Sn Alloy System Research Articles

Transient eutectic solidification in In–Bi–Sn: Two-dimensional experiments and numerical simulation

A technique widely used for the in situ observation of microstructure formation in transparent organic systems was applied to metallic alloys with low melting temperature. In the ternary eutectic alloy system In–Bi–Sn, we observed by light microscopy steady state and transient eutectic microstructure formation during unidirectional solidification in thin (5–10 μm) glass capillaries. Starting from an equilibrated planar single-phase front in a slightly off-eutectic alloy we studied the dynamic processes like nucleation of univariant, and finally invariant ternary eutectic when the liquid transforms into three distinct solid phases. Numerical microstructure simulation was performed by applying a general multiphase and multi-component phase field model which couples directly to the complete thermodynamic dataset of the In–Bi–Sn alloy system. Via comparison of the experimental to the simulated data some thermo-physical values like diffusion coefficients and critical undercooling for nucleation have been evaluated.

Multilayered microstructure of a Pb–Sn alloy coating obtained by electrochemical deposition

Electrodeposition is an efficient technique for producing new material with specific chemical and physical properties. These properties stem from the novel morphology and microstructure of deposits. In this paper, we study the morphology and microstructure of the Pb–Sn codeposit by quasi-two-dimensional electrodeposition. A codeposition mechanism is suggested from the analysis by the electrochemical reaction dynamics. Based on this mechanism, the proposal for the microstructure-controlled electrodeposition is offered and an artificial multilayered microstructure is prepared in Pb–Sn alloy system.

Bulk glass formation in the Ni–Zr–Ti–Nb–Si–Sn alloy system

In this study, the effect of addition of Nb on glass formation in Ni–Ti–Zr–Si–Sn alloys has been studied. The composition range for bulk glass formation with Dmax > 2 mm (Dmax, maximum diameter for glass formation by injection cast method) becomes wider when compared with the non-Nb–containing alloy. The ΔTx (= Tx – Tg; Tx, crystallization onset temperature; Tg, glass transition temperature), Trg (= Tg/Tl; Tl, liquidus temperature) and γ [= Tx/(Tl + Tg)] values for the alloys Dmax > 2 mm are in the range of 40–59, 0.638–0.651, and 0.410–0.419, respectively. The compositions of the alloys (Dmax > 2 mm) are closer to pseudo-eutectic composition than that of the alloy without Nb, showing an improved glass forming ability. The critical cooling rate for glass formation (Dmax = 5 mm) is estimated to be order of approximately 40 K/s.

The Effect of Heat Treatment on the Fe—Sn Alloy System

SUMMARYThe diffusion reaction of tin into pre-flow melted bright tinplate has been studied. It has been shown that the power index for the diffusion of tin to form the intermetallic layer increases from approximately 2 below 232°C to 5.6 at 350°C. Furthermore, the rate constant for alloy formation increases from 1 at 100°C to 331 at 225°C and to 2 × 106 at 250°C. At 350°C it reaches 6.3 × 106. The activation energy for the formation of FeSn2 is reducedfrom 19 kJ mol−1 K−1 for temperatures below the melting point of tin, to 7 kJ mol−1 K−1 for those above the melting point. Evidence for the presence of iron—tin alloys other than FeSn2 is also presented. These alloys are only formed when the processing temperature exceeds 350°C and all the free tin has been depleted. These results provide a better understanding of the diffusion reaction between tin and iron when hot processing is used on tinplate and can be used to give better control to some processes. This improved control will minimise the adverse affects of heat treatment of tinplate that can result in both greying of the surface and maximise the amount of tin that can be reclaimed from scrap used tinplate.

AuCu–Sn pseudobinary phase diagram

A pseudobinary phase diagram was determined from powder X-ray diffraction (XRD) data derived from the addition of varying amounts of Sn to the AuCu alloy system. Prior to XRD studies, the alloy samples were initially solution-treated and quenched. They were then subjected to annealing at lower temperatures ranging from 200 to 450°C for a duration of 20 000 min and then subsequently quenched in ice brine. The resulting phase diagram presented two significant results. First, it showed the existence of a AuCu III phase which was previously reported only in the Au–Cu–Ga ternary system. And second, it shows the existence of a AuCu III′ phase which Karlsen and co-workers designated as the ‘B’ phase in his early work concerning the Au–Cu–Sn alloy system.

