Anisotropy of mechanical properties of Sm-Co permanent magnets doped with dysprosium

Sintered SmCo permanent magnets are widely applied in space, aviation and the military-related industries due to their advantages under high temperature over NdFeB magnets. However, poor mechanical performance compared to their magnetic properties is not satisfactory. The brittleness in manufacturing results in 20-30% of raw materials wasted, which is urged to be solved[1]. For many years, various investigations on their bending strength, impact toughness and thermal expansion have been performed[2-4], but results on an effective method to improve the fracture-resistance are rarely found. In this paper, fracture behavior of sintered (Sm_1-xDy_x)(Co_0.695Fe_{0. 2}Cu_0.08Zr_0.025)_7.2 (x=0, 0.2, 0.4, 0.6, 0.8) magnets are studied and recorded. Highly micro-twins are observed by using transmission electron microscopy (TEM) and indexed by simulated selected area electron diffraction (SAED) patterns. Based on the researches that twinning may contribute to the improvement of bending strength in many metals, the mechanism of anisotropy in mechanical properties is analyzed from the influence of the micro-twin structure and the correlation between mechanical anisotropy and magnetic properties.