Papers by Keyword: Triple Junctions

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Authors: Sergiy V. Divinski, Leonid N. Larikov
Authors: Eugen Rabkin, V. Semenov, W. Gust, Lasar S. Shvindlerman
Authors: Hiromi Miura, Sutandyo Andiarwanto, Tetsuo Sakai, John J. Jonas
Abstract: The preferential initiation of dynamic recrystallization (DRX) at triple junctions (TJs) in stainless steel polycrystals was investigated in compression at 1123 K to 1323 K at a strain rate of 2 x 10-4 s-1. Nucleation appeared at TJs at strains as low as 0.1. This strain is only about 1/5 to 1/2 of the peak strain at which DRX is conventionally believed to occur extensively. Furthermore, DRX nucleation was not observed to take place at grain boundaries or in the matrix at this strain. The probability of DRX nucleation at TJs increased monotonically with strain and temperature. It also depended on the angle, y, between the compression axis and the sliding boundary. That is, when the angle, y, approaches 45 degrees, the probability of DRX nucleation at TJs is higher. These results reveal the important role of grain-boundary sliding (GBS) on DRX nucleation at TJs. It should also be noted that more than 90% of the grains nucleated at TJs were twins. Such dynamic twinning suggests that the essential DRX nucleation mechanism is twinning.
Authors: Steven Van Boxel, Marc Seefeldt, Bert Verlinden, Paul van Houtte
Abstract: The substructure of a single grain in an electron backscatter diffraction (EBSD) data map is studied, focusing on the influence of the grain boundary configuration on the misorientation to the average grain orientation of data points close to the grain boundary. For most grain boundary segments a certain degree of linking between the misorientations to the average orientation of the grain exists and large deviations from the average orientation of the grain are observed close to the triple junctions of the boundary segments. Changes of the misorientation over one boundary segment are analysed and possible explanations for these variations are discussed. It is suggested that the variations of the misorientation over the boundary segment can be attributed to the requirements of stress equilibrium and strain compatibility. Also the tendency of the grain boundary to lower its surface energy might have a significant influence on the misorientation profile and therefore on the subdivision behaviour of the grains.
Authors: A.W. Larsen, C. Gundlach, Henning Friis Poulsen, L. Margulies, Q. Xing, Dorte Juul Jensen
Abstract: A new method for in-situ studies of nucleation in bulk metals based on high energy synchrotron radiation is presented. Copper samples cold rolled 20% are investigated. The crystallographic orientations near triple junctions are characterized using non-destructive 3DXRD microscopy before, during, and after annealing for 1 hour at 290°C. This method allows in-situ identification of new nuclei and the deformed material, which spawns the nuclei. Also, since data is acquired during annealing nucleation kinetics can be studied.
Authors: Cornelia Pein, Bernhard Sonderegger, Christof Sommitsch
Abstract: The influence of the microstructure of metallic materials on its creep behavior is complex. Besides the chemical composition, the distinct configuration of the microstructural elements has a major influence on the deformation processes. In the presented work a physically based Finite Element model has been applied to study creep behavior on a microstructural level. The main focus is set on the local influence of grain boundaries and triple points on creep straining. The results indicate that such microstructural configurations lead to a highly heterogeneous creep strain distribution. Thus, this study is an important step to a deeper understanding of complex local interactions of creep phenomena.
Authors: K. Bhanumurthy, A. Laik, G.B. Kale
Abstract: The incremental diffusion couples are used for evaluating interdiffusion couples in a narrow composition range and these results are extrapolated to get an estimate of impurity diffusion coefficients. In fact, several incremental couples are needed to get impurity diffusion coefficients at different compositions. This process is generally tedious. The present method describes a relatively simple method for evaluating the diffusion coefficients using “step diffusion couples”. A simple experimental method is described to prepare a step diffusion couple. This method involves preparation of diffusion couples in two stages. In the first stage, diffusion couple is made between the two materials in a conventional way and annealed for extended period of time to have a large diffusion zone typically of the order of 2-3 mm. In the second stage, the starting materials are placed on the diffusion couple in a direction perpendicular to the diffusion zone and annealed at a suitable temperature for diffusion to occur between the diffusion zone and the starting materials. This method is applied to study the interdiffusion behavior in the b phase of the Ti-Zr system. Boltzmann-Matano and Hall’s methods were used to determine the interdiffusion coefficients and their composition dependence. Kirkendall shift is observed towards Ti side and the intrinsic diffusion coefficients of Ti is approximately three times that of Zr. The width of the diffusion zone is strongly dependent on the composition of the step diffusion couple. It is observed that the interdiffusion coefficients evaluated at the terminal compositions matched well those published values in the Ti-Zr system. This experimental technique offers an easy and elegant method to determine the diffusion parameters without the tedious preparation of incremental diffusion couples.
Authors: Valerie Randle
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