Silver Solid Solution Research Articles

Effect of copper interlayer to the microstructure and strength of alumina/304 stainless steel joint brazed with silver‐copper‐titanium filler

AbstractAlumina and 304 stainless steel were brazed with silver‐copper‐titanium filler+copper foil. The effect of adding copper foil to the filler on the microstructure of the alumina/304 joint was studied, and the reasons for the effect of adding copper foil with different thicknesses on the joint performance were also analyzed. The standard microstructure of alumina/304 joint with silver‐copper‐titanium+copper foil filler is alumina ceramic/copper compound with titanium and oxygen (3 : 3 : 1) (Cu3Ti3O) continuous layer+copper titanide (TiCu)/silver solid solution+copper solid solution/titanium compound with iron (1 : 2) (TiFe2)+iron‐chromium compound/304 stainless steel. The added copper foil inhibits the diffusion of titanium elements, thereby reducing the formation of the brittle copper compound with titanium and oxygen (3 : 3 : 1) (Cu3Ti3O) and alleviating the residual stress. In addition, after adding copper foil, the copper solid solution is distributed in blocks in the joint, which also improves the plastic deformation ability of the joint. Under the synergistic effect of these two effects after adding copper foil, the joint strength is improved. When the copper foil was 200 μm, the shear strength is 198.10 MPa.

Methods for Properties Analysis of Crystalline Materials Based on Solid Solutions of Silver and Thallium (I) Halides

The paper presents a set of methods developed for properties control of new optical crystals based on solid solutions of silver and thallium (I) halides. Crystals and optical products based on them are used for optical and optoelectronic systems in the middle and far infrared range. In this regard, to analyze the properties of new infrared materials, new analysis methods are required, which provide high accuracy and repeatability of the results. The authors have developed methods for studying the optical, mechanical and electrical properties of materials. The studies’ results carried out by these methods for various systems of silver and thallium (I) halides solid solutions are presented.

Plasmon induced photoluminescent emission from PED Ag–In alloy

Blending of two metals possessing localized surface plasmon resonance (LSPR) alters the optical behavior and aids in tuning the resonance frequency of oscillating electrons and controlling the emission. In this study, the silver solid solution with indium as solute has been synthesized using pulsed electrodeposition technique and is reported. The obtained particles retained the cubic structure on varying the precursor concentration of silver and indium in the electrolyte. The average crystallite size was estimated to be ~ 25 nm using Scherrer’s formula. Parameters such as applied current density, complexing agent and increase in silver concentration all favored the alignment of particles in the form of dendrites. This LSPR in the nanoparticles is evidenced through photoluminescent emission, and fluorescence decay time is estimated to be 2 ns. The LSPR leads to the photoluminescent emission from Ag–In particles while exciting them at 300 nm. The thermal stability of the samples has been studied using TGA analysis.

Spectral oil analyzer

We worked out a spectral oil analyzer, implemented the method of Fourier transform infrared spectroscopy, which allow simultaneous detecting characteristic peaks of water absorption and sulfur-containing substances in oil within the wavelength range from 0.2 to 25.0 µm. The usage of fiber-optic delivering channels makes it possible to produce online industrial probes for the control of chemical composition and concentration, what is demanded at oil producing platforms and oil refinery plants. As identifiers, we used the most intense absorption peaks of water (λ – 1.45 µm, 1.95 µm, 3.00 µm, 6.00 µm), oil (λ – 1.72 µm, 2.31 µm, 3.41 µm) and sulfur-containing heterocycles (λ – 8.00 µm). The spectral analyzer consists of a broadband-light source, a flow-cell, a fiber-optic assembly, narrow-band optical filters and photodetectors. For delivering a broadband optical signal, a fiber-optic assembly was developed. It comprises silica fibers and polycrystalline fibers derived from solid solutions of silver and thallium (I) halides. It was calculated the effective area and diameter of each fiber type in the assembly, taking into account attenuation coefficients and overall optical losses of the system. Using eight channels for the probe at the same time, we were able to measure the content of water and sulfur-containing substances in oil in concentrations from 0.1 to 100.0 wt %.

