Microstructure and properties of aluminium-high entropy alloy composites fabricated by mechanical alloying and spark plasma sintering

Abstract

High-quality aluminium-CuZrNiAlTiW high-entropy alloy (HEA) composites were fabricated by mechanical alloying and spark plasma sintering (SPS). The microstructures, mechanical properties and corrosion resistance of these composites were investigated. The as-milled HEA powders consist of a single body-centered cubic (BCC) solid solution phase. Besides the Al and BCC phases, the NiAl-rich B2 and WAl12 phases were in-situ formed in the sintered composites due to the large concentration gradient of Al between the matrix and HEA reinforcement. Compared to the SPS-ed Al bulk, the Al-HEA composites show higher microhardness and strength, caused by the dispersion strengthening of BCC phase and precipitation strengthening of B2 and WAl12 phases, as well as the serious lattice distortion. The core-shell microstructure in the composite with 10 vol.% HEA (Al10) contributes to its good compression properties with high yield strength and good plasticity. The Al20 composite exhibits a high fracture strength of 544 MPa, owing to the uniform size and distribution of BCC particles. Additionally, W and Ni could improve the stability of protective layer, and thus enhance the pitting resistance of the Al-HEA composites in seawater. The Al10 composite possesses the relatively positive corrosion potential and low corrosion rate, revealing a good general corrosion resistance.