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2. Grain refinement in titanium prevents low temperature oxygen embrittlement

Author

Chong, Yan, Gholizadeh, Reza, Tsuru, Tomohito, Zhang, Ruopeng, Inoue, Koji, Gao, Wenqiang, Godfrey, Andy, Mitsuhara, Masatoshi, Morris, JW, Minor, Andrew M, and Tsuji, Nobuhiro

Subjects
Engineering, Macromolecular and Materials Chemistry, Materials Engineering, Chemical Sciences
Abstract

Interstitial oxygen embrittles titanium, particularly at cryogenic temperatures, which necessitates a stringent control of oxygen content in fabricating titanium and its alloys. Here, we propose a structural strategy, via grain refinement, to alleviate this problem. Compared to a coarse-grained counterpart that is extremely brittle at 77 K, the uniform elongation of an ultrafine-grained (UFG) microstructure (grain size ~ 2.0 µm) in Ti-0.3wt.%O is successfully increased by an order of magnitude, maintaining an ultrahigh yield strength inherent to the UFG microstructure. This unique strength-ductility synergy in UFG Ti-0.3wt.%O is achieved via the combined effects of diluted grain boundary segregation of oxygen that helps to improve the grain boundary cohesive energy and enhanced dislocation activities that contribute to the excellent strain hardening ability. The present strategy will not only boost the potential applications of high strength Ti-O alloys at low temperatures, but can also be applied to other alloy systems, where interstitial solution hardening results into an undesirable loss of ductility.

Published
2023

11. Heterostructured materials: superior properties from hetero-zone interaction

Author

Zhu, Yuntian, Ameyama, Kei, Anderson, Peter M, Beyerlein, Irene J, Gao, Huajian, Kim, Hyoung Seop, Lavernia, Enrique, Mathaudhu, Suveen, Mughrabi, Hael, Ritchie, Robert O, Tsuji, Nobuhiro, Zhang, Xiangyi, and Wu, Xiaolei

Subjects
Engineering, Materials Engineering, Resources Engineering and Extractive Metallurgy, Heterostructured materials, synergy, heterostructures, hetero-deformation induced (HDI) hardening, back stress, forward stress, Materials engineering, Resources engineering and extractive metallurgy
Abstract

Heterostructured materials are an emerging class of materials with superior performances that are unattainable by their conventional homogeneous counterparts. They consist of heterogeneous zones with dramatic (>100%) variations in mechanical and/or physical properties. The interaction in these hetero-zones produces a synergistic effect where the integrated property exceeds the prediction by the rule-of-mixtures. The heterostructured materials field explores heterostructures to control defect distributions, long-range internal stresses, and nonlinear inter-zone interactions for unprecedented performances. This paper is aimed to provide perspectives on this novel field, describe the state-of-the-art of heterostructured materials, and identify and discuss key issues that deserve additional studies.

Published
2021

14. Neighborhood-level socioeconomic factors moderate the association between physical activity and relative age effect: a cross-sectional survey study with Japanese adolescents

Author

Mori, Takaaki, Aoki, Takumi, Oishi, Kan, Harada, Tetsuo, Tanaka, Chiaki, Tanaka, Shigeho, Tanaka, Hideki, Fukuda, Kazuhiko, Kamikawa, Yasuko, Tsuji, Nobuhiro, Komura, Keisuke, Kokudo, Shohei, Morita, Noriteru, Suzuki, Kazuhiro, Watanabe, Masashi, Kasanami, Ryoji, Hara, Taketaka, Miyazaki, Ryo, Abe, Takafumi, Yamatsu, Koji, Kume, Daisuke, Asai, Hedenori, Yamamoto, Naofumi, Tsuji, Taishi, Nakaya, Tomoki, and Ishii, Kojiro

Published
2022
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18. Qualitative Research on the Development of Japanese Female Primary School Teachers' Perceptions of the Impact of Gender on Their Careers

Author

Akashi, Ai and Tsuji, Nobuhiro

Abstract

This study examined how Japanese female primary school teachers who have continued to study physical education (PE) perceive gender consciousness. The other, more important, purpose of this study was to demonstrate factors that enhance teachers' commitment to study PE and their development processes and its effect on their teaching careers. Using a semi-structured interview, qualitative data were collected from 14 female primary school teachers who have worked as PE chiefs. Data were analysed using the modified-grounded theory approach. As for gender consciousness, participants thought their physical strength limits them as they age; this often prompts them to resign as PE chiefs. However, they did not think that difficulties arise from gender consciousness in the continued study of PE. As for their teaching careers, this study demonstrated development processes focusing on factors generating continuation of PE study and the influence of each factor on each generation. In conclusion, providing opportunities that could promote factors to prompt teacher development in each generation is important for increasing the number of female teachers who study PE in primary schools in Japan.

