Ternary Eutectic Alloy Research Articles

Investigation of the Some Physical Properties of the Directionally Solidified Al–Cu–Co Ternary Eutectic Alloy

The Al–23.9% Cu–1.2% Co (wt%) ternary eutectic alloy was prepared using a vacuum melting furnace and a casting furnace. The samples were directionally solidified upwards at a constant growth velocity (18.8 μm/s) under different temperature gradients (1.23–5.66 K/mm) and at a constant temperature gradient (5.66 K/mm) under different growth velocities (8.3–166 μm/s) in a Bridgman-type directional solidification furnace. The dependence of the eutectic spacing on the solidification parameters (temperature gradient and growth rate) and that of the microhardness and compressive strength on the eutectic spacing and solidification parameters were investigated. The electrical resistivity measurements of the studied alloy were performed and the temperature coefficient of the resistivity was calculated from the curve of the resulting ρ–Τ plot. The thermal conductivities of the sample grown at a constant temperature gradient and growth rate were obtained using the Wiedemann–Franz and Smith–Palmer equations.

Nanosize effect in Germanium Nanowire Growth with Binary Metal Alloys

ABSTRACTThis article describes feasible and improved ways towards enhanced nanowire growth kinetics by reducing the equilibrium solute concentration in the liquid collector phase in a vapor-liquid-solid (VLS) like growth model. Use of bi-metallic alloy seeds (AuxAg1-x) influences the germanium supersaturation for a faster nucleation and growth kinetics. Nanowire growth with ternary eutectic alloys shows Gibbs-Thompson effect with diameter dependent growth rate. In-situ transmission electron microscopy (TEM) annealing experiments directly confirms the role of equilibrium concentration in nanowire growth kinetics and was used to correlate the equilibrium content of metastable alloys with the growth kinetics of Ge nanowires. The shape and geometry of the heterogeneous interfaces between the liquid eutectic and solid Ge nanowires were found to vary as a function of nanowire diameter and eutectic alloy composition.

Microstructural evolution of ternary Ag33Cu42Ge25 eutectic alloy inside ultrasonic field

Ultrasonic field with a frequency of 20kHz is introduced into the solidification process of ternary Ag33Cu42Ge25 eutectic alloy from the sample bottom to its top. The ultrasound stimulates the nucleation of alloy melt and prevents its bulk undercooling. At low ultrasound power of 250W, the primary ε2 phase in the whole alloy sample grows into non-faceted equiaxed grains, which differs to its faceted morphology of long strip under static condition. The pseudobinary (Ag+ε2) eutectic transits from dendrite shape grain composed of rod type eutectic to equiaxed chrysanthemus shape formed by lamellar structure. By contrast, the ultrasound produces no obvious variation in the morphology of ternary (Ag+Ge+ε2) eutectic except a coarsening effect. When ultrasound power rises to 500W, divorced ternary (Ag+Ge+ε2) eutectic forms at the sample bottom. However, in the upper part, the ultrasonic energy weakens, and it only brings about prominent refining effect to primary ε2 phase. The microstructural evolution mechanism is investigated on the cavitation, acoustic streaming and acoustic attenuation.

Mechanical, electrical, and thermal properties of the directionally solidified Bi-Zn-Al ternary eutectic alloy

A Bi-2.0Zn-0.2Al (wt%) ternary eutectic alloy was prepared using a vacuum melting furnace and a casting furnace. The samples were directionally solidified upwards at a constant growth rate (V = 18.4 μm/s) under different temperature gradients (G = 1.15–3.44 K/mm) and at a constant temperature gradient (G = 2.66 K/mm) under different growth rates (V = 8.3–500 μm/s) in a Bridgman-type directional solidification furnace. The dependence of microstructure parameter (λ) on the solidification parameters (G and V) and that of the microhardness (Hv) on the microstructure and solidification parameters were investigated. The resistivity (ρ) measurements of the studied alloy were performed using the standard four-point-probe method, and the temperature coefficient of resistivity (α) was calculated from the ρ-T curve. The enthalpy (ΔH) and the specific heat (C p ) values were determined by differential scanning calorimetry analysis. In addition, the thermal conductivities of samples, obtained using the Wiedemann-Franz and Smith-Palmer equations, were compared with the experimental results. The results revealed that, the thermal conductivity values obtained using the Wiedemann-Franz and Smith-Palmer equations for the Bi-2.0Zn-0.2Al (wt%) alloy are in the range of 5.2–6.5 W/Km and 15.2–16.4 W/Km, respectively.

