Primary Solidification Phase Research Articles

Liquidus projection and isothermal section at 650 °C of ternary Co–Sb–Ga system

Co–Sb–Ga ternary system is of interests for thermoelectric applications. Alloys quenched from completely molten state with compositions of the entire Co–Sb–Ga regime and alloys equilibrated at 650°C with compositions in the CoSb3–CoGa–Ga–Sb regime were prepared and analyzed. The liquidus projection and isothermal section at 650°C of ternary Co–Sb–Ga system were determined based on these experimental results and the phase diagrams of its three constituent binary systems. The liquidus projection has 10 primary solidification phase regions. They are Co, CoSb, CoSb2, CoSb3, Sb, GaSb, Ga, CoGa3, CoGa and a ternary compound, Co3Sb2Ga4, which is newly found. There are three class I and six class II invariant reactions involving with liquid phase. Except for the L↔Co+CoSb+CoGa, L+CoGa↔Co3Sb2Ga4+GaSb reaction, the reaction temperatures are determined using DTA. In the CoSb3–CoGa–Ga–Sb region, there are 5 tie-triangles, which are CoSb3+Liquid+GaSb, Co3Sb2Ga4+CoSb3+GaSb, CoGa+Co3Sb2Ga4+GaSb, CoGa+GaSb+CoGa3, and CoGa3+GaSb+Liquid. The ternary solubilities in most of the binary compounds are not significant, and the highest is 3.5at.% Sb in the CoGa.

Liquidus Projection and Isothermal Section of the Ag-In-Zn Ternary System

This study experimentally determines the liquidus projection and phase equilibria isothermal section at 773.2 K (500°C) of the Ag-In-Zn ternary system. There are ten primary solidification phases of the Ag-In-Zn ternary system. In addition to the (Ag) (In) and (Zn) phases, there are seven binary compounds: β-(Ag3In), ζ-(Ag3In), γ-(Ag9In4), AgIn2, β-(AgZn), γ-(Ag5Zn8), and e-(AgZn3). No ternary compounds were found. Among all these phases, the γ-(Ag9In4) primary solidification phase has the largest compositional regime. Five invariant reactions, two Class I reactions, two Class II reactions, and one Class III reaction, are determined by thermal analysis in this study. The reactions with the lowest and highest reaction temperatures are Liquid = (In) + AgIn2 + γ-(Ag5Zn8) at 413.5 K (140.3°C) and Liquid + (Ag) + β-(AgZn) = ζ-(Ag3In) at 964.9 K (691.7°C), respectively. In the isothermal section at 773.2 K, there are six tie-triangles: (Ag) + ζ-(Ag3In) + β-(AgZn), ζ-(Ag3In) + γ-(Ag9In4) + β-(AgZn), ζ-(Ag3In) + γ-(Ag9In4) + Liquid, γ-(Ag9In4) + β-(AgZn) + Liquid, β-(AgZn) + γ -(Ag5Zn8) + Liquid, and γ-(Ag5Zn8) + e-(AgZn3) + Liquid.

Optimal Ag addition for the elimination of voids in Ni/SnAg/Ni micro joints for 3D IC applications

In micro joints, in which the height of solder is smaller than 10μm, the reaction between Sn and Ni is known to produce microvoids. Although it was recently shown that the addition of Ag can inhibit the formation of such microvoids, the optimal concentration of Ag has not yet been established. This study systematically investigates the effects of Ag concentration in the range of 0–8wt.%, with the objective of identifying the optimal Ag addition. It is found that the optimal weight percentage of Ag is between 2.4 and 3.5wt.%; when it is lower than 2.4wt.%, not all of the microvoids are eliminated, while when it is substantially higher than 3.5wt.%, Ag3Sn becomes the primary solidification phase and large Ag3Sn plates form. Furthermore, the addition of Ag is found to have no effect on the growth kinetics of Ni3Sn4.

