Ag-Zn Alloys Research Articles

Characterization and interpretation on the new crystallographic features of a twin-related ε′-Mg54Ag17 precipitates in an Mg–Sn–Mn–Ag–Zn alloy

Twin related ε′-Mg54Ag17 precipitates adopting different orientation relationships (ORs) with the matrix were observed in an Mg–Sn–Mn–Ag–Zn alloy. One of the ORs together with the associated precipitates morphology are common to those observed from single-crystal particles. The other OR is new, as expressed by (0 0 −1)ε′ || (0 0 0 1)α, [2 0 0]ε′ deviating about 6.9° from [1 0 −1 0]α. The particle with the new OR is characterized with three (pairs of) side facets in irrational orientations with respect to the matrix. These orientations are explained based on a Δg analysis, good matching site distribution and a secondary constrained coincidence site lattice (II-CCSL) calculation.

Formation and optical absorption property of nanometer metallic colloids in Zn and Ag dually implanted silica: Synthesis of the modified Ag nanoparticles

Nanometer metallic colloids in silica glasses were fabricated by dual implantation of Zn and Ag ions in different implantation sequences. In the case of Zn ions followed by Ag ions, Ag nanoparticles (NPs) were formed, which had small size, narrow size distribution and high volume fraction, as well as modified dielectric environment. As a result, the Zn first and then Ag implanted samples presented an intense absorption peak around 435 nm, which was much stronger than that at about 406 nm detected in the Ag singly implanted specimen at the same Ag ion fluence. Variation of Zn ion fluence only gave rise to slight change of the absorption signal. In contrast, a dual implantation of Ag first and then Zn ions resulted in formation of Ag, Zn, and Ag–Zn alloy NPs, consequently inducing a weak and broad absorption band lying between those related to monometallic Ag and Zn NPs. The underlying mechanisms for the above findings were discussed. Especially, an enhanced deposition process of Ag implants caused by the prior Zn implantation was proposed.

Theoretical investigation on structural and thermodynamic properties of the intermetallic compound in Mg–Zn–Ag alloy under high pressure and high temperature

A theoretical investigation on structural and thermodynamic properties of intermetallic compounds MgAg, Mg4Zn8 and Mg4Zn4Ag8 in Mg–Zn–Ag alloy at high pressure and high temperature are performed by employing the first-principles method based on the density functional theory. The calculated values are generally speaking in good agreement with experiments and similar theoretical calculations. Theoretical calculated results indicate that intermetallic compounds MgAg, Mg4Zn8 and Mg4Zn4Ag8 are elastically stable at zero temperature and pressure. Mg4Zn8 and Mg4Zn4Ag8 are the ductility phases, and MgAg is the brittleness phase. In addition, the calculations of elastic constants and Young modulus show that the plasticity of Mg4Zn4Ag8 is the best in the three intermetallic compounds, and MgAg is the worst. Based on the quasi-harmonic Debye model, the vibrational internal energy, vibrational Helmholtz free energy, vibrational entropy, heat capacity, thermal expansion coefficient, Grüneisen parameter and Debye temperature of the intermetallic compounds in Mg–Zn–Ag alloy at high pressure and high temperature are discussed.

Formation and microstructure of nanoporous silver by dealloying rapidly solidified Zn–Ag alloys

The electrochemical dealloying of rapidly solidified (RS) Zn–Ag alloys in a 5wt.% HCl solution and 1M NaCl solution has been investigated using electrochemical measurements and microstructural analysis. The results show that the electrochemical properties of the RS Zn–Ag alloys are associated not only with the alloy composition, but with the phase constitution of the alloys. Nanoporous silver (NPS) ribbons can be fabricated through potentiostatically dealloying the RS Zn–Ag alloys in both solutions. Moreover, a minor difference in the applied potential has a significant influence on the dealloying process and formation of NPS. The critical potential and polarization behavior of the Zn–Ag alloys have also been discussed, as well as surface diffusion of Ag adatoms.