Solid solution softening and enhanced ductility in concentrated FCC silver solid solution alloys

The major adoptions of silver-based bonding wires and silver-sintering methods in the electronic packaging industry have incited the fundamental material properties research on the silver-based alloys. Recently, an abnormal phenomenon, namely, solid solution softening, was observed in stress vs. strain characterization of Ag-In solid solution. In this paper, the mechanical properties of additional concentrated silver solid solution phases with other solute elements, Al, Ga and Sn, have been experimentally determined, with their work hardening behaviors and the corresponding fractography further analyzed. Particularly, the concentrated Ag-Ga solid solution has been discovered to possess the best combination of mechanical properties, namely, lowest yield strength, highest ductility and highest strength, among the concentrated solid solutions of the current study. Microscopically, a clear evidence of narrow twin lamella feature has been observed in the Ag-Ga solid solution, and further identified as the deformation twinning, using high resolution transmission electron microscopy (HRTEM). To explain solid solution softening mechanism in low Peierls potential FCC metals, the authors have proposed a self-contained theoretical interpretation associated with fractional kink-pairs formation, and originally introduced the concept of the short range order (SRO) induced localized homologous temperature (LHT). Furthermore, the mechanism of twinning-induced plasticity (TWIP) can be referred as the underlying reason of the enhanced ductility in the Ag-Ga solid solution alloy. With such excellent mechanical properties, the Ag-Ga solid solution alloy is expected to have a great potential in the development of advanced joining materials for the various applications in electronics industries.

Structure modeling and manufacturing PCFs for the range of 2–25 μm

Photostable and flexible materials transparent at the wide spectral range are necessary for the development of optical fiber units. Solid solutions of silver and monadic thallium halides are the most suitable crystal media for this purpose. The goal of our research was the search of optimum structure for the fibers with a single mode operation and a rather large core diameter. We modelled fiber structures (solid-core, hollow-core, active-core PCF) with various ratio of inserts diameters and increments between the inserts, basing on two crystal systems: AgCl-AgBr and AgBr-TlI. Then we chose the single mode fiber structure and manufactured it by means of extrusion.

Evolution of Microstructure in Brazed Joints of Austenitic-Martensitic Stainless Steel with Pure Silver Obtained with Ag-27Cu-5Sn Brazing Filler Material

Brazing of an austenitic-martensitic stainless steel (AMSS) with pure silver was carried out at 1053 K, 1073 K, and 1093 K (780 °C, 800 °C, and 820 °C) with Ag-27Cu-5Sn (wt pct) as brazing filler material (BFM). Wettability of the liquid BFM over base AMSS surface was found to be poor. Application of nickel coating to the steel was observed to enhance the wettability and to enable the formation of a good bond between BFM and the steel. The mechanism responsible for enhanced metallurgical bonding of the BFM with AMSS in the presence of nickel coating was explained based on diffusional interactions and uphill diffusion of iron, chromium and nickel observed in the brazed microstructure. Good diffusion-assisted zone was observed to form on silver side at all three temperatures. Four phases were encountered within the joint including silver solid solution, copper solid solution, Cu3Sn intermetallic and Ni-Fe solid solution. The Cu3Sn intermetallic was present in small amounts in the joints brazed at 1053 K and 1073 K (780 °C and 800 °C). The joint formed at 1093 K (820 °C) exhibited the absence of Cu3Sn, fewer defects and larger diffusion-assisted zone. Hardness of base AMSS was found to reduce during brazing due to austenite reversion and post-brazing sub-zero treatment for 2.5 hours was found suitable to recover the hardness.