Thermodynamic properties and microstructure evolution of ternary Al–10%Cu–x%Sn immiscible alloys

The vertical phase diagram of ternary Al–10%Cu–x%Sn (x% from 3 to 75wt.%) alloys is experimentally established with differential scanning calorimetry (DSC) method. The enthalpy of fusion during melting process is determined, which decreases linearly with the increase of Sn content. The undercoolability of those liquid alloys solidifying with the primary (Al) solid solution phase can be further enhanced by increasing the cooling rate. However, the increase of cooling rate has little influence on the other alloys with the preferential liquid phase separation. As Sn content rises, three kinds of liquid separation patterns are observed, which are the dispersed pattern of very fine L2(Sn) droplets distributed within primary (Al) interdendritic areas, the segregated pattern of several large L2 blocks enveloped by the Al-rich phase and the layered pattern consisting of top Al-rich zone and bottom Sn-rich zone.

SPE–UPLC–UV Method for the Determination of Toltrazuril and its Two Metabolite Residues in Chicken and Porcine Tissues

Ultra high performance liquid chromatography with UV detection was developed and validated for the simultaneous determination of residues of toltrazuril and its two metabolites, namely, toltrazuril sulphone and toltrazuril sulphoxide, in edible tissues (chicken and porcine muscle, liver and kidney). Acetonitrile was used to extract analytes from tissues, which were then cleaned using primary secondary amine and Oasis™ MAX solid phase extraction cartridges. Chromatographic separation was performed on a C18 column with gradient elution. The analytes were determined using a UV detector. The regression coefficients of matrix-matched calibration curves showed linearity of >0.99. Calibration ranged from 25 to 1,000 μg kg−1 for toltrazuril and toltrazuril sulphone, and 37.5–1,500 μg kg−1 for toltrazuril sulphoxide. The accuracy was between 80 and 110 %, and the inter and intraday RSDs were lower than 15.2 and 18.3 %, respectively. The limits of detection for toltrazuril, toltrazuril sulphone and toltrazuril sulphoxide were between 10 and 37.5 μg kg−1 in all the tissues. The developed method was successfully applied to detect toltrazuril, toltrazuril sulphone and toltrazuril sulphoxide in tissues of medicated chicken.

Non-destructive high-resolution X-ray micro computed tomography for quantifying dry water particles

Dry water, a powder containing up to 98%wt. water and 2–6%wt. hydrophobic nanoparticles, is a novel material for novel applications like CO2 capture, transportation and storage in the form of clathrate hydrates. In this study, novel high-resolution X-ray micro computed tomography (HRXMT) was used as an in situ, non-destructive tool to visually and quantitatively examine the inner structure of dry water that has not been accessible previously. Specifically, the HRXMT was used to study the effect of silica/water wt. ratio on the number, surface area and volume distributions of dry water. The results showed that dry water was stable under ambient condition for long time. The technique was also successful in characterizing the structure changes in dry water after exposing to low temperature, high pressure and stirring. Low temperature did not affect the structure significantly, while high pressure and slow stirring broke the structure fairly readily with separation of dry water into the primary solid and liquid phases. These findings are useful to our understanding of the role of dry water in promoting the formation of CO2 and gas hydrates.

Isothermal solidification in peritectic systems

The peritectic reaction consists in the growth of the peritectic solid phase along the metastable interface between the primary solid phase and the liquid phase. We study theoretically the two-dimensional isothermal peritectic reaction in the limit of small undercoolings using the boundary-integral technique. First, we focus on the case where the liquid phase occupies a semi-infinite space and the peritectic phase presents a finger-like shape. Secondly, we investigate the case where the growth takes place in a channel of liquid phase and the peritectic phase fills the whole channel as a product of the transformation. It is found that for a critical channel width, the velocities of the channel filling and the finger-like solutions are equal. For smaller (larger) widths, the channel filling (finger-like) solution has a larger velocity and is likely to be predominant. This confirms some previously reported qualitative results of time-dependent phase-field calculations (Boussinot et al., 2010) [5]. We also discuss the relevance of our study to directional solidification experiments.

Pore-scale study of diffusion–reaction processes involving dissolution and precipitation using the lattice Boltzmann method

A pore-scale model combining the lattice Boltzmann method (LBM) and a fluid–solid interface tracking method is employed to simulate the diffusion–reaction processes involving dissolution and precipitation. Coupled sub-processes including mass transport, chemical reactions, and solid structure evolution are considered. Effects of the precipitation of the secondary solid phase on the dissolution of the primary solid phase are investigated under different dissolution–precipitation reaction kinetics, molar volumes of the primary and secondary solid phases, powder size, surface roughness, and nucleation and crystal growth mechanisms. Different morphologies of the precipitates are predicted by the pore-scale simulations. It is found that the precipitation has opposite effects on the underlying dissolution processes. The favorable effect is that the precipitation reaction consumes the product of the dissolution reaction, thus facilitating the dissolution; while the adverse effect is that the generated precipitates cover the surface of the primary solid phase, thus separating the reactive surface from the reactive components. Based on the extent to which the precipitates affect the dissolution, four types of coupled dissolution–precipitation processes are identified and discussed.

