Effects of the Disproportionation Stage of the HDDR Process on Magnetic Properties and Microstructure of Pr $_13$Fe $_80$B $_7$ Alloys

Effects of the heat treatment conditions of the disproportionation stage on magnetic properties of hydrogenation disproportionation desorption recombination (HDDR) Pr $_13$Fe $_80$ B $_7$ material are investigated. The results show that the HDDR Pr $_13$Fe $_80$B $_7$ material disproportionated by heating from room temperature under hydrogen (C-HD), has high coercivities and low remanences while that heated up to 800 $^circ$C under vacuum, and then disproprotionated by exposing to hydrogen (V-HD), show high remanences with low coercivities. Further investigations show that this difference of magnetic properties of HDDR Pr $_13$Fe $_80$ B $_7$ materials, which is caused by the C-HD and V-HD treatment, might be related to the disproportionation at low temperature (650 $^circ$C) in the C-HD treatment. At the same time, it is also found that the microstructure of the Pr $_13$Fe $_80$ B $_7$ alloys disproportionated by C-HD treatment is mainly spherical while that of the alloys disproportionated by V-HD treatment is mainly rod-like.