Structure Evolution of Au50Cu50 Alloy from Melt to the Disordered Solid Solution

This is the authors' abstract. We don't add key points for this paper.

The liquid local structure of Au50Cu50 solid solution was detected by high-temperature X-ray diffraction experiment and Reverse Monte Carlo (RMC) simulation. The clusters in the liquid Au50Cu50 alloy comprise the 12-coordinated polyhedron with Au center, which was the same as the clusters in the liquid pure Au. In the case of alloying, there was a high population of Au-Au bonds, and the local structure around Cu atoms was changed. In the case of solidification, the 12-coordinated clusters around Au atoms were preserved into the AuCu alloy, forming the disordered solid solution structure. The strong tendency for Cu-Cu bonds was weakened from 2.35 Å in the liquid to 2.81 Å in the solid solution, and the local structure around Cu atoms rearranges. It is shown that the liquid structure of the Au50Cu50 alloy plays a crucial role in the solid solution. Our findings elucidate that the disordered solid solution structure in AuCu alloy stems from the highly dominated 12-coordinated clusters associated with centered Au atom in the melt.