Anisotropic corrosion behavior of sintered (Ce0.15Nd0.85)30FebalB permanent magnets

In this work, the corrosion behavior of the surface parallel to the oriented c-axis (c parallel to) and perpendicular to c-axis (c perpendicular to) in the (Ce0.15Nd0.85)(30)FebalB dual main phase magnet was studied. With the addition of Ce, the volume fraction of RE-rich phase shown in the backscattered electron (BSE) images is basically approximate on the two surfaces. The free corrosion potential (E-corr) of the c parallel to surface is more negative, which shows the worse corrosion resistance from the perspective of thermodynamics. While the reaction kinetics parameters with the smaller free corrosion current (i(corr)) land the larger transfer resistance (R-ct) react the opposite conclusion in 3.5 wt% NaCl solution. Moreover, the c parallel to surface performs smaller ions concentration of corrosion product and less damaged corrosion morphology compared to c perpendicular to surface after the free corrosion. The inconformity is not affected by the RE-rich phase, but by the anisotropy of the grains that the c parallel to surface has larger density of the atoms and the lower ratio of (Nd, Ce)/Fe. (C) 2019 Published by Elsevier B.V. on behalf of Chinese Society of Rare Earths.