Magnetic properties of 1% Al‐iron and its applications

A study was carried out to improve permeability and coercivity of pure iron without decreasing its saturation magnetization. It was found that about 1‐wt % addition of aluminum in combination with a high‐temperature annealing process greatly increases its permeability (μm) up to 60 000, which is close to that of Permalloy B, and reduces its coercivity (Hc) to 0.2 Oe without decreasing the high‐saturation magnetization of pure iron. This marvelous effect of the 1‐wt %‐Al addition can be attributed to a stabilization of the ferrite phase which enables ferrite grains to coarsen drastically due to abnormal grain growth during the high‐temperature annealing. The ferrite stabilization also helps to avoid both residual strain and grain refining due to the austenite‐ferrite phase transformation, which are thought to be undesirable for soft magnetic properties. In the present paper, the performance of this Fe–1‐wt %‐Al soft magnetic alloy, and an example of its practical application to the magnetic shielding, will...