Investigation of Hydrogen Influence on Structure of Amorphous Alloys Mg-Cu-Y and Mg-Ni-Y by New Method of Diffraction from Atomic Coordinate Spheres

Abstract

This work is based on using Ehrenfest’s formula in processing X-ray patterns from amorphous alloys. The radius of the first coordinate sphere ( CSR) and the content of the corresponding amorphous phase in an alloy were calculated from the position and intensity of the first peak in the pattern. A decrease in the peak intensity down to its complete disappearance under hydrogen charging was attributed to the appearance and growth of a certain amorphous phase, which may contain a set of various CSR and therefore reflection from the first coordinate sphere is not detectable. We named this phase as “very disordered”. For Ni-containing alloys, CSR did not change under hydrogen charging and was equal to the average CSR in the corresponding crystalline alloy with a body centered cubic (BCC) structure. For Cu-containing alloys, CSR changed from the value of the average CSR in the corresponding BCC crystalline alloy to that in the face-centered cubic (FCC) alloy. Under hydrogen charging the FCC phase disappeared completely, thus the amount of the very disordered phase reached 100 %. With further hydrogen charging two amorphous phases precipitated.