Microstructure and properties of in-situ high entropy alloy/tungsten carbide composites by mechanical alloying.

Al_0.1CoCrFeNi-high entropy alloy (HEA) /tungsten carbide (WC)metal matrix composite was successfully prepared by mechanical alloying and subsequent spark plasma sintering. The different volume fraction of WC was distributed evenly by varying the powder milling parameters from gentle milling (~1.37% WC) and intensive milling (~14.27% WC). Sintering of gently milled powder has resulted in the evolution of three-phased microstructure: α-fcc and Cr- rich σ-phase with some WC-phase distributed in the HEA matrix. On the other hand, the sintering of intensively milled powder has resulted in a two-phased microstructure: α-fcc phase with even and dense distribution of WC-phased particles without any Cr- rich σ-phase. The absence of σ-phase is attributed to a complete alloying of Cr in the HEA matrix. Microhardness analysis and compression test indicate that a ~ 13% difference in WC fraction has resulted in an enhancement in hardness (46%) and compressive strength (~ 500 MPa).