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

Abstract

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 (Hc) 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, ΔσOrowan increases. Therefore, the strength of composite increases but work hardening capacity (Hc) 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).