High energy product of isotropic bulk Sm-Co/α-Fe(Co) nanocomposite magnet with multiple hard phases and nanoscale grains. (20th October 2021)

• Record Type: Journal Article
• Authors: Li, Shuo; Ma, Longfei; Fan, Jinkui; Yang, Jianping; Zheng, Qiang; Bian, Baoru; Zhang, Jian; Du, Juan
• Is Part Of: Journal of materials science & technology. Volume 88(2022)
• Page Start: 183
• Page End: 188
• Publication Date: 2021-10-20
• Subjects: Hard/soft phase nanocomposite -- Isotropic bulk -- Magnetic properties -- Grain size -- Phase constitution; Metals -- Periodicals; Materials science -- Periodicals; Materials science; Metals; Periodicals; 620.1105
• DOI: 10.1016/j.jmst.2021.01.083
• Languages: English
• ISSNs: 1005-0302

Abstract

Graphical abstract: Bulk nanocomposite magnets with grain size of 14 nm of hard phase and 17 nm of soft phase were obtained. All the magnets fabricated from 475 to 550 °C had a high (BH)max of 20 MGOe or larger values, and the one fabricated at 525 °C had the highest value of 23.6 MGOe. Highlights: Bulk magnets were fabricated from ball milled amorphous/nanocraystalline powders by two step compression at relatively low temperatures. High density more than 97% theoretical density was obtained in bulk nanocomposite magnets with grains below 20 nm. Bulk nanocomposite magnets with grain size of 14 nm of hard phase and 17 nm of soft phase were obtained. Multiple hard magnetic phases contributed to a high coercivity in the obtained bulk nanocomposite magnets. A new record-high energy product ( BH )max of 23.6 MGOe was obtained in isotropic Sm-Co/α-Fe nanocomposite bulk magnet. Abstract: Nanocomposite magnets consisting of hard and soft magnetic phases have potential applications to be the next generation of permanent magnets with very high energy product and less expensive rare-earth elements. But it is still a big challenge to obtain bulk magnets with ideal microstructure and high performance. In this work, two - step warm processing at relative low temperatures had been adopted to obtain nearly theoretical density bulk nanocomposite magnets from amorphous/nanocrystalline powder precursors. Novel nanostructures consisting of multiple Sm-Co hard phases (SmCo5 as main phase, SmCo3, SmCo7, Sm2 Co17 as minor phases) and 25 wt% α-Fe(Co) soft phase, nanoscale grain size below 20 nm for both the hard phase and soft phase, and the diffusion of Fe and Co compositions had been obtained in bulk isotropic magnets. Besides the ideal nanostructures, a high coercivity of 5.9 kOe, Mr /Ms value of 0.78 and a high square degree of demagnetization curve S = 0.47 were obtained. All of these factors together brought a new record-high energy product (BH)max of 23.6 MGOe. These results make an important step toward fabricating novel nanostructure with high performance.