Determination of pressure effects on the alpha - gamma phase transition and size of Fe in Nd-Fe-B spring exchange magnets

Abuin Herraez, Manuel; Turgut, Zafer; Aronhime, Natan; Keylin, Vladimir; Leary, Alex; DeGeorge, Vincent; Horwath, John; Lee Semiatin, S.; Laughlin, David E. y McHenry, Michael E. (2015). Determination of pressure effects on the alpha - gamma phase transition and size of Fe in Nd-Fe-B spring exchange magnets. "Metallurgical and Materials Transactions A", v. 46 (n. 11); pp. 5002-5010. ISSN 1073-5623. https://doi.org/10.1007/s11661-015-3120-0.

Descripción

Título: Determination of pressure effects on the alpha - gamma phase transition and size of Fe in Nd-Fe-B spring exchange magnets
Autor/es:
  • Abuin Herraez, Manuel
  • Turgut, Zafer
  • Aronhime, Natan
  • Keylin, Vladimir
  • Leary, Alex
  • DeGeorge, Vincent
  • Horwath, John
  • Lee Semiatin, S.
  • Laughlin, David E.
  • McHenry, Michael E.
Tipo de Documento: Artículo
Título de Revista/Publicación: Metallurgical and Materials Transactions A
Fecha: Noviembre 2015
Volumen: 46
Materias:
Escuela: E.T.S.I. Telecomunicación (UPM)
Departamento: Electrónica Física
Licencias Creative Commons: Reconocimiento - Sin obra derivada - No comercial

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Resumen

Pressure effects in RE-lean Nd2Fe14B-based nanocomposite systems developed from nanocrystalline precursors are studied in this work. In particular, the pressure dependence of the α → γ phase transformation in the Fe phase is examined along with the suppression of coarsening (growth) in both phases at higher pressures. By synchrotron X-ray diffraction we determined that the α → γ-phase transformations occur at temperatures of 1120 K (847 °C) at 1 GPa and 960 K (687 °C) at 5 GPa. A composition rich in Fe appears to have an ~373 K (100 °C) range of temperature over which the α, γ-phases coexist for atmospheric pressure. We compare our experimental data with other reported observations for Fe and with equations of state (EOS) determined from first principle calculations. From this study we observe an important feature: the phase transition begins at a higher temperature in flake samples than in powder samples. We consider the magnetic contribution to the heat capacity in the EOS for Fe and describe the implications of dipole moments on the slope of the Clapeyron equation for the P–T phase diagram in Fe. Additionally, the phase transition occurs at temperatures where growth by diffusional coarsening is also operative. This is significant since the size of soft Fe nanostructures is important to spring exchange. Suppression of the phase transition and Fe coarsening at higher pressures suggest that there may be interesting mechanical processing routes to be investigated to optimize spring exchange effects in Nd-Fe-B permanent magnets.

Más información

ID de Registro: 41097
Identificador DC: http://oa.upm.es/41097/
Identificador OAI: oai:oa.upm.es:41097
Identificador DOI: 10.1007/s11661-015-3120-0
URL Oficial: http://link.springer.com/article/10.1007/s11661-015-3120-0
Depositado por: Memoria Investigacion
Depositado el: 03 Jul 2016 07:38
Ultima Modificación: 01 Dic 2016 23:30
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