In situ characterisation of slip bands behaviour in ferrite under mechanical loading

TL;DR

This paper uses in situ high-resolution electron backscatter diffraction to analyze slip band behavior and dislocation activity in ferrite grains of stainless steel under mechanical load, revealing dislocation dynamics and deformation mechanisms.

Contribution

It introduces a novel in situ HR-EBSD method to measure dislocation densities and activity at slip bands in ferrite, providing new insights into slip band evolution under load.

Findings

Slip bands mainly consist of edge dislocations.

The blooming zone at slip band tips expands with load.

Dislocation activity is dominated by immobile edge dislocations.

Abstract

This study investigates the behaviour of slip bands, terminated mid-grain in the ferrite grains of age-hardened stainless steel, under different conditions to understand their dislocation activity and response to varying loads. The full Nye lattice curvature tensor was measured in situ using high-resolution electron backscatter diffraction (HR-EBSD) to estimate the total geometrically necessary dislocation density and individual mobile and immobile dislocations activity at the slip band scale. We found that slip bands primarily consist of edge dislocations, marked by a 'blooming zone' at its tip, indicating significant shear deformation and loss of mobile dislocations. The blooming zone expands as the load increases while the slip band thickness remains constant. Coupled with the correlation between mobile and immobile dislocations within the loaded slip bands observed in situ, we observed that the dislocation activities at the slip band were mainly from immobile edge dislocations to maintain the geometrical distortion of the slip band.