R-(Fe, Co)-B Sintered Magnet and Making Method

• Main Authors: Nakamura Hajime, Hirota Koichi, Kamata Masayuki, Hashimoto Takahiro
• Format: Patent
• Language: English
• Published: 18.05.2017
• Subjects: ALLOYS; BASIC ELECTRIC ELEMENTS; CASTING; CHEMISTRY; ELECTRICITY; FERROUS OR NON-FERROUS ALLOYS; INDUCTANCES; MAGNETS; MAKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; METALLURGY; PERFORMING OPERATIONS; POWDER METALLURGY; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES; TRANSFORMERS; TRANSPORTING; TREATMENT OF ALLOYS OR NON-FERROUS METALS; WORKING METALLIC POWDER

An R-(Fe,Co)-B base sintered magnet consisting essentially of 12-17 at % of R containing Nd and Pr, 0.1-3 at % of M1 (typically Si), 0.05-0.5 at % of M2 (typically Ti), B, and the balance of Fe, and containing R2(Fe,Co)14B as a main phase has a coercivity of at least 10 kOe. The magnet contains a M2 boride phase at a grain boundary triple junction, and has a core/shell structure that the main phase is covered with a grain boundary phase. The grain boundary phase is composed of an amorphous and/or nanocrystalline R′-(Fe,Co)-M1′ phase consisting essentially of 25-35 at % of R′ containing Pr, 2-8 at % of M1′ (typically Si), up to 8 at % of Co, and the balance of Fe. A coverage of the main phase with the R′-(Fe,Co)-M1′ phase is at least 50%, and the bi-granular grain boundary phase has a width of at least 50 nm.