Synthesis of an intermetallic powder with a hard magnetic phase τ-MnAl by calcium thermal reduction

IF 4.8 2区材料科学 Q2 CHEMISTRY, PHYSICAL

Intermetallics Pub Date : 2025-08-16 DOI:10.1016/j.intermet.2025.108961

Adit Sharma , M.V. Gorshenkov , S.N. Yudin , T.A. Morozova , E.R. Khusainova , N.M. Vazhinskii , K.S. Nechaev , J.C. Qiao

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Abstract

This study investigates the synthesis parameters of MnAl(C) powders using the calcium-thermal reduction of aluminum oxide (Al₂O₃) and manganese oxide (MnO), aiming to produce Mn-Al alloys within the compositional range of the metastable hard magnetic phase (τ-MnAl). Pure graphite was used as the carbon source for the alloying. This study explored the impact of Al₂O₃/MnO ratio, CaH₂ content, and compaction method. Hydrothermal purification with acetic acid yielded irregularly shaped Mn-Al powders (20–50 μm). Analysis of the Mn/Al compositions indicated that a 50–100 % excess of the initial aluminum was needed to obtain an alloy composition laying within τ-MnAl phase. The powder obtained in air-cooled container had small τ-phase content. Approximately 50 % τ-MnAl was achieved by conducting the reaction in pre-evacuated steel containers at 1250 °C for 2 h, followed by water quenching from 950 °C. This resulted in a low-cost powder with a magnetization of 50 A m²/kg and a coercive force of 38 A/m. While the formation of the τ-phase is promising, its limited fraction (≈50 %) significantly reduces the magnetic performance. This currently makes the material unsuitable for additive manufacturing or mechanical grinding followed by compaction. Further optimization is required to increase the τ-phase fraction before considering practical applications.

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钙热还原法制备硬磁相τ-MnAl金属间粉

本文研究了氧化铝（Al2O3）和氧化锰（MnO）的钙热还原法制备MnAl(C)粉末的工艺参数，旨在制备亚稳硬磁相（τ-MnAl）成分范围内的Mn-Al合金。采用纯石墨作为合金碳源。本研究探讨了Al2O3/MnO比、CaH2含量和压实方法的影响。用乙酸水热提纯得到形状不规则（20 ~ 50 μm）的Mn-Al粉末。Mn/Al成分分析表明，要获得位于τ-MnAl相内的合金成分，需要初始铝含量超过50 - 100%。在风冷容器中得到的粉末τ相含量小。通过在预抽真空的钢容器中在1250℃下反应2 h，然后在950℃水淬，可以获得约50%的τ-MnAl。这导致了低成本的粉末，磁化强度为50 a / m2/kg，矫顽力为38 a /m。虽然τ相的形成很有希望，但其极限分数（≈50%）显著降低了磁性能。这使得目前的材料不适合增材制造或机械研磨，然后压实。在考虑实际应用之前，需要进一步优化以提高τ相分数。

本文章由计算机程序翻译，如有差异，请以英文原文为准。

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来源期刊

Intermetallics 工程技术-材料科学：综合

CiteScore

7.80

自引率

9.10%

发文量

291

审稿时长

37 days

期刊介绍： This journal is a platform for publishing innovative research and overviews for advancing our understanding of the structure, property, and functionality of complex metallic alloys, including intermetallics, metallic glasses, and high entropy alloys. The journal reports the science and engineering of metallic materials in the following aspects: Theories and experiments which address the relationship between property and structure in all length scales. Physical modeling and numerical simulations which provide a comprehensive understanding of experimental observations. Stimulated methodologies to characterize the structure and chemistry of materials that correlate the properties. Technological applications resulting from the understanding of property-structure relationship in materials. Novel and cutting-edge results warranting rapid communication. The journal also publishes special issues on selected topics and overviews by invitation only.