Nanocrystalline Fe–Zr–Si(Cu) boron-free alloys

Amorphous precursors Fe80ZrxSi20−x−yCuy (x = 7, 10 and y = 0, 1), in which boron was completely replaced by silicon as a glass forming element, have been obtained by melt quenching. Nanocrystalline alloys have been prepared by annealing the amorphous precursors at temperatures ranging from the crystallization onset temperature (530 °C) to the second crystallization step (above 700 °C), which were determined by the differential scanning calorimetry. The crystalline phases formed were identified by the X-ray diffraction (XRD) and Mössbauer spectroscopy measurements. Their transformation versus annealing temperature was followed. Both the XRD and Mössbauer measurements have shown the primary nanocrystallization product to be the bcc-Fe(SiZr) solid solution, which transformed to the bcc-Fe(Si) phase upon rising the annealing temperature. The average grain size of the nanocrystalline phase was estimated from the XRD patterns by the Williamson–Hall method. The grain size increased from below 20 nm to about 80 nm for x = 7 alloys as the annealing temperature rises from 530 °C to 750 °C. The XRD and Mössbauer study was supplemented by conventional measurements of hysteresis loops. The coercivity was found to increase strongly with increasing annealing temperature.