Behaviour of ultrasonic velocities and elastic constants in Ag-Zn alloys

The ultrasonic properties of the hexagonal closed packed structured Ag-Zn alloys have been studied at room temperature for their characterization. For the investigations of ultrasonic properties, I have also computed second order elastic constants using Lennard–Jones Potential. The velocities V1 and V2 have minima and maxima respectively with 45 0 with unique axis of the crystal, while V3 increases with the angle from unique axis. The inconsistent behaviour of angle dependent velocities is associated to the action of second order elastic constants. Debye average sound velocities of these alloys are increasing with the angle and has maximum at 550 with unique axis at room temperature. Hence when a sound wave travels at 55 0 with unique axis of these alloys, then the average sound velocity is found to be maximum. Ag0.2Zn0.8 alloy is more suitable for industrial and other uses, as it having highest elastic constants and lowest attenuation in comparison to other Ag-Zn samples. The mechanical and ultrasonic properties of these alloys will not be better than pure Ag and Zn due to their low SOEC and high ultrasonic attenuation. Achieved results have been discussed and compared with available experimental and theoretical results.

Assessment of the diffusional mobilities in the face-centred cubic Ag–Zn alloys

Based on the available thermodynamic information and diffusion coefficient data of the Ag–Zn binary system, the atomic mobilities of Ag and Zn in face-centred cubic (fcc) Ag–Zn alloys have been assessed as a function of temperature and composition in terms of the CALPHAD method using the DICTRA software package. Optimized mobility parameters are presented. Comparisons between the calculated and measured diffusion coefficients show that most of the experimental information can be satisfactorily reproduced in the present work. The obtained mobility parameters can also predict reasonable concentration profiles of the diffusion zone in the binary Ag–Zn diffusion couples.

Effect of solidification parameters on the microstructure of Sn-3.7Ag-0.9Zn solder

In this work, Sn–Ag–Zn alloy of eutectic composition (Sn-3.7wt.%Ag-0.9wt.%Zn) was directionally solidified upward at a constant temperature gradient ( G = 4.33 K/mm) in a wide range of growth rates ( V = 3.38–220.12 μm/s) and a constant growth rate ( V = 11.52 μm/s) with different temperature gradients ( G = 4.33–12.41 K/mm) using a Bridgman type directional solidification furnace. The microstructure was observed to be a rod Ag 3Sn structure in the matrix of β–Sn from the directionally solidified Sn-3.7wt.%Ag-0.9wt.%Zn samples. The values of eutectic spacing ( λ) were measured from transverse section of samples. The dependency of eutectic spacing on the growth rate ( V) and temperature gradient ( G) were determined with linear regression analysis. The dependency of λ on the values of V and G were found to be λ = 10.42 V − 0.53 and λ = 0.27 G − 0.48 , respectively. The values of bulk growth were also determined to be λ 2 V = 86.39 μm 3/s by using the measured values of λ and V. The results obtained in present work were compared with the previous similar experimental results obtained for binary and ternary alloys.

Fabrication of porous Ag by dealloying of Ag–Zn alloys in H2SO4 solution

In the present work, the fabrication of porous silver through the dealloying of Ag24.3Zn75.7, Ag33.4Zn66.6, and Ag57.6Zn42.4 alloys in dilute H2SO4 solution is reported. Different length scales and distribution could be achieved through varying the alloy’s composition and concentration of H2SO4 solution. Multi-porosity distribution of Ag33.4Zn66.6 alloy also indicates the possibility to tailor the microfilter’s structure by using common microstructure controlling method in materials science.

