Effects of Length-to-Width Ratio on Magnetic and Microstructural Properties of Die-Upset Nd-Fe-B Magnets

• Published in: Materials 2024-10, Vol.17 (21), p.5236
• Main Authors: Lee, Sang-Hyub, Kang, Min-Suk, Kim, Yang-Do, Kim, Dong-Hwan
• Format: Article
• Language: English
• Subjects: Coercivity; Cracks; Deformation; Grain growth; Grain size distribution; Hot pressing; Magnetic fields; Magnetic properties; Magnets; Neodymium; Pressure distribution; Ratios; Remanence; Stress concentration; Stress distribution
• ISSN: 1996-1944; 1996-1944
• DOI: 10.3390/ma17215236

In this study, the effects of the length-to-width ratio on the magnetic and microstructural properties of die-upset Nd-Fe-B magnets were examined. A die-upset magnet with a uniform shape and no significant cracking was successfully developed. During the die-upset process, the applied pressure was not uniform across the magnet and varied depending on its shape and position. In the case of the magnet with a 4:1 ratio, which had the largest length-to-width ratio, there was a higher concentration of stress at the edges compared to the center, resulting in easier grain deformation and growth at the edges, which led to the lowest remanence and ( ) . As the length-to-width ratio approached 1:1, the grain size increased slightly, reducing the coercivity; however, the magnets maintained a uniform grain-size distribution. The change from a rectangular to a square pressing surface resulted in a more uniform stress distribution, particularly at the center and corners, which improved the consistency of the magnetic properties across different regions of the magnet. Consequently, an 11.9% enhancement in ( ) , reaching 285.6 kJ/m , was achieved in the 1:1 ratio die-upset magnet, which is attributed to the uniform grain size and improved grain alignment.