Interfacial Diffusion Annealing of Al-Si Alloy for Enhanced Properties of Al-Si/Fe Soft Magnetic Composites

Abstract

Soft magnetic composites have found extensive application in medium-to-low frequency power electronics devices due to their advantages of low magnetic loss and high saturation magnetic flux density. The further optimization of their AC magnetic properties remains a crucial factor limiting their broader application. This study focuses on enhancing these properties through interfacial diffusion technology, using spherical iron powder as the matrix and aluminum-silicon alloy as the diffusion source to fabricate Al-Si/Fe soft magnetic composites. The effects of annealing temperature and annealing time on the material's microstructures and magnetic properties were systematically investigated. The results indicate that the interfacial diffusion of the Al-Si alloy effectively fills the gaps between iron powder particles, enhancing the material's density. By modifying the interfacial structure of the Fe particles, the magnetic properties of the Al-Si/Fe samples are significantly improved, leading to an increase in effective permeability and a notable reduction in magnetic loss. Optimal magnetic properties are achieved at an annealing temperature of 900°C for 2 hours, with a magnetic loss of 3769.6 kW/m3 at 500 kHz and 5 mT. The grain boundary diffusion of the Al-Si alloy not only enhances the magnetic properties of the iron-based soft magnetic composites but also significantly improves their high-frequency magnetic characteristics and DC bias performance. These insights expand the theoretical application of grain boundary diffusion technology and provide new approaches and methods for the design and development of high-performance SMCs.

Keywords: Soft magnetic composites, Interfacial diffusion, Al-Si alloy, Annealing temperature, Annealing time