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

Y Xiao and QL Zeng and KH Xun and J Ding and LJ Wang and L Wang and YJ Liang and K Jin and SX Zhu and Y Ren and G Sha and L Wang and HS Chen and YF Xue, ACTA MATERIALIA, 296, 121280 (2025).

DOI: 10.1016/j.actamat.2025.121280

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.

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