Leveraging miscibility gap via low-temperature annealing for enhanced hard magnetic properties in laser additively processed Alnico-8H

IF 5.6 2区材料科学 Q2 MATERIALS SCIENCE, MULTIDISCIPLINARY

Scripta Materialia Pub Date : 2025-09-16 DOI:10.1016/j.scriptamat.2025.116996

Saikumar Dussa , Sudip Kumar Sarkar , Sameehan S. Joshi , Rajarshi Banerjee , Narendra B. Dahotre

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Abstract

This study delves into the miscibility gap present in the phase diagram to tune nanoscale microstructure through controlled annealing for enhanced hard magnetic properties in laser-directed energy deposition fabricated Alnico-8H using a blend of constituent elemental powders. Through strategic annealing, intrinsic coercivity as high as 1392 Oe was achieved by altering conventional annealing parameters from 830 °C-10 min (935 Oe) to 650 °C-34 hrs (1392 Oe). Atom probe tomography investigations revealed that lower annealing temperature in conjunction with longer time generated a nearly three times smaller spatial dimension of α₁ (Fe-Co-rich) and α₂ (Ni-Al-Ti-rich) phases, a steeper concentration gradient between α₁ and α₂ phases, and Cu-rich (finer rod) core-shell (Ni-Al-rich)-type precipitates in higher number density (1.1 × 10²²/m³). Notably, intrinsic coercivity value achieved in this research approach characteristics of conventionally thermo-magnetically processed multi-step anisotropic Alnico alloys. Thus, findings of this study present a simplified pathway for designing isotropic Alnico magnets through a simple single-step heat-treatment process.

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利用混相间隙低温退火提高激光增材加工铝镍合金的硬磁性能

本研究深入研究相图中存在的混相间隙，通过控制退火来调整纳米级微观结构，以增强激光定向能沉积中使用组成元素粉末制备的Alnico-8H的硬磁性能。通过策略退火，将常规退火参数从830°C-10 min （935 Oe）改变为650°C-34 hrs (1392 Oe)，获得了高达1392 Oe的本征矫顽力。原子探针层析成像研究表明，较低的退火温度和较长的退火时间使α1（富fe - co）和α2（富ni - al - ti）相的空间尺寸减小了近3倍，α1和α2相之间的浓度梯度增大，富cu（细棒状）核壳（富ni - al）型析出相的数密度增大（1.1 × 1022/m3）。值得注意的是，本研究获得的本征矫顽力值接近常规热磁加工多步各向异性铝镍合金的特征。因此，本研究的发现为通过简单的单步热处理工艺设计各向同性铝镍钴磁体提供了一种简化的途径。

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来源期刊

Scripta Materialia 工程技术-材料科学：综合

CiteScore

11.40

自引率

5.00%

发文量

581

审稿时长

34 days

期刊介绍： Scripta Materialia is a LETTERS journal of Acta Materialia, providing a forum for the rapid publication of short communications on the relationship between the structure and the properties of inorganic materials. The emphasis is on originality rather than incremental research. Short reports on the development of materials with novel or substantially improved properties are also welcomed. Emphasis is on either the functional or mechanical behavior of metals, ceramics and semiconductors at all length scales.