Binary Fe--Nd metastable phases in the solidification of Fe--Nd--B alloys

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

DOI:https://doi.org/10.1063/1.350061· OSTI ID:5165189

Landgraf, F J.G. ^[1]; Missell, F P ^[2]; Knoch, G; Grieb, B; Henig, E ^[3]

---

1. Instituto de Pesquisas Tecnologicas do Estado de Sao Paulo, Sao Paulo (Brazil)
2. Instituto de Fisica, Universidade de Sao Paulo, Sao Paulo, SP (Brazil)
3. Max-Planck-Institut fuer Metallforschung, PML, Stuttgart (Germany)

It has been shown that a binary Fe--Nd metastable phase {ital A}{sub 1} is responsible for coercivity of {congruent}5 kOe in Fe80Nd5B as-cast alloys. It is rapidly transformed into Fe{sub 14}Nd{sub 2}B after a very short annealing at 600 {degree}C and it is also present in alloys of magnet composition. Thus it may account for the lower coercivity of as-sintered magnets. Here we discuss how this phase can be formed in the solidification of Fe--Nd--B magnets. The microstructure and thermal events of DTA samples of constant 60 at. % Nd were used to construct a vertical section of the Fe--Nd--B ternary phase diagram. The solidification of alloys related to magnet compositions did not follow the path predicted by the known phase diagrams which leads to a ternary eutectic. Instead, they pass through a transition reaction, involving Fe{sub 4}NdB{sub 4}, liquid, Fe{sub 14}Nd{sub 2}B, and Nd, which may reach the binary Fe--Nd eutectic, giving rise to different metastable phases, depending on the cooling rate: {ital A}{sub 1}, {ital A}{sup {prime}}{sub 1} or Fe{sub 17}Nd{sub 2}. A new version of the liquidus projection of the Nd-rich corner of the ternary phase diagram is presented.

• OSTI ID: 5165189
• 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
360102* -- Metals & Alloys-- Structure & Phase Studies
ALLOYS
BORON ALLOYS
CRYSTAL STRUCTURE
DIAGRAMS
IRON ALLOYS
MAGNETS
MICROSTRUCTURE
NEODYMIUM ALLOYS
PERMANENT MAGNETS
PHASE DIAGRAMS
PHASE TRANSFORMATIONS
RARE EARTH ALLOYS
SOLIDIFICATION