Effect of Al on Local Structures of Zr–Ni and Zr–Cu Metallic Glasses

Abstract

In order to investigate the role of Al on the thermal stability of supercooled liquid state, the local structures of Zr70M30 and Zr70M20Al10 (M=Ni, Cu) metallic glasses have been studied by the X-ray diffraction and EXAFS measurements. It is found that the different effect of Al substitution on the local structures around Cu and Ni elements is exhibited. No characteristic change is observed in the local structure in the Zr–Cu metallic glass by Al substitution, whereas a drastic change in the environment around Ni atom can be confirmed in the Zr–Ni metallic glass. That is, the coordination number of Zr around Ni decreases significantly by substitution of Al in the Zr–Ni metallic glass. This would be caused by the preferential correlation between Al and Zr. This result suggests that Al plays a dominant role on the formation of novel local structure with a decomposition of the tetragonal Zr2Ni-like local environment in the Zr–Ni binary alloy. We conclude that the novel local structure contributes to the stability of the supercooled liquid state in the Zr–Al–Ni metallic glass.