Phase evolution during crystallization of nanocomposite alloys with Co:Fe ratios in the two-phase region of the binary Fe–Co phase diagram

Abstract

A series of alloys was prepared to investigate the crystallization of Co-rich HiTPerm-type alloys [(Co1−xFex)88Zr7B4Cu1] with Fe:Co ratios within or near the two-phase (bcc+fcc) region of the binary phase diagram. The goal of this work is to better understand the phase evolution and crystallization of alloys in which the Fe–Co binary phase diagram predicts more than one transition metal rich primary crystalline phase to be present in equilibrium at the primary crystallization temperature. X-ray diffraction, transmission electron microscopy, and high-temperature vibrating-sample magnetometry have been performed to identify the first phase to crystallize and to follow the evolution of phases during crystallization. The bcc phase appears to be the primary crystalline phase that forms first after annealing at 450°C for 1h, in agreement with previous work on Co-rich nanocomposite alloys. We observe that as the Co concentration is increased, the fcc crystalline phase forms at lower annealing temperatures and its volume fraction increases for a given annealing temperature.