Order-disorder transformations in Sm-Co and Sm-Co-ZrC systems with 2-17 stoichiometry

摘要

This work investigates the order-disorder transformations utilizing time-resolved x-ray diffraction at the Advanced Photon Source. The metastable phases that can form during the order-disorder transformations in the Sm-Co intermetallics have the potential to produce materials with enhanced permanent magnetic properties. The high-temperature experiments transformed the disordered alloys with the TbCu_7-type structure obtained by rapid solidification into the mixture of the hexagonal and rhombohedral ordered structures at 1375 K. The ordering process and the role of the ZrC alloying on the phase formation and ordering transformations were examined. The results showed the formation of shoulders of the fundamental peaks and superlattice peak broadening prior to complete ordering. The lattice parameters expanded linearly up to the onset of ordering, after which an abrupt change of slope was observed. The change in slope suggests a nucleation and growth mechanism for the ordering transformation. The effect of ZrC alloying promoted the formation of the disordered structure in the as-solidified state and lowered the onset of the ordering temperature.