Orientation dependence of the nano-indentation behaviour of pure tungsten

TL;DR

This study investigates how the nano-indentation behavior of pure tungsten varies with crystal orientation, revealing orientation-dependent dislocation and strain patterns that challenge current simulation models.

Contribution

It provides new insights into the orientation dependence of residual lattice strains and dislocation structures in tungsten, highlighting limitations of existing CPFE simulations.

Findings

Dislocation movement is confined to narrow channels in certain orientations.

Residual lattice strains depend strongly on crystal orientation.

CPFE simulations fail to reproduce some observed behaviors.

Abstract

Coupling of nano-indentation and crystal plasticity finite element (CPFE) simulations is widely used to quantitatively probe the small-scale mechanical behaviour of materials. Earlier studies showed that CPFE can successfully reproduce the load-displacement curves and surface morphology for different crystal orientations. Here, we report the orientation dependence of residual lattice strain patterns and dislocation structures in tungsten. For orientations with one or more Burgers vectors close to parallel to the sample surface, dislocation movement and residual lattice strains are confined to long, narrow channels. CPFE is unable to reproduce this behaviour, and our analysis reveals the responsible underlying mechanisms.