Decomposition Kinetics of Bulk Amorphous Zr41Ti14Cu12.5Ni10Be22.5 Alloys Studied by Computer Simulation and Small-Angle Neutron Scattering

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∝t1/2).