A nanocrystalline fcc phase via devitrification of a Ni36Fe32Ta7Si8B17 amorphous alloy

Various multicomponent alloys containing Ni-Fe-Si-B and refractory metals h ave been rapidly solidifed in order to check their tendency to produce glas sy phases and their devitrification behaviour has been studied. Among these a Ni36Fe32Ta7Si8B17 alloy presents primary crystallization with production of fee nanocrystals embedded in the glassy matrix. The kinetics of the tra nsformation is determined at 530 degrees C showing that it consists in two steps: fast nucleation and growth of nanocrystals plus homogenization of th e remaining matrix with crystal coarsening. Evidence based on TEM observati ons, XRD patterns and DSC experiments, are reported in favour of a homogene ous mechanism of nucleation. Faceting of nanocrystals is observed for the f irst time in such transformations and is attributed to a stress effect on t he particles. (C)1999 Acta Metallurgica Inc.