Liquidus Projection of the Ag-Sn-Te Ternary System

The Ag-Sn-Te ternary system is of interest to thermoelectric applications and its liquidus projection is determined in this study. Forty Ag-Sn-Te ternary alloys are prepared and their primary solidification phases are determined. These different primary solidification phase regions include three terminal solid solutions: Ag, Sn, and Te; six binary intermediate phases: SnTe, β-Ag5Te3, Ag1.9Te, Ag2Te (assuming no phase transformation), ζ-Ag4Sn, and e-Ag3Sn; and one ternary compound, AgSnTe2. These data, together with the phase diagrams of the three constituent binary systems, are employed to construct the univariant lines of the liquidus projection. The temperature-descending directions of these univariant lines are determined using thermal analysis results and mass balance concept. The types of invariant reactions and the reaction temperatures are determined from the temperature-descending directions of the univariant lines and by thermal analysis. There are two Class I reactions, five Class II reactions, and one Class III reaction. The invariant reaction with the highest reaction temperature is L + Ag = Ag2Te + e-Ag3Sn, at 992.7 ± 4 K (719.5 ± 4 °C), and that with the lowest reaction temperature is L = Sn + e-Ag3Sn + SnTe, at 494.2 ± 4 K (221 ± 2 °C).

Microstructure and Tensile Properties of As-Cast Mg-5Sn-4Cu Alloy

The microstructure and tensile properties of permanent-mould cast Mg-5wt%Sn-4wt%Cu alloy was investigated by transmission electron microscopy (TEM), scanning electron microscopy (SEM) and tensile test in this paper. The result indicated that the microstructures of the as-cast samples consist of 30-40 μm size primary solidification phase, primary dendrite Mg2(Cu,Sn) which is a network-like interdendritic eutectic intermetallic compounds along grain boundaries and particle like Mg2(Sn,Cu) phases. The Mg-5Sn-4Cu alloy exhibit maximum ultimate tensile strength and yield strength, and the values are 142 MPa and 91 MPa at room temperature. This improved mechanical property is mainly ascribed to the formation of network-like secondary phases of primary dendrite Mg2(Cu,Sn).

Liquidus Projections of Sn-Co-Ni and Sn-Rich Sn-Ag-Co-Ni Systems

Alloys based on Sn and Sn-Ag are commonly used as Pb-free solders, and Ni is frequently used in barrier layers. Co has been studied as a possible alloying element in both solders and barrier layers. Thus, the Sn-Co-Ni and Sn-Ag-Co-Ni alloy systems are important for electronic soldering. Forty-nine Sn-Co-Ni alloys and 24 Sn-rich Sn-Ag-Co-Ni alloys were prepared. The primary solidification phases of these as-cast alloys were determined, and based on these results and the available phase diagrams of the constituent systems, the liquidus projections of Sn-Co-Ni ternary and Sn-Ag-Co-Ni quaternary systems at 90 at.% and 95 at.% Sn were determined. In the Sn-Co-Ni system, no ternary compound was found; (Ni,Co)3Sn2 and (Ni,Co) are continuous solid solutions, and there are eight kinds of primary solidification phases: Sn, CoSn3, CoSn2, CoSn, (Ni,Co)3Sn2, (Ni,Co), Ni3Sn, and Ni3Sn4. In the 90 at.% and 95 at.% Sn isoplethal sections of the Sn-Ag-Co-Ni liquidus projection, the primary solidification phases are CoSn2, CoSn, Ni3Sn4, and Ag3Sn.

Evolution of primary α-Al particles during isothermal transformation of rheocast semi solid metal billets of A356 Al–Si alloy

Semi solid metal (SSM) processing is a relatively new technology for metal forming, different from the conventional metal shaping technologies that use either solid or liquid metals as the starting material. Semi solid metal processing deals with semi solