Effect of CaCl2 and NdCl3 on the manufacturing of Nd-Fe-B by the reduction-diffusion process

Abstract

The effect of an additional amount of CaCl2 and the amount of NdCl3 to replace Nd2O3 on the characteristics of the washed Nd-Fe-B powder alloys, and the role of chlorides on the disintegration process have been investigated. CaCl2, CaO, and unreacted Ca surrounded Nd2Fe14B grains uniformly as the chloride amount exceeded 10 wt. %. The residual Ca and oxygen content of the washed powder alloys from high chloride amount samples were relatively low; residual Ca ∼400–800 ppm, oxygen content ∼2600–4000 ppm. After sintering and heat treatment, the magnet made using CaCl2 has remarkable magnetic properties; Br ≂ 11.5 kG, iHc ≂ 10.3 kOe, and (BH)max ≂ 29 mGOe. However, the magnet made using NdCl3 has much lower coercivity, Br = 11 kG, iHc = 6.4 kOe, (BH)max = 25 mGOe.