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Title: Determination of grain boundary mobility during recrystallization by statistical evaluation of electron backscatter diffraction measurements

Abstract

One of the key aspects influencing microstructural design pathways in metallic systems is grain boundary motion. The present work introduces a method by means of which direct measurement of grain boundary mobility vs. misorientation dependence is made possible. The technique utilizes datasets acquired by means of serial electron backscatter diffraction (EBSD) measurements. The experimental EBSD measurements are collectively analyzed, whereby datasets were used to obtain grain boundary mobility and grain aspect ratio with respect to grain boundary misorientation. The proposed method is further validated using cellular automata (CA) simulations. Single crystal aluminium was cold rolled and scratched in order to nucleate random orientations. Subsequent annealing at 300 °C resulted in grains growing, in the direction normal to the scratch, into a single deformed orientation. Growth selection was observed, wherein the boundaries with misorientations close to Σ7 CSL orientation relationship (38° 〈111〉) migrated considerably faster. The obtained boundary mobility distribution exhibited a non-monotonic behavior with a maximum corresponding to misorientation of 38° ± 2° about 〈111〉 axes ± 4°, which was 10–100 times higher than the mobility values of random high angle boundaries. Correlation with the grain aspect ratio values indicated a strong growth anisotropy displayed by the fast growing grains.more » The observations have been discussed in terms of the influence of grain boundary character on grain boundary motion during recrystallization. - Highlights: • Statistical microstructure method to measure grain boundary mobility during recrystallization • Method implementation independent of material or crystal structure • Mobility of the Σ7 boundaries in 5N Al was calculated as 4.7 × 10{sup –8} m{sup 4}/J ⋅ s. • Pronounced growth selection in the recrystallizing nuclei in Al • Boundary mobility values during recrystallization 2–3 orders of magnitude larger vis-à-vis curvature driven motion.« less

Authors:
; ; ; ;
Publication Date:
OSTI Identifier:
22587168
Resource Type:
Journal Article
Resource Relation:
Journal Name: Materials Characterization; Journal Volume: 117; Other Information: Copyright (c) 2016 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved.; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; 77 NANOSCIENCE AND NANOTECHNOLOGY; ALUMINIUM; ANISOTROPY; ANNEALING; ASPECT RATIO; BACKSCATTERING; CORRELATIONS; CRYSTAL STRUCTURE; DATASETS; ELECTRON DIFFRACTION; GRAIN BOUNDARIES; MOBILITY; MONOCRYSTALS; ORIENTATION; RANDOMNESS; RECRYSTALLIZATION

