| The magnetic properties and microstructures of1:5type sintered Ce-Co permanent magnets have been investigated in this article. Effects of different powder technology, sintering process and heat-treated process, copper content and iron content on microstructures and magnetic properties have been studied systematically. The coercivity mechanism of Ce-Co sintered magnets have been discussed with some emphasis.The magnetic properties of magnets prepared by hydrogen decrepitation are no different than that by attrition milling. In consideration of time spent in hydrogen decrepitation is more, we selected attrition milling as our technology of crude powder. The optimal sintering temperature is located in1025℃～1O55℃. The optimal heat-treated temperature is about360℃.Fe content increasing, remanence Br and maximum energy product (BH)m increase first and then decrease. The optimal magnetic properties of Ce(Co0.865-xCu0.135Fex)5sintered magnets are obtained:Br=0.685T,(BH)m=85.6kJ/m3. The increase of Br is mainly influence by Fe content of1:5matrix which can properly increase the saturation induction Bs, the rapidly increasing of the amount of Ce-rich phase and5:19phase gives rise to the deterioration of the magnets when x>0.155.Influence of copper on the magnetic properties, phase structures and crystalline/magnetic microstructures of CaCu5-type Ce(Co0.865-yCuyFe0.135)(y=0-0.225) sintered magnets has been investigated. Initial magnetization curves of the samples indicate that the coercivity mechanism is "nucleation-controlled" one when y is less than0.09, and then changes to "domain wall pinning-controlled" one at y beyond0.45. It is found that the domain wall pinning-controlled-type samples exhibit much narrower the average domain width as compared with the nucleation-controlled-type magnets. The coercivity mechanism is intuitively proved by the evolution of magnetic domains for Ce-Co-Cu-Fe sintered magnets. |
