A discrete lattice plane analysis of the composition profile and surface energy of binary H.C.P. alloys with applications to γ AlAg

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Department of Materials Science and Engineering


The discrete lattice plane (DLP) model has been used to make a nearest neighbor (n.n.), broken bond, regular solution calculation for the composition profile and surface energy of h.c.p. alloys as a function of surface orientation and temperature. This appears to be the first such calculation for h.c.p. alloys. The surface energy and the anisotropy of surface energy thus calculated were compared to the experimental values of these quantities concurrently determined on a γ AlAg alloy by Hyland et al. using the zero-creep and thermal grooving method. An oscillating, diffuse composition profile was obtained, with the former characteristic arising from the negative regular solution constant. A recent FIM/AP study of γ AlAg precipitates by Osamura et al. is in qualitative agreement with this prediction. Calculations of the surface energy of the γ AlAg phase show rough agreement with the experimentally determined value at 873 K but poor agreement at 773 K. The DLP model predicts a much smaller temperature dependence of surface energy than is experimentally observed when the regular solution model is employed. It appears from these results and those of related studies that the frequently used nearest neighbor model is unable to provide an adequate accounting for the surface energy of Al-base alloys.

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Acta Metallurgica Et Materialia