Effects of multi-stage aging on the microstructure, domain structure and magnetic properties of Fe-24Cr-12Co-1.5Si ribbon magnets

• Published in: Journal of alloys and compounds 2017-02, Vol.694, p.103-110
• Main Authors: Han, Xu-hao, Bu, Shao-jing, Wu, Xin, Sun, Ji-bing, Zhang, Ying, Cui, Chun-xiang
• Format: Article
• Language: English
• Subjects: Coercivity; Domain structure; Domain walls; Ferromagnetism; Heat treatment; Lorentz transmission electron microscopy; Magnetic fields; Magnetic ordered materials; Magnetic properties; Magnetization; Magnets; Melt spinning; Microstructure; Phase transitions; Rapid-solidification; Solidification; Transmission electron microscopy
• ISSN: 0925-8388; 1873-4669
• DOI: 10.1016/j.jallcom.2016.09.316

Fe-24Cr-12Co-1.5Si ribbons were prepared by melt spinning at a roller speed of 40 m/s, which were then treated by multi-stage aging between 647 °C and 540 °C. This article focuses on the microstructure and domain structure changes in the aging process by Lortenz transmission electron microscopy. It has been found that the phase change reaction of Cr(M) + α→α1+α2 occurs during aging. After that, the ribbons are composed of ferromagnetic α1 phase (about 92.4 vol%-98 vol%) and weakly magnetic α2 phase (about 7.6 vol%-2 vol%). These two phases form a uniform and periodical spinodal structure, characterized by maze magnetic domain structure. Two types of domain walls can be formed between adjacent α1 phases, one is 90° and the other is 180°. The pinning mechanism in which α2 phase works as the pinning center is the main magnetization mechanism of the ribbons, and magnetization process is carried out mainly through the rotation of magnetic moments. The coercivity as high as 742 Oe can be achieved in the ribbons even if they have not been heat treated in magnetic fields. [Display omitted] •Fe-Cr-Co-type ribbons were prepared by melt spinning combined with heat treatment.•The coercivity as high as 742 Oe can be achieved.•The microstructure and domain structure changes during heat treatment were investigated.•Magnetization process is observed by Lortenz transmission electron microscopy.•The models of phase transition and coercivity mechanism are built up.