Hysteresis characteristics of sintered permanent magnets based on (Dd(1-x)MM(x))-(Fe, Co)-B alloys (x=0-1)

The magnetic properties of sintered permanent magnets made from (Dd(1-x)MM( x)) - (Fe, Co) - B alloys (x = 0-1) in the initial state (after sintering a t 1060 and 1080 degrees C) and after annealing at 490-610 degrees C are con sidered. It is shown that the hysteresis properties of the magnets may be v aried over a fairly broad range by changing the ratio of the components (th e base alloys Dd-Fe-B and MM-Fe-B) in the powder mixtures for producing the magnet ingots and the heat-treatment parameters: B-r = 0.95-1.10 T, H-ci = 400-900 kA/m, (BH)(max) = 175-220 kJ/m(3). Increasing the concentration of the basic alloy based on misch metal (MM) in the powder mixture depresses the energy characteristics, the coercive force of the magnets, the suscepti bility of the permanent magnets to the annealing conditions, and the optima l sintering temperature. For all the sintered permanent magnets considered, the greatest increase in the hysteresis properties is observed after annea ling at 550 degrees C. The mechanisms underlying the dependence of the hyst eresis characteristics on the alloy composition and heat-treatment conditio ns are discussed. These sintered permanent magnets based on alloy mixtures that do not contain expensive pare rare-earth metals may be used instead of ferrites in domestic appliances operating at room temperature.