2000 Fiscal Year Final Research Report Summary
Elasticity Effects on the Microstructure Changes in Ordered Alloys Strengthened by Precipitation
| Project/Area Number |
11650677
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Physical properties of metals
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| Research Institution | Nagoya Institute of Technology |
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Principal Investigator |
DOI Minoru Nagoya Institute of Technology, Department of Materials Science and Engineering, Professor, 工学部, 教授 (60135308)
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| Co-Investigator(Kenkyū-buntansha) |
KOYAMA Toshiyuki Nagoya Institute of Technology, Department of Materials Science and Engineering, Research Associate, 工学部, 助手 (80225599)
KOZAKAI Takao Nagoya Institute of Technology, Department of Materials Science and Engineering, Associate Professor, 工学部, 助教授 (80110253)
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| Project Period (FY) |
1999 – 2000
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| Keywords | phase transformation / phase decomposition / Ostwald ripening / bifurcation / elastic interaction / non-linear / superalloy / order-disorder transformation |
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| Research Abstract |
Microstructure changes in Ni-base γ and TiAl intermetallics were investigated with transmission electron microscopy and theoretical calculations. Main results obtained are as follows :
1) Aγ phase of a Ni-Al-Ti alloy sometimes decomposes into a two-phase state of γ+γ, and spherical particles of disordered γ appear in the γ matrix. In the course of coarsening, γ particles clcange their shapes from spheres to plates parallel to {100}. Such a change in the equilibrium shape is a result of the elastic constraint and is quantitatively justified by theoretical calculations based on a microelasticity theory.
2) The shape changes from spherical particles to plates and/or rods increase the probability that a particle contacts with the neighbouring particles, which results in the accelerated coarsening of γ particles.
3) An α-Ti phase of a Ti-Al alloy sometimes decomposes into a two-phase state of Ti_3A1+α-Ti, and spherical ordered Ti_3Al particles appear in the disordered α-Ti matrix. In the course of coarsening, Ti_3Al particles change their shapes from spheres to rods, which is quantitatively justified by energy calculations based on a micrelasticity theory.
4) An Al-rich TiAl intermetallic phase sometimes decomposes into a two-phase state of Ti_3Al_5+TiAl, and ordered Ti_3Al_5 particles appear in the ordered TiAl. At the early stage of decomposition, the two-phase structure sometimes exhibits the so-called tweed structure. At the later stage of decomposition, Ti_33Al_5 morphology exhibits a kind of rafted structure. The computer simulations based on a phase-field method successfully reproduce the morphological changes of Ti_3Al_5 in the TiAl matrix.
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