Influence of ball‐milling on the oxidation behavior of Ag–Zn alloy powders

AbstractThe gas atomized Ag–15.2 at% Zn alloy powders were treated using ball‐milling. The effect of ball‐milling on surface morphology, microstructure, and oxidation behavior of the alloy powders was investigated. The results showed that ball‐milling treatment enhanced the oxidation rate of Ag–Zn alloy powders due to the increase of dislocation density and the decrease of the diffusion distance of oxygen during internal oxidation. The fully oxidized time of Ag–Zn alloy powders decreases with the ball‐milling time. In addition, the ball‐milling treatment not only changes the oxidation mechanism but also improves microstructure and properties of the Ag–ZnO materials fabricated by internal oxidation.

Effects of thermal treatment on microstructure and microhardness of rapidly solidified Sn–Ag–Zn eutectic solder

The structural stability of rapidly solidified (about 104 K/s) Sn–3.7Ag–0.9Zn eutectic solder was explored by high-temperature annealing. For the as-cast solders, the applied fast cooling rate had a significant influence on the microstructure of the solders. The faster the applied cooling rates, the smaller the β-Sn dendrites. After annealing at 473 K for 20 and 50 h, β-Sn dendrites congregated together into bulk ones for minimizing the interfacial energy, and Ag3Sn intermetallic compounds (IMCs) as well as ternary Ag–Zn–Sn IMCs segregated on the grain boundary of the β-Sn dendrites. It seems that the coarsening of the β-Sn dendrites in the rapidly solidified specimen brought a significant softening during annealing of the explored Sn–Ag–Zn alloy. Finally, the β-Sn dendrites vanished gradually with increase of the annealing period, which leads to a kind of softening.

Effects of aging on structural evolution of the rapidly solidified Sn–Ag–Zn eutectic solder

The structural stability of the rapidly solidified eutectic Sn-3.7 wt.%Ag-0.9 wt.%Zn solder was explored by aging at room temperature (298 K). After aging for 2 weeks, the microstructure varied a lot in the morphology of intermetallic compounds (IMCs) in the investigated Sn–Ag–Zn solder. Dot-like Ag 3 Sn IMCs in the rapidly solidified solder congregated and formed bulk ones in order to minimize the system energy, which is contrary to a stable microstructure in the slowly cooled specimen. It seems that the coarsening of the IMCs in the microstructure of the rapidly solidified specimen brought a significant softening during aging of the explored Sn–Ag–Zn alloy. Furthermore, with the addition of zinc, the solder system becomes harder than the eutectic Sn–Ag system and the Ag–Zn phase dispersed in the eutectic Sn–Ag–Zn solder could strengthen the system as a reinforcing secondary phase.

Phase equilibria of the Sn–Zn–Ag system and interfacial reactions in Sn–Zn/Ag couples

The phase equilibria of the Sn–Zn–Ag ternary system and interfacial reactions between Sn–Zn alloys and Ag were experimentally investigated at a specific temperature. Ternary Sn–Zn–Ag alloys were prepared and annealed at 260 °C to determine the Sn–Zn–Ag ternary system isothermal section. The experimental results reveal that no ternary compound was formed, and noticeable Zn solubility was observed in the Ag 4Sn phase. Three Ag–Zn intermetallic compounds, AgZn 3, Ag 5Zn 8 and AgZn, were formed on the Sn–9Zn/Ag interface at 260 °C. As the Zn content was gradually decreased in the Sn–Zn alloy, the intermetallic compound microstructures changed. If the Zn content was less than 2 wt% in the Sn–Zn alloy, Ag–Sn IMCs were then formed on the Ag surface and massive spalling of Ag–Zn IMC layers occurred from the Ag–Sn IMC surface.

