Compression of refractory high-entropy alloy nanoparticles: Size and short-range order effects

Abstract

This study investigates the mechanical behavior of BCC HfNbTaTiZr high-entropy alloy (HEA) nanoparticles (NPs) subjected to compression by a flat indenter using molecular dynamics simulations. NPs with random atomic distribution and diameters from 10 to 50 nm were considered. For comparison purposes, a 20 nm NP with chemical short-range order (CSRO) was also explored. The mechanical response revealed an increasing trend of the Young's modulus with respect to the NP size. However, maximum stress, yield stress, and flow stress showed negligible variations. Furthermore, the NP with CSRO showed enhanced mechanical properties, attributed to SRO cluster formation. Analysis of plastic activity revealed surface-dominated dislocation emission and absorption, with CSRO NP exhibiting an increase in dislocation density as the strain increased. Structural analysis elucidated persistent twin formation in all NPs, with a remarkable increase in the HCP population observed in the CSRO NP. These findings further improve our understanding of the mechanical behavior of HEA NPs, contributing to the design and development of advanced materials.