Masahiko Demura

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Organization: National Institute for Materials Science (NIMS) , Japan
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Title: (PhD)
Co-reporter:Masahiko Demura, Ya Xu, Kyosuke Kishida, Toshiyuki Hirano
Acta Materialia 2007 Volume 55(Issue 5) pp:1779-1789
Publication Date(Web):March 2007
DOI:10.1016/j.actamat.2006.10.040

Abstract

In Ni3Al the cold-rolled Goss texture changed to a complicated one after primary recrystallization and returned to the original Goss during the subsequent grain growth, which can be referred to as the texture memory effect. In this study, we examined the evolution of grain orientations during the grain growth using the electron backscatter diffraction (EBSD) method. It was found that just after the primary recrystallization most of the grains had a 40°〈1 1 1〉 rotation relationship to the Goss texture, the remaining grains being Goss and other textures. The formation of the 40°〈1 1 1〉 rotated grains can be explained by a multiple twinning mechanism. In the grain growth, the Goss grains, which were surrounded by the 40°〈1 1 1〉 rotated grains, grew preferentially due to the high mobility of the 40°〈1 1 1〉 grain boundaries, leading to the texture memory effect.

Co-reporter:M. Demura, D. Golberg, T. Hirano
Intermetallics 2007 Volume 15(Issue 10) pp:1322-1331
Publication Date(Web):October 2007
DOI:10.1016/j.intermet.2007.04.007
An athermal deformation model was proposed for the yield stress anomaly in Ni3Al based on the concept that dislocation multiplication versus the immobilization by the Kear–Wilsdorf (KW) locking controls the plastic deformation. In the model dislocations, superkinks lying between two KW locks multiply through expansion in an athermal manner. Regarding the KW locking, the entire screw segment cross-slips onto (010) to form long KW locks in one thermal activation event. The model can explain the macroscopic characteristics of the deformation, the strain-rate independent of the yield stress and the compliance with Schmid's law, which were recently revealed in binary, stoichiometric Ni3Al single crystals. Quantitative assessment proved that the model reproduces the temperature dependence of the yield stress with reasonable fitting parameters. The driving force for the KW locking, one of the most important parameters for the yield stress anomaly, was evaluated at 127 mJ m−2. This value is in good agreement with those calculated from the anti-phase boundary energies on {111} and {100} reported in the literature.
Co-reporter:Masahiko Demura, Kyosuke Kishida, Yozo Suga, Motohiro Takanashi, Toshiyuki Hirano
Scripta Materialia 2002 Volume 47(Issue 4) pp:267-272
Publication Date(Web):20 August 2002
DOI:10.1016/S1359-6462(02)00139-2
Cold rolling of single-crystalline Ni3Al was performed to fabricate thin foils of 23 μm in thickness and 50 mm in width. The rolling texture and basic mechanical properties of the foils were examined. The rolling texture consisted of two components, (1 0 1)[1 2 ] and (1 0 1)[ 2 1]. The foils exhibited high tensile fracture strength without plastic elongations. However, their bending ductility was quite remarkable.
nickel, compound with tin (3:1)
Nickel, compd. with tin (3:2)
Aluminum, compd. with nickel (1:3)