The growth and tensile deformation behavior of the silver solid solution phase with zinc

The growth of homogeneous silver solid solution phase with zinc are conducted at two different compositions. X-ray diffraction (XRD) and Scanning electron microscope/Energy dispersive X-ray spectroscopy (SEM/EDX) are carried out for phase identification and chemical composition verification. The mechanical properties of silver solid solution phase with zinc are evaluated by tensile test. The engineering and true stress vs. strain curves are presented and analyzed, with those of pure silver in comparison. According to the experimental results, silver solid solution phase with zinc at both compositions show tempered yield strength, high tensile strength and large uniform strain compared to those of pure silver. Fractography further confirmed the superior ductility of silver solid solution phase with zinc at both compositions. Our preliminary but encouraging results may pave the way for the silver based alloys to be applied in industries such as electronic packaging and structure engineering.

Investigating the light stability of solid-solution-based AgCl-AgBr and AgBr-TlI crystals

For the development of mid-infrared fiber-optical elements, one needs light-stable, flexible materials that are transparent within this spectral band. Solid solutions of silver and monadic thallium halides prove to be the most suitable crystalline media for these needs. We study the light stability variation of high-purity AgCl1?xBrx (0≤x≤1) and Ag1?xTlxBr1?xIx (0≤x≤0.05) crystals by measuring the optical transmission change as functions of the composition and UV exposure time. The former is executed in a broad spectral range from 6500?350 cm?1, within which we choose three wavelengths to trace the transmission change. For thallium-monoiodide-containing samples, an effect is observed that we assumed to be translucence.

On the Possibility of Formation and Properties of Copper–Silver Solid Solutions Under Severe Plastic Deformation

Mechanical alloying of Cu and Ag powders in concentrations Cu1–x–Agx (х at.% = 0.1, 0.2, …, 0.9) under high-pressure torsion is investigated. The alloys obtained have a structure of nanograined nonequilibrium FCC solid solutions with positive deviation from Vegard’s law. The hardness of the alloys is 4–6 times higher than of the initial components – copper and silver. The energy and power parameters of treatment of the solid solutions and stages of their formation are calculated from the shear stress measured in situ under high pressure. Thermally induced decomposition of the solid solutions begins from aging under normal conditions, is accelerated upon heating, and ends by short-term heating up to 500°C. It is accompanied by simultaneous development of the processes of gathering recrystallization.

The growth and stress vs. strain characterization of the silver solid solution phase with indium

Silver solid solution phase with indium has been discovered to have great mechanical properties and anti-tarnishing property, as shown in the results of our previous study. It is important to know the stress vs. strain curve before adopting this material in industrial applications. The growth of the homogeneous silver solid solution phase with indium is first described. The X-ray diffraction (XRD) patterns and scanning electron microscope/energy dispersive X-ray spectroscopy (SEM/EDX) results are reported to verify the chemical composition of silver solid solution phase with indium samples. Based on the results, one could reversely determine the indium element composition in (Ag)–xxIn solid solution by examining the lattice constant value using XRD for unknown compositions. The preparation of ASTM tensile test samples and tensile test experimental setting are explained in details. The intrinsic mechanical material properties of silver solid solution phase with indium, i.e., characteristic stress vs. strain curves, are presented and analyzed, with pure silver stress vs. strain curve in comparison. According to the experimental results, silver solid solution phase with indium exhibits low yield strength, high ultimate tensile strength, and large elongation value before fracture, compared to pure silver. In addition, fractography of the fracture surface of the tested sample has been studied to confirm the superior ductility of silver solid solution phase with indium. These superior mechanical properties may bring silver solid solution phase with indium new applications in various industries such as electronics and brazing.

