2004 Fiscal Year Final Research Report Summary
Role of Local Microstructure Parameters in the Evolution Process of Interfacial Microstructures of Joints
| Project/Area Number |
13450295
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| Research Category |
Grant-in-Aid for Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Material processing/treatments
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| Research Institution | Osaka University |
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Principal Investigator |
SHIBAYANAGI Toshiya Osaka University, Joining and Welding Research Institute, Associate Professor, 接合科学研究所, 助教授 (10187411)
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| Co-Investigator(Kenkyū-buntansha) |
MAEDA Masakatsu Osaka University, Joining and Welding Research Institute, Assistant Professor, 先端科学イノベーションセンター, 助手 (00263327)
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| Project Period (FY) |
2001 – 2004
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| Keywords | EBSP method / microstructure / friction stir welding / solid state diffusion bonding / Monte Carlo simulation / grain growth / interfacial reaction / grain boundary migration |
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| Research Abstract |
This project aims to characterize microstructure of joint regions focusing on the role of microstructural parameters such as phases, shape and size of grains, grain orientations and grain boundary structures. Electron Back-Scattering Pattern analysis was utilized to characterize microstructures of Aluminum alloy joint fabricated by friction stir welding(FSW). 111 oriented grains tended to exist almost parallel to the rotating tool, indicating a heavy shear deformation is taking place around the rotating pin during FSW. This texture component is different from those appeared in Al alloys fabricated by conventional processing such as rolling, extrusion and so on. The microstructure of FSW joints is unstable at elevated temperature, showing an abnormal grain growth. FSW can produce peculiar microstructure in a localized region but the microstructure has some important information to be acting as a trigger effect of abnormal grain growth.
A Monte Carlo simulation based on Potts model was pe
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rformed to elucidate the role of local microstructure parameters in grain growth process of single and dual phase structures under uniform or heterogeneous temperature fields. Some new algorithms were established in the present research. Grain boundary migration, which is an essential and fundamental process for the grain growth, was strongly affected by second phase or temperature gradient. Retardation of grain growth was observed in the region where second phase particles exist or temperature was lower than the other area. Preferential grain growth such as abnormal grain growth was taking place when a steep temperature field was applied in a localized area. This result gave us a new idea for microstructure control, that is spot heating techniques for coding microstructure information into polycrystalline materials.
Solid-state diffusion bonding of ceramics to metals was performed concerning the interfacial reaction. A concept of chemical potential diagram was utilized for describing phase sequence in the interfaces between silicon nitride and metals such as vanadium, niobium, titanium and titanium aluminide, and so on.
The present project focused on the interfacial microstructures that show wide variety depending on the spatial distributions of microstructure parameters. Based on the findings of the present study, it should be noted that we can control local microstructure utilizing heterogeneous field of strain, temperature and compositions. Less
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