A nanocrystalline fcc phase via devitrification of a Ni36Fe32Ta7Si8B17 amorphous alloy

Various multicomponent alloys containing Ni-Fe-Si-B and refractory metals have been rapidly solidifed in order to check their tendency to produce glassy 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 transformation is determined at 530 degrees C showing that it consists in two steps: fast nucleation and growth of nanocrystals plus homogenization of the remaining matrix with crystal coarsening. Evidence based on TEM observations, XRD patterns and DSC experiments, are reported in favour of a homogeneous mechanism of nucleation. Faceting of nanocrystals is observed for the first time in such transformations and is attributed to a stress effect on the particles. (C)1999 Acta Metallurgica Inc.