Crystallization kinetics and magnetostriction properties of amorphous Fe80-xCoxP14B6 metallic glasses

Abstract Formation mechanism and crystallization kinetics were studied in series of rapidly solidified metallic glasses Fe80-xCoxP14B6 with x = 23, 25, 28, 32, 35 and 40 at.%. As soft magnetic materials, they surpass characteristics of commercial Iron-Nickel Metglas® 2826 alloy: differential permeability of as quenched amorphous ribbons is of about 110000, the saturation induction μoMs = 1.45-1.5 T, coercive field as low as 4 A/m, Curie temperature above 700 K, and significantly higher thermal stability. Isochronal and isothermal differential scanning calorimetry was employed to record the latent heat developed during crystallization. For both regimes, X-ray diffraction revealed two immiscible bcc α-FeCo and bct (Fe,Co)3(P,B) phases that crystallize from completely miscible amorphous glass matrix. Theoretical description of observed kinetics of crystallization process was convincingly accomplished within Kolmogorov-Johnson-Mehl-Avrami model. Enhanced thermal stability of iron-rich Fe80-xCoxP14B6 glasses that crystalize at higher temperatures relies upon higher crystal/glass interfacial energy.