Crystallization behavior of melt-spun NdFeB
permanent magnets
permanent magnets
(Institute of Materials Science and Engineering,
Shanghai University, Shanghai 200072, China)
Shanghai University, Shanghai 200072, China)
Abstract: The crystallization behavior of melt-spun Nd8.5Fe78Co5Cu1Nb1B6.5 ribbons was investigated using dynamic differential scanning calorimetry (DSC) and X-ray diffractometry (XRD). It was found that the as-spun ribbons crystallize in two steps: at first the Nd3Fe62B14+α-Fe phases are formed and subsequently Nd3Fe62B14 transformed to Nd2Fe14B and α-Fe upon heating above 680℃. The effective activation energy of two crystallization peaks are 332.0kJ/mol and 470.5kJ/mol, respectively. As the wheel speed increases, the magnetic properties of the magnet change obviously. When the wheel speed is 18m/s, the best magnetic properties of the magnet was obtained after the sample was annealed at 690℃ for 8min: Br=0.74T, iHc=421.7kA/m, (BH)max=64.5kJ/m3.
Key words: nanocomposite magnet；crystallization behavior；activation energy