Solidification, quenching gas and magnetic properties in melt-spun Nd/sub 2/Fe/sub 14/B

Magnetic measurement and cross-sectional Magnetic Force Microscopy images were obtained from Nd/sub 2/Fe/sub 14/B ribbons melt-quenched at a circumferential wheel speed of 10 m/sec in three different atmospheres: 1 atm Ar, 1 atm He and 1/3 atm He. The striking effects of the quenching gas type upon the microstructure is correlated with room-temperature demagnetization curves that confirm the presence of multiple, yet discontinuous, grain size zones. A model for the rapid solidification of Nd/sub 2/Fe/sub 14/B based on consideration of recalescence relative to the peritectic temperature is invoked to explain the experimental results. The recalescence causes breakup of the Nd/sub 2/Fe/sub 14/B dendrites formed during the first phase of solidification and results in a layered structure within the ribbon possessing distinct transition regions where the solidification front temperature crosses the peritectic temperature.