Magnetostriction of Fe 1-x Co x (x=50-90 at%) alloys prepared by forging and subsequent cold-rolling was studied as functions of alloy compositions and thermomechanical treatments. Magnetostriction of the as-forged Fe 25 Co 75 alloy was 108 ppm and that of the as-cold rolled Fe 25 Co 75 alloy measured parallel to the rolling direction (RD) was 128 ppm. The cold-rolled Fe 25 Co 75 alloy possessed a nearly {100}<011> texture, leading to the maximum magnetostriction of 140 ppm when measured at an angle of 45° to RD. Moreover, the fully annealed Fe 25 Co 75 and Fe 20 Co 80 alloys were gradually cold rolled and magnetostriction were measured. Results showed that the magnetostriction of those cold-rolled alloys drastically increased with increasing reduction rate. According to the XRD and TEM observations, intensity of the fcc peak gradually decreased with increasing reduction rate and that the alloys became to be in a bcc single state at a reduction rate higher than 90%, leading to a drastic increase in magnetostriction.

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X-ray photoelectron spectroscopy (XPS), ellipsometry, and cathode luminescence were utilized for characterizing oxide films formed on the surfaces of FeCo-V alloys (Permendur) that contained small amounts of aluminum via annealing under a low partial pressure of oxygen. XPS spectra showed that the oxide films were composed primarily of aluminum oxide, which was a result of preferential oxidation of aluminum on the surfaces of the alloys during annealing. The thicknesses of the oxide films were estimated from XPS depth profiles coupled with the sputtering rate of a SO2/Si film, and the thicknesses were compared with those of the oxide films measured via non-destructive ellipsometry. The thicknesses obtained from the depth profiles may have been overestimated because of a difference in sputtering rate between silicon oxide and aluminum oxide. As measured via ellipsometry, the thickness of the aluminum oxide thin film, which was less than 100 nm, increases with the aluminum content in the alloys. Wide XPS spectra from the sample surfaces with different roughness suggested that the aluminum oxide thin films were homogenously formed on the smooth surfaces, whereas metallic elements in the alloy substrates were detected on the rough surfaces. Furthermore, the electrical resistivity of the alloys with the smooth surfaces increases significantly with the aluminum content, which may be attributable to the formation of the aluminum oxide thin film. These results indicate that the addition of a small amount of aluminum and surface smoothness are important for controlling formation of the aluminum oxide thin films with high resistivity in FeCo-V alloys by annealing under a low partial pressure of oxygen.

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Although conventional free‐cutting soft‐magnetic stainless steel contains Pb to facilitate machining, the replacement and elimination of Pb is required from the standpoint of environmental protection. In this article, the authors report the development of new Pb‐free machinable soft‐magnetic stainless steels in which titanium carbo‐sulfide is used as an inclusion. The microstructural evolution, magnetic properties, corrosion resistance, machinability and mechanical properties of these new free‐cutting stainless steels are presented.