Phase Structure Evolution and its Effect on Magnetic and Mechanical Properties of B-Doped Sm2co17-Type Magnets with High Iron Content

Abstract

The unique cellular microstructure of Fe-rich Sm2Co17-type permanent magnets is closely associated with the solid solution precursor. In general, the lower the solid solution ordering, the more favorable the formation of cellular structure. In this article,the phase structure, magnetic properties, and mechanical behavior of B-doped Sm2Co17-type magnets with high iron content are investigated. The doping of B atom can enter the interstitial vacancy, resulting in lattice expansion and producing more microtwin structures and highly ordered 2:17R phases in the solid solution stage after B doped treatment, with an increase of about 24% in the 2:17R phase, and more B doped produces a solid solution precursor with higher order. In magnets with high solid solution ordering, the high density of ordered microdomains and reversed domain boundaries disrupts the homogenization of the physical phase organizational structure during the solid solution stage, which inhibits the ordered transformation of 1:7H during aging and affects the generation of the cellular structure, leading to a decrease in magnetic properties. However, the resulting second phase plays a dominant role, resulting in a decrease in magnetic properties, yet the interface formed between it and the matrix phase hinders the movement of dislocations and enhances the mechanical properties. Hence, the high toughness grain boundary phase precipitation induced by B element is also a new and effective way to improve the toughness of Sm2Co17-type magnets. Our study provides a new understanding of the Phase structure evolution and its effect on the magnetic and mechanical properties of Sm2Co17-type magnets with high iron content.

Keywords: Sm2Co17-type magnets, magnetic and mechanical properties, high iron