Nanoscratching and mechanical behaviors of high-entropy alloys with different phase constituents

Abstract

High-entropy alloys (HEAs) exhibit unique microstructural features and properties in nanoscale and atomic scale because of their multi-element alloy system. The nanoscratching behaviors of three HEAs with different phase constituents, relative to the microstructure and mechanical properties of the HEAs, were investigated. Three typical phase constituents were selected: face-centered cubic (FCC) structure, body-centered cubic (BCC) structure, and a dual-phase structure containing both FCC and BCC phases. Despite the fact that the FCC alloy has the highest ductility and strain hardening capability, it exhibited inferior scratch resistance due to the over-softening of hardness. Due to the brittle failure mode, the BCC alloy hardly exhibited desirable scratch resistance despite its highest hardness. By contrast, the nanostructured dual-phase alloy exhibited the best scratch resistance because of its good combination of strength and ductility, as well as the ductile failure mode. This research suggests that the HEA with structure comprising nanoscale hard and soft phases is desirable for nanoscratch resistance, and possesses appropriate hardness for industrial applications.