Effects of Nb minor addition on atomic structure and glass forming ability of Zr55Cu30Ni5Al10 bulk metallic glass

This work aims to show Nb micro-alloying role on structural changes and glass forming ability (GFA) of Zr55Cu30Ni5Al10 bulk metallic glass. Pair distribution function (PDF) analysis indicates that the minor Nb addition forms Nb-centered clusters at the short range scale. It is also revealed that the atomic rearrangement happens in the medium range order and loosely-packed structure changes to a densely-packed one. This means that the clusters tend to form interpenetrating structures at the medium range scale. This event is related to the strong interaction of Zr and Nb elements in the material. Moreover, the thermal analyses demonstrate that the sample with Nb has a greater supercooled liquid region and better GFA. The relaxation enthalpy decreases in the Nb-content sample which is due to the formation of denser clusters at short range scale and a structural shrinkage at the medium range order of the bulk metallic glass.