Cu In System Research Articles

Phase Formation and Diffusivity in the Ternary Cu-Zn-In System

Formation of the phases in Cu-Zn-In system was investigated by means of diffusion multiples annealed in isothermal conditions. The annealing of three different configurations of joints was performed at increasing temperatures (130, 350, 450 °C): below and above melting temperature of In and above Zn melting temperature. It was found that In revealed the ability for the preferential diffusion in Zn along the grain boundaries, forming the eutectic phase. In all applied temperatures, pure Cu was the barrier for the diffusion of In, while the diffusion of Zn proceeded easily, leading to the formation of binary CuZn phases; the phases from the Cu-In system were not found. The ternary Cu-Zn-In phases were formed at temperatures of 350 and 450 °C, at which the simultaneous diffusion of In and Zn in Cu took place, with participation of liquid In and Zn. The obtained results are the starting point for the calculation of the Cu-Zn-In phase diagram which remains unavailable, in spite of fact that all Cu-Zn, In-Zn and Cu-In binary diagrams are well known.

Reversible “Wetting” of grain boundaries by the second solid phase in the Cu-In system

The reversible wetting of grain boundaries by the second solid phase in the copper-indium system has been observed. With an increase in the temperature, the contact angle θ between the (Cu)/(Cu) grain boundary in a Cu-based solid solution based and particles of the δ-phase (Cu70In30) decreases gradually. Above TW = 370°C, the first (Cu)/(Cu) grain boundaries completely “wetted” by the δ phase appear in Cu-In polycrystals. In other words, the δ phase forms continuous layers along grain boundaries and θ = 0. At 440°C, the fraction of completely wetted grain boundaries reaches a maximum (93%), whereas the average contact angle reaches a minimum (θ = 2°). With a further increase in the temperature, the fraction of completely wetted grain boundaries decreases and vanishes again at TDW = 520°C. This phenomenon can be explained by an anomalous shape of the solubility limit curve of indium in a solid solution (Cu).

On the control of copper colloidal distribution by humic substances in the Penzé estuary

In this study, we investigated the variations of colloidal Cu in a temperate macrotidal estuarine system (Penzé, NW France). The originality of this work resides on examining seven colloidal/dissolved fractions at seven different periods of the year whereas previous studies on estuaries generally considered two or three fractions and were focused on a unique survey. A high proportion of Cu (∼90%) was generally found as colloids (5kDa–0.45μm) throughout the salinity gradient with divergent size distributions being observed over the seasonal cycle. This consisted essentially in two contrasted periods, i.e. winter-spring with a greater association of Cu with high molecular weight (HMW) compounds (50kDa–0.45μm) and summer-autumn with Cu being found mainly as low molecular weight (LMW) forms (5–50kDa). The comparison of Cu with humic substances (HS) data allowed to us to highlight the importance of the pedogenic refractory organic matter in controlling the concentrations and the size distribution of Cu in the estuary. In the mixing zone, Cu behaved conservative in autumn and winter but important additions of HMW compounds were observed in spring in the lower estuary as the result of particulate organic matter degradation in the sediment. Although HS appears to be the background chelators of Cu in the systems, the strong benthic inputs occurring in spring may be of different (biotic) origin and may be in part responsible for the higher association of Cu with HMW compounds.

Discontinuous Precipitation and Dissolution in Cu-4, 6 at% In Alloy under the Effect of Plastic Deformation and the Temperature

The study of the discontinuous precipitation reaction and the lamellar precipitate dissolution in the alloy Cu-In system provoked a considerable benefit and has been the subject of many theoretical and experimental investigations. The aim of this work is to make the evidence on the one hand the effect of the plastic deformation on the mechanism of the discontinuous precipitation reaction such as nucleation, growth and lamellar coarsening and in other hand the effect of temperature on the characteristics and front behavior movement of the opposite reaction (discontinuous dissolution). Different techniques of analysis have been used in this respect such as the optical microscopy, the differential thermal analysis and the microhardness Vickers. The obtained results confirm various works achieved in this field.

A thermodynamic optimization of the Cu-In system

The Cu-In liquid phase exhibits an important short range disordering between the liquidus line and 1100°C. Kao et al. [1993Kao] have proposed a thermodynamic phase diagram optimization using a constant excess CP versus temperatures in the liquid phase, which seems unrealistic for low and high temperatures far extrapolations. On the contrary, we suggest in this new model to use a description of the liquid phase without any excess CP: the considered liquid phase is modelized only with high temperatures experimental data and the disordering enthalpy of the liquid is added to the melting enthalpy of the various solid phases. This artefact allows to correctly modelize the complete phase diagram using all the available thermodynamic data for formation of the solid phases.

Experimental determination and thermodynamic calculation of the phase equilibria in the Cu-In-Sn system

The phase equilibria of the Cu-In-Sn system were investigated by means of the diffusion couple method, differential scanning calorimetry (DSC) and metallography. The isothermal sections at 110–900 C, as well as vertical sections at 10wt.%Cu–70wt.%Cu were determined. It was found that there are large solubilities of In in the e(Cu3Sn), δ(Cu41Sn11), and η phases in the Cu-Sn system, and large solubilities of Sn in the γ, η, and δ(Cu7In3) phases in the Cu-In system. The η phase was found to continuously form from the Cu-In side to the Cu-Sn side, and a ternary compound (Cu2In3Sn) was found to exist at 110 C. Thermodynamic assessment of the Cu-In-Sn system was also carried out based on experimental data of activity and phase equilibria using the CALPHAD method, in which the Gibbs energies of the liquid, fcc and bcc phases are described by the subregular solution model and that of compounds, including two ternary compounds, are represented by the sublattice model. The thermodynamic parameters for describing the phase equilibria were optimized, and agreement between the calculated and experimental results was obtained.

