Experiments on nanostructured Fe73.5Cu1Nb3Si13.5B9 formed due to short-time annealing

For technical applications the commonly used thermal processing of the amorphous Fe73.5Cu1Nb3Si13.5By alloy consists of one-hour anneals at about 550 degrees C. This procedure leads to very soft magnetic properties due to the formation of the nanocrystalline Fe(Si) phase in the remaining amorphous matrix. In order to study the onset and development of the nanocrystalline phase the as-quenched amorphous samples were annealed in an Ar atmosphere at temperatures of 550 degrees C and 650 degrees C for different annealing times: 15 s, 30 s, 60 s, 90 s, 120 s, 180 s and 300 s. For sample characterization we used the conventional Mossbauer effect technique and additionally Mossbauer measurements in radiofrequency magnetic fields, which are very sensitive to magnetostriction and magnetic anisotropies. The measurements were supplemented with electron transmission microscopy and electron diffraction studies. Our short-rime annealing experiments clearly show that in order to form good magnetically soft properties the annealing times of 1-2 min at 550 degrees C and of only 15-30 s at 650 degrees C are sufficient.