Mössbauer study of heat-treated iron-rich Ni-Fe alloys

The effect of annealing on the magnetic properties of cold-rolled samples of iron-rich Ni-Fe alloys was studied over the composition range between 20 and 40 percent Ni. The plastically deformed samples had a thickness reduction of about 99 percent, Changes in the crystallographic and magnetic heterogeneities were followed by means of the Mössbauer effect. The results are discussed in terms of the coexistence of fine dispersions of both paramagnetic and ferromagnetic α and γ phases, as well as by concentration fluctuations within each phase. It was shown that, at room temperature, marked changes in technical saturation magnetization loop squareness took place in the alloys with a composition close to 70 percent Fe, at which the α-γ phase boundary appears. The investigated quasi-static magnetic loops were cycled with a frequency of 2 Hz.