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Outline of Research

Contents of Research

The project aims to systematically clarify the relationship between the peculiar properties of BNMs and their structures through close collaboration of researchers in various fields. During 5-years' research period, the project focuses on these three topics shown below:

  1. Establish concept of structure design of BNMs (Group A01)
  2. Establish various fabrication processes of BNMs (Group A02)(A02)
  3. Clarify the mechanism of peculiar mechanical properties of BNMs (Group A03)

The targets of the groups in this project and the relationship between the groups are illustrated in Fig.3. Each group consists of two sub-groups: one is focusing on experimental studies, the other on theoretical and simulation studies. This is because the project intends to conduct research efficiently by close collaboration of experimental studies and theoretical / simulation studies. The research project aims to create new methodology and research field in novel materials science through integrating experimental studies and simulation studies. As Japan has the high international competitiveness of both fundamental research field and applied research field in metallic material science, it is very meaningful to conduct this research project in Japan. Recently, development of the state of the art nanostructure analysis in materials science, such as three dimensional transmission electron microscope tomography, three dimensional atom probe, etc, is remarkable, and the project involves such novel techniques. In addition, recent large-scale computer simulation based on atomic models, which can be applicable for the study of BNMs, is also used within the project as well. This project involves many leading researchers in these fields, and can give the opportunity for integrating the various research fields.and the project involves such novel techniques. In addition, recent large-scale computer simulation based on atomic models, which can be applicable for the study of BNMs, is also used within the project as well. This project involves many leading researchers in these fields, and can give the opportunity for integrating the various research fields.and the project involves such novel techniques. In addition, recent large-scale computer simulation based on atomic models, which can be applicable for the study of BNMs, is also used within the project as well. This project involves many leading researchers in these fields, and can give the opportunity for integrating the various research fields.

Fig.3 Well-Designed Scheme for the Project
Fig.3 Well-Designed Scheme for the Project

Characteristics of this research plan

Contents of each plan group (Click each title to see detail)

A01 Research project : Design of BNMs
The target of this plan group is to establish the best material design concept of the bulk nanometal that shows an excellent characteristic in which break conventional common sense of coexisting both strength and ductility. This study is particularly focusing on the phase transformation and precipitation phenomena of bulk nanometal, a material filled with grain boundaries and boundary interface. Even though precipitation and phase transformation are an important metallurgical phenomena that determine the material structure, precipitation and phase transformation of nanometal has not yet been studied in the world at all. Moreover, this study also attempts on the structure control of bulk nanometal having good coherent boundaries of special twin boundaries. This projects also contributes to the research on production through processing of group A02, and to the research on mechanical characteristics of group A03, by clarifying not only the effect of the alloy plasticity, but also the principle of the optimal nano-structure formation through the solid phase reactions of the phase transformations and precipitations, etc., and by quantitive analysing on bulknanometal microstructure and its microstructural evolution using nano structure analysis such as 3D atom probe, cutting-edge electron microscopy method including three demonsional tomography, etc.

Research representative : Prof. Nobuhiro Tsuji, Dept. of Materials Science and Engineering, Kyoto University.
A01 Research project : First principle calculation of basic physical properties
This group quantitatively clarify internal factors of material characteristics on Bulk Nanostructured Metal, such as elastic properties of crystals, ideal strength of crystal, mechanical stability of crystal, structure of boundary, stacking fault, dislocation, twin, point defect, physical properties and interactions among these factors on various metals and alloys based on analysis grounded in First-principles calculations, and contributes to the achievement of research topic A01. In addition, while focusing on the change of crystal stability and defect behavior to the change of external factors such as grain size, strain rate, ambient temperature, and applied stress, by construction of multi-scale model in space-time and analysis base on it, this group also determines the extent of these internals and externals factors may affect to the bulk characteristics. Furthermore, collaborated with group A03, group A01 aims to acquire the basic physical design guidelines for controlling mechanical properties and the understanding of expression mechanism on universal mechanical properties, and resolves what would determines the characteristic time and scale which peculiar mechanical properties of Bulk Nanostructured Metal develop.

