Novel mechanism of ultra-high adiabatic shear susceptibility in FCC-based high-entropy alloys via high-content nanoprecipitate dissolution

Adiabatic shear bands (ASBs) are a crucial failure mechanism of metals and alloys subjected to impact loading. The formation mechanism of ASBs in an FCC-based high-entropy alloy (HEA) featuring high-content coherent nanoprecipitates was investigated. Unlike traditional FCC-structured alloys, which generally exhibit low shear banding capabilities, the FCC-structured HEA presented herein displays ultrahigh adiabatic shear susceptibility (ASS) under dynamic loading. A novel mechanism induced by the instantaneous dissolution of high-content L1₂ nanoprecipitates at relatively low temperatures is proposed to be responsible for the enhanced shear instability. At room temperature, these high-content L1₂ nanoprecipitates significantly increase the strength; however, under dynamic loading, deformation concentration causes a local temperature rise, triggering the instantaneous dissolution of nanoprecipitates. This induces a dramatic reduction in the local shear strength and promotes ASB formation. The combined effects of the nanosized features, low-energy interfaces, and spinodal-like structures of the precipitates contribute to the instantaneous dissolution process at relatively low temperatures. This novel shearing-band mechanism suggests a novel approach for designing ductile alloys with enhanced ASS.