Characterization and Control of Clustering of Different Foreign Elements in Environmentally Friendly Copper-based Alloys

点击翻译按钮获取中文摘要

The optimum composition and processing for preparing environmentally friendly copper based alloys, which are not contain toxic beryllium but reveal high performance in the strength and conductivity, were investigated. In order to reduce impurity elements, copper-titanium and copper-nickel-silicon alloys showing aging characteristics were prepared from high purity materials. The hardness and electrical resistivity of different alloys were systematically measured during isochronal annealing. The results showed that precipitation took place in the temperature range between 600K and 750K in these alloys.Small angle X-ray scattering (SAXS) and other techniques were used for characterizing clustering of alloying elements in the alloys, which were annealed at 720K isothermally. The results showed that the hardness increased and the resistivity decreased (that is an increase of the conductivity), when the effective radius estimated in the distance distribution function was from 2 nm to 3 nm. However, the samples were aged for more long time, the hardness of the alloys decreased again, indicating overaging. Thus, there is the optimum distribution of clustering of alloying elements for obtaining the high properties.In addition, anomalous small angle X-ray scattering (ASAXS) was utilized for characterizing the clustering of nickel in Cu-Ni-Si alloys. The results revealed that nickel were precipitated in a size of ca. 2-3 nm. X-ray absorption spectroscopy was also utilized for analyzing the local structure of nickel in Cu-Ni-Si alloys. The EXAFS and XANES spectra showed that the local structure and electric state of nickel precipitated were different from that in those fcc alloy matrix