X-ray diffraction experiments on the solidification process of Cu80Ag20 alloy

The atomic structure in the solidification process (from 1200 to 780 °C, Tl and Tm is about 950 and 780 °C respectively) of Cu80Ag20 binary alloy has been investigated by X-ray diffraction technique. The correlation radius rc and the atom numbers Nc of the cluster show a little increasing with the temperature decreasing bellow 1100 °C. The correlation length D shows almost a linear change with the temperature. All these results indicate a quite stable structure change in the solidification process of Cu80Ag20 alloy. This is quite different from our former study on In30Sn70 alloy, which shows an abrupt increasing both for rc, Nc and D around its liquidus. As liquid clusters play a crucial role in the forming of crystalline nucleus and they may serve as the embryo of the nucleus, which means two different nucleus forming mechanism. We consider the Cu80Ag20 like as stabilization mode and the In30Sn70 like as saltation mode. In addition, the moving of atoms in the solidification process is also discussed by the Gaussian peaks decomposing of the RDF(r).