Slip band interactions and GND latent hardening in a galling resistant stainless steel

TL;DR

This study investigates slip band interactions and GND accumulation in Nitronic 60 stainless steel, revealing how slip interactions contribute to work hardening and galling resistance at the grain scale.

Contribution

It provides new insights into slip band interactions, GND generation, and their role in hardening mechanisms using combined high-resolution imaging and modeling.

Findings

Multiple slip bands active within grains lead to significant interactions.

Crossing slip bands generate high GND densities, over three times higher.

Slip blocking regions exhibit the highest GND accumulation.

Abstract

Slip activation, slip band interactions, and GND densities in iron-base, galling resistant alloy Nitronic 60 have been characterised at the grain length scale using small-scale mechanical testing with high resolution digital image correlation and high-angular resolution electron backscatter diffraction. By correlating the two measurement techniques, new insight into slip band interactions, the generation of lattice curvature and the corresponding accumulation of geometrically necessary dislocations (GNDs) is provided. Multiple discrete slip bands are typically active within single grains, resulting in significant slip band interactions. Crossing slip bands were found to generate accumulations of GNDs. Regions where slip bands block other slip bands were associated with the highest GND densities, in excess of three time the densities of crossing slip bands. Representative crystal plasticity modelling investigations have demonstrated that discrete slip blocking events are responsible for locally elevated GND density. This behaviour is rationalised in terms of lattice curvature associated with the differing levels of constraint provided by the crossing or blocking-type behaviours. Ferrite grains are also found to contribute to the generation of GNDs. Together, these two effects provide significant work hardening mechanisms, likely to be key to the development of future iron-base hard facing alloys.