Nitriding of iron-based ternary Fe–V–Si alloy: The precipitation process of separate nitrides
| Autor: | Ewald Bischoff, Eric J. Mittemeijer, R. E. Schacherl, Benjamin Schwarz, Sai Ramudu Meka |
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| Rok vydání: | 2014 |
| Předmět: |
Materials science
Polymers and Plastics Annealing (metallurgy) Precipitation (chemistry) Metallurgy Alloy Metals and Alloys Analytical chemistry Nitride engineering.material Microstructure Electronic Optical and Magnetic Materials Amorphous solid Ceramics and Composites engineering Ternary operation Nitriding |
| Zdroj: | Acta Materialia. 76:394-403 |
| ISSN: | 1359-6454 |
| DOI: | 10.1016/j.actamat.2014.05.017 |
| Popis: | Iron-based ternary Fe–V–Si and binary Fe–Si alloy specimens were nitrided in a NH 3 /H 2 gas mixture at 580 °C (853 K) with a nitriding potential of r N = 0.1 atm −1/2 until nitrogen saturation in the specimens was achieved. In contrast to previously investigated iron-based ternary Fe–Al–Cr and Fe–Ti–Cr alloys, no so-called “mixed” nitrides developed in the Fe–V–Si alloy. Instead, in the first stage, all vanadium precipitated as crystalline VN and, subsequently, all silicon precipitated as amorphous Si 3 N 4 . Moreover, the precipitation rate of Si 3 N 4 in the nitrided ternary Fe–V–Si alloy was much lower than in the binary Fe–Si alloy nitrided under identical conditions. This much lower Si 3 N 4 -precipitation rate is attributed to the presence of first precipitated VN: coherency strains caused by the (semi-) coherent VN precipitates interact with the strain fields surrounding the Si 3 N 4 precipitates and are obstacles to the movement of dislocations necessarily introduced in the ferrite matrix by growing Si 3 N 4 precipitates. This interpretation is supported by additional experiments, in which the first precipitated VN platelets were coarsened by annealing before subsequent nitriding led to, now much faster, Si 3 N 4 precipitation. |
| Databáze: | OpenAIRE |
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