Research representative : Shigenobu Ogata, Department of Mechanical Science and Bioengineering, Graduate School of Engineering Science, Osaka University, Professor
A02 Research project : Precise structure control of BNMs
In this study, this team receives material design guidlines from team A01 and invent bulk-nanometal, which precisely structure-controlled in nano level. In addition, while collaborates with team A03, team A01 clarifies the correlation of nano structure and mechanical characteristic. Severe Plastic Deformation, thermo-mechanical control process, non-equilibrium PM process, electrolytic deposition process are applied in inventing bulk nanometal. The role of nano-structured bulk lattice defects introduced in severe plastic deformation is clarified. This team also clarifies not only the role of nano-structured heterogeneous phase interface and shear band formed during phase transformation and nonequilibrium phase formation, but also the role of twin observed on metals where stacking fault easily occurs with the correlation of grain boundaries and those typical crystal defect of dislocations. Effects of difference on external factors, such as applied stress, ambient temperature, and strain introduction mode on nano-structurization by mechanical process. On the other hand, this team aims to process nano-structure using electrodeposition method which introduce small amount of lattice defect unlike severe plastic deformation method, and to clarify the effects of mechanical process differences on nanostructure and mechanical characteristics. This planning team invents precisely controlled nanometal, provides sample and process information to other groups, shares the understanding on the relation of the analytical evaluation result of mechanical properties and microstructure, and ties to the acomplishment of the goals in all areas of this study.

Research representative : Zenji Horita, Department of Materials Science and Engineering, Faculty of Engineering, Kyusyu University, Professor
A02 Research project : Computer and physical simulation of BNMs
Understanding quantitatively the effect of large deformation including reversing the direction of deformation, or the effect of large deformation including strong shear deformation on nanostructure formation by severe plastic deformation and thermo mechanical process including phase transformation, is an important step to understand the mechanism of Bulk Nanostructured Metal creation. Here, the stress reduction due to the Bauschinger effect,structural change due to (repeatition of) plastic deformation which mainly shear, and change of dislocation structure etc. which is considered to involve in controlling above aspects, is the basic technique that can be applied not only in formation of Bulk Nanostructured Metal, but also to other field such as fatigue and wear. In this study, under the above ideas, we aim to understand the formation of ultrafine grained structure of Bulk Nanostrucured Metal due to thermo mechanical process, including phase transformation, by numerical simulation and physical simulation using thermal processing reproduction test machine etc. The resulting process design ideas are provided then to team A02-3, to contribute to the effective development of the actual creation process. Moreover, the results obtained by this team closely relate to the clarification of the mechanical characteristic aimed by team A03.

Research representative : Jun Yanagimoto, Department of Mechanical Engineering and Biofunctional Systems, Institute of Industrial Science, The University of Tokyo, Professor
A03 Research project : Mechanical properties and deformation theory of BNMs
If the behavior of dislocation inside fine confined-crystal in submicron size can be schematically clarified and new deformation and strengthening mechanism which considers these aspects can be proposed, a revolutionary and dramatical contribution in development and advancement of understanding on material's mechanical characteristics can be achieved. Of course, new deformation and strengthening mechanisms, and various phenomena obtained experimentally should be able to be explained rationally. For instance, strength increases as the crystal grain diameter becomes small, and the temperature dependence and the transformation speed dependency of strength become remarkable, etc. In the present study, we challenge on fundamental analysis of mechanical properties of Bulk Nanostructured Metals having fine confined crystal space from both experiment by various approaches and theory based on dislocation theory and micro mechanics. Inside the planinng team, the rolepart is divided where each researcher clarifies strength, ductility, destruction toughness, fatigue behavior, and external factor dependency, etc. Moreover, neutron in-situ deformation analysis using J-PARC is a powerful experiment tool for this team. This study is promoted in integration with the approach of the calculation method of team A03-6, not to mention that discussions and close collaborations are also carried out inside planning team. Research results obtained by this plan study have significant implications for the material design of team A01 and the process construction of team A02.

Research representative : Masaharu Kato Department of Materials Science and Engineering, Interdisciplinary Graduate School of Science and Engineering, Tokyo Institute of Technology, Professor
A03 Research project :Analysis of mechanical characteristics of BNMs by large-scale computing on the defects evolution.
In Bulk Nanostructured metals, the unit of structure becomes a nano-scale and the volume fraction of grain boundary and interface (plane defects) rapidly increases. Thus, it is considered as the factor in which the development of lattice defects through grain boundaries caused the anomalous mechanical characteristics. In this study, based on two different scales, the development of complicated interior lattice defect in Bulk NanoStructured Metals is expressed by the large-scale calculation by the atomistic model which can directly express atomic structure of grain boundary (Molecular Dynamics method) and the continuum modeling considering the effect of grain boundaries (crystal plasticity theory for severe plastic deformation). The various expression mechanism of mechanical characteristic got from A3 group is clarified and the results are given back to other groups including A01 and A02, and it contributes to construct the basis of materials science of multi-scale calculation for Bulk NanoStructured Metals. Research representative of this group acquired a large number of excellent knowledge by the large-scale calculation on the deformation of the ultra-fine grained materials in the previous innovative area research, “Giant straining process”, and it is possible to carried out the research of this area immediately by utilizing the knowledge.

Research representative : Tomotsugu Shimokawa, Division of Innovative Technology and Science, Graduate School of Natural Science & Technology, Kanazawa University, Associate professor

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