Citation Formats

Basu, I., E-mail: basu@imm.rwth-aachen.de, Chen, M., Loeck, M., Al-Samman, T., and Molodov, D.A. Determination of grain boundary mobility during recrystallization by statistical evaluation of electron backscatter diffraction measurements. United States: N. p., 2016. Web. doi:10.1016/J.MATCHAR.2016.04.024.
Basu, I., E-mail: basu@imm.rwth-aachen.de, Chen, M., Loeck, M., Al-Samman, T., & Molodov, D.A. Determination of grain boundary mobility during recrystallization by statistical evaluation of electron backscatter diffraction measurements. United States. doi:10.1016/J.MATCHAR.2016.04.024.
Basu, I., E-mail: basu@imm.rwth-aachen.de, Chen, M., Loeck, M., Al-Samman, T., and Molodov, D.A. 2016. "Determination of grain boundary mobility during recrystallization by statistical evaluation of electron backscatter diffraction measurements". United States. doi:10.1016/J.MATCHAR.2016.04.024.
@article{osti_22587168,
title = {Determination of grain boundary mobility during recrystallization by statistical evaluation of electron backscatter diffraction measurements},
author = {Basu, I., E-mail: basu@imm.rwth-aachen.de and Chen, M. and Loeck, M. and Al-Samman, T. and Molodov, D.A.},
abstractNote = {One of the key aspects influencing microstructural design pathways in metallic systems is grain boundary motion. The present work introduces a method by means of which direct measurement of grain boundary mobility vs. misorientation dependence is made possible. The technique utilizes datasets acquired by means of serial electron backscatter diffraction (EBSD) measurements. The experimental EBSD measurements are collectively analyzed, whereby datasets were used to obtain grain boundary mobility and grain aspect ratio with respect to grain boundary misorientation. The proposed method is further validated using cellular automata (CA) simulations. Single crystal aluminium was cold rolled and scratched in order to nucleate random orientations. Subsequent annealing at 300 °C resulted in grains growing, in the direction normal to the scratch, into a single deformed orientation. Growth selection was observed, wherein the boundaries with misorientations close to Σ7 CSL orientation relationship (38° 〈111〉) migrated considerably faster. The obtained boundary mobility distribution exhibited a non-monotonic behavior with a maximum corresponding to misorientation of 38° ± 2° about 〈111〉 axes ± 4°, which was 10–100 times higher than the mobility values of random high angle boundaries. Correlation with the grain aspect ratio values indicated a strong growth anisotropy displayed by the fast growing grains. The observations have been discussed in terms of the influence of grain boundary character on grain boundary motion during recrystallization. - Highlights: • Statistical microstructure method to measure grain boundary mobility during recrystallization • Method implementation independent of material or crystal structure • Mobility of the Σ7 boundaries in 5N Al was calculated as 4.7 × 10{sup –8} m{sup 4}/J ⋅ s. • Pronounced growth selection in the recrystallizing nuclei in Al • Boundary mobility values during recrystallization 2–3 orders of magnitude larger vis-à-vis curvature driven motion.},
doi = {10.1016/J.MATCHAR.2016.04.024},
journal = {Materials Characterization},
number = ,
volume = 117,
place = {United States},
year = 2016,
month = 7
}
  • A combination of in situ annealing and electron backscattered diffraction in the SEM has been used to determine the mobility of high angle grain boundaries in a deformed single-phase Al-Si alloy. It is found that the boundary velocity is directly proportional to the driving pressure and that the activation energy for boundary migration over all the conditions investigated is consistent with control by lattice diffusion of the solute. It is confirmed that tilt boundaries of recrystallized grains misoriented by 40 {+-} 10{degree} about axes within {+-}10{degree} of {l_angle}111{r_angle} have an increased mobility compared to other high angle boundaries, whereas themore » mobilities of 40{degree} {l_angle}111{r_angle} twist boundaries are similar to those of general high angle boundaries. The mobility maximum for the 40{degree} {l_angle}111{r_angle} tilt boundaries is very broad, which is in contrast to the sharp mobility peaks reported for curvature-driven grain growth, and possible reasons for these differences are discussed.« less
  • In this study, the evolution of the recrystallization texture and microstructure was investigated after annealing of 50% and 90% cold-rolled FePd alloy at 530 °C. The FePd alloy was produced by vacuum arc melting in an atmosphere of 97% Ar and 3% H{sub 2}. The specimens were cold rolled to achieve 50% and 90% reduction in thickness. Electron backscatter diffraction measurements were performed on the rolling direction–normal direction section. With increased deformation from 50% to 90%, recrystallized texture transition occurs. For the 50% cold-rolled alloy, the preferred orientation is (0 1 0) [11 0 1], which is close to themore » cubic orientation after 400 h of annealing. For the 90% cold-rolled alloy, the orientation changes to (0 5 4) [22–4 5] after 16 h of annealing. - Highlights: • Texture and microstructure in cold-rolled FePd alloy was investigated during annealing using EBSD. • The recrystallized texture of 50% cold-rolled FePd is (0 1 0) [11 0 1] at 530 °C for 400 hours. • The recrystallized texture of 90% cold-rolled FePd is changed to (0 5 4) [22–4 5] at 530 °C after 16 hours.« less