A novel GaAs flip-chip power MODFET with high gain and efficiency

A novel GaAs flip-chip power MODFET with a spike-gate structure has been developed for high-gain and high-efficiency operation under extremely low supply voltages. The spike-gate MODFET is featured by a unique gate structure that has almost zero effective gate length. The spike gate provides both a low on-resistance of 1.5 Ω mm and a high transconductance of 280 mS/mm without increasing the drain conductance. The flip-chip bonding, with an Au–Sn alloy system, has been used for mounting of the spike-gate power MODFET on an AlN substrate. The thermal resistance of the flip-chip power MODFET is 12°C/W which is lower than that of a conventional wire-bonded MODFET. The power-added efficiency (PAE) of 71% at the output power of 30.0 dBm can be obtained even when the supply voltage is reduced to 1.5 V. By eliminating parasitic wire inductance, the linear gain of the MODFET is 2 dB higher and the PAE is 5% higher than that of the conventional wire-bonded MODFET.

An adsorption model of the heterogeneous nucleation of solidification

An adsorption model has been developed to describe the heterogeneous nucleation of solidification in an A–B eutectic or monotectic alloy system. The interface between A-rich α solid and B-rich liquid is treated as a mixture of A solid, B solid, A liquid and B liquid atoms, randomly distributed as a monolayer between the two phases. The interfacial energy is calculated by summing pairwise bonding energies, and is then minimised to determine the equilibrium interface solid fraction and composition. With decreasing temperature, the interface monolayer changes sharply from liquid to solid, with a composition close to pure B. This sharp onset of interface adsorption of solid B atoms corresponds to α acting as a catalyst for the heterogenous nucleation of B-rich β solid. Adsorption close to the eutectic temperature and therefore efficient nucleation catalysis is promoted by a large difference between the melting points of A and B, and a small difference between the solid and liquid immiscibilities of A and B. Predicted undercoolings for the onset of adsorption and nucleation catalysis can be obtained directly from simple phase diagram data, and give good agreement with previous measurements in the AgPb and AlSn alloy systems.

Embedded droplet measurements and an adsorption model of the heterogeneous nucleation of solidification

An adsorption model has been developed to describe the heterogeneous nucleation of solidification in an A-B eutectic or monotectic alloy system. The interface between A-rich α solid and B-rich liquid is treated as a mixture of A solid, B solid, A liquid and B liquid atoms, randomly distributed as a monolayer between the two phases. The interfacial energy is calculated by summing pairwise bonding energies, and is then minimized to determine the equilibrium interface solid fraction and composition. With decreasing temperature, the interface monolayer changes sharply from liquid to solid, with a composition close to pure B. This sharp onset of interface adsorption of solid B atoms corresponds to α acting as a catalyst for the heterogeneous nucleation of B-rich β solid. Adsorption close to the eutectic temperature and therefore efficient nucleation catalysis is promoted by a large difference between the melting points of A and B, and a small difference between the solid and liquid immiscibilities of A and B. Predicted undercoolings for the onset of adsorption and nucleation catalysis can be obtained directly from simple phase diagram data, and give good agreement with previous measurements in the AgPb and AlSn alloy systems.

Electronic structure of the BaA 1- xB xO 3 (A, B = Pb, Bi, Sn, Sb) alloy systems : Implications for superconductivity

Coherent potential approximation studies of the electronic structure of the BaA 1- x B x O 3 (where A and B are different combinations of the elements Pb, Bi, Sn and Sb) alloy systems have been performed with accurate tight-binding hamiltonians. The calculations show how semiconducting BaSnO 3 evolves into a metal upon alloying with Sb or Bi. Common characteristics of the densities of states are pointed out. Using the rigid muffin-tin approximation an analysis of the superconducting properties is given.

Onset of solutal convection during directional solidification of a binary alloy in a cylinder

The onset of solutal convection during directional solidification of a binary alloy growing in a cylinder is determined for the axisymmetric and selected nonaxisymmetric flow states. The Tau–Chebyshev projection method is used to solve the system of linearized partial differential equations. The Pb–Tl and Pb–Sn alloy systems are investigated, which, respectively, correspond to k=1.1 and to k=0.3. A critical convective pattern with an azimuthal wave number α=1 is obtained when the aspect ratio β of the cylinder is less than about 6.5. At this value a transition to axisymmetric modes (α=0) is evidenced. Finally, the comparison with previous results for growth in a vertical slot shows the enhancement of the hydrodynamic stability associated to the 3-D confinement by the cylinder.

