Eutectic Monbta(Wc)X Composites with Excellent Elevated Temperature Strength

Abstract

To develop materials with promising utilization future in the extreme environments of aerospace, the MoNbTa(WC) x composites were prepared by vacuum arc melting, of which the crystal structure, microstructure, and compression properties at elevated temperature were investigated. The MoNbTa(WC) x composites had eutectic structures that consisted of body-centered cubic (BCC) phase and eutectoid structures. The lamellar fine eutectoid structures were composed of BCC structured high entropy alloy (HEA) Mo-Nb-Ta-W and FCC structured carbide Mo-Nb-Ta-W-C. It was demonstrated that the ductility and elevated temperature strength was enhanced simultaneously combined with the effect of eutectic structures and WC addition. The optimal true yield strength and true fracture strain reached 1205 MPa and 29.2% in MoNbTa(WC) 0.9 at 1200 ℃, meanwhile, the fracture strain at ambient temperature was 13.96%. Distinct strain hardening was observed at the initial deformation stage of MoNbTa(WC) 0.9 at 1200 ℃. The compression performances of MoNbTa(WC) x were superior in comparison with most refractory high entropy alloys.

Keywords: Refractory high entropy alloy, eutectic structure, mechanical property, strain hardening.