2007 Fiscal Year Final Research Report Summary
Quantification of Hierarchal Microstructures of Metallic Materials and the Prediction of the strength by Homogenization Method
| Project/Area Number |
17360337
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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 |
Structural/Functional materials
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| Research Institution | Nagoya University |
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Principal Investigator |
MURATA Yoshinori Nagoya University, Graduate School of Engineering, Associate Professor (10144213)
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| Co-Investigator(Kenkyū-buntansha) |
KOYAMA Toshiyuki National lnstitute for Materials Science, CompulationalMaterials Science Center, Senior Remember (80225599)
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| Project Period (FY) |
2005 – 2007
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| Keywords | system free energy / superalloy / heat resistant steel / hierarchy structure / rafted structure |
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| Research Abstract |
Microstructural changes of materials axe emerged as a result of interactions of multi-Sixes in it. In metallic materials, the properties have been designed by using the inhomogeneousity of the microstructure The purposes of this study are to elucidate quantitatively the microstructural evolution of the inhomogeneous microstructure and to estimate the change of properties of heat resistant metallic materials, which show a complex hierarchy multi-phase. In order to perform these purposes, we employed the concept of “System Free Energy" and quantified the degree of the microstructural change using the concept This quantification made it possible to obtain the relationship between the microstructural al evolution and the strength change of the materials For example, a series of microstructural evolution from the formation to collapse the rafted structure in nickel-based superalloys was simulated by the Phase-field method, and the results were considered for understanding the creep strength
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of the alloys. It was found that the symmetry of the eigen strain changed from cubic to tetragonal as a result of the increase of the creep strain with increasing creep time. As a result the rafted structure formed perpendicular to [001] direction of the gamma-prime phase became wavy shape by changing the stable direction of the structure. The change in the stability of the rafted structure was strongly related to the creep strength of the superalloys, i.e. the creep strength was kept high when the rafted structure was stable. Furthermore, it was found that the creep strain was able to deduce from the shape of the rafted structures. The relationship between the creep strength and the hierarchal microstructure of ferritic heat resistant steels was also obtained, i.e., the stability of the lath, block and packet of the martensite phase was directly related to the long-term creep strength of them.
The effects of alloying elements on the stability of the hierarchal microstructures were elucidated by the c cross-interdiffusion coefficients obtained from a series of diffusion experiments using ternary systems. In ternary systems, four interdiffusion coefficients were obtained by the diffusion experiments, and the interactions between the alloying elements in the host metal were emerged as the sign of two cross interdiffusion coefficients. Less
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