Papers by Author: Eiji Akiyama

Paper TitlePage

Authors: T. Sundararajan, Eiji Akiyama, Kaneaki Tsuzaki
Abstract: Crevice corrosion experiments on pure iron were carried out in a 0.5 M acetate buffer with varied chloride concentrations. Changes in resultant currents and morphology due to crevice attack were explained by IR potential drop mechanisms. The specimens experienced potential drop inside the crevice, which resulted in the formation of passive, active, and hydrogen evolution regions. The passive region did not exist in the electrolyte containing 0.05 M and 0.5 M chloride. Hydrogen evolution, which occurred inside the crevice was measured on rear side of the specimen using hydrogen permeation test. The results suggest that the hydrogen produced inside the crevice is measurable using a permeation test. The entry of diffusible hydrogen showed a significant increase with the addition of chloride into the acetate buffer.
97
Authors: M. Mehmood, Eiji Akiyama, H. Habazaki, A. Kawashima, Katsuhiko Asami, K. Hashimoto
629
Authors: Zuo Gui Zhang, Eiji Akiyama, Yoshimi Watanabe, Yasuyuki Katada, Kaneaki Tsuzaki
Abstract: In this study, an Al-7 wt% Si-1.5 wt% Cu alloy was subjected to severe plastic deformation (SPD) by an equal-channel angular pressing (ECAP) technique. The ECAP process was repetitively carried out up to 8 passes using a strain introduction method of route BC, at a temperature of 25 °C and a pressing rate of 0.33 mm s-1. Microstructures of the samples before and after ECAP were observed by a scanning electron microscopy (SEM). Electrochemical properties of the Al-Si-Cu alloy fabricated by ECAP have been investigated in a borate-boric acid buffer solution containing Cl¯ ions at pH 8.3 and 25 °C by potentiodynamic polarization test. Corrosion pits on the sample surface after anodic polarization were investigated by means of SEM. The anodic polarization showed that as-cast Al-Si-Cu alloy with plate-shaped Si particles has poor resistance against pitting corrosion comparing to quenched sample without ECAP. Pitting potentials of ECAPed Al-Si-Cu alloy samples were higher than that of the sample without ECAP. In the Al-Si-Cu alloy, the corrosion pits were found in the region of Si particles and the size of pits formed on the ECAPed samples became smaller than that without ECAP. It is considered that the improvement of the pitting resistance of ECAPed Al-Si-Cu alloy is due to homogenous distribution of spherical Si particles generated during ECAP process.
2892
Authors: Mao Qiu Wang, Eiji Akiyama, Kaneaki Tsuzaki
Abstract: We examine the hydrogen embrittlement susceptibility of a high-strength AISI 4135 steel by means of a slow strain-rate test (SSRT) using notched round bar specimens. Hydrogen was introduced into the specimens by electrochemical charging and its content was measured by thermal desorption spectrometry (TDS). It was found that the maximum tensile stress decreased in a power law manner with increasing diffusible hydrogen content. Finite element method (FEM) calculations demonstrated that the peak value of the maximum principal stress and the peak value of the locally accumulated hydrogen concentration at the maximum tensile stress were in good agreement with one power law relationship for the specimens with different stress concentration factors.
55
Authors: K. Asami, Eiji Akiyama, Yoshihiko Murakami, Hisamichi Kimura, Masanori Kikuchi, K. Hashimoto
789
Authors: Zuo Gui Zhang, Eiji Akiyama, Yoshimi Watanabe, Yasuyuki Katada, Kaneaki Tsuzaki
Abstract: The influence of microstructure on the electrochemical properties of an Al-5 wt% Cu binary alloy which was severely deformed by equal-channel angular pressing (ECAP) has been investigated in a borate-boric acid buffer solution containing Cl¯ ions at pH 8.3 and 25°C by potentiodynamic polarization test. The anodic polarization results showed that pitting potentials of ECAPed Al-Cu alloy samples were higher than that of the sample without ECAP and increased with repetitive ECAP passes. The pitting corrosion attack of Al-Cu alloy samples took place in the surroundings of Al2Cu (θ) phase. It is considered that the grain refinement of θ phase and the solid solution generated in Al matrix during ECAP process are responsible for the improvement of the corrosion resistance of ECAPed Al-Cu alloy.
705
Authors: K. Hashimoto, P.Y. Park, J.H. Kim, Eiji Akiyama, H. Habazaki, A. Kawashima, K. Asami
779
Authors: Eiji Akiyama, H. Habazaki, A. Kawashima, K. Asami, K. Hashimoto
809
Authors: Katsuhiko Asami, Eiji Akiyama, Koji Hashimoto
79
Showing 1 to 9 of 9 Paper Titles