A Study of Bulk Amorphous Alloys Formed by Solid-State Reaction in Elemental Composites

Abstract

Bulk amorphous Zr- and Er- based alloys have been synthesized by solid-state reaction in elemental composites prepared by mechanical deformation. For the Er- based composites, complete amorphization was achieved by near- isothermal rolling near room temperature. The driving force for the reaction was found to be a large negative enthalpy of mixing between the constituent elements. Strain and interfacial energies have been estimated and found to modify the driving force only slightly. X-ray diffraction and differential scanning calorimetry have been used to characterize the structure and crystallization behavior of the alloys obtained. Comparison to corresponding amorphous alloys prepared by liquid quenching and sputtering gave good agreement. The diffusion of Au in amorphous Au-Y and Au-La thin films produced by co-evaporation has been studied by means of X-ray diffraction and Rutherford backscattering. An estimated diffusion coefficient agrees with those obtained by other authors for diffusion of Au in several amorphous alloys. The results confirm that there can be bulk self-diffusion in an amorphous alloy without crystallization. Thus, one does not need to assume short-circuit diffusion during the growth of an amorphous phase by solid-state reaction.