Ternary Eutectic Alloy Research Articles

Development of High-Strength High-Temperature Cast Al-Ni-Cr Alloys Through Evolution of a Novel Composite Eutectic Structure

Aiming to develop high-strength Al-based alloys with high material index (strength/density) for structural application, this article reports a new class of multiphase Al alloys in the Al-Ni-Cr system that possess impressive room temperature and elevated temperature (≥ 200 °C) mechanical properties. The ternary eutectic and near eutectic alloys display a complex microstructure containing intermetallic phases displaying hierarchically arranged plate and rod morphologies that exhibit extraordinary mechanical properties. The yield strengths achieved at room temperatures are in excess of 350 MPa with compressive plastic strains of more than 30 pct (without fracturing) for these alloys. The stability of the complex microstructure also leads to a yield stress of 191 ± 8 to 232 ± 5 MPa at 250 °C. It is argued that the alloys derive their high strength and impressive plasticity through synergic effects of refined nanoeutectics of two different morphologies forming a core shell type of architecture.

Effect of laser surface remelting on the microstructure and properties of Al-Al2Cu-Si ternary eutectic alloy

Bimodal ultrafine eutectic composites (BUECs) exhibit a good combination of strength and plasticity owing to a dual-hierarchy in eutectic length-scales in the microstructure. The present study investigates the variation of phase, morphology, feature length-scales and modality of microstructures obtained in a Al81Cu13Si6 (at. %) ternary alloy after laser surface remelting. A novel approach of varying component bimodal eutectic volume fractions by controlling the cooling rate of the laser solidification process has been presented. The volume fraction of the fine eutectic matrix has a profound effect on the flow strength. Laser remelted microstructures with volume fractions of the fine eutectic varying from 25 to 40% exhibiting compressive flow strengths ranging from 500 to 900 MPa have been obtained. The volume fraction of the fine eutectic decreased with cooling rate and completely ceased to exist at cooling rates greater than 4times {10}^{4},^circ {rm{C}}/{rm{s}}.

Lead free Sn-Ag-Cu solders reinforced by Ni-coated graphene nanosheets prepared by mechanical alloying: Microstructural evolution and mechanical durability

As one of the key technologies for high performance electronic devices, composite solders have been developed to improve the thermal and mechanical properties of soldered joints. In this research, mechanical alloying was employed to fabricate the lead-free tin-based nanocomposite solders. The nanocomposite composed of a Sn-Ag-Cu ternary eutectic alloy reinforced by graphene nano-sheets (GNSs). Since the tin alloy melt do not wet the surfaces of GNSs, interface bonding between the metal matrix and these inclusions was promoted with decorating of the nano-sheets by a thin layer of chemically-deposited nickel. It was shown that nickel coating significantly improves the distribution of GNSs throughout the SAC matrix prepared by the severe plastic deformation route. Additionally, brittle and elongated intermetallic compounds were significantly refined to distribute the particles with an average diameter of a few hundred nanometers. Microstructural studies also revealed a recrystallized fine-grained and eutectic morphology for the SAC alloy matrix before and after soldering, respectively. The role of Ni-coated GNSs on retarding the growth of intermetallic phases upon soldering process is presented. We have employed a solid-state post ageing process to enhance the mechanical properties of the developed soldered joints by precipitation hardening mechanism assisted by nano-sheets, as well. Enhanced strength and ductility of the copper soldered joints prepared by the nanocomposite solder is shown. A maximum enhancement of ~ 65% in the tensile-shear strength is reported, while the ductility preserved up to ~ 63%, as well.

