Comminution of Fe 80B 20 metallic glass

Abstract

Fe 80B 20 (Metglas 2605) in an unrelaxed state was comminuted by vibratory milling, cryomilling and jet milling. Surface area, particle size and morphology were examined as a function of comminution parameters. After comminuting the as-received glassy ribbon for 20 min, a surface area of 2.48 m 2/g was obtained by cryomilling compared with 0.97 m 2/g by vibratory milling. A maximum surface area of 3.46 m 2/g was obtained by cryomilling for 150 min. The maximum surface obtained by vibratory milling was 1.01 m 2/g after 60 min. Little deformation was observed by SEM or optical microscopy for products produced by cryomilling or vibratory milling. Jet milling was not effective in increasing the surface area or reducing particle size and appears to have no effect on the morphology of the feed material. No structural changes were observed either by XRD or by TEM diffraction for any comminution product. Also, no change in the crystallization temperature or enthalpy of crystallization, as measured by differential scanning calorimetry (DSC), of the comminuted products, as compared with the as-quenched glass, was observed for any of the comminution methods utilized. Thus, both the vibratory milling and cryomilling of Fe 80B 20 increased the surface area with no effect on the glass structure or stability. The effectiveness of the cryomilling appears to come from comminution below the ductile to brittle transition temperature.