In-situ observations of nanoscale effects in germanium nanowire growth with ternary eutectic alloys.

Vapour-liquid-solid (VLS) techniques are popular routes for the scalable synthesis of semiconductor nanowires. In this article, in-situ electron microscopy is used to correlate the equilibrium content of ternary (Au0.75 Ag0.25 -Ge and Au0.65 Ag0.35 -Ge) metastable alloys with the kinetics, thermodynamics and diameter of Ge nanowires grown via a VLS mechanism. The shape and geometry of the heterogeneous interfaces between the liquid eutectic and solid Ge nanowires varies as a function of nanowire diameter and eutectic alloy composition. The behaviour of the faceted heterogeneous liquid-solid interface correlates with the growth kinetics of the nanowires, where the main growth facet at the solid nanowire-liquid catalyst drop contact line lengthens for faster nanowire growth kinetics. Pronounced diameter dependent growth kinetics, as inferred from liquid-solid interfacial behaviour, is apparent for the synthesised nanowires. Direct in-situ microscopy observations facilitates the comparison between the nanowire growth behaviour from ternary (Au-Ag-Ge) and binary (Au-Ge) eutectic systems.

Microstructural, mechanical and electrical characterization of directionally solidified Al–Si–Mg eutectic alloy

Al–12.95wt.% Si–4.96wt.% Mg alloy was directionally solidified upward at a constant temperature gradient (G=9.39K/mm) with different growth rates (V=8.64–165.20μm/s) by using a Bridgman type directional solidification furnace. The ternary eutectic alloy consists of irregular Si plates and Mg2Si Chinese’s script within an aluminum matrix. The dependencies of lamellar spacings (λSi and λMg2Si), microhardness, tensile strength and electrical resistivity on growth rates were obtained as HV=119.9 (V)0.07, σt=222.84 (V)0.20 and ρ=32.31×10−8 (V)0.13, respectively for Al–Si–Mg eutectic alloy. The bulk growth rates were determined as λSi2V=847.69 and λMg2Si2V=597.5μm3/s by using the measured values of λSi, λMg2Si and V. A comparison of present results was also made with the previous similar experimental results.

Size-controlled growth of germanium nanowires from ternary eutectic alloy catalysts

We report the simultaneous manipulation of both solute and equilibrium concentration of Ge to synthesise high aspect-ratio Ge nanowires.

Thermophysical properties and rapid solidification of Al-Cu-Ge alloys

Al-Cu-Ge alloy system, a typical ternary eutectic alloy system, has been used widely in the industries. Our research is helpful for better understanding its thermophysical properties and improving its structural performance. In this paper, the specific heat values and thermal expansion coefficients of Al55Cu10Ge35, Al70Cu10Ge20 and Al80Cu10Ge10 alloys are investigated. The microstructural characteristics and the solidification paths of these alloys under near-equilibrium solidification and rapid solidification conditions are studied comparatively. Their specific heat values increase as Al content increases and Ge content decreases. The softening temperature is 666 K, and the thermal expansion coefficient fluctuates around 1.5×10-5 K-1 in the temperature range of 370–650 K. Under a near-equilibrium solidification condition, the last formation microstructure is (Al)+(Ge) pseudobinary eutectic instead of ternary eutectic. This means that (Al), (Ge), and CuAl2 phases are difficult to nucleate simultaneously or grow cooperatively. In comparison, during rapid solidification, the nucleation of primary phase is depressed, pseudobinary eutectic and ternary eutectic are much easier to form in these alloys.

