Effect of refractory additives on coercivity of sintered (Nd, Dy)(Fe, Co) BM magnets (M=Cr/W/Zr/Nb/Ta) (abstract)

Journal Article · Fri Nov 15 04:00:00 EST 1991 · Journal of Applied Physics; (United States)

DOI:https://doi.org/10.1063/1.349947· OSTI ID:5060029

Lin, K D; Tzuoo, U C ^[1]; Tung, J Y; Chin, T S ^[2]

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1. High-End Metals Corporation, Hsinchu Industrial Park, Hukou, 303, Taiwan (Republic of China)
2. Department of Materials Science and Engineering, Tsing Hua University, Hsinchu, 300, Taiwan (Republic of China)

In a trial to develop heat-resistant sintered Nd{sub 2}Fe{sub 14}B magnets, a refractory element (Cr/W/Zr/Nb/Ta) was selected as an additive incorporating Dy and Co in the Nd-Fe-B composition. Nd{sub 13}Dy{sub 1.5}Fe{sub 72{minus}{ital x}}Co{sub 6}B{sub 7.5}M{sub {ital x}} alloys (M=Cr/W/Nb/Ta, {ital x}=0, or 3.5) were arc-melted, pulverized, compacted, and sintered by the conventional powder metallurgy method. It was found that W/Cr greatly enhances the as-sintered intrinsic coercivity ({sub {ital i}H{ital c}}, in kA/m), e.g., from 510 ({ital x}=0) to 810 (W, {ital x}=3.5) or 740 (Cr, {ital x}=3.5). An additional two-stage annealing at 900 and 600 {degree}C for 1 h each led to an even higher {sub {ital i}H{ital c}} of 1000 (W, {ital x}=3.5). While Nb/Ta moderately enhanced as-sintered {sub {ital i}H{ital c}}, and responded less to additional annealing. Temperature coefficients of remanence was found to be greatly improved by the W or Cr addition, e.g., 0.43%/{degree}C for {ital x}=0 and 0.06%/{degree}C for M=W, {ital x}=3.5 ({ital p}=1, 20--150 {degree}C). They are thus very suitable for applications at temperatures up to 150 {degree}C. EPMA analyses showed the possible existence of a M{sub 2}FeB{sub 2} (M=W/Nb/Ta) phase at grain boundaries. Thermomagnetic analyses and detailed microstructure of the sintered and/or annealed magnets are discussed.

• OSTI ID: 5060029
• Journal Information: Journal of Applied Physics; (United States), Journal Name: Journal of Applied Physics; (United States) Vol. 70:10; ISSN 0021-8979; ISSN JAPIA
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360104* -- Metals & Alloys-- Physical Properties
ALLOYS
ANNEALING
BORON ALLOYS
COBALT ALLOYS
COERCIVE FORCE
CRYSTAL STRUCTURE
DYSPROSIUM ALLOYS
FABRICATION
GRAIN BOUNDARIES
HEAT TREATMENTS
IRON ALLOYS
MATERIALS
MICROSTRUCTURE
NEODYMIUM ALLOYS
RARE EARTH ALLOYS
REACTIVITY COEFFICIENTS
SINTERED MATERIALS
SINTERING
TEMPERATURE COEFFICIENT