Published
2015

22. Exploring unusual Lüders deformation in ultrafine-grained high-Mn austenitic steel.

Author

Hwang, Sukyoung, Kato, Hirokazu, Okada, Kazuho, Park, Myeong-heom, Lavakumar, Avala, Gholizadeh, Reza, Adachi, Hiroki, Sato, Masugu, and Tsuji, Nobuhiro

Subjects
DIGITAL image correlation, STRESS-strain curves, DEFORMATIONS (Mechanics), AUSTENITIC steel, TENSILE tests, ALUMINUM-magnesium alloys, X-ray diffraction
Abstract

Ultrafine-grained (UFG) high-Mn austenitic steel exhibited unusual discontinuous yielding on its stress-strain curve, characterized by a yield drop followed by a stress plateau, indicative of Lüders deformation. Utilizing the digital image correlation (DIC) technique, a strain-localized region known as a Lüders band was observed to propagate during Lüders deformation. Following microstructural observations using state-of-the-art techniques such as in-situ synchrotron XRD measurement during the tensile test and ex-situ S/TEM and SEM-ECCI, dislocation multiplication, rather than twinning, was theoretically identified as the primary deformation mechanism responsible for the unusual Lüders deformation in UFG high-Mn austenitic steel. [ABSTRACT FROM AUTHOR]

Published
2024
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46. Stress partitioning in harmonic structure materials at the early stages of tensile loading studied in situ by synchrotron X-ray diffraction

Author

Sjögren-Levin, Elis, Pantleon, Wolfgang, Ahadi, Aylin, Hegedüs, Zoltan, Lienert, Ulrich, Tsuji, Nobuhiro, Ameyama, Kei, Orlov, Dmytro, Sjögren-Levin, Elis, Pantleon, Wolfgang, Ahadi, Aylin, Hegedüs, Zoltan, Lienert, Ulrich, Tsuji, Nobuhiro, Ameyama, Kei, and Orlov, Dmytro

Abstract

In situ X-ray diffraction was employed to gain insight into the tensile deformation behavior of harmonic structure (HS) nickel. HS consists of a continuous network of fine grains encompassing islands of coarse grains. With the aid of a newly developed separation algorithm, the X-ray diffraction signals from coarse and fine grains were analyzed separately. Using line profile analysis, the evolution of local stresses and microstrains in the respective grain fractions were examined. Several stages were identified during yielding and the onset of plastic deformation in HS nickel. The mechanical behavior of the individual fractions was related to the macroscopic behavior of the HS and compared to that of homogeneous counterparts with similar average grain sizes as the grain fractions. The analysis reveals that the stress partitions between the grain fractions and that the plastic deformation of coarse grains within the HS are constrained by the network of fine grains.

Published
2023

49. Influence of microtexture on ultrasonic reflection in Ti-6Al-4V alloy hot-forged in α+β region

Author

Ito Yoshinori, Takamatsu Hiroyuki, Saeki Shogo, and Tsuji Nobuhiro

Subjects
Engineering (General). Civil engineering (General), TA1-2040
Abstract

Morphological change in regions with microtexture, i.e., macrozones, in Ti-6Al-4V alloy after hot-forging in α+β phase region was analyzed using SEM/EBSD technique, and then the correlation with ultrasonic reflection was investigated. Starting material had colony-type microstructure consisting of lamellar-α with the same crystallographic orientation. Forging (cogging and upsetting) was conducted in α+β phase region to produce a cylindrical material with smaller cross section, followed by air cooling. Thus, resulting microstructure consisted of granular-α. To estimate local change in elastic modulus within the materials, we analyzed crystallographic orientations of α-phase using SEM/EBSD in terms of an inclination angle of c-axis. The regions having the nearly common crystallographic orientations of α-phase were found. Shapes of such regions with microtexture were elongated along the axial direction, which formed quasi-periodic variation of the inclination angle, i.e., elastic modulus, of α-phase along the radial direction of the forged material. Ultrasonic measurement was conducted at a frequency of 5 MHz along the radial direction and the axial direction. Relationship between the morphology of regions having microtexture and the amplitude of backscattered noises was evaluated. It was considered that the quasi-periodicity of the inclination angle correlated with the amplitude of backscattered noises in ultrasonic measurement.

Published
2020
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