Journal of Non-Crystalline Solids 117/118 (1990) 601-604 601 North-Holland EFFECT OF FREE VOLUME ON THE KINETICSOF CHEMICAL SHORT RANGE ORDERING IN AMORPHOUS Fe4oNi4oB2o G.W. Koebrugge, J. van der Stel, J. Sietsma and A. van den Beukel Delft University of Technology, Laboratory of Metallurgy Rotterdamseweg 137, 2628 AL Delft Measurements are presented on the change of electrical resistivity and anelastic strain during structural relaxation in amorphous Fe4oNi4oB2o in order to find a relation between the ordering kinetics and the concentration of defects. It was found that the rate of chemical ordering decreases with decreasing concentration of flow defects, nearly proportional to ~]-~-f. This is in agreement with results presented earlier. 1. INTRODUCTION Isothermal changes of the electrical resistivity (due to temperature cycling) and anelastic strain (due to stress cycling) have been measured during structural relaxation in amorphous Fe4oNi4oB2o. The results are analysed in terms of the mixed model, which distinguishes between changes in chemical and topological short range ordering (CSRO resp. TSRO). In previous work it was found (e.g. 1) that the process of topological ordering can be described by the free volume model. The kinetics of annihilation of flow defects cf is given by -1 -1 -El cf - cfo = Co t exp(-~-), (1) which is the solution of the "bimolecular" differential equation for the annihilation of flow defects. In this equation, Ef is an activation energy (250 kJ mole-l), Co is a constant (1.63.1025 s-1) and CfoiS the initial concentration of flow defects in as- quenched 1 Fe40Ni4oB20 . Changes in the concentration of flow defects, which determines the amount of free volume, were found to be irreversible. It was shown that CSRO consists of a series of processes with a spectrum of activation energies and is therefore described by the activation energy spectrum model (AES)2. It is found to be reversible with temperature. The CSRO processes are considered to be governed by diffusion. Like in crystals vacancies are important in diffusion processes, in glasses the presence of 'diffusion defects' is assumed, the concentration of which is called cd. The relaxation time ~ for an ordering process with activation energy E is inversely proportional to Cd: = v" 1 ~1 exp (~T), (2) where v is a frequency factor. Generally it is assumed 3 that the atomic 0022-3093/90/$03.50 (~) Elsevier Science Publishers B.V. (North-Holland)