| It is known that the industrial application of demixing alloy is limited because of its solid microstructure is usually separates between each other by gravity. With the development of science and special technologies, particular structure of this material that is different with the one made under regular temperature can be prepared, which have expanded its scope of application. By studying the melting processing and microstructure of demixing alloy, people will find the way to produce the alloy with better performance. Actually, experiments are limited on observing alloy melt under high temperature directly, which, nevertheless, can be realized by computer simulation. Basing on the theory of embedded atom method (EAM) proposed by Zhou, this thesis has finished the representations of cu-co alloy with the help of Molecular dynamics simulation (MD). Furthermore, by making Cu-Co alloy with rapid solidification, it has analyzed the influences to organization of solidification brought by cooling rate. It has studied the characterizations of Cu-Co alloy through the combination of simulation as well as experimentation. At last, by increasing the glass forming ability through adding Zr in order to get demixing glassy alloy, it has got the results which can be listed as follows.It has finished the research of the cu-co alloys of different composition, including the calculation of the pair correlation functions (PCFs), Bhatia-Thornton(B-T) structure factor, and enthalpy of mixing. The calculation of pair correlation functions indicates the peak of same atoms. And all different compositions of cu-co have positive enthalpy of mixing, Scc(q) will increase sharply. What’s more, indirect diffusion coefficient is also shows centrally symmetric parabolic trend. The results above show the apparently demixing trend.It has finished the system simulation of Cu50-Co50 structure properties and dynamics features. The results, which are represented by the coordination numbers (CNs) and some other structure parameters, reflected that homogeneous atom pairs are existed in Cu50Co50, and that means demixing tendency is exist. According to atomic trajectory figure, it can be found that the cluster degree of each kind of atoms tend to augment as the temperature reducing, after which the cu-rich region and co-rich region can be distinguished easily. The calculation of Cu50CO50 mean square displacement (MSD) turns out that Cu-Co has low-glass-forming ability. By studying the microstructure of Cu50Co50 alloy under different cooling rate, it can be found that the distribution of composition is uniform with no apparent drops under faster cooling rate(by single roller quenching method). With the reduce of cooling rate(mold sputtering), little drops appeared on Cu rich basement because of enough to gather, and these drops grown into dendritic structure gradually with the cooling rate reduce farther.By analyzing the solidification process of the alloy strips with different composition and different cooling rate(with single roller quenching method), it turns out that secondary phases precipitation was restrained because of the solubility of heterogeneous atom in solid is different, which is because of the liquid-liquid phase separation periods are different due to the different composition. At last, by adding Zr in Cu-Co alloy, we can come to the conclusion that Co can restrain the Cu-Co-Zr glass forming ability by analyzing the test results of differential scanning calorimeter (DSC) of different Cu-Co-Zr glass strips. But no demixing glass formed because of Cu and Co were dissolved in Zr, which can restrain the demixing function between Cu and Co. |
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