SPECTRA INVESTIGATION ON HALL-PETCH RELATIONSHIP IN NANOCRYSTALLINE FE78S9B13 ALLOY

A complicated behavior was indicated in nanocrystalline Fe78Si9B13 all oy with grain size lower than 65 nm. No sign of dislocations after def ormation has been found in nanocrystalline material, suggesting that i t is unlikely that the dislocation pileup is involved. The reduction o f the mean hyperfine field is attributed to a decrease in the number o f nearest neighbor atoms on the grain boundaries, which may be respons ible for the softening behavior in nanocrystalline material with an av erage crystallite size of 65 nm. An increasing peak of the phonon mode near 900 cm(-1), reflecting strong electron-atom coupling in grain bo undary of nanocrystalline material, was observed. (C) 1996 American In stitute of Physics.