Severe plastic deformation of Mn-Al permanent magnets

IF 3 Q2 MATERIALS SCIENCE, MULTIDISCIPLINARY

Materialia Pub Date : 2024-09-29 DOI:10.1016/j.mtla.2024.102251

Thomas Keller , Gheorghe Gurau , Ian Baker

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Abstract

Manganese-aluminum permanent magnets are promising candidates to fill the cost and performance gap between lower-performance bonded ferrites and high-performance magnets based on rare-earth elements. This is due to the favorable combination of saturation magnetization and magnetocrystalline anisotropy in the Mn-Al τ phase combined with low raw material cost. However, the τ phase is metastable and prone to decomposition at high temperatures, making processing by conventional milling and sintering difficult. Severe plastic deformation (SPD) is an alternative processing route to control the microstructure of a material by applying very high amounts of strain. In this study, equal-channel angular extrusion (ECAE) and high-speed high-pressure torsion (HS-HPT) were both tested as SPD processing routes. ECAE improved magnetic energy product, (BH)_max, by 220 % by refining the grain size and imparting a high density of dislocations. HS-HPT enabled a rapid phase transformation from the high-temperature ε phase to the τ phase but lowered H_ci, making it better suited to soft magnet processing.

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锰铝永磁体的严重塑性变形

锰铝永磁体有望填补低性能粘结铁氧体与基于稀土元素的高性能磁体之间的成本和性能差距。这是因为锰铝τ相具有饱和磁化和磁晶各向异性的有利组合，而且原材料成本低。然而，τ 相在高温下易变且易分解，因此难以采用传统的铣削和烧结工艺进行加工。严重塑性变形（SPD）是通过施加极高的应变来控制材料微观结构的另一种加工方法。在这项研究中，等通道角挤压（ECAE）和高速高压扭转（HS-HPT）都作为 SPD 加工途径进行了测试。ECAE 通过细化晶粒尺寸和赋予高密度位错，将磁能积 (BH)max 提高了 220%。HS-HPT 实现了从高温 ε 相到 τ 相的快速相变，但降低了 Hci，因此更适合软磁加工。

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来源期刊

Materialia MATERIALS SCIENCE, MULTIDISCIPLINARY-

CiteScore

6.40

自引率

2.90%

发文量

345

审稿时长

36 days

期刊介绍： Materialia is a multidisciplinary journal of materials science and engineering that publishes original peer-reviewed research articles. Articles in Materialia advance the understanding of the relationship between processing, structure, property, and function of materials. Materialia publishes full-length research articles, review articles, and letters (short communications). In addition to receiving direct submissions, Materialia also accepts transfers from Acta Materialia, Inc. partner journals. Materialia offers authors the choice to publish on an open access model (with author fee), or on a subscription model (with no author fee).