Phase relationships in Bi–In–Sn alloy system

Phase relationships in Bi–In–Sn alloy system

Phase relationships in Bi–In–Sn alloy system

AbstractThermal and metallographic analyses of a series of samples having compositions on or near the line joining Sn and the BiIn2 phase have been carried out. This showed the existence of a quasibinary section in the ternary diagram comprising a quasibinary eutectic of the form L → γ-Sn+BiIn2, where γ-Sn is the γ-phase of the In–Sn system. A previously unreported ternary eutectic reaction of the form L → γ-Sn+BiIn2+Bi3In5 was also found.MST/404

Formation and low-temperature electronic properties of liquid-quenched Ag-Cu-X (X=Mg, Si, Sn and Sb) metallic glasses

The glass-forming region in liquid-quenched Ag-Cu-X (X=Mg, Al, In, Si, Sn and Sb) alloy systems was investigated by utilising the melt-spinning technique. The electrical resistivities were measured in the range 2-700K and the low-temperature specific heats in the range 1.5-6K for these Hume-Rothery-type simple metallic glasses. A distinct difference is found to exist in the low-temperature electronic properties between the low-resistivity Ag-Cu-Mg and Ag-Cu-Sn alloys and high-resistivity Ag-Cu-metalloid alloys. The temperature dependence of the electrical resistivity can be discussed within the framework of the extended Ziman theory. The sign of the TCR can be well correlated with Ziman's parameter 2kF/Kp only for the low-resistivity alloys. The saturation effect develops in the high-resistivity alloys. This can be easily identified from the unique temperature dependence of the resistivity at low temperatures below about 100K. The electronic specific heat coefficient data for the low-resistivity Ag-Cu-Mg alloys can be well understood in terms of the free-electron model. Furthermore, it turns out that the 2kF=Kp condition does not noticeably affect the density of states at the Fermi level. However, some depression of the density of states at the Fermi level is apparently present in the case of Ag-Cu-metalloid metallic glasses.

Concentration Change of Sn in the Surface Layers of Cu–Sn Alloy System due to Friction

Changes in the composition and structure of Cu-5w%Sn alloy system due to friction or heating were examined with X-ray technique, electron probe microanalysis and Auger emission spectroscopy. It was found that the intensities of Auger spectra of Sn on the surface increased rapidly with friction process or heating temperature, and that after heating at 500°C for 30 min their maximum was about 40% of that from pure Sn. The structural changes of the surface of polycrystalline ε-Cu3Sn and η-Cu6Sn5 due to friction were examined. The results obtained were as follows: (1) the structure of ε-Cu3Sn remained unaffected by the friction and (2) η-Cu6Sn5 decomposed partially into ε-Cu3Sn during the friction process, and a thin film of Sn arose from its decomposition at the surface.

Effect of Impurities upon Critical Temperature of Anisotropic Superconductors

The changes in critical temperature upon doping a superconductor are accounted for theoretically by solving a BCS-like model which includes anisotropy. This anisotropy is introduced via a factorable pairing potential ${V}_{p{p}^{\ensuremath{'}}}=[1+a(\stackrel{^}{\ensuremath{\Omega}})]V[1+a({\stackrel{^}{\ensuremath{\Omega}}}^{\ensuremath{'}})]$ which depends on the momenta of the paired particles relative to the crystal axes. The impurities have two effects upon ${T}_{c}$: They gradually change the gross properties of the system and, hence, produce a linear change in ${T}_{c}$ (valence effect), and in addition they abruptly reduce ${T}_{c}$ by reducing the anisotropy of the energy gap (mean-free-path effect). By adjusting parameters representing the strengths of these effects, we have fit theory to experiments on Sn, In, and Al alloy systems. We find $〈{a}^{2}〉\ensuremath{\sim}0.01$, while valence parameters vary strongly with impurity and do not depend simply on valence. The major gap in the theory is in the unknown ratio of the mean collision times for smoothing out anisotropy and for transport.