Papers by Author: Hajime Kato

Paper TitlePage

Authors: Yoshimasa Takayama, Jerzy A. Szpunar, Hajime Kato
Abstract: Intragranular misorientation reflects strain generated during deformation with dislocation glide. The SEM/EBSP (scanning electron microscope/ electron back scatter diffraction pattern) technique provides is “kernel average misorientation (KAM)” as the most appropriate quantity to evaluate the strain or the stored energy for a given point. The KAM is defined for a given point as the average misorientation of that point with all of its neighbors. In the present paper two analyses of the intragranular misorientation using the SEM/EBSP technique for a cyclic deformation at room temperature and a high temperature deformation in an Al-Mg-Mn alloy are reviewed.
Authors: Yoshimasa Takayama, T. Tozawa, Hajime Kato, Norio Furushiro
Authors: Genjiro Hagino, Hayao Eguchi, Yoshimasa Takayama, Hajime Kato
Abstract: The influences of solution treatments, prior cold drawings and aging treatments on mechanical properties in Corson alloy with high contents more than 8.0 mass% of Ni and Si have been investigated. As a result of the optimization of conditions, the maximum hardness and tensile strength reached 306HV and 968MPa, respectively. Effects of temperatures of solution treatment and aging on the mechanical properties were analyzed based on solid solute concentrations in matrix phase, which were estimated by using the linear analysis and calculated from the electrical conductivity. The solute concentrations were also measured directly by SEM-EDS. Consequently, the precipitation hardening of the alloys was governed mainly by the solute concentrations of Ni and Si in matrix phase in solution treatment. The hardness depended on not only the solute concentrations but also the excess of Ni and Si in the alloys.
Authors: Yoshimasa Takayama, T. Abe, T. Yashiro, Hideo Watanabe, Hajime Kato
Abstract: The composite accompanied with a function of thermoelectric conversion has been fabricated. It was a fiber metal laminate (FML) consisting of two aluminum alloy sheets of 0.5mm thickness and a central layer of glass fiber reinforced plastic (GFRP). The central layer with a thickness of 1mm included thermoelectric elements of Bi-Te based alloys between glass fibers. The mechanical properties of FML with and without the thermoelectric elements were evaluated by tensile and bending test. The thermomechanical properties were measured by a potentiometer for a module with heated and cooled sides, and plotted a potential as a function of difference in temperature between both sides.
Authors: Yoshimasa Takayama, Y. Otsuka, Toshiya Shibayanagi, Hajime Kato, Kunio Funami
Abstract: Grain refinement and high temperature deformation in two kinds of magnesium alloys subjected to friction stir processing (FSP) have been investigated. One was a rolled sheet of LA141Mg and another was a cast plate of AZ91Mg. FSP was developed by adapting the concepts of friction stir welding to obtain a fine grain size in a stirred zone. Grain refinement was achieved by FSP to give fine grain sizes of 11.4μm and 8.4μm for LA141 and AZ91 alloys, respectively. For LA141 alloy, the maximum stress of the FSPed sample was higher than that of the as-received one in the range of 300K to 523K while the elongation to failure of the former was considerably smaller than that of the latter. On the other hand, the elongation for the FSPed sample of AZ91Mg showed three times larger elongation with a lower maximum stress than the as-received cast one at 523K and 2.8×10-3s-1. Further difference in high temperature deformation for both magnesium alloys was discussed based on microstructural change and stress-strain curves.
Authors: Yoshimasa Takayama, Takanori Itoh, Eiji Harunari, Hajime Kato, Norio Furushiro
Authors: Yoshimasa Takayama, Nobuyuki Ishikawa, Hajime Kato, Hideo Watanabe
Authors: Masakazu Kobayashi, Yoshimasa Takayama, Hajime Kato, Hiroyuki Toda
Abstract: In-situ SEM/EBSP analysis has been performed during the evolution of the cube texture in a pure aluminum foil. In general, foils for capacitor are manufactured in an industrial process of casting, homogenizing, hot rolling, cold rolling (CR), partial annealing (PA), additional rolling (AR) and final annealing (FA). The foil samples after CR or AR in the process were analyzed by the SEM/EBSP technique at a constant temperature which was step-heated repeatedly by 10-20K from a room temperature to 623K or 598K. In a CRed sample, cube ({001}<100>) grains begin to grow preferentially at 503K to cover the sample. On the other hand, in a sample subjected to PA at 503K and AR, cube grains coarsened rapidly and preferentially at more than 533K in contrast to other oriented small grains remaining their sizes. Further, intragranular misorientation analysis revealed that the misorientation, which corresponds to dislocation density or strain, was much smaller in cube grains than in S ({123}<634>) and Cu ({112}<111>) ones.
Authors: Yoshimasa Takayama, H. Ochiai, Norio Furushiro, Hajime Kato, Hideo Watanabe
Abstract: Severely rolled sheets of Al-4.5%Mg-0.7%Mn based alloys have been prepared to achieve grain refinement leading to low temperature superplasticity. Rolling is one of straining technique which has a high possibility of industrial application. The alloys used were T1: base one adding 0.08%Zr and 0.05Ti for suppression of grain growth, F1: 0.80%Fe addition and F2: 1.92%Fe addition to increase nucleation sites of recrystallization. For comparison, M1: Al-4.2%Mg was also prepared. All of samples were 99.8% cold rolled to thin sheet 0.1mm thick. The maximum elongation of 150%, which was markedly large in consideration of specimen thickness of 0.1mm, was obtained at 533K and 1.4×10-3s-1 for T1 sample while the elongations for F1 and F2 showed less than 100%. On the other hand, M1 exhibited larger elongation of 190% at 533K and 1.4×10-3s-1. Further, difference in superplastic deformation of these alloys was investigated by using SEM/ EBSP analysis of intragranular misorientation, which reflects strain or stored energy generated during deformation with dislocation glide, to discuss the deformation mechanism.
Authors: Yoshimasa Takayama, S. Sasaki, Hajime Kato, Hideo Watanabe, Akio Niikura, Yoichiro Bekki
Showing 1 to 10 of 19 Paper Titles