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

The composition of an Al–Cu–Mg ternary eutectic alloy was chosen to be Al–30 wt% Cu–6 wt % Mg to have the Al2Cu and Al2CuMg solid phases within an aluminum matrix (α-Al) after its solidification from the melt. The alloy Al–30 wt % Cu–6 wt % Mg was directionally solidified at a constant temperature gradient (G = 8.55 K/mm) with different growth rates V, from 9.43 to 173.3 μm/s, by using a Bridgman-type furnace. The lamellar eutectic spacings (λE) were measured from transverse sections of the samples. The functional dependencies of lamellar spacings λE ( $${\lambda _{A{l_2}CuMg}}$$ and $${\lambda _{A{l_2}Cu}}$$ in μm), microhardness H V (in kg/mm2), tensile strength σT (in MPa), and electrical resistivity ρ (in Ω m) on the growth rate V (in μm/s) were obtained as $${\lambda _{A{l_2}CuMg}} = 3.05{V^{ - 0.31}}$$ , $${\lambda _{A{l_2}Cu}} = 6.35{V^{ - 0.35}}$$ , $${H_V} = 308.3{\left( V \right)^{ - 0.33}}$$ ; σT= 408.6(V)0.14, and ρ = 28.82 × 10–8(V)0.11, respectively for the Al–Cu–Mg eutectic alloy. The bulk growth rates were determined as $$\lambda _{A{l_2}CuMg}^2V = 93.2$$ and $$\lambda _{A{l_2}Cu}^2V = 195.76$$ by using the measured values of $${\lambda _{A{l_2}CuMg}}$$ , $${\lambda _{A{l_2}Cu}}$$ and V. A comparison of present results was also made with the previous similar experimental results.

Microstructural, mechanical, electrical, and thermal properties of the Bi-Sn-Ag ternary eutectic alloy

The development of lead-free solders has emerged as one of the key issues in the electronics packaging industries. Bi-Sn-Ag eutectic alloy has been considered as one of the lead-free solder materials that can replace the toxic Pb-Sn eutectic solder without increasing soldering temperature. We investigated the effects of temperature gradient and growth rate on the mechanical, electrical and thermal properties of the Bi-Sn-Ag ternary eutectic alloy. Bi-47 wt%Sn-0.68 wt%Ag alloy was directionally solidified upward with different temperature gradients (G=2.33-5.66 K/mm) at a constant growth rate (V=13.25 μm/s) and with different growth rates (V=6.55-132.83 μm/s) at a constant temperature gradient (G=2.33 K/mm) in the growth apparatus. The microstructures (λ), microhardness (HV), tensile stress (σ), electrical resistivity (ρ), and thermal properties (ΔH, C p, T m) were measured on directionally solidified samples. The dependency of the λ, HV, σ, and ρ on G and V was investigated. According to the experimental results, λ values decrease with increasing G and V, but HV, λ, and ρ values increase with increasing G and V. Variations of electrical resistivity (ρ) for cast samples with the temperature in the range of 300-400 K were also measured by using a standard dc four-point probe technique. The enthalpy of fusion (ΔH) and specific heat (C p) for the same alloy was also determined by means of differential scanning calorimeter (DSC) from heating trace during the transformation from eutectic liquid to eutectic solid.

Deformation mechanisms to ameliorate the mechanical properties of novel TRIP/TWIP Co-Cr-Mo-(Cu) ultrafine eutectic alloys

In the present study, the microstructural evolution and the modulation of the mechanical properties have been investigated for a Co-Cr-Mo (CCM) ternary eutectic alloy by addition of a small amount of copper (0.5 and 1 at.%). The microstructural observations reveal a distinct dissimilarity in the eutectic structure such as a broken lamellar structure and a well-aligned lamellar structure and an increasing volume fraction of Co lamellae as increasing amount of copper addition. This microstructural evolution leads to improved plasticity from 1% to 10% without the typical tradeoff between the overall strength and compressive plasticity. Moreover, investigation of the fractured samples indicates that the CCMCu alloy exhibits higher plastic deformability and combinatorial mechanisms for improved plastic behavior. The improved plasticity of CCMCu alloys originates from several deformation mechanisms; i) slip, ii) deformation twinning, iii) strain-induced transformation and iv) shear banding. These results reveal that the mechanical properties of eutectic alloys in the Co-Cr-Mo system can be ameliorated by micro-alloying such as Cu addition.

