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The crystallographic orientations and residual stresses within recrystallizing grains in partially recrystallized β titanium—Gum Metal—were examined non-destructively in 3D using synchrotron Differential Aperture X-ray Microscopy. Contrary to common assumptions, significant local stresses and stress variations are observed within the recrystallizing grains. The results reveal that the development of these local residual stresses depends on the plastic deformation mode and material's elastic constants, rather than grain properties such as size and orientation, or even the material's yield stress. This work provides insights valuable for the design of advanced materials with heterogeneous microstructures. [ABSTRACT FROM AUTHOR]

The intragranular strains and the microstructure within recrystallizing grains in single phase pure iron have been systematically studied in 3D using synchrotron micro-diffraction. In contradiction to common knowledge we observe that residual elastic strains of up to 1–2 × 10−3 are present in the recrystallizing grains. The local strain variations within individual grains can be similar in magnitude to those between different grains. The effects of processing parameters, including rolling reduction, recrystallized volume fraction, and cooling rate, as well as microstructural parameters, including grain size, orientation and internal misorientation, on the development of local residual elastic strains and microstructure have been quantified. It is suggested that the difference in local defect density between recrystallized grains and the surrounding deformed matrix, as well as the redistribution of medium to long-range residual stresses in the deformed grains, are the main reasons for the development of such strains in the recrystallized grains. The local residual stress levels are calculated and their possible impact on the mechanical properties and recrystallization processes are discussed. [Display omitted] • Local residual stresses in partially recrystallized iron have been mapped in 3D. • Residual elastic strains of up to 1–2 × 10−3 are present in recrystallizing grains. • Deviatoric strain components along different sample directions are different. • Mechanisms for the formation of local residual stresses in recrystallizing grains are clarified. • Importance of local residual stresses for recrystallization process is highlighted. [ABSTRACT FROM AUTHOR]

Boundary migration during recrystallization in the heterogeneous microstructure near a hardness indent in lightly rolled pure Al was followed in 3D. The microstructure after multiple steps of ex-situ annealing was examined using synchrotron white-beam differential-aperture X-ray microscopy, supplemented by scanning electron microscopy. Heterogeneous recrystallization boundary migration was observed and analyzed in terms of driving force and boundary characteristics. The results reveal very similar local stored energies and boundary misorientations for the migrating and stationary boundary segments, whereas the grain boundary normals differ significantly. Effects of grain boundary mobility and deformation microstructure morphology on the migration are discussed. [Display omitted] [ABSTRACT FROM AUTHOR]

Boundary migration during recrystallization has been followed by an ex situ electron channelling contrast technique, and protrusions/retrusions formed locally on recrystallization boundaries have been quantified. The results show that the motion of recrystallization boundaries is much more complex than generally appreciated. Locally protrusions/retrusions can provide a driving force comparable in magnitude to the driving force from the stored energy in the deformed matrix. The stop–go motion of the recrystallization boundaries is also discussed and related to the formation of protrusions and retrusions. [ABSTRACT FROM AUTHOR]

Effects of the geometrical alignment of an idealized deformation microstructure on the migration of recrystallization boundaries are studied using a phase-field model. A deformation field consisting of two sets of regularly arranged bands is used as an example to mimic typical deformed microstructures, while the migration of both initially flat and circular recrystallization boundaries are considered. The results show that for both cases the local variations in the deformation field affect not only the local shape of the migrating boundary but also the overall distances traveled. It is revealed that boundary migration into heterogeneously distributed energy fields are not uniform neither in space nor time, and can therefore not be expressed by the classic migration model with a uniform migration assumption, even when averaged over the whole boundary and long time. [ABSTRACT FROM AUTHOR]

Changes in the microstructure and mechanical properties during annealing at 800 °C have been characterized in a 90% cold-rolled AlCoCrFeNi 2.1 eutectic high-entropy alloy containing the FCC and B2 (ordered BCC) phases. In the as-rolled condition, the FCC phase is found to contain a high frequency of finely spaced deformation-induced boundaries, which provides a high driving force for recrystallization within this phase. Quantitative analysis of electron backscatter diffraction data from the annealed samples indicates that recrystallization progresses faster in the FCC phase than in B2 regions. Although recrystallization leads to substantial coarsening of the microstructure, the average recrystallized grain size remains in the submicron range even after 2 h at 800 °C. Tensile test data demonstrate that combinations of high yield strength and good ductility are obtained in partially recrystallized samples produced by annealing for 2.5–10 min. However, the work-hardening capacity of each annealed sample is lower than that of the cold-rolled sample. Furthermore, for the samples annealed for at least 5 min a yield drop is observed soon after the onset of plastic deformation. Analysis of the microstructure and mechanical behavior in several annealed AlCoCrFeNi 2.1 samples indicates a clear correlation between the magnitude of the yield drop and the recrystallized fraction. The mechanical behavior of the AlCoCrFeNi 2.1 alloy studied in this work is compared with that reported in previous publications. [ABSTRACT FROM AUTHOR]

[Display omitted] The local migration of recrystallization boundaries into spatially varying deformation fields which are typical for metals deformed to low and high strains is investigated using quantitative phase-field simulations. It is found that the average migration velocities as well as the local velocities of the recrystallization boundaries critically depend on the spacing between planar geometrically necessary boundaries (GNBs) which are present in the deformation microstructure. Also the morphology of the deformation field reflecting low and high strain deformation cases strongly affect the migrating boundary during recrystallization. Additional simulations were performed as a function of the two critical parameters- stored energy and GNB spacing - independently. Two regimes are found suggesting that these two parameters are closely linked. Previous experimental results are interpreted based on these novel simulation results. [ABSTRACT FROM AUTHOR]

Abstract Synchrotron diffraction contrast tomography (DCT) is for the first time used to characterize recrystallized grains in partially recrystallized Al. The positions, orientations and 3D shapes of >900 recrystallized grains are reconstructed within a gauge volume. The results are compared with those obtained using electron backscattered diffraction based on a statistical analysis. It is found that recrystallized grains with size larger than 10 μm, corresponding to ~98% of the total recrystallized volume of the sample, are well characterized by DCT. The advantages of DCT for recrystallization studies and new possibilities with DCT on new generation synchrotron sources are discussed. Graphical abstract Unlabelled Image [ABSTRACT FROM AUTHOR]

Recent synchrotron X-ray measurements examined three-dimensional boundary migration during recrystallization [Scripta Mater 205 (2021) 114187]. To analyze possible correlations between grain boundary mobility and the observed heterogeneous boundary migration, molecular dynamics simulations were carried out. Migration of two selected boundary segments were simulated in both planar and spherical bicrystal atomistic models. These two segments were chosen because in the experiment one was observed to migrate much faster than the other. The simulations reveal that mobility cannot account for the experimentally observed heterogeneous migration. The result points to the possibility that recrystallization boundary migration strongly depends on features within the deformed microstructure. [Display omitted] [ABSTRACT FROM AUTHOR]