Site Competition Effect of Impurities and Grain Boundary Stability in Iron and Tungsten
ARMY RESEARCH LAB WATERTOWN MA MATERIALS DIRECTORATE
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Impurities, such as H, P, S, B, etc, have a very low solubility in iron and tungsten, and therefore prefer to segregate at the grain boundaries GBs. In order to analyze the energetics of the impurities on the iron GB and the GB stability, the LMTO calculations were performed on a simple 8-atom supercell emulating a typical capped trigonal prism GB environment. The so- called environment-sensitive embedding energies were calculated for H, B, C, N, O, Al, Si, P, and S, as a function of the electron charge density due to the host atoms at the impurity site. It was shown that, at the electron charge density typical of a GB, both in Fe and W, boron and carbon have the lowest energy among the analyzed impurities, and thus would compete with them for the site on the GB, tending to push the other impurities off the GB.
- Properties of Metals and Alloys