Effects of flash annealing and external magnetic field on magnetic properties of relatively high Nd content (37% by weight) NdFeB alloy

Abstract

Post modifications such as alloying element addition and/or heat treatment are applied to improve the magnetic properties of NdFeB permanent magnets. In this study, effects of external magnetic field and flash annealing at different temperatures (680 degrees C and 710 degrees C) and durations of 5 and 10 min on the magnetic properties of relatively high Nd content (37 wt.%) NdFeB magnet alloys were investigated. Melt spinning method was used in production of the NdFeB magnet alloys. Heat treatment was applied to various NdFeB magnet ribbons at 680 degrees C and 710 degrees C temperatures for 5 and 10 min by the flash annealing at heating and cooling rates of 300 K/s. In addition, before vibrating sample magnetometer tests, various samples were magnetized under an external magnetic field of 5 Tesla. After melt spinning, semi-amorphous structure was obtained and Nd2Fe14B hard and alpha-Fe soft magnetic phases were crystallized at nanoscale by flash annealing. These crystallizations formed between approximately 350 degrees C and 430 degrees C. After the flash annealing, residual amorphous structures were observed without complete crystallization. The highest remanence and coercivity were obtained in the sample flash annealed for 10 min at 710 degrees C, 57.64 emu/g and 10,419.07 Oe, respectively. The maximum energy product improved thanks to the high remanence and coercivity, important for the NdFeB magnets resulted in a high value of 87.79 kJ/m(3) in the same sample. This flash annealing procedure provides a cost-effective and simple platform to improve the magnetic features of NdFeB magnets.