Significantly improved strength and plasticity of a refractory high-entropy alloy at small length scale.

Refractory high-entropy alloy (RHEA) VNbMoTaW exhibits remarkably high strength in a much wide temperature range, whereas the brittle fracture behavior limits the applications. Here we show a significant size effect on the strength, plasticity and fracture behaviour of the VNbMoTaW RHEA. As sample size goes from millimeter to sub-micrometer scale, the brittle cracking behavior of the RHEA is greatly suppressed, along with a simultaneous enhancement of strength and plasticity. The improved mechanical properties can be attributed to the disappearance of crack initiation sites, the size-dependent dislocation plasticity at small length scale and the size-dependent competition in thermodynamics driving-force for cleavage cracking and plastic yielding. The results imply a promising potential of the RHEA for making microscale devices with high temperature environment. • Significant size effects on mechanical behaviors of RHEA were observed. • In microscale samples, brittle cracking behavior is greatly suppressed. • A size-induced simultaneous enhancement of strength and plasticity is found. • The crack initiation mechanisms of the brittle RHEA under compression were summarized. [ABSTRACT FROM AUTHOR]