In-situ STEM study on thermally induced phase transformation of magnetic (Nd0.75Ce0.25)2Fe14B ribbons

Studying the phase transformation and microstructure evolution of magnetic Nd-Ce-Fe-B nanocrystalline melt-spun ribbon is of paramount significance in developing this important class of magnetic materials. In this work, the thermal-induced phase transformation of (Nd0.75Ce0.25)2Fe(14)B nanocrystalline sample was revealed via in-situ heating scanning transmission electron microscopy (STEM) experiment (RT750 celcius). Starting from a single-phase (Nd0.75Ce0.25)2Fe(14)B nanocrystalline matrix at room temperature (RT), grain boundary (GB) diffusion behavior was investigated at an atomic scale. Our result shows that the rare earth elements accumulate at GB area from 200 degrees C and form a uniform thin amorphous layer between grains. The decomposition of the primary phase was observed at about 350 celcius and crystalized as BCC-Fe, Fe2B, and (Nd0.75Ce0.25)(2)O-3 phases driven by thermal activation at a higher temperature. This work provides the essential information of phase transformation and microstructure evolution of NdCeFeB-based magnets at high temperatures and new insights into thermal treatment designing and thermal stability considerations. (C) 2022 The Author(s). Published by Elsevier Ltd.

Automated summary

This study investigated the phase transformation and microstructure evolution of magnetic Nd-Ce-Fe-B nanocrystalline melt-spun ribbon. The results revealed the accumulation of rare earth elements at grain boundary areas and the formation of an amorphous layer between grains at high temperatures. Additionally, the primary phase decomposed and transformed into other phases at elevated temperatures.