Deformation mechanism of highly textured Alnico magnets

Deformed Alnico magnets were prepared by hot isostatic pressing (HIP) spherical powders and hot rolling (HR), and the hot-rolled magnets were solution-treated at 1250 degrees C, magnetic heat treated at 835 degrees C, and three-stage aged at 600 - 500 degrees C, respectively. The results show that Alnico spherical powder comprises 77.5% alpha phase, 8.6% alpha 1 phase, and 13.9% alpha 2 phase. The HIP magnet has spinodal decomposed during the preparation, and HR improved alpha content. The magnet has spinodal decomposed thoroughly after magnetic heat treatment (MHT) and aging heat treatment (AHT), composed of 62.1% alpha 1 phase with a B2 structure and 37.9% Fe2NiAl-type alpha 2 phase with the L21 structure. Moreover, the HIP and HR magnet preferentially pro-duces the < 100 > texture, which is also enhanced along the < 211 > directions. The preferred deformation of the alpha 1 phase is carried out under the synergistic action of the alpha 2 phase. The HIP deformation mechanism is that composition diffusion and structural transformation are carried out in different stages, resulting in four kinds of two-phase structures. The rolling deformation mechanism is that the grains parallel or nearly parallel to the rolling direction are directly rolled into lath-like ones, and four kinds of microstructures are formed in the grains. Compared to the HIP magnet, the MHT and AHT promote the formation of the fibrous structure, and the maximum aspect ratio of alpha 1 phase reaches similar to 35:1. The coercivity of the heat-treated magnet increased by 160.9%, and the remanence and magnetic energy product also increased simulta-neously.(c) 2023 Elsevier B.V. All rights reserved.