Age-hardening associated with precipitation reaction and spinodal decomposition in a commercial dental low-carat Au-Ag-Cu-Pd alloy.

Two distinguishable hardening mechanisms, depending on the temperature, were found by isothermal ageing in a commercial dental low-carat Au-Ag-Cu-Pd alloy. Age-hardening was attributed to the precipitation of the metastable AuCu I' and equilibrium AuCu I ordered phases and spinodal decomposition depending on the ageing temperature. It was clearly visible, by using the direct-ageing method, that the XRD peaks of the parent phases showed a shift during transformation.