Surface segregation of cadmium atoms at the interface of mechanically renewable Ag–Cd alloy electrode with surface-inactive electrolyte solution

The surface segregation of cadmium atoms at the interface of mechanically renewed electrodes of the Ag–Cd alloy (containing 1 at % Cd; the region of cadmium solid solutions in silver) with a surface-inactive electrolyte solution is studied in the potential range of ideal polarizability by means of impedance spectroscopy and cyclic voltammetry. It is shown that method of mechanic renewal makes it possible to obtain well reproducible data on the kinetics of electrode surface enrichment with atoms of cadmium which is the surface-active component of this alloy. As follows from the analysis of dependences of the electric double layer (EDL) capacitance on the potential (C vs. E curves) pertaining to different times after the electrode renewal, these dependences can be well described in terms of the model of capacitors connected in series (“the common dense layer”). Using this model, the dependences of the alloy surface coverage with cadmium atoms on the time of exposure of the freshly renewed electrode surface to the electrolyte solution are calculated. The mechanism of surface segregation of cadmium atoms is proposed. It allows the kinetics of relaxation processes that occur in the alloy surface layer to be consistently interpreted. The electrochemical data are supplemented and compared with the results of analysis of the surface composition and the data of the profile analysis over the depth of the same alloy at its interface with vacuum, performed by means of Auger electron spectroscopy.

Crystals based on solid solution of Ag1?xTlxBr1?xIx for the manufacturing of IR fibers

For the development of fiber optics for the range from 0.2 to 50.0 μm, one needs light-stable, nonhygroscopic, ductile crystals that would be transparent within this spectral range and have a lack of cleavage, and from which the flexible infrared (IR) fibers are extruded. The crystals based on solid solutions of silver and monadic thallium halides meet the conditions listed above. Consequently, by differential thermal and x ray analyses, we study the TlBr–TlI phase diagram using the crystals with optimal compositions, which we grow ourselves. We also manufacture light-stable nanocrystalline IR fibers that are transparent at longer wavelengths compared with AgCl–AgBr fibers.

Structure modeling and growing AgClхBr1−х, Ag1−xTlxBr1−xIx, and Ag1−xTlxClyIzBr1−y−z crystals for infrared fiber optics

In this paper we describe the aggregate technology of producing variable composition crystals, based on the solid solutions of silver and Tl+-doped halides for creating infrared photonic crystal fibers in the spectral range of 2–40μm by extruding, we also produce all the necessary equipment. We specified the minimum melting point position for the AgCl–AgBr phase diagram. We also investigated the fundamental physical properties of new crystals and fibers: transmission losses, transmission range, refraction index, hardness, and density.

Electrophysical properties of solid solutions of silver in PbTe

The thermopower coefficient α0 and the electrical conductivity σ of Pb1 − xAgxTe solid solutions, where x = (0–0.007), are measured at T = 300 K. The hole concentration p is calculated. All samples are of the p type. With increasing silver content, α0 decreases, while p and σ increase. For undoped crystals, α0 = 251.0 μV/K, p = 1.1 × 1018 cm−3, and σ = 165 Ω−1 cm−1. At the silver-solubility limit for x = 0.007, α0 = 193.8 μV/K, p = 2.3 × 1018 cm−3, and σ = 216 Ω−1 cm−1. The hole concentration in all samples is much lower than the concentration of introduced silver atoms. The hole gas in Pb1 − xAgxTe solid solutions is weakly degenerate in the entire silver-concentration range.

TEM Studies of Structure of Ag Base Nanocomposite Strengthened with Amorphous NiNbTiZr Alloy Intended for Electric Contact Materials