  • The evolution of microstructure and texture during cross-rolling and annealing was investigated by electron backscatter diffraction in a ferritic–austenitic duplex stainless steel. For this purpose an alloy with nearly equal volume fraction of the two phases was deformed by multi-pass cross-rolling process up to 90% reduction in thickness. The rolling and transverse directions were mutually interchanged in each pass by rotating the sample by 90° around the normal direction. In order to avoid deformation induced phase transformation and dynamic strain aging, the rolling was carried out at an optimized temperature of 898 K (625 °C) at the warm-deformation range. Themore » microstructure after cross warm-rolling revealed a lamellar structure with alternate arrangement of the bands of two phases. Strong brass and rotated brass components were observed in austenite in the steel after processing by cross warm-rolling. The ferrite in the cross warm-rolling processed steel showed remarkably strong RD-fiber (RD//< 011 >) component (001)< 011 >. The development of texture in the two phases after processing by cross warm-rolling could be explained by the stability of the texture components. During isothermal annealing of the 90% cross warm-rolling processed material the lamellar morphology was retained before collapse of the lamellar structure to the mutual interpenetration of the phase bands. Ferrite showed recovery resulting in annealing texture similar to the deformation texture. In contrast, the austenite showed primary recrystallization without preferential orientation selection leading to the retention of deformation texture. The evolution of deformation and annealing texture in the two phases of the steel was independent of one another. - Highlights: • Effect of cross warm-rolling on texture formation is studied in duplex steel. • Brass texture in austenite and (001)<110 > in ferrite are developed. • Ferrite shows recovery during annealing retaining the (001)<110 > component. • Austenite shows recrystallization during annealing retaining the deformation texture. • The deformation of recrystallization of two phases is independent of one other.« less
  • Static and metadynamic recrystallization of an AISI 304L austenitic stainless steel was investigated at 1100 °C and 10{sup −} {sup 2} s{sup −} {sup 1} strain rate. The kinetics of recrystallization was determined through double hit compression tests. Two strain levels were selected for the first compression hit: ε{sub f} = 0.15 for static recrystallization (SRX) and 0.25 for metadynamic recrystallization (MDRX). Both the as-deformed and the recrystallized microstructures were investigated through optical microscopy and electron back-scattered diffraction (EBSD) technique. During deformation, strain induced grain boundary migration appeared to be significant, producing a square-like grain boundary structure aligned along themore » directions of the maximum shear stresses in compression. EBSD analysis revealed to be as a fundamental technique that the dislocation density was distributed heterogeneously in the deformed grains. Grain growth driven by surface energy reduction was also investigated, finding that it was too slow to explain the experimental data. Based on microstructural results, it was concluded that saturation of the nucleation sites occurred in the first stages of recrystallization, while grain growth driven by strain induced grain boundary migration (SIGBM) dominated the subsequent stages. - Highlights: • Recrystallization behavior of a stainless steel was investigated at 1100 °C. • EBSD revealed that the dislocation density distribution was heterogeneous during deformation. • Saturation of nucleation sites occurred in the first stages of recrystallization. • Strain induced grain boundary migration (SIGBM) effects were significant. • Grain growth driven by SIGBM dominated the subsequent stages.« less
  • In this paper, a new automatic procedure for determining critical recrystallization parameters, which are important when studying recrystallization kinetics, is presented. The method is based on electron backscatter patterns (EBSP) line scans using a scanning electron microscope, where three parallel lines are scanned. The concepts of equivalence and connectivity are used to group the data points into those originating in recrystallized grains and those originating in the deformed matrix. The computer program implementing the automatic procedure is tested in three different ways: three short scans are performed, where the calculations are also done by hand; the results of two longmore » scans are compared to the direct observation of the microstructure seen in orientation image maps (OIMs) [Mater. Sci. Eng. A. 166 (1993) 59], and the results of scans from a series of samples are compared to statistical results obtained manually. A good correlation was achieved in all three cases.« less