Effect of grain alignment distribution on magnetic properties in (MM, Nd)-Fe-B sintered magnets

H-cj of (MMxNd1-x)-Fe-B sintered magnets decreases distinctly with x increasing when misch metal (MM) content (x) ranges from 0.3 to 1. Practical application is taken into consideration so that the (MM0.6Nd0.4)-Fe-B components are chosen to analyze the changes in behavior of the magnetic properties. Both Magnet II and Magnet III belong to (MM0.6Nd0.4)-Fe-B sintered magnets, however, it should be noted that Magnet II is prepared by the single alloying method (SAM) and Magnet III is prepared by the double main phase alloy method (DMPAM). Core-shell structures of the magnets prepared by DMPAM can result in the higher H-cj and lower knee-point coercivity (H-k) compared with that by SAM. Furthermore, for Magnet II, the abnormal grain growth contributes to a better grain alignment and smaller distribution coefficient (sigma) defined as the degree of grain alignment, which will enforce a higher tendency of the H-cj decreasing and Hk increasing. The expression of their normalized coercivity h(sigma) is deduced by combining Gao's starting field model with Kronmuller's nucleation mechanism. Based on the overall h(sigma) similar to sigma curve, the best desirable h(sigma) value is calculated when sigma = 0.09. Theoretically, for Magnet III, the resultant larger sigma should be attributed to the more uniform grain alignment. In addition, the deviations of grain size distributions on the c-plane become more remarkable with more MM concentrates, which can be presented by SEM images. Meanwhile, by means of the pole figures, it is also verified that the grain alignment distribution becomes much more diverse with x increasing. Therefore, it can be predicted whether the grain alignment distribution is significant for H-k and H-cj of (MMxNd1-x)-Fe-B sintered magnets (x not equal 0.6) prepared by SAM/DMPAM or not.