The Effect of Thermal Relaxation on the Short-Range Order in Melt-Quenched Zr-Co and Zr-Ni Alloys

Abstract

The Zr₈₀3d₂₀ (3d = Co, Ni) metallic glasses and the partially crystalline Zr₇₆Ni₂₄ metallic glass were prepared by melt spinning. The effect of thermal relaxation on the short-range order in melt-quenched the Zr₈₀3d₂₀ (3d = Co, Ni) metallic glasses and the partially crystalline Zr₇₆Ni₂₄ metallic glass during heat treatment at different heating rates has been investigated by means of the differential scanning calorimeter (DSC) and the X-ray powder diffraction (XRD) measurements in temperature interval from 300 K to 823 K. According to the XRD results, for the partially crystalline Zr₇₆Ni₂₄ metallic glass, melt-quenched alloy consists of a fraction of metastable Zr₃Ni crystalline phase and an amorphous phase. The estimated volume of the fraction of the Zr₃Ni crystalline phase was ≈ 9.6%. The crystalline peaks of the Zr₃Ni crystalline phase were fitted to the orthorhombic structure type. The Zr₃Ni crystallite size was estimated using the Sherrer formula to be from 15 nm to 30 nm. Crystallization studies have shown that the existence of the orthorhombic Zr₃Ni crystalline phase does not change the thermal stability of the amorphous phase against further crystallization and remains unchanged during the annealing of the samples up to 823 K. On the basis of the DSC and XRD obtained data it was possible to identify the phases which occur in the heat treatment of the Zr₈₀3d₂₀ (3d = Co, Ni) metallic glasses and of the partially crystalline Zr₇₆Ni₂₄ metallic glass up to 823 K. The average crystallite sizes of these nanocrystalline phases were from 10 nm to 24 nm.