Papers by Keyword: Silver Alloy

Abstract: The first-principles calculations were performed to research effects of elements X (Au, Be, Pd, Y, Ca, Cu, In and Zn) on mechanical and electronic properties of Ag with the density function theory (DFT). A supercell consisting of 107 atoms of Ag and one solute atom X was used. It was found that the bulk modulus of Ag dilute solutions were affected by the bulk modulus of pure alloying elements as well as their volume. The shear modulus G trend to decrease with increase of volume of Ag caused by alloying addition, but Ag-X covalent bond had positive correlation with shear modulus G. All of Ag₁₀₇X alloys were ductility since theirs B/G ratio, Poisson's ratios ν were larger than 1.75 and 0.33, respectively. Comparing to other calculated Ag₁₀₇X alloys, Ag₁₀₇Be and Ag₁₀₇Cu had the larger Vickers hardness, the value of which were 3.96GPa, 3.86GPa, respectively. There were not only metallic bonds (Ag-Ag) but also covalent bonds (Ag-X) in Ag₁₀₇X alloys. The strong covalent bonds between Y, Zn, Ca and Ag were mainly caused by orbital hybridization between Y-5p orbital, Zn-3d orbital, Ca-3d orbitals and Ag-4d, 5s and 5p orbitals.

Abstract: It is well known that the rare-earth elements (RE) have exhibited favorable microalloying effects on the microstructure and properties of silver alloys. In the present investigation, a detailed description of the microstructure of a Silver-4wt.%Copper-0.3wt.% Nickle as–cast alloy containing 0.2wt. % of a cerium element was presented. Particles types occurring and their distribution in the microstructure, as well as the distribution of elements in the phases were described. The result show that the second phase in Ag-Cu-Ni Alloy is Cu-Ni-rich solution phase, some of which forms interdendritic segregation in Ag matrix as eutectic colonies. Trace additions of cerium to the alloy decrease eutectic proportion and size of the Cu-Ni-rich phase, result in finer and more uniform secondary phases distributed in the α-Ag matrix. Besides Cu-Ni-rich phase, the Ni-Cu-Ce-rich and Ag-Cu-Ce-rich phases were found in the alloy. The Ni-Cu-Ce-rich should be the (NiCu)₅Ce, which is distributed as dispersive particle in the Ag matrix, and Ag-Cu-Ce-rich phases should be (AgCu)₄Ce, which is distributed as fibrous particle of eutectic colonies. Some of (AgCu)₄Ce phases are located at the interface between α-Ag matrix and Cu-Ni-rich phases, which indicate that Ce could be segregated at the frontier of Cu-Ni-rich phases during the growth, causing Cu-Ni-rich phase refinement.

Abstract: The aim of this paper is to study the microstructures and hardness of silver alloys after internal oxidation process. The Ag-5Sn and Ag-5Cu alloys were prepared by melting and cast into ingots and then they were internal oxidized at the temperature range from 550 to 750°C, for 24 hours under oxidizing atmosphere by feeding oxygen gas with the pressure of 1 kg/cm², gas flow rate 5 l/min and cooled in the furnace. The microstructures, Vickers microhardness and phase compositions were investigated. The results showed that the microstructures of the based metal revealed dendritic structure and they were transformed to equiaxed grains after internal oxidation. The internally oxidized layer of Ag-5Sn alloy is SnO₂ with the hardness about 106-133 HV. The internally oxidized layer of Ag-5Cu alloy is CuO with the hardness about 65-73 HV.

Abstract: The variety of industrial use of brazing solders is associated in one way with plastic properties (more plastic materials are producing in the form of wires, sheets, bands, metal leafs, meshes etc, low plastic materials in the form: pig sows, bars, powders) and in another way with the kind of joining and use soldering or brazing method. Hard solders, which include analyzed solder BAg7, have a very wide range of melting points (from 400 to 2000°C) and are applied in those cases when very high values of strength are required for soldered joint. The research was carried out for the silver-based solder designated as Bag7 according to American Standard ANSI/AWSA 5.8-92. This solder has a typical application for the brazing process of food handling equipment requiring low melting values and for brazing aluminium alloys. In the literature, except for chemical composition and temperature of brazing, we cannot find the details concerned with the method of plastic working of BAg7. In the reported research work the metallographic analysis of rolling process was performed and optimal parameters of rolling process for the considered solder were determined.