Papers by Keyword: Cu-Ag

Abstract: In this paper, the diffusion isotope effect and diffusion mechanism are investigated by means of molecular dynamics simulations in two liquid alloys, Ni-Ag and Ni-Cu. The values for the diffusion isotope effect parameter allow for the estimate of the number of atoms which are moving cooperatively in a basic diffusion event as experienced by a given atomic species. It is shown that the composition dependence of N_D is typically very small. However, the temperature dependence of this parameter is much more pronounced. In addition, it is shown that, on average, in these alloys and temperatures considered, N_D is limited to the range: 5<N_D<17. This is consistent with results of molecular dynamics simulations on the average coordination number calculations. This would suggest that, together with a given atom, depending on temperature, the neighbouring atoms are all involved in the basic diffusion event.

Abstract: In this study Cu-Ag or Cu-Cr layer was sandwiched by Ti and Fe plates and the three layers of Ti/Cu-8Ag/S20C were clad by High Pressure Torsioning(HPT). The effect of post-HPT heat treatment on the interfacial reaction products and the mechanical performance in Ti/Cu-Ag/S20C and Ti/Cu-Cr/S20C clad material were studied. Cu₄Ti₃ and Cu₄Ti Intremetallic compound layers were observed at the Ti/Cu-Ag and Ti/Cu-Cr interfaces in the clad heat-treated at 500°C where as no intermetallic compounds were observed at the Cu-Ag/S20C and Cu-Cr/S20C interfaces. The strength of as-HPTed Ti/Cu-8Ag/S20C is much higher than that of Ti/Cu-1Cr/S20C. The strengthening mechanism of Cu-Ag deformed severely is the interface and strain hardening in which dislocations are deposited at the Cu/Ag interfaces and can contribute to the strengthening of the clad composite just after HPT processing, rendering the high strength just after processing. In both clad composites, the strength and ductility increased after heat treatment at 350°C, which are likely caused by the enhanced bonding at the interfaces.

Abstract: In order to build the phase diagram of Cu-Ag nanoalloys, we study a 405-atom nanoparticle by means of Monte Carlo simulations with relaxations using N-body interatomic potentials. We focus on a range of nominal concentrations for which the cluster core remains Cu-pure and the (001) facets of the outer shell exhibit two original phenomena. Within the (N,m_Ag-m_Cu,P,T) ensemble, a structural and chemical bistability is observed, which affects all the (001) facets together. For a nanoparticle assembly, this will result in a bimodal distribution of clusters, some of them having their (001) facets Cu-rich with the usual square shape, the other ones having their (001) facets Ag-rich with a diamond shape. This bistability is replaced in the (N_Ag,N_Cu,P,T) ensemble by a continuous evolution of both the structure and the concentration of the (001) facets from Cu-rich square-shaped to Ag-rich diamond-shaped facets as the number of Ag atoms increases. For a nanoparticle assembly, this will result in an unimodal distribution of the cluster population concerning the properties of the (001) facets. This comparison between pseudo grand canonical and isothermal-isobaric results shows that the distribution of a population of bimetallic nanoparticles depends strongly on the conditions under it is elaborated.

Abstract: In this paper, the process of Cu-Ag contact wire with adding rare-earth elements was presented. The additive process of the rare-earth elements and the function of the rare earth were chiefly analyzed. Adding the rare-earth elements into melt alloy, the oxide and sulfur can be removed from the liquid, so we can get the purified alloy. At the same time, adding rare-earth can reduce the external crack flaws which produced during the casting and makes the grain refined, as the result, the properties of the Cu-Ag alloy contact wire can be greatly improved and meliorated. Such as the conductivity, the specific elongation, tensile strength and so on, are improved.

Abstract: An overview of the microstructure evolution, mechanical properties, electrical conductivity and microalloying is presented and some further research fields are suggested for Cu-Ag microcomposites. The nanostructures of filamentary morphology in these microcomposites can be obtained by heavy deformation. Both the mechanical and electrical properties depend upon the material composition, strain degree, intermediate heat treatments and final annealing processes. These factors strongly affect the phase proportion, microstructure morphology, precipitate volume, hardening level and filamentary distribution. Optimum technology of materials preparation makes the microcomposites possess high strength and conductivity. Some third constituents added to the alloys improve the strength but generally decrease the conductivity. It is considered that relative mechanisms and processes should be further investigated for the development and application of the microcomposites.