Xu-hao Han

Study of Structure and Magnetic Properties of SmCo10 Alloy Prepared by Different Methods

In this paper, the phase compositions, microstructures, atomic structures, and magnetic properties of Co-rich SmCo10 alloys prepared by arc-melting, annealing, and melt-spinning were studied. It was found that as-cast alloy is composed of Th2Zn17-type Sm2Co17 matrix with an average grain size of ∼45  m accompanied by lamellar eutecticum (consisting of α-Co and Th2Zn17-type Sm2Co17) distributed at grain boundaries. The annealed alloy has the same phase composition and phase distribution as the as-cast alloy except that the average grain size decreases to ∼35  m, and the eutecticum has more homogeneous distribution on the matrix. Simultaneously, the atomic structure of Sm2Co17 is unchanged with only a decrease in structural disorder after annealing. The as-spun ribbons are composed of ∼95.5 vol.% TbCu7-type Sm2Co17 and the rest α-Co. The short rod-shaped α-Co grains are intermittently distributed at the grain boundaries of equiaxed Sm2Co17 grains. The as-spun ribbons show a higher coercivity, and the annealed alloy shows maximum magnetization. The structural parameters were calculated by Extended X-ray Absorption Fine Structure (EXAFS), and the relationship between structure and magnetic properties was discussed in detail.

Effects of Si and/or Ti Addition on the Microstructure and Magnetic Properties of Fe–Cr–Co Ribbons

Fe–Cr–Co hard magnetic ribbons with low Co content were prepared by melt-spinning coupled with multistep aging process, in which a certain amount of Si and Ti were added separately or together. This paper focuses on three types of ribbons, which are 61Fe–26Cr–12Co–1Si, 62Fe–25Cr–12Co–1Ti, and 62Fe–24Cr–12Co–1Si–1Ti ribbons, to investigate systematically the effects of single or combined addition of Si and Ti on phase structure, microstructure, magnetic structure, and magnetic properties of Fe–Cr–Co based ribbons at different states. It has been found that single Si addition is effective to improve the coercivity, whose value can reach up to 1026.6 Oe in 61Fe–26Cr–12Co–1Si ribbons, even higher than that of traditional bulk Fe–Cr–Co alloys. Single Ti addition facilitates the orientation growth along < 100 > directions of body centered cubic-type phases in as-spun ribbons, resulting in higher remanence. Furthermore, combined addition of the Si and Ti can enhance the orientation degree of not only the as-spun ribbons but also the aged ones. Consequently, the highest remanence of 10106.7 Gs can be achieved in 62Fe–24Cr–12Co–1Si–1Ti ribbons treated by seven-step aging.