Manipulating the Growth Kinetics of Vapor–Liquid–Solid Propagated Ge Nanowires

This article describes an innovative approach in which bimetallic alloy seeds of AuxAg1-x are used to enhance the growth kinetics of Ge nanowires, via a vapor-liquid-solid (VLS) growth technique. The decreased equilibrium concentration and increased supersaturation of Ge in the liquid alloy seeds, compared to pure Au seeds, results in favorable growth kinetics and the realization of high-aspect ratio millimeter-long Ge nanowires. Also detailed is the manifestation of the Gibbs-Thompson effect resulting in diameter-dependent nanowire growth rates as a function of the Au-Ag-Ge eutectic composition. Significantly, AuxAg1-x alloy seeds lower the critical diameter of the Ge nanowires in this liquid-seeded growth approach. In situ TEM heating experiments established the correlation between the growth kinetics and equilibrium eutectic compositions in the ternary growth systems. The fundamental insights of nanowire growth demonstrated with the ternary eutectic alloys opens up opportunities to engineer the aspect ratio and morphology of a range of semiconductor nanowires.

X-ray diffraction study of the NaF-LiF-NdF3 eutectic in the liquid and solid states

The ternary eutectic alloy with the composition 33 mol % NaF + 53 mol % LiF + 14 mol % NdF3 has been studied in the liquid and crystalline states using differential thermal analysis and X-ray diffraction at room and high temperatures. The results demonstrate that the alloy undergoes no phase transformations below its melting point: the only phases identified with certainty are NaF, LiF, and NaNdF4. The melt contains complex microgroups differing in cation composition. Analysis of structural models for the melt indicates that there is no dense noncrystalline packing of the fluorine anions, in contrast to what was observed previously in the eutectic NaF-LiF-LaF3 melt.

Prediction of the solidification path of Al-4.37Cu-27.02Mg ternary eutectic alloy with a unified microsegregation model coupled with Thermo-Calc

Abstract An extended unified microsegregation model with solid back diffusion effects and five different dendrite morphologies was used to investigate the solidification path of Al-4.37Cu-27.02Mg (wt.%) ternary eutectic alloy at different cooling rates and solid back diffusion coefficients, coupled with Thermo-Calc. It was indicated that the cooling rates (Rf ) had no obvious effect on the solidification path which was (L + α) → (L + α + T) → (L + α + β + T); but the solid back diffusion coefficient (Φ) had a great effect on the solidification path, which evolved gradually from (L + α) → (L + α + T) → (L + α + β + T) into (L + α) → (L + α + T) when Φ increased from 0 to 1. The volume fractions of primary α phase (V α), binary eutectic (V 2E) and ternary eutectic (V 3E) at each solidification path were calculated. It was shown that V 2E decreased with the increase of Rf whereas V 3E increased and V α was almost invariant. The dependence of V 2E, V 3E and Rf were determined by linear regression analysis given as: V 2E = −2.5lgRf + 47.5; V 3E = 6.4lgRf + 47. Increase in Φ lead to increases in V α and V 2E and decrease in V 3E. The predicted soldification paths and volume fractions of Al-4.37Cu-27.02Mg ternary eutectic alloy at different cooling rates were in good agreement with experimental results.

Formation mechanism of ternary NiAl-Mo eutectic alloy under quenching condition

The rapid solidification of ternary NiAl-Mo eutectic alloy is investigated by using melt-spinning technique, and the conventional casting is also carried out for a comparison study. The phase constitutions of the alloy samples obtained from different experiments each include both B2-NiAl intermetallic and bcc-Mo solid solution, which are both presented in the 〈110〉priority growth direction. The growth orientation relationship of the coupled two eutectic phases are obtained to be (110)NiAl//(110)Mo. The cast alloy is composed mainly of two regular eutectic phases in structure and exhibits daisy-like eutectic cells. However, the melt-spinning ribbons show the microstructures of the columnar grain near the roller surface zone and the equiaxed grain near the air zone. With the wheel speed increasing from 10 m/s to 50 m/s, the cooling rate of the alloy ribbons increases from 1.01×107 K/s to 2.46×107 K/s, while the thickness of alloy ribbons decreases from 49.4 μm to 22 μm. Meanwhile, the volume fraction of columnar grain zone increases gradually, and the grains are refined obviously. The cooling rate in the melt-spinning experiment for alloy ribbon is obviously higher than that in the conventional casting test, which leads to a significant difference in solidification microstructure between two techniques.

