Construction of high-performance multi-main-phase Nd-Dy-Fe-B sintered magnets with strengthened chemical heterogeneity

By designing the [(Pr20Nd80)100-xDyx]30.5FebalM1.3B1.0 components (x = 0, 10, 25, 50, 75 wt.%, denoted as Dy0, Dy10, Dy25, Dy50, Dy75), we constructed a series of multi-main-phase (MMP) and single-main-phase (SMP) Nd-Dy-Fe-B bulk magnets with same average composition of (Pr20Nd80)27.5Dy3.0FebalM1.3B1.0 but with different chemical heterogeneities, as evaluated by Dy concentration discrepancy between Dy-rich shell and Dy-lean core (triangle C). triangle C increases from 2.8 wt.% for MMP Dy3-I magnet (-39.4 % Dy25 and -60.6 % Dy0), to 3.1 wt.% for MMP Dy3-II magnet (-19.7 % Dy50 and -80.3 % Dy0), further to 3.4 wt.% for MMP Dy3-III magnet (-13.1 % Dy75 and -86.9 % Dy0), compared to 0 wt.% for SMP Dy3 magnet (100 % Dy10). Corresponding magnetic performance at 20-180 degrees C is positively related with triangle C value, as evidenced by the best magnetic properties of MMP Dy3-III magnet with highest triangle CIII value than others. Further phase-field simulation underlies the governing mechanism for strengthened chemical heterogeneity in MMP Nd-Dy-Fe-B magnets, while also provides design principles for concentration graded magnetic materials.