Microstructure-dependent nanoindentation deformation behavior of TaTiZrV refractory high-entropy alloy

DQ Doan, INTERNATIONAL JOURNAL OF REFRACTORY METALS & HARD MATERIALS, 123, 106769 (2024).

DOI: 10.1016/j.ijrmhm.2024.106769

This study employs molecular dynamics (MD) simulations to investigate the mechanical behavior and microstructure development of TaTiZrV refractory high -entropy alloy (RHEA) with microstructural variations during nanoindentation. The influence of crystallographic orientations, including 001, 110, and 111, on mechanical responses reveals that the 111 -oriented substrate exhibits the highest average hardness due to the presence of a complex dislocation network. The evolution of crystal defects, such as dislocation loops and vacancy defects, varies depending on the crystal directions, affecting the distribution of shear strain and residual stress. The recovery ratio emphasizes crystal -specific reflections, with the 110 -oriented sample exhibiting a greater elastic recovery ratio compared to other samples. Examination of RHEA with varying grain sizes reveals that reducing grain size leads to earlier pop -in phenomena, decreased indentation force, and reduced hardness. The small grain size with a high density of grain boundaries causes higher levels of shear strain and residual stress compared to specimens with larger grain sizes. Furthermore, the grain boundary acts as a barrier that resists the movement of dislocations in larger grains, enhancing hardness, while smaller grains demonstrate predominant grain rotation, reducing hardness. The highest elastic recovery in a sample with a grain size of 97.82 ?, is related to the smallest dislocation length, while larger dislocation lengths in specimens with grain sizes of 73.75 ?, and 141.07 ?, result in lower recovery capabilities.

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