Recrystallization and Grain Growth

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Authors: Takeshi Murakami, Shouichi Ochiai
Abstract: Grain growth in cube-textured aluminum was investigated by transmission Laue photographs obtained at the same point in specimens with progressing annealing at the heating rate of 20 deg/h. High purity aluminum for electrolytic capacitor was cold rolled to 98 % reduction, and subsequently partially annealed at 230 °C for 6 h and rolled 22 % reduction. On the light rolling, asterisms toward RD were observed near by direct beam, suggesting that lattice rotation around TD was caused in cube grains by light rolling. After annealing to 300 deg, fine Laue spots were detected in the asterisms. Those fine spots were indexed as 100 spots due to diffraction in {100} nearly parallel to the ND-TD plane. After disappearance of Debye arcs due to diffraction in untransformed matrix, cube texture was observed with orientational spread around TD. With continuing annealing to 540 °C , grain growth occurred at the expense of cube grains whose orientations deviated from the exact cube orientation around TD , resulting in sharp cube texture formation.
899
Authors: Koichi Nakashima, K. Imakawa, Y. Futamura, Toshihiro Tsuchiyama, Setsuo Takaki
Abstract: The effect of copper (Cu) addition on the grain growth behavior of austenite was investigated in a low carbon steel and a Cu bearing low carbon steel. Cu addition to the steel does not affect the nucleation rate of reversed austenite on heating in the martensitic structure but markedly retards the grain growth of the austenite during holding at 1173K (austenitization). As a result, the grain size of austenite in the Cu bearing steel becomes about one-third times smaller than that in the base steel after austenitization for 14.4ks. TEM observations in the Cu bearing steel revealed that Cu particles precipitated during aging treatment had completely dissolved in 1.2ks of austenitization. Therefore, the retardation of grain growth of austenite can not be explained by the grain boundary pinning effect of Cu particles but by the dragging effect of Cu atoms in the austenitic solid solution.
905
Authors: Václav Paidar, Pavel Lejček, M. Polcarová, J. Brádler, Alain Jacques
Abstract: Grain boundary motion was studied in situ at elevated temperatures by x-ray topography using synchrotron radiation. In addition to the position of grain boundary, other crystal defects that may interact with the moving boundary were observed simultaneously. Two types of bicrystals with the [001] rotation axis were selected for the experiments, the first one with a high coincidence S5 misorientation of about 37° and the other one with no coincidence of two crystals for the misorientation of 45°. The geometrical differences between chosen bicrystals are examined and attention is also paid to faceting – local orientations of the boundary plane.
911
Authors: Hyun Park, Young Chang Joo, Doh Yeon Kim, Jong Tae Park, Jae Kwan Kim, Nong Moon Hwang
917
Authors: N. Rouag, H. Afer, Richard Penelle
Abstract: The abnormal grain growth is related to the material texture, in the magnetic sheets Fe3%Si of HiB type, with AlN and MnS inhibitors. The onset of abnormal growth of Goss grains seems to be linked to the existence of a local favourable crystallographic neighbourhood. The grains which abnormally grow do not have a size greater than the average size in the matrix, their ability to grow in an abnormal way can be related to the local evolution around that considered grain, the whole effect of the matrix can hide the effect of matrix heterogeneity.
923
Authors: David San Martín, Francisca García Caballero, Carlos Capdevila, C. Carcía de Andrés
Abstract: Grain growth is a thermally activated process in which the average grain size increases as temperature and time increases. The driving force for grain growth results from the decrease in the free energy associated with the reduction in total grain boundary energy. There are several known factors that influence the migration of grain boundaries such as second phase particles precipitated in the matrix and the solute elements segregated at grain boundaries. The austenite grain boundaries are revealed using the thermal etching method. Carbon extraction replicas were prepared to determine the composition and size of precipitates present in the matrix. In this work, the evolution of the average prior austenite grain size (PAGS) of a low carbon steel microalloyed with niobium is studied as a function of temperature and heating rate. Austenite grains show a two-stage growth. It has been found that as heating rate increases, the grain coarsening temperature (TGC) increases and the grain size at that temperature decreases. TGC temperature lies around 40-60°C below the temperature for complete dissolution of carbonitrides (TDISS).
929
Authors: Sandra Piazolo, Vera G. Sursaeva, David J. Prior
Abstract: First results from grain growth experiments in a columnar structured Al foil show several interesting features: (a) the grain size distribution remains heterogeneous even after up to 300 min. annealing and (b) the Von Neumann-Mullins relation is not always satisfied. To clarify the underlying reasons for these features, in-situ heating experiments within a Scanning Electron Microscope (SEM) were combined with detailed Electron Backscatter Diffraction (EBSD) analysis. These show that the movement of boundaries can be strongly heterogeneous. For example, the complete replacement of one grain by a neighbouring grain without significant change of the surrounding grain boundary topology is frequently seen. Experiments show that grain boundary energy and/or mobility are anisotropic both with respect to misorientation and orientation of grain boundary plane. Low energy and/or mobility boundaries are commonly low angle boundaries, twin boundaries and boundaries that form traces to a low index plane of at least one of the adjacent grains. As a consequence the Von Neumann-Mullins relation is not always satisfied.
935
Authors: Kim Verbeken, Leo Kestens
Abstract: After primary recrystallization, on further annealing, abnormal grain growth occurred in ultra low carbon steel. Texture evolution was studied by comparing the orientations after complete secondary recrystallization, with on one hand the nuclei for abnormal grain growth and on the other hand the selective growth products of the primary recrystallized matrix. The influence of both mechanisms could be identified in the final texture.
941
Authors: Naoki Maruyama, George D.W. Smith
Abstract: Atomic-scale interface segregation behaviour of Nb and Mo during different stages of recrystallisation of a-Fe has been investigated using a three-dimensional atom probe (3DAP). Experimental procedures to analyse a specific region of interest in the specimens and to determine an orientation relationship between analysed contiguous grains are briefly described, and then analytical artefacts which may affect the measured solute distribution are discussed. Atom probe analysis reveals that Gibbs free energy of segregation of Nb is larger than that of Mo in a-Fe, implying that a stronger solute Nb-interface interaction can be a reason for the larger retardation effect of recrystallisation by Nb addition. The comparison of measured solute profiles at migrating recrystallisation interfaces with calculated solute profiles show that Cahn’s solute drag model gives a reasonable fit to solute profiles for migrating interfaces.
949
Authors: Olivier Arnould, Olivier Hubert, François Hild
957

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