Abstract
The difference in microstructure and mechanical properties of Sm_2(Co, Fe, Cu, Zr)_<17> type magnet due to the processing variables, such as starting powders and sintering temperatures of spark plasma sintering (SPS) is investigated. The starting powders are the homogeneous powder consisted of the TbCu_7 type main phase and the as-cast powder consisted of the Th_2Zn_<17> type phase, ThCu_7 type phase, SmCu-rich phase (Ce_2Ni_7 type phase), Zr-rich phase and Cu-rich phase. The homogeneous compacts and the as-cast compacts are almost same relative densities (about99%) by using spark plasma sintering process condition with 39MPa at 1323 K for 7 minutes. The relative densities of the as-cast and homogeneous compacts sintered at 1223k for 7 minutes are 98% and 87%, respectively. Namely, the sinterability of the as-cast powder was higher than that of the homogeneous powder. This can be attributed to the existence of SmCu rich phase in the as-cast powder. Furthermore, the grain growth can be suppressed by spark plasma sintering process and the grain size was about one third of that sintered by the conventional process. The Vickers hardness increase by about 20%.