Microstructure and corrosion behavior of Mg–Zn–Ag alloys

The majority of Mg components currently in use in the automotive and electronic industries are produced by conventional casting processes. However, there is a strong need to develop new high strength wrought alloys for wide-spread application of Mg alloys in near future. In the present study, new Mg–Zn–Ag alloys were developed and characterized. In order to evaluate the effects of Ag addition on the mechanical properties of the extruded Mg–Zn alloys, the age hardening response and mechanical properties were examined with different amounts of alloying element. The microstructures of the specimens were examined with optical microscopy and transmission electron microscopy. The grain sizes of the alloys in as-extruded condition were markedly reduced with the addition of Ag. The hardness was found to increase more rapidly in the alloys with double aging treatment compared to those with single aging treatment. The peak hardness was also found to be higher in the alloys with double aging treatment. In all heat treatment conditions, the hardnesses of the Mg–Zn–Ag alloys were found to be higher than those of the Mg–Zn alloys. Moreover, the addition of Ag to the Mg–Zn alloys increased the corrosion rate measured by immersion test.

Solid-Phase Diffusion at a Galvanostatic Anodic Dissolution of Zn-Ag and Cu-Au Alloy

The ionization stages of copper and zinc at a galvanostatic anodic dissolution of Zn-Ag and Cu-Au alloys in acidic chloride environment are found to be electrochemically nonequilibrium. Selective dissolution of the alloys is limited by the transient mutual diffusion of components within a nonequilibrium surface layer. In terms of diverse theoretical models of the solid-phase mass transfer, the effects of the electrode surface microroughness, the apparent shift of the alloy-electrolyte interface boundary, and the relaxation of the vacancy subsystem are analyzed. The parameters of the diffusion layer, namely, its thickness, diffusivities, mutual diffusivities, and the over-equilibrium vacancy concentration were found. The latter characteristic is determined by the dissolution rate of the electrochemically negative alloy component, and, hence, the diffusivities and the Sand parameter of the diffusion kinetics substantially increase with an increase in the current density.

Cellular growth of Zn-rich Zn–Ag alloys processed by rapid solidification

Abstract Rapid solidification experiments were carried out on single-phase Zn-rich Zn–Ag alloys processed by laser remelting and melt-spinning techniques. For comparison, Bridgman solidification was performed as well. Three solidification morphologies were mainly identified with increasing growth velocity from 0.02 to 300 mm/s: regular cells or dendrites of η, plate-like cells of η, and plane front of η. Plate-like and regular cells were found to be velocity-dependent and occurred in high-velocity and low-velocity domains, respectively. The development of solidification interface morphologies in the present Zn–Ag alloys was proposed accordingly over a wide range of growth velocities from the limit of constitutional supercooling to the limit of absolute stability. Four microstructure transitions were identified: low-velocity plane front of η→low-velocity plate-like cells of η→regular cells or dendrites of η→high-velocity plate-like cells of η→high-velocity plane front of η. It implies that a plate-like cell would be the favorable morphology at growth conditions approaching a stable planar solid/liquid interface in comparison with the regular one.

Thermodynamic behaviour of zinc in Fe-C and CaO-FeO-CaF2slag at high temperatures

The distribution ratio of zinc between Ag-Zn and Fe-Zn alloys was measured to clarify the thermodynamic behaviour of zinc in Fe-C melt at high temperatures. Also, the distribution ratio between Ag-Zn alloy and CaO-FeO-CaF 2 slag was measured to understand the dissolution mechanism of zinc in molten slags. The activity coefficient of zinc in Ag-Zn alloy was preliminarily measured as a fundamental thermodynamic data for the activity of zinc in Fe-C melt. From the dependence of the activity coefficient of zinc in Fe-C melts on temperature and carbon content, the following equation could be obtained at 1473 - 1623 K: lnγ Fe-C Zn =35.1- 42200/T +20.9(X C -X satd C ) (1573 K ≤ T ≤ 1623 K). The distribution ratio of zinc between Ag-Zn alloy and CaO-FeO-CaF 2 slag increased by increasing both the oxygen potential and slag basicity. The stoichiometric coefficients of the dissolution reaction were obtained by considering the relationship between zinc distribution ratio and slag basicity or oxygen partial pressure, when one of these two independent variables was fixed. The dissolution reaction of zinc into the slags could be described as follows: Zn(l) + 2O 2- (slag)+1/2O 2 (g) = ZnO 4- 3 (slag).

