3D Mapping of Intragranular Residual Strain and Microstructure in Recrystallized Iron Using Dark-Field X-ray Microscopy

TL;DR

This study uses dark-field X-ray microscopy to directly measure and analyze three-dimensional residual elastic strain distributions within fully recrystallized iron grains, revealing heterogeneity and potential implications for grain growth.

Contribution

First direct experimental 3D measurements of intragranular residual strains in recrystallized iron using dark-field X-ray microscopy, highlighting heterogeneity and dislocation effects.

Findings

Heterogeneous strain distributions within grains.

Localized strain signatures around dislocations and particles.

Implications for grain boundary migration and growth models.

Abstract

Grain growth is a key process in the thermomechanical treatment of metals. Recently, the presence of local residual stresses within fully recrystallized grains has attracted increasing interest in connection with shear-coupled grain boundary migration mechanisms. In this work, we provide the first direct experimental measurements of residual elastic strain variations in fully recrystallized commercial-purity iron, on the order of $10^{-4}$. Using dark-field X-ray microscopy (DFXM), we performed non-destructive three-dimensional measurements of strain and orientation variations within individual grains. Our results reveal heterogeneous strain distributions across all measured grains. In one case, we observed several isolated dislocations accommodating two second-phase particles, exhibiting a localized strain signature with no detectable long-range effect. The formation mechanisms of intragranular residual strains and their potential influence on grain boundary migration during subsequent grain growth are discussed. This work highlights the importance of accounting for such residual elastic strains in future grain growth models.