THERMAL VACANCY FORMATION AND SELF-DIFFUSION IN INTERMETALLIC FE3SI NANOCRYSTALLITES OF NANOCOMPOSITE ALLOYS

Combined high-temperature studies of positron lifetime and Fe-59 trace r diffusion show thermal vacancy formation and rapid self-diffusion in the nanocrystallites of intermetallic-amorphous Fe73.5Si13.5B9Nb3Cu1 nanocomposites. In combination with an intergranular amorphous phase a nd densely packed interfaces between these interlayers and the nanocry stallites the unique behavior arises where self-diffusion in interfaci al regions is slower than in crystallites. Slow atomic ordering proces ses during crystallization are ascribed to low diffusivities on the Si sublattice of the nanocrystallites.