ISSN:
1600-5767
Source:
Crystallography Journals Online : IUCR Backfile Archive 1948-2001
Topics:
Geosciences
,
Physics
Notes:
The decomposition behaviour during annealing in the undercooled liquid regime of Zr41Ti14Cu12.5Ni10Be22.5 is studied by means of small-angle neutron scattering (SANS). In this temperature range, a microstructure consisting of precipitates of an amorphous phase is formed. The scattering curves show a characteristic maximum which becomes more and more intense with increasing annealing time until a saturation state is reached. All scattering curves at different annealing times obey a universal scaling law by scaling the intensity and the q axis by the intensity and the position of the maximum, respectively. In order to interpret the scattering curves, the scattering behaviour of a system of interacting particles and its time evolution are simulated. The centres of the precipitates are modelled (either analytically or numerically) by a hard-core point field, i.e. they have a minimum distance from each other (`excluded volume'). At each of these points, a nucleus is created according to a given nucleation rate, either instantaneously (all nuclei start growing at the same time) or continuously (in each time interval, a constant number of nuclei starts growing). Variation of the parameters of the hard-core point field, the nucleation mechanism and the growth law for the precipitates and comparison of the calculated and measured small-angle scattering curves allow the following interpretation: The amorphous precipitates are distributed according to a hard-core structure and the nucleation is continuous. The growth of the precipitates is diffusion controlled (a ∝ t 1/2).
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1107/S0021889897001362
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