熱間加工磁石の磁気特性に与える加工条件の影響

概要

論文の詳細を見る
Nd-Fe-B metal magnets are produced by different two methods. One is hot deformed method and the other is sintered one. Sintered magnets are made from cast alloy and the crystalline alignment is controlled in external magnetic field. On the other hand, hot deformed magnets are made from melt-spun ribbons with nano structure. Hot deformed magnets have so fine structure that coercivity is higher than that of sintered one. Crystalline alignment with their c-axis parallel to the press axis is promoted by plastic deformation at high temperature. It is apparent that hot deformation conditions play an important role on crystalline alignment. The magnet samples are made by upsetting method and it is studied that the influence of hot deformation conditions (Reduction ratio:R, Upsettng temperature:T and Strain rate:ε) on the crystalline structures in order to obtain a high performance hot deformed magnet. The conditions of R and T influence on the remanence, while that of R and T influence on the coercivity. It is found that the remanence of the hot deformed magnet increased with increasing R, related to a crystalline alignment associates with the predominant c-plane growth in their crystals. By optimizing these conditions, magnet with the composition of 30.4Nd-6.0Co -0.91B-0.56Ga-bal.Fe (wt%) shows high performance, and the remanence Br, coercivity HcJ and maximum energy product (BH)max are 1.37 T, 1138 kA/m and 347.3 kJ/m3, respectively.