Microstructure and mechanical properties of an aluminium composite with carbon-containing medium entropy alloy MoNbWTa0.5C0.5 reinforcement

Abstract

The work reports the synthesis and microstructural and mechanical characterization of an aluminium composite with carbon-containing medium entropy alloy (C-MEA), MoNbWTa_0.5C_0.5 as reinforcement. High energy ball milling of the C-MEA composition resulted in a pre-dominantly BCC phase. The Al-(C-MEA) composite was subsequently fabricated via a melting (at 800 °C) and solidification route and the FE-SEM and XRD characterization of the resultant composite revealed intermetallics of Al₅(W, Mo), Al₃(Ta, Nb) along with MoNbWTaC single-phase particles dispersed within the matrix of aluminium. The nano-hardness and elastic modulus of the C-MEA particles was observed to be 13 GPa and 190 GPa respectively. The microhardness of the bulk Al-(C-MEA) composite was found to be 686 MPa which is 89 % higher than aluminium at 353 MPa. Owing to the presence of hard and stiff C-MEAs and intermetallic particles, the yield strength of the composite was observed to be 102 % higher than aluminium. The Miedema's semi-empirical model was invoked to discuss the phase stability of the MEA particles and rationalize the formation of the Al₅(W, Mo), Al₃(Ta, Nb) intermetallics within the aluminium matrix.