The effect of microstructure on magnetic properties of TLP bonded Sm2Co17 hard magnets

A Sm 2 Co 17 permanent magnet was successfully transient liquid phase bonded using AWS BNi-2 interlayer at 1100 °C for 60 min. Microstructural evolutions and chemical composition changes after TLP bonding of the samples were analyzed using optical microscopy, scanning electron microscopy and energy-dispersive spectroscopy. The changes of magnetic properties of the base material due to the TLP process were evaluated using vibrating sample magnetometry. It was found that the bonded sample by 50-μm-thick interlayer foil majorly contained athermally solidified zone and brittle second phase, indicating that the bonding time is not sufficient for joining, while the bonded sample by 25-μm-thick foil was almost solidified isothermally. Also, the results showed that a considerable increase in coercivity, remanence and also maximum energy product was occurred after TLP bonding of Sm 2 Co 17 permanent magnet. This increase was mainly attributed to the strong magnetic exchange coupling between FeCo- and Fe-rich borides (as soft magnets) and Sm–Co matrix (as hard magnet).