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Metals 2014, 4(1), 8-19; doi:10.3390/met4010008
Article

Magnetism-Structure Correlations during the ε→τ Transformation in Rapidly-Solidified MnAl Nanostructured Alloys

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 and
1,*
1 Department of Chemical Engineering, Northeastern University, 360 Huntington Ave., Boston, MA 02115, USA 2 Department of Materials Science and Engineering, Case Western Reserve University, Cleveland, OH 44106-7204, USA
* Author to whom correspondence should be addressed.
Received: 13 December 2013 / Revised: 14 January 2014 / Accepted: 16 January 2014 / Published: 21 January 2014
(This article belongs to the Special Issue Manganese-based Permanent Magnets)
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Abstract

Magnetic and structural aspects of the annealing-induced transformation of rapidly-solidified Mn55Al45 ribbons from the as-quenched metastable antiferromagnetic (AF) ε-phase to the target ferromagnetic (FM) L10 τ-phase are investigated. The as-solidified material exhibits a majority hexagonal ε-MnAl phase revealing a large exchange bias shift below a magnetic blocking temperature TB~95 K (Hex~13 kOe at 10 K), ascribed to the presence of compositional fluctuations in this antiferromagnetic phase. Heat treatment at a relatively low annealing temperature Tanneal ≈ 568 K (295 °C) promotes the nucleation of the metastable L10 τ-MnAl phase at the expense of the parent ε-phase, donating an increasingly hard ferromagnetic character. The onset of the ε→τ transformation occurs at a temperature that is ~100 K lower than that reported in the literature, highlighting the benefits of applying rapid solidification for synthesis of the rapidly-solidified parent alloy.
Keywords: nanostructured magnetic materials; Mn-based magnets; rapid-solidification nanostructured magnetic materials; Mn-based magnets; rapid-solidification
This is an open access article distributed under the Creative Commons Attribution License (CC BY 3.0).
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Jiménez-Villacorta, F.; Marion, J.L.; Oldham, J.T.; Daniil, M.; Willard, M.A.; Lewis, L.H. Magnetism-Structure Correlations during the ε→τ Transformation in Rapidly-Solidified MnAl Nanostructured Alloys. Metals 2014, 4, 8-19.

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