Plastic deformation mechanisms during nanoindentation of W, Mo, V body-centered cubic single crystals and their corresponding W-Mo, W-V equiatomic random solid solutions

TL;DR

This study uses molecular dynamics simulations to compare plastic deformation mechanisms in pure BCC metals and their equiatomic solid solutions, revealing how alloying elements influence dislocation behavior and material hardening.

Contribution

It provides a detailed comparison of nanoindentation-induced plasticity in pure BCC metals and their equiatomic solid solutions, highlighting the effects of alloying on deformation mechanisms.

Findings

Mo and V increase resistance to deformation in W matrices.

W-V alloys show suppressed plastic zone size, indicating better hardening.

Nanoindentation responses suggest pathways for designing mechanically robust alloys.

Abstract

Deformation plasticity mechanisms in alloys and compounds may unveil the material capacity towards optimal mechanical properties. We conduct a series of molecular dynamics (MD) simulations to investigate plasticity mechanisms due to nanoindentation in pure tungsten, molybdenum and vanadium body-centered cubic single crystals, as well as the also body-centered cubic, equiatomic, random solid solutions (RSS) of tungsten--molybdenum and tungsten--vanadium alloys. Our analysis focuses on a thorough, side-by-side comparison of dynamic deformation processes, defect nucleation, and evolution, along with corresponding stress--strain curves. We also check the surface morphology of indented samples through atomic shear strain mapping. As expected, the presence of Mo and V atoms in W matrices introduces lattice strain and distortion, increasing material resistance to deformation and slowing down dislocation mobility of dislocation loops with a Burgers vector of 1/2 $\langle 111 \rangle$. Our side-by-side comparison displays a remarkable suppression of the plastic zone size in equiatomic W--V RSS, but not in equiatomic W--Mo RSS alloys, displaying a clear prediction for optimal hardening response equiatomic W--V RSS alloys. If the small-depth nanoindentation plastic response is indicative of overall mechanical performance, it is possible to conceive a novel MD-based pathway towards material design for mechanical applications in complex, multi-component alloys.