforced Al-2Cu aluminum alloy matrix composites by mechanical milling and hot press method: Microstructural,mechanical and tribological characterization

In this research, super-high strength nanostructured B₄C reinforced Al-2Cu aluminum alloy matrix composites produced by mechanical milling and hot press method. Nanostructured Al-2Cu powder containing 4, 6 and 10?wt.% B₄C reinforcement particles synthesized using a high-energy attritor under argon atmosphere. Results showed that with increasing the content of B₄C particles the matrix grain size decreased. Since the compressibility of mechanically milled powders is very low, hot press processing used for consolidation of nanostructured Al-2Cu/B₄C powders. The hot pressed Al-2Cu/10?wt.%B₄C nanocomposite, when tested in compression, exhibited extremely high strength (1.1?GPa) which is 735?MPa higher than that of coarse grain Al-2Cu sample. Moreover, the hardening capacity (H_c) of hot pressed nanocomposites decreased with the increase in the content of B₄C particles. According to Orowan strengthening mechanism, since B₄C particles act as a barrier to the dislocations movement, the increase of B₄C particles leads to the increase of barriers and as a result, Δσ_Orowan increases. Therefore, the strength of composite increases but work hardening capacity (H_c) decreases. The results of wear test indicated that wear rate and friction coefficient declined gradually as the B₄C particles fraction increased. Based on this result, hot-pressed sample containing 10?wt.% B₄C showed the lowest wear rate and friction coefficient (1.9?×?10^?5 mm³/m and 0.48 respectively).