Phase formation in isothermally annealed (Co0.95Fe0.05)89Zr7B4 Nanocrystalline alloys

This report focuses on the phase relations and transformations in a (Fe0.05Co0.95)(89)Zr7B4 melt-spun alloy with an emphasis on crystallization and its effects on thermomagnetic properties. When as-spun ribbons are annealed at relatively low temperatures (near primary crystallization), the nucleation and growth of nonequilibrium body-centered-cubic (bee) crystalliteS occurs in a residual amorphous matrix, as determined by transmission electron microscopy ITEM) and X-ray diffraction (XRD). At intermediate temperatures, bee crystallites continue to grow with the addition of a small Volume fraction of the equilibrium face-centered-cubic (fee) phase. It is expected that after the bee nuclei are formed, the grains coarsen as bee phase and do not transform to the more stable fee phase at intermediate temperatures. At temperatures where the amorphous matrix phase dissociates into Zr intermetallics, the bee phase is transformed into fee and the grains coarsen significantly. Thermodynamic modeling has been used to support the nucleation of the nonequilibrium bee phase during the early stages of crystallization. Thermomagnetic results show little reduction in the saturation magnetization as a function of annealing temperature LIP to the primary crystallization temperature (similar to 420 degrees C).