Europhys. Lett., 61 (2) , pp. 261-267 (2003)
By which mechanism does coarsening in phase-separating alloys proceed?R. Weinkamer and P. Fratzl
Erich Schmid Institut für Materialwissenschaft Österreichische Akademie der Wissenschaften & Institut für Metallphysik Montanuniversität Leoben - Jahnstraße 12, A-8700 Leoben, Austria
(Received 18 July 2002; accepted in final form 7 November 2002)
The precipitate coarsening at late stages of phase separation in solids is generally agreed to proceed via a preferential diffusion of individual atoms from smaller precipitates to larger ones. Recently, computer simulations have indicated that an alternative coarsening mechanism, which dominates in liquids, may also be of importance in solids. This mechanism is essentially linked to vacancy diffusion which can lead to an enhanced mobility of whole precipitates and, hence, to a coagulation mechanism where precipitates grow by coalescing with others. Here, we use Monte Carlo computer simulations to investigate quantitatively the conditions when the classical evaporation-condensation mechanism or precipitate coagulation dominates. We find that the essential parameter is the affinity of the vacancy to either the matrix or the precipitates. Since the quantities easily accessible by experiment, such as precipitate size distributions, structure functions and growth exponents of the average precipitate size, show only marginal differences between the two coarsening mechanisms, we propose an experiment based on synchrotron X-ray speckle spectroscopy to test the predictions of our model calculations.
81.30.Mh - Solid-phase precipitation.
64.75.+g - Solubility, segregation, and mixing; phase separation.
02.70.Rr - General statistical methods.
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