New In-Pd mechanical loss peak in ternary gold alloys

A point defect relaxation peak has been observed in a ternary 18-carat gold alloy with the composition Au62.5Pd32.5In5. It shows a Curie Weiss dependence on the temperature, as is commonly observed for a Zener peak. However, the peak is absent in the binary alloys AuPd and AuIn and therefore it is a new type of relaxation that is due to In-Pd pairs. The relaxation strength shows a linear dependence on the indium concentration. We have developed a model of elastic dipoles containing one palladium and one indium atom in a gold matrix. The model is based on the reorientation under stress of InPd dipoles in a gold matrix and takes into account the atom ordering. The model accounts for a linear dependence of the relaxation strength on the indium concentration in a dilute alloy and is also valid for more concentrated alloys. (C) 2013 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.