The effect of the minor Al addition on microstructure and soft magnetic properties for (Fe0.5Co0.5)73.5Si13.5Nb3Cu1B9 nanocrystalline alloy

Abstract

(Fe0.5Co0.5)73.5Si13.5Nb3Cu1B9-xAlx (x = 0.2, 0.4, 0.6, 0.8) nanocrystalline alloys were investigated with the aim of improving the soft magnetic properties and keeping thermal stability of initial permeability. The temperature dependence of initial permeability (μi - T) was measured from room temperature up to 720 °C for all the alloys. The differential scanning calorimetry and X-ray diffractometry were performed for analyzing crystallization process and microstructure. Experimental results pointed out that the partial replacement of B with Al significantly decreased onset temperature of the primary crystallization (Tx1) from 498 °C to 466 °C and slightly increased the crystallized interval temperature (ΔTx) from 210 °C to 226 °C. μi of alloys annealed at 600 °C maintained a relatively stable value from ambient temperature up to 650 °C. Moreover, μi showed a slight increase with the increase of Al content from 0.2 to 0.6, which could be ascribed to the formation of the uniform nanostructure with small grain size and high volume fraction of crystals. As a result, (Fe0.5Co0.5)73.5Si13.5Nb3Cu1B8.4Al0.6 nanocrystalline alloy annealed at 600 °C exhibited excellent soft magnetic properties at high temperature.