Magnetic field intensity dependent microstructure evolution and recrystallization behavior in a Co–B eutectic alloy

Abstract

• Magnetic field-dependent microstructure evolution and recrystallization were studied. • Composition segregation resulting in the formation of FCC-Co/Co2B eutectic under 20 T. • The application of the magnetic field was found to promote recrystallization. Systematic understanding on the magnetic field intensity dependent microstructure evolution and recrystallization behavior in a Co-B eutectic alloy under a constant undercooling (∆ T ≈100 K) were carried out. Absent of the magnetic field, the comparable size of divorced FCC-Co and Co 3 B eutectic ellipsoidal grains coexist with a few regular lamellas. When the magnetic field is less than 15 T, the elongated primary FCC-Co dendrites parallel to the magnetic field with the dispersed FCC-Co nano-particles embedded within the Co 3 B matrix occupy the inter-dendrite regions. Once the magnetic field increases to 20 T, the FCC-Co/Co 2 B anomalous eutectic colonies dominate. The formation mechanism of Co 2 B phase is discussed from several aspects of the competitive nucleation, the chemical redistribution induced by the thermomagnetic-induced convection and magnetic dipole interaction, and the strain-induced transformation. Furthermore, the application of magnetic field is found to promote recrystallization, proved by the lower density of misorientation, the appearance of FCC-Co annealed twins and more Co 3 B sub-grains. This work could further enrich our knowledge about the magnetic-dependent microstructure evolution and recrystallization process in the undercooled Co-B system and provide guidance for controlling the microstructures and properties under extreme conditions.