Limitations of a regular associated solution approximation in describing the thermodynamic behaviour of complex liquid alloys

The validity of the regular associated solution (RAS) model for describing the thermodynamic properties of complex liquid alloys has been analysed by applying it to the Cu-In system. The presence of Cu 3In as the associated species in equilibrium with the free atoms in the liquid state was assumed. Liquid copper-indium alloys exhibit a very complex thermodynamic behaviour where the deviations from ideality of activities and integral enthalpy of mixing vary from positive to strongly negative and the properties are strongly temperature dependent. It is seen that a regular solution type interaction among species is insufficient to model the thermodynamic properties of liquid Cu-In alloys and the temperature dependence of interaction energies among the species has to be taken into account. A modified associated solution model incorporating volume effects and temperature dependence of interaction energies could successfully describe the thermodynamic properties of liquid Cu-In alloys.

Kinetics of the eutectoid transformation in the Cu-In system

The present study concerns a detailed investigation of the kinetics of the eutectoid transformation in the Cu–In system based on both the isothermal growth rate of the eutectoid colony (monitored by microstructural change) and enthalpy changes during non-isothermal heating (determined by differential scanning calorimetry) of solution-treated and quenched samples. The maximum growth distance of the eutectoid cells and the equilibrium interlamellar spacing have been determined by optical and scanning electron microscopy in the temperature range 600–825 K. The reaction front velocity was observed to increase with the isothermal ageing temperature in the temperature range studied. A detailed analysis of the isothermal growth kinetics through the models available in the literature has yielded an activation energy of 125–127 kJ mol-1 for the operating diffusion process, which is comparable with that for discontinuous precipitation in Cu–In or for grain boundary tracer diffusion of 115In in Cu, but significantly lower than that for volume diffusion of In in the β Cu–In alloy. A subsequent differential scanning calorimetric study has indicated a similar activation energy of 133 kJ mol-1 for the concerned eutectoid transformation. It is thus concluded that the eutectoid transformation in the Cu–In system is a boundary-diffusion-controlled process.

Metastable and Equilibrium Decomposition of the Eutectoid β-Phase in the Cu-In System

The β-phase in the Cu-In system is known to decompose into α and δ below 847 K through a eutectoid transformation controlled by interphase boundary diffusion. The present study with the Cu-20.15 at.% In eutectoid alloy investigates the morphology, identity and origin of a duplex microstructure in the prior β region ahead of the eutectoid reaction front. A detailed investigation through optical, scanning and transmission electron microscopy and X-ray diffraction analysis indicates that the prior β region undergoes a time dependent pre-precipitation of a transient phase through a static boundary mode. The latter precedes/accompanies the moving boundary eutectoid transformation initiated at the prior β grain boundaries.

The η-phase field of the CuIn system

The η-phase field of the CuIn phase diagram has been investigated by means of electron and X-ray diffraction. This phase field contains three distinct phase regions: A, B, and C. All phases are based on the B8-type (NiAsNi 2In type) structure. The A-phase is a high-temperature monoclinic phase. It is converted to the B-phase, which can be seen by the continuous rotation of satellite reflections in the diffraction pattern. Hence the B-phase has many modifications. The different diffraction patterns of the B-phase link together the patterns of the A-phase and the C-phase. The C-phase is a low-temperature phase with a large orthorhombic supercell.

Phase equilibria of the cu-in system I: Experimental investigation

Portions of the Cu-In phase diagram were redetermined experimentally, specifically in the compositional region from 32.0 to 100 at % In. The experimental techniques used were differential scanning calorimetry (DSC), differential thermal analysis (DTA), powder X-ray diffraction (XRD), and electron probe microanalysis (EPMA).

Phase equilibria of the cu-in system II: Thermodynamic assessment and calculation of phase diagram

The phases in the Cu-In binary were modelled thermodynamically using the Redlich-Kister expression for the Gibbs energies of the solution phases, the Wagner-Schottky model for those of the η (η)’)-Cu2ln phase (taking η and η)’ to be a single phase), and assuming line compound behavior for the other intermetallic phases. The model parameters were obtained using primarily the thermodynamic data, as well as the phase equilibrium data. The thermodynamic values for the various phases calculated from the models are in reasonable agreement with the experimentally determined thermodynamic data that are available in the literature. The entropies of melting for the intermetallic phases obtained from the models are in accord with the values calculated from the empirical formulas suggested by Kubaschewski.

A comment on: A thermodynamic study of an associated solution model for liquid alloys

The validity of the regular associated solution (RAS) model for describing the thermodynamic properties of complex liquid alloys has been analysed by applying it to the Cu-In system. The presence of Cu3In as the associated species in equilibrium with the free atoms in the liquid state was assumed. Liquid copper-indium alloys exhibit a very complex thermodynamic behaviour where the deviations from ideality of activities and integral enthalpy of mixing vary from positive to strongly negative and the properties are strongly temperature dependent. It is seen that a regular solution type interaction among species is insufficient to model the thermodynamic properties of liquid Cu-In alloys and the temperature dependence of interaction energies among the species has to be taken into account. A modified associated solution model incorporating volume effects and temperature dependence of interaction energies could successfully describe the thermodynamic properties of liquid Cu-In alloys.