1989 Fiscal Year Final Research Report Summary
Mechanism of Cellular Precipitation of Alloy Carbides and Nitrides in Multi-component Alloy Systems
| Project/Area Number |
62460192
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| Research Category |
Grant-in-Aid for General Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Research Field |
金属材料(含表面処理・腐食防食)
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| Research Institution | Tokyo Institute of Technology |
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Principal Investigator |
KIKUCHI Makoto Tokyo Institute of Technology Faculty of Engineering Profess, 工学部, 教授 (30089817)
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| Project Period (FY) |
1987 – 1989
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| Keywords | Cellular Precipitation / Grain Boundary Reaction / Fe-Cr-Ni-N Alloys / Cr_2N / Electron Probe Micro-Analysis / Long Range Diffusion / Nitrogen Analysis |
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| Research Abstract |
1. Nitrogen Analysis by Electron Probe Microanaiyzer:
A method of nitrogen analysis was established for solution nitrogen in Cr-Ni austenitic steels in a concentration range between 0 and 1 wt% with an accuracy of 0.01 wt%. Seven calibration curves for nitrogen were determined in austenitic steels with different Cr, Ni and Mo concentrations. A newly developed dispersion element designed for nitrogen analysis was employed.
2. Nitrogen Concentration Profiles in both Untransformed Matrix and Cell: Nitrogen concentration profiles in both untransformed matrix and cell in a 25Cr-2ONi-0.59N austenitic steel aged at 800ﾟC were experimentally measured in terms of the newly established method described the previous section. It was directly confirmed that nitrogen flows into cell through a long range diffusion from the untransformed matrix to the cell, accompanying with the cell growth.
3. Model for a Growth Mechanism of Cellular Precipitation in Multi-Component Systems: A model, developed by Hillert to explain growth features for the cellular precipitation in substitutional binary systems, has successfully been extended to a multi-component system involving both substitutional and interstitial alloying elements. Our model explains apparently unusual growth features of the cellular precipitation of Cr_2N in high nitrogen Cr-Ni austenitic steels. The long range diffusion of nitrogen described in the previous section reduces the driving force for cell boundary migration. This reduction of migration rate of the cell boundary leads to chromium diffusion ahead of the migrating boundary, which in turn further reduces the driving force for the cell boundary migration.
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Research Products
(4 results)
