AMORPHOUS TO NANOCRYSTALLINE TRANSFORMATION IN METALLIC GLASSES

Amorphous to nanocrystalline transformation in some Cu and Nb containi ng metallic glasses has been studied. The nanocrystalline phase is fou nd to have a DO3 structure with Si concentration <25 at.%. The crystal lite size increases with increasing annealing time reaching a maximum of similar to 10nm after 10 min of annealing at 540 degrees C. Precipi tation of the nanocrystalline phase is accompanied by development of a high degree of compositional inhomogeneity in the remaining amorphous phase. In contrast to some earlier studies, the specimen with higher Si concentration is found to have a relatively faster crystallization rate. This result reflects the effect of the variation in free-volume and/or quenched-in nuclei in the as-prepared amorphous specimens, on t he crystallization kinetics.