Dislocation-mediated and twinning-induced plasticity of CoCrFeMnNi in varying tribological loading scenarios

TL;DR

This study investigates how different tribological loading conditions influence the dominant deformation mechanisms, such as dislocation slip and twinning, in CoCrFeMnNi alloy, revealing the effects of force variations and crystal orientations.

Contribution

It provides new insights into how normal and friction forces, along with crystal orientations, determine whether dislocation slip or twinning dominates deformation in this alloy.

Findings

Dislocation slip dominates under low friction conditions.

Twinning is prominent with certain crystal orientations and higher friction.

Different twin types and mechanisms were identified and characterized.

Abstract

Coarse-grained, metallic materials undergo microstructure refinement during tribological loading. This in turn results in changing tribological properties, so understanding deformation under tribological load is mandatory when designing tribological systems. Single-trace experiments were conducted to understand the initiation of deformation mechanisms acting in various tribological systems. The main scope of this work was to investigate the influence of normal and friction forces as well as crystal orientations on the dominating deformation mechanism in a face-centred cubic concentrated solid solution. While varying the normal force is easily realised, varying friction forces were achieved by using several counter body materials paired against CoCrFeMnNi. The subsurface deformation layer was either mediated through dislocation slip or twinning, depending on the grain orientation and on the tribological system. A layer dominated by dislocation-based deformation is characterised by lattice rotation, the formation of a dislocation trace line or subgrain formation. Such behaviour is observed for tribological systems with a low friction coefficient. For systems dominated by deformation twinning, three types of twin appearance were observed: small twins interacting with the surface, large twins and grains with two active twin systems. Two different twinning mechanisms are discussed as responsible for these characteristics.