Characteristic Features of Rolling Texture Development in FCC Alloys Having Very Low Stacking Fault Energies

The aim of this paper is to clarify the difference in textural behavior during rolling between low and very low stacking fault energy fcc materials. The rolling texture developments of pure silver and Ag-Zn solid solution alloys containing 8 mass% and 18 mass%Zn were investigated in detail by means of the X-ray texture analysis including the reliable calculations of the orientation distribution function for a wide range of rolling reduction. At higher reductions in thickness (> 95%), the terminal textures in all specimens of Ag and Ag-Zn alloys were almost similar, and they exhibited the typical brass type rolling texture in which the dominant {110} was developed with the minor component of { 110} . However, it was found at medium degrees of reduction (approximately 50%-75%) that the Ag-Zn alloys having very low stacking fault energies behaved in remarkably different fashion compared to the silver alloy with a moderately low value of stacking fault energy. In such a medium region of rolling reduction, the formation of {111} type component which should be considered as a distinct texture component of very low stacking fault energy alloys, such as Ag-Zn alloys, were enhanced with increasing Zn content. This characteristic feature appearing in the rolling texture of very low stacking fault energy alloys is discussed in terms of the non-Wassermann effect of deformation twinning which has been suggested by one of the authors already.

Ultrasonic Attenuation in Binary Alloys

An attempt was made to study the ultrasonic attenuation in Cu-Zn, Ag-Cd, Ag—Mg and Ag-Zn alloys, dne to phonon-phonon interaction at 300 K. The Morse potential was used to evaluate the second and third order elastic constants. How far the neighbouring atoms are effective and contributing to ultrasonic attenuation was studied. It is concluded that most of the ultrasonic attenuation is covered by the atoms from 1st to 8th shell. The contribution to ultrasonic attenuation due to 9th shell to 12th shell is very small. It is also concluded that alloys behave more or less in the same manner as metals.

Critical Temperature for Ordering and B2 Domain Structure in Ag–Zn β Phase Alloys

The critical temperature for the order-disorder transition, T c , and the ordered domain structure of the B2 phase have been investigated by electrical resistivity measurements and electron microscopic observations in Ag-Zn alloys containing 38, 40 and 42 at%Zn. Specimens quenched from the disordered β phase were all found to be ordered in the B2 structure. Resistivity change measured during aging of the B2 phase shows a plateau at the initial stage of aging. This indicates the degree of order reaches the equilibrium value immediately after the start of aging. The B2 domain size as measured after aging and quenching increases as the aging temperature increases. However, it takes a smaller value when the aging temperature is beyond T c . Values of T c were determined by monitoring the domain size as 441, 405 and 367 K for the 42, 40 and 38Zn alloys, respectively. The ragging or fluctuating of anti-phase domain boundaries was recognized in the specimens aged at a temperature just below T c . The activation energy for the domain growth was obtained by measuring growth rates as 49.3 kJ/mol, which was judged to correspond to the migration energy of excess vacancies.

The β′→ζ Transformation in Equiatomic AgZn Alloy

An analysis was made of the X-ray diffraction intensity distribution in a series of single crystal patterns of an equiatomic AgZn alloy recorded at the initial stage of the phase transformation from β′ (B2-type ordered structure) to ζ (trigonal structure). It was shown that the displacements of atoms and the partial disordering, the two atomistic mechanisms involved in the transformation, proceed simultaneously. The ζ phase nuclei grow gradually in the β′ phase matrix with a definite orientation relationship. Two types of the nuclei form; one with a structure similar to the structure proposed for the ζ phase by Edmunds and Qurashi (ζ phase-type structure) and the other with a structure obtained by reversing the direction of the displacements of some of the atoms in the ζ phase-type structure (anti-ζ phase-type structure).