Thermal vacancy formation and self-diffusion in intermetallic Fe3Si nanocrystallites of nanocomposite alloys

Combined high-temperature studies of positron lifetime and Fe-59 tracer 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 and densely packed interfaces between these interlayers and the nanocrystallites the unique behavior arises where self-diffusion in interfacial regions is slower than in crystallites. Slow atomic ordering processes during crystallization are ascribed to low diffusivities on the Si sublattice of the nanocrystallites.