The nanocrystalline silver powder and the amorphous powders of composition Ni49,5Ti20,5Nb15Zr15 (numbers indicate at%) were prepared by ball milling in the planetary Fritsch mill for 40 hours. TEM studies confirmed almost complete amorphization of milled alloys powders allowed to detect a small fraction of a small intermetallic inclusions within the amorphous matrix. The erosion of composites during contact cycling was similar as in Ag-W composites known as a good contact materials. SEM and TEM studies have shown a low solubility of tungsten in silver after ball milling and no solubility of silver in tungsten. The grain size of silver crystals within powders drastically decreased after milling down to about 30 nm and only a small increase in the grain size up to 200 nm was observed after hot pressing. These results were confirmed using TEM studies of composites after hot pressing. TEM microstructures have shown very narrow transition layer at the amorphous/silver interface (between 10-30 nm thick) containing all elements from the amorphous powders plus silver due to short time of hot pressing. The amorphous part has shown growth of intermetallic phases there, however diffused ring from the amorphous part was still visible. The composites prepared from silver and tungsten have shown presence of coherent tungsten rich precipitates showing typical strain field contrast within fine grains near 100 nm formed most probably during hot pressing of silver solid solution formed during mechanical alloying. The structure of tungsten has shown less defects and consequently less grain refinement than silver particles. SEM studies of the compression tested samples of silver-amorphous composites have shown crack formation at the interfaces of both components most probably due to presence of a brittle transition phase containing all elements.

Direct method for determining the segregation in silver-copper solid solutions not prone to brittle breakage of grain boundaries

A new method is proposed for measuring the chemical composition of grain boundaries (GBs) in copper-based alloys not prone to embrittlement of boundaries. This method is based on embrittlement of copper GBs by bismuth penetrating from the gas phase of bismuth telluride (Bi2Te3). Chemical analysis of the GB surface is performed via Auger-electron spectroscopy. The GB composition is measured in a solid solution of silver (its volume concentration is 1.4 at %) and copper. The segregation annealing temperature is 570°C. The silver concentration across the broken surface of the GB (its thickness is five to ten atomic layers) is 4.7 at %. Therefore, the ratio between silver concentrations within the GB and the grain volume (the enrichment coefficient) is approximately 3.5.

Microstructural analysis in the vacuum brazing of copper to copper using a phosphor–copper brazing filler metal

Abstract Brazing of copper to copper using phosphor–copper brazing filler metal has been carried out using vacuum brazing technology. The wettability, melting performance, microstructure and phase constitution in the joint were studied by means of differential thermal analysis, metallography, energy dispersive X-ray detector and X-ray diffraction. Experimental results obtained showed that the structure in the joint consisted of hypoeutectic alloy. The primary phase is copper solid solution (α(Cu)) and silver solid solution (α(Ag)). The eutectic phase is copper solid solution (α(Cu)), silver solid solution (α(Ag)) and Cu3P. The optimum process parameters are: brazing temperature T = 820–850°C, vacuum level p = 10−3 Pa, holding time t = 5–10 min.

Crystal structure of solid solutions of silver in PbTe

The crystal lattice period of the Pb1 − x Agx Te solid solutions is studied as a function of the silver content. The a parameter is found to decrease sharply with an increase in the dopant concentration. The solubility of silver in PbTe corresponds to x = 0.007. A possible mechanism of silver dopant incorporation into the PbTe lattice is considered on the basis of the quantitative interpretation of the obtained data.

Radiation defects induced by helium implantation in gold-based alloys investigated by positron annihilation spectroscopy

The formation of gas bubbles in metallic materials may result in drastic degradation of in-service properties. In order to investigate this effect in high density and medium-low melting temperature (T M) alloys, positron annihilation spectroscopy measurements were performed on helium-implanted gold–silver solid solutions after isochronal annealing treatments. Three recovery stages are observed, attributed to the migration and elimination of defects not stabilized by helium atoms, helium bubble nucleation and bubble growth. Similarities with other metals are found for the recovery stages involving bubble nucleation and growth processes. Lifetime measurements indicate that He implantation leads to the formation of small and over-pressurized bubbles that generate internal stresses in the material. A comprehensive picture is drawn for possible mechanisms of helium bubble evolution. Two values of activation energy (0.26 and 0.53 eV) are determined below and above 0.7T M, respectively, from the variation of the helium bubble radius during the bubble growth stage. The migration and coalescence mechanism, which accounts for these very low activation energies, controls the helium bubble growth.