Influence of Ag substitution on the local structure and glass-forming ability of Al86Ni(8-x)Y6Agx (X=0,1,2) liquids

摘要

The local structure of Al86Ni(8-x)Y6Agx (X=0,1,2) molten and glassy alloy was investigated by abinitio molecular dynamics simulation. It transpired that the Al86Ni(8-x)Y6Agx alloy can be considered as a combination of Ni- and Y-centred Al clusters with Ag as glue atoms'. First and second Ag-Ag coordination was scarcely found in Al86Ni7Y6Ag1, but a medium-range order between 7.5 and 9 angstrom was observed. The enhanced glass-forming ability and thermal stability of the alloy compared with Al86Ni8Y6 can be attributed to the medium-range order of the Ag-Ag correlation. A second Ag-Ag coordination occurs in Al86Ni6Y6Ag2 and results in a decrease in glass-forming ability. The inter-atomic distances between all constituting elements increase during cooling. This increase is ascribed to a change in distribution of clusters around Al atoms towards clusters with higher coordination number around Al.