Microstructure refinement of Fe40Ni40B20 alloy in non-equilibrium solidification: possibility of nanostructure formation

Microstructure refinement of ternary eutectic Fe40Ni40B20 alloy in undercooling and rapid cooling solidification has been studied. In natural cooling conditions, two kinds of microstructure refinement take place with increasing undercooling. For melts with the same undercooling, the as solidified microstructure refines first and then coarsens with increasing cooling rate. On this basis, repeatable experiments show that the combination of melt undercooling at ∼50 K with Ga–In alloy bath rapid cooling produces very fine eutectic cells (∼5 μm in diameter with the lamellae spacing <100 nm). This indicates that an appropriate initial melt undercooling combined with a proper cooling rate is a potential way to produce a bulk nanostructure in ternary Fe40Ni40B20 alloy.

Microstructure development in Al-Cu-Ag-Mg quaternary alloy

The solidification behaviour of multi-component and multi-phase systems has been largely investigated in binary and ternary alloys. In the present study, a quaternary model system is proposed based on the well known Al-Cu-Ag and Al-Cu-Mg ternary eutectic alloys. The quaternary eutectic composition and temperature were determined by EDS (Energy Dispersive Spectrometry) and DSC (Differential Scanning Calorimetry) analysis, respectively. The microstructure was then characterised by SEM (Scanning Electron Microscope). In the DSC experiments, two types of quaternary eutectics were determined according to their phase composition. For each type of eutectic, various microstructures were observed, which result in different eutectic compositions. Only one of the determined eutectic compositions was further studied by the controlled growth technique in a vertical Bridgeman type furnace. In the initial part of the directionally solidified sample, competing growth between two-phase dendrites and three-phase eutectics was obtained, which was later transformed to competing growth between three-phase and four-phase eutectics. Moreover, silver enrichment was measured at the solidification front, which is possibly caused by Ag sedimentation due to gravity and Ag rejection from dendritic and three-phase eutectic growth, and its accumulation at the solidification front.

Formation of ordered nano-wire microstructures in thermoelectric Pb–Ag–Sb–Te

Regular arrays of nano-wire microstructures containing Ag2Te rods with diameter <400nm and inter-rod distance <1μm are formed in a matrix of AgSbTe2+δ-Sb2Te, which makes an ordered nano-wire composite thermoelectric material. This microstructure is formed during eutectic solidification processing. To understand and guide production of uniform bulk samples of this composite, the liquidus projection of quaternary Pb–Ag–Sb–Te system at 36.0at.% Te isoplethal section is constructed experimentally, using quenched samples. A three-phase univariant reaction of the quaternary Pb–Ag–Sb–Te system, L→AgSbTe2+Ag2Te+δ-Sb2Te, is investigated, between a ternary-eutectic melt (Ag–40.0at.% Sb–36.0at.% Te) and a quaternary melt (Pb–22.0at.% Ag–40.0at.% Sb–36.0at.% Te), at 496.1°C and 503.9°C, respectively. High-resolution transmission electron microscopy confirms that these three phases are simultaneously present at the nanometer scale. Furthermore, unidirectional solidification experiments of the ternary eutectic alloy using the Bridgman method are carried out to examine the alloy’s solidification behavior.

Phase Selection and Microstructure Evolution in Nonequilibrium Solidification of Fe40Ni40B20 Alloy

Phase selection and microstructure evolution in nonequilibrium solidification of ternary eutectic Fe40Ni40B20 alloy have been studied. It is shown that γ-(Fe, Ni) and (Fe, Ni)3B prevail in all the as-solidified samples. No metastable phase has been found in the deeply undercooled samples. This is explained as resulting from the size effect of undercooled solidification. At small and medium undercoolings, the dendrite γ-(Fe, Ni) appears as the leading phase. This is ascribed to the existence of the skewed coupled growth zone in FeNiB alloy. With increasing undercooling, the amount of dendrites first increases and then decreases, accompanied by a transition from regular eutectic to anomalous eutectic. The formation mechanisms of the anomalous eutectics are discussed. Two kinds of microstructure refinement are found with increasing undercooling in a natural or water cooling condition. However, for melts with the same undercooling, the as-solidified microstructure refines first, and then coarsens with an increasing cooling rate. The experimental results show that the nanostructure eutectic cell has been obtained in the case of Ga-In alloy bath cooling with an initial melt undercooling of approximately 50 K (50 °C).

