Interfacial energies of textured silicon iron in the presence of oxygen

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Abstract
Absolute surface and grain boundary energies have been measured on silicon iron as a function of bulk silicon content, oxygen potential of the controlled atmosphere and temperature. At 1410°c, the silicon concentration at the free surface of Fe–3% Si is approximately 13%. A similar silicon enrichment occurs at grain boundaries. By far the most important effect is that of oxygen adsorption, which reduces the surface energy severely, the saturation surface coverage at 1330°c being 0·47 of a monolayer. An oxygen potential greater than that equivalent to pH2O/pH2=10−4 develops a (100) secondary recrystallization texture on thin foils, by virtue of the preferential adsorption of oxygen on (100) planes. At pH2O/pH2 < 10−4, the foils show a (110) texture. In addition, the temperature coefficient of surface energy which is -0·36 ergs cm−2°c−1 for a clean surface, becomes positive and equal to 0·55 ergs cm−2°c−1 in the presence of oxygen adsorption. The relevance of the present observations to the secondary recrystallization mechanism is discussed.