Mechanically robust high magnetic performance Sm2Co17 sintered magnets via microstructure modification with Al2O3 doping

Abstract

In this work, a small amount of Al2O3 powders (≤0.3 wt%) were incorporated into the Sm2Co17-type sintered magnets, obtaining both high mechanical and magnetic properties. It is found that 0.1 % weight percentage of Al2O3 doping is enough to enhance the flexural strength by about 20 % (∼ 180 MPa for the case of the c-axis parallel to height). Meanwhile, the (BH)max remains around 219 kJ/m3, and Hcj is 2052 kA/m, which is over 95 % of that of the original magnets without doping. The promising improvement in flexural strength is mainly attributed to the grain size effective refinement caused by Sm2O3 particles including newly-formed ones from the reaction of the Al2O3 powder and Sm in the matrix. Furthermore, the grain size of the magnets decreases significantly with increasing of Al2O3 doping up to 0.3 wt%. Especially, the grain size of 0.3 wt% Al2O3 doped magnets is refined by 37 %. However, the flexural strengths (for the c-axis parallel to height and the c-axis parallel to width cases) of the magnets decrease sequentially and are even lower than that of the original magnet. The microstructure investigations indicate that the decrease in flexural strength may closely be correlated to the larger cell size and the incomplete cell boundaries phase. The obtained results infer that the flexural strength is susceptible to not only grain size but also the cellular structure of the magnets.