Hydrogenation of nanostructured alloys and composites based on magnesium

The capability of sorbing hydrogen was studied for the magnesium alloys and related composites. The microstructures of the Mg-Ni binary eutectic alloys and Mg-La-Ni and Mg-Mm-Ni ternary eutectic alloys were studied. Both the initial alloys and alloys modified by the method of equal channel angular pressing were used as objects of the study. Features of interaction of the alloys with hydrogen were revealed. Sorption of hydrogen by the metal hydride composites based on alloys and “pseudoalloys,” viz., alloys obtained by sintering of mechanochemically treated highly dispersed powders formed by the hydride dispersion of metallic phases, was studied. Metal—carbon composites based on highly dispersed magnesium alloys or pseudoalloys and carbon nanostructures were formed, and the absorption of hydrogen by these composites was examined.

Theoretical and numerical study of lamellar eutectic three-phase growth in ternary alloys

We investigate lamellar three-phase patterns that form during the directional solidification of ternary eutectic alloys in thin samples. A distinctive feature of this system is that many different geometric arrangements of the three phases are possible, contrary to the widely studied two-phase patterns in binary eutectics. Here, we first analyze the case of stable lamellar coupled growth of a symmetric model ternary eutectic alloy, using a Jackson-Hunt-type calculation in thin film geometry, for arbitrary configurations, and derive expressions for the front undercooling as a function of velocity and spacing. Next, we carry out phase-field simulations to test our analytic predictions and to study the instabilities of the simplest periodic lamellar arrays. For large spacings, we observe different oscillatory modes that are similar to those found previously for binary eutectics and that can be classified using the symmetry elements of the steady-state pattern. For small spacings, we observe a new instability that leads to a change in the sequence of the phases. Its onset can be well predicted by our analytic calculations. Finally, some preliminary phase-field simulations of three-dimensional growth structures are also presented.

Rapid solidification of acoustically levitated Al-Cu-Si eutectic alloy under laser irradiation

Al-27%Cu-5.3%Si ternary eutectic alloy was melted using a YAG laser and then solidified while being acoustically levitated. A maximum undercooling to 195 K (0.24 T L) was achieved with a cooling rate of 76 K/s. The solidification microstructure was composed of (Al+θ+Si) ternary eutectics and (Al+θ) pseudobinary eutectics. During acoustic levitation, the (Al+θ+Si) ternary eutectics are refined and the (Al+θ) pseudobinary eutectics have morphological diversity. On the surface of the alloys, surface oscillations and acoustic streaming promote the nucleation of the three eutectic phases and expedite the cooling process. This results in the refinement of the ternary eutectic microstructure. During experiments, the reflector decreases with increasing alloy temperature, and the levitation distance always exceeds the resonant distance. Because of the acoustic radiation pressure, the melted alloy was flattened, and deformation increases with increasing sound pressure. The maximum aspect ratio achieved was 6.64, corresponding to a sound pressure of 1.8×104 Pa.

Effect of Ag-content on structure, corrosion behaviour and mechanical properties of Sn-9Zn lead-free solder alloy

The effect of (0.5–3.5) wt.% Ag additions on microstructure, melting, corrosion and mechanical properties of Sn-9Zn eutectic lead-free solder alloy has been studied and analyzed. The study included X-ray diffraction and scanning electron microscopy (SEM) to identify the microstructure of these alloys. The results showed that, continuous additions of Ag caused formation of Ag-Zn and Ag-Sn compounds which led to decrease the precipitations of Zn in Sn-matrix. These compounds led to increase the melting point of the alloys, which confirmed by the formation of small endothermic peaks in the higher temperature range followed the main peak of the DTA curves. Also, the DTA measurements confirmed that the alloy of composition Sn-9Zn-3.5Ag is the ternary eutectic alloy. Vicker's micro-hardness number of Sn-9Zn alloy increases with small additions of 0.5 and 1 wt.% Ag. Furthermore, it decreases to lower values with further increase of Ag content. Also, micro-creep behaviour, creep rate and corrosion behaviour of the Sn-9Zn-Ag alloys have been measured at room temperature.