An ultra-high strength CrMoNbWTi-C high entropy alloy co-strengthened by dispersed refractory IM and UHTC phases

Abstract

A novel CrMoNbWTi-C refractory high entropy alloy (RHEA) co-strengthened by fine-grained intermetallics (IM) and ultra-high temperature carbides (UHTC) particles was fabricated by mechanical alloying (MA) and hot-press sintering (HPS). Mechanical alloying behavior, microstructure, phase constitution and mechanical properties of the CrMoNbWTi-C RHEA were investigated systematically. Combined with the empirical criteria and experimental results, the phase transformation during MA and HPS were analyzed and discussed in detail. During the MA process, a supersaturated BCC solid solution was formed. Subsequently, during HPS, the IM of Cr2Nb and UHTC of (Ti,Nb)C were precipitated from the BCC solid solution. The as-sintered RHEA with multiphase structure exhibited an ultra-high fracture strength of 3094 MPa and superior hardness of 8.26 GPa, respectively. The excellent mechanical properties were attributed to the combined effects of grain boundary strengthening, substitutional solid solution strengthening and the IM & UHTC co-strengthening.