Математическая модель кинетики движения переходной зоны при нагреве цилиндрического тела из трехкомпонентного сплава

If due to heating or cooling of an object, a phase transition occurs, the propagation of heat significantly changes. Behavior of the enthalpy, heat capacity, density, coefficient of the heat-conductivity as a function of temperature, changes in a complicated manner. For example, when a ternary eutectic alloy is cooling, one solid phase is formed first, then the second, and finally the entire alloy crystallizes. By heating the surface of the solid metal cylindrical object with three-component composition above the liquidus temperature, the two- or three-phase zone occurs at the surface, and moves to the cylinder axis. We propose a method of introducing “effective” specific heat that allows calculating the speed of this zone movement, as well as the temperature of the object at any point and at any time. The ordinary equation of heat conductivity with variable coefficients was used. For each point of a sample for each corresponding temperature, the fractions of liquid and all solid phases were calculated. Specific volume, thermal conductivity and specific enthalpy were calculated as the weighted average of the corresponding values for the liquid and solid states. The specific heat was calculated as the derivative of the enthalpy with respect to temperature. The resulting system of differential equations is reduced to finite-difference equations. A compu­ter program was developed to solve the resulting system of difference equations. Results of one of such calculations are given in the article. The developed method allows to calculate the velocity of the phase boundary, as well as the object temperature at any point and at any time. The presented method may be useful for metallurgists (calculation of heating of parts in heat treatment, calculation of heating of pieces of charge in the steel smelting furnace), for metrologists (self-testing temperature sensors) and others.

Extraction of reduced-order process-structure linkages from phase-field simulations

Phase-field simulations have achieved notable success in capturing characteristic details of microstructure evolution in directional solidification of ternary eutectic alloys. In spite of the impressive advances in high performance computations, phase-field simulations for most practical problems in materials design are resource intensive because of the need to incorporate multiple physical fields over large-scale three-dimensional domains. There is, therefore, a need to learn and capture the underlying materials knowledge embedded in the results produced by such expensive simulations, and facilitating an easy transferability to new problems of interest. This paper demonstrates the viability of extracting the salient process-structure linkages from phase-field simulations, while casting them in forms amenable for a rapid and efficient exploration of a relatively large process space. The presented framework is based on low dimensional representation of material structure obtained through principal component analysis (PCA) of 2-point spatial correlations.

Nano-eutectic structure formation and soft magnetic properties of bulk ternary Fe-B-M (M = Si, Cu) alloys

The bulk Fe-B-M (M = Si, Cu) ternary eutectic alloys with nano-lamellar structure and excellent soft magnetic properties were successfully prepared by undercooling combined with Cu-mold casting. Different effects of Si and Cu elements on the structural refinement and soft magnetic properties were studied. The results show that the lamellar spacing can be decreased to less than 50 nm with addition of Si or Cu of 1 at. % into the Fe-B eutectic alloy. Based on the classical random anisotropy model, a quantitative correlation between the intrinsic coercivity (HC) and the lamellar spacing (λ) was also obtained.

Effect of alumina nanoparticles on the microstructure and mechanical durability of meltspun lead-free solders based on tin alloys

As one of the key technologies for high performance electronic devices, composite solders have been recently developed to improve thermal and mechanical properties of solder joints. In this research, melt spinning was employed to fabricate a lead-free based nanocomposite solder for electronic application materials via introducing Ni-coated Al2O3 nanoparticles (0.1 wt%) into a Sn-Ag-Cu ternary eutectic alloy during rapid solidification. These surface-modified nanoparticles were synthesized by an in situ chemical reduction method. The effect of rapid solidification on the distribution of reinforcing nanoparticles, microstructural evolution, and solderability of the tin alloy were studied. Microstructural studies determined that rapid solidification refined brittle and elongated intermetallic compounds (IMCs) into small particles with an average diameter of a few hundred nanometers. The particles were uniformly dispersed into an amorphous/recrystallized fine-grained eutectic morphology of the solder matrix. It was also found that the addition of Ni-coated Al2O3 nanoparticles could effectively suppress the growth of IMC layers, which enhanced the reliability of solder joints. Effects of solid-state ageing phenomenon on the tensile and shear properties of the soldered joints were also evaluated. Higher strength and ductility was measured for joints prepared from the nanocomposite solder as compared with the unreinforced solder. A maximum enhancement of ∼20% in the shear strength was obtained.

Dependency of structure, mechanical and electrical properties on rotating magnetic field in the Bi–Sn–Ag ternary eutectic alloy

Abstract In the present study, cylindrical samples of the Bi – Sn – Ag ternary eutectic alloy were exposed to a rotating magnetic field (RMF) during upward solidification. The dependence of the eutectic spacing (λ), microhardness (HV), tensile stress (σ) and electrical resistivity (ρ) of the Bi – Sn – Ag eutectic alloy on the RMF-driven flow was investigated in this study. With the increase in the RMF, the eutectic grains are fragmented and gradually refined until a transition from coarser plate-like structure to a fine fibrous eutectic structure for the alloy. It was found that with the increasing of RMF, λ decreases but HV, σ and ρ increase. The enthalpy of fusion (ΔH) and specific heat (C p ) for the same alloy was determined by means of differential scanning calorimetry from the heating trace during the transformation from the eutectic liquid to eutectic solid. The results obtained in the present work were compared with published data available in the literature.

Quantification and classification of microstructures in ternary eutectic alloys using 2-point spatial correlations and principal component analyses

Eutectic solidification gives rise to a number of distinct microstructure patterns that might include lamella, rods and labyrinths in binary alloys. However, as the number of phases and components increases, the number of possible patterns that might be obtained during bulk solidification also become larger. While the morphological attributes of binary eutectic solidification have been fairly well understood, the same is not true for ternary and higher multicomponent alloys. In this paper, we study and quantify microstructures in ternary alloys as a function of two essential parameters, namely, the volume fraction of the solid phases and the surface energies of the interfaces (in particular the solid–liquid interfaces). For the selected ensemble of microstructures, quantification and classification were carried out using a recently developed data-driven (objective) approach based on principal component analyses of 2-point correlations. It is demonstrated that the method is capable of analyzing and quantifying the similarity/difference measures between the elements of the selected ensemble of microstructures.

Microstructures in a ternary eutectic alloy: devising metrics based on neighbourhood relationships

Ternary eutectics, where three phases form simultaneously from the melt, present an opportunity to study the fundamental science of microstructural pattern formation during the process of solidification. In this paper we investigate these phenomena, both experimentally and by phase-field simulations. The aim is to develop necessary characterisation tools which can be applied to both experimentally determined and simulated microstructures for a quantitative comparison between simulations and experiments. In SEM images of experimental cross sections of directionally solidified Ag-Al-Cu ternary eutectic alloy at least six different types of microstructures are observed. Corresponding 3D phase-field simulations for different solidification conditions and compositions allow us to span and isolate the material parameters which influence the formation of three-phase patterns.Both experimental and simulated microstructures were analysed regarding interface lengths, triple points and number of neighbours. As a result of this integrated experimental and computational effort we conclude that neighbourhood relationships as described herein, turn out to be an appropriate basis to characterise order in patterns.

Large-scale phase-field simulations of ternary eutectic microstructure evolution

The microstructure evolution of ternary eutectic alloys is subject of current research for multicomponent alloys, due to the large variety of patterns and their widely adjustable properties. In experiments, contact zones between the different aligned patterns are commonly observed. However, their formation and influence on the microstructure evolution was not yet investigated. To study 3D patterns and the integrated contact zones, large-scale phase-field simulations of an idealized system are conducted, enabling the quantification of the rod shapes. First, the lamellar spacing with the minimum undercooling λJH from the Jackson–Hunt approach is numerically determined. Then, the domain size and initial filling are systematically varied, to analyze the influence of these two quantities on the pattern formation and to determine the required computational domain size for statistical volume elements (SVE). The statistical measures indicate a minimum size of 400×400 voxel cells, equivalent to 4.3λJH×4.3λJH, parallel to the solidification front and the necessity of large scale simulations to resolve SVEs. Different stable patterns, beside the hexagonal structures, are found, depending on the domain size, the initial filling and the undercooling of these patterns. In large-scale simulations, the formation and evolution of contact zones is observed, which are reported from experiments.

Influência na microestrutura e na microdureza decorrente da adição de 4%Ag na liga Al-4%Cu solidificada unidirecionalmente

RESUMO Diversas aplicações industriais, tais como nos setores automotivo e aeronáutico, que necessitam de resistência e tenacidade, utilizam ligas do sistema Al-Cu. As ligas do sistema ternário Al-Cu-Ag são empregadas como modelo para o estudo de ligas eutéticas ternárias, além do uso em certo número de aplicações técnicas. Estudos relacionados aos efeitos da adição de Ag em ligas do sistema Al-Cu solidificadas em regime transitório, sob aspectos microestruturais e de microdureza, não são encontrados na literatura. Nesse sentido, o objetivo principal deste trabalho consiste na investigação dos efeitos da adição de 4%Ag na liga Al-4%Cu solidificada unidirecionalmente no sentido vertical ascendente em regime transitório, abordando análises de microestrutura, microdureza e parâmetros de solidificação dados pela velocidade de crescimento (VL) e pela taxa de resfriamento (Ṫ). São apresentadas leis experimentais para as ligas Al-4%Cu e Al-4%Cu-4%Ag que correlacionam os espaçamentos dendríticos primário (λ1) e secundário (λ2) com VL e Ṫ. Foram realizadas análises de Difração de Raios-X (DRX) para a caraterização das fases cristalinas dos compostos presentes na microestrutura das ligas. O difratograma da liga binária mostrou a presença dos intermetálicos θ-Al2Cu, Al-Cu, Al4Cu9 e Al6Fe e, para o caso da liga ternária, adicionalmente foi detectado o intermetálico µ-Ag3Al. Composições químicas de regiões do contorno da dendrita, assim como de seu interior, foram obtidas com o auxílio de um microscópio eletrônico de varredura (MEV) acoplado a um sistema de análise por energia dispersiva (EDS). Diversas posições ao longo do lingote foram analisadas através da técnica de Fluorescência de Raios-X (FRX) com objetivo de se detectar a existência de macrossegregação. Constatou-se que a microdureza não é influenciada pelas duas formas de espaçamentos da matriz rica em Al. Os intermetálicos ρ-Ag2Al e µ-Ag3Al são responsáveis pelo aumento de dureza devido a sua interação com o espaçamento dendrítico terciário e outros intermetálicos.

Solidification paths in the iron-rich part of the Fe–Ti–B ternary system

Iron-rich alloys in the Fe–Ti–B system are being studied for their potential as a new generation of lightened steel-matrix composites reinforced by titanium diborides. In this work, the iron-rich corner of the Fe–Ti–B ternary system was investigated at temperatures between 1150 °C and 1400 °C. For this purpose, fourteen key alloys containing up to 5 mass % Ti and B were selected on the basis of preliminary thermodynamic calculations and processed in an induction furnace by melting the starting materials at 1630 °C for 1 h. Two types of experiments were performed: (i) long-duration annealing experiments, involving a liquid phase, performed by the electromagnetic phase separation technique at temperatures between 1175 °C and 1250 °C and (ii) differential thermal analysis of samples during heating up to 1400 °C and cooling with different cooling and heating rates (2, 5 and 10 °C min−1).Samples were characterized by X-ray diffraction, scanning electron microscopy, field electron gun scanning electron microscopy and complementary chemical analysis, combining electron microprobe analysis, inductively coupled plasma and secondary ion mass spectrometry, were performed. On the basis of an analysis of the solidification paths of the fourteen alloys as well as solid/liquid equilibria investigations, a partial liquidus projection in the investigated region was proposed. Moreover, the composition and melting temperature of the γFe–TiB2–Fe2B ternary eutectic alloy are determined with good accuracy. This study is a first step towards an extended experimental work on the iron-rich corner of the Fe–Ti–B ternary system.

Characterization of a Directionally Solidified Sn–Pb–Sb Ternary Eutectic Alloy

A Sn–40.5wt%Pb–2.6wt%Sb ternary eutectic alloy was prepared using a vacuum melting furnace and a casting furnace. The samples were directionally solidified at a constant growth rate (V = 16.5 μm/s) under different temperature gradients (G = 1.05–3.88 K/mm) and at a constant temperature gradient (G = 3.88 K/mm) under different growth rates (V = 8.3–498 μm/s). The effects of G and V on lamellar spacing (λ), microhardness (HV), and ultimate tensile strength (σ) were determined. The lamellar spacing and microhardness were measured from both longitudinal and transverse sections of the sample. The relationships between solidification parameters (G, V), microstructure parameters (λL, λT), and mechanical properties (HV, σ) were determined from linear regression analysis. It was found that the microhardness and tensile strength increase with increasing G and V as well as with decreasing λ.

Effect of rotating magnetic field on the microstructures and physical properties of Al–Cu–Co ternary eutectic alloy

The solidification microstructures and physical properties of Al–Cu–Co ternary eutectic alloy were studied in a rotating magnetic field (RMF). The RMF-driven flow was the key factor causing grain refinement and uniformity of solidification microstructures. The temperature distributions during solidification were recorded under the conditions with and without RMF. The dependence of the eutectic spacing (λ), the microhardness (HV), tensile strength (σt) and compressive strength (σc) on the RMF were investigated. Electrical resistivity (ρ) measurements of the studied alloy were also performed by using the four-point probe method and the dependence of the resistivity on temperature and RMF were determined. Besides, the enthalpy (ΔH) and the specific heat (Cp) values were determined by the differential scanning calorimeter (DSC) analysis. Important changes were found in the microstructure, microhardness, tensile strength, compressive strength and electrical resistivity of the studied alloy with increasing RMF.

Mg-Zn-Al Eutectic Alloys as Phase Change Material for Latent Heat Thermal Energy Storage

Abstract The aim of this study is to investigate high thermal conductivematerials such as metallic alloys for latent heat energy storage in CSP applications. For this purposes, two ternary eutectic alloys,Mg 70 Zn 24.9 Al 5.1 and Zn 85.8 Al 8.2 Mg 6 , have beeninvestigated. The structural and thermophysical characterizations have permitted to obtain their relevant properties needed for the designof thermal energy storage systemssuch as latent heat, melting/solidification temperatures, thermal conductivity andspecific heat. Also, the thermal stability study has been accomplished in order to analyze the thermal performance of these materials after 700 cycles. Finally, the chemical compatibility tests between the Mg 70 Zn 24.9 Al 5.1 alloy and the 304, 304L, 316 and 316L stainless steels have been performed. The results have confirmed the high potential of the investigated alloys for thermal energy storage application.

A method for coupling the phase-field model based on a grand-potential formalism to thermodynamic databases

In this paper we derive an approach for the effective utilization of thermodynamic data in phase-field simulations. While the most widely used methodology for multi-component alloys is following the work by Eiken et al. (2006), wherein, an extrapolative scheme is utilized in conjunction with the TQ interface for deriving the driving force for phase transformation, a corresponding simplistic method based on the formulation of a parabolic free-energy model incorporating all the thermodynamics has been laid out for binary alloys in the work by Folch and Plapp (2005). In the following, we extend this latter approach for multi-component alloys in the framework of the grand-potential formalism. The coupling is applied for the case of the binary eutectic solidification in the Cr–Ni alloy and two-phase solidification in the ternary eutectic alloy (Al–Cr–Ni). A thermodynamic justification entails the basis of the formulation and places it in context of the bigger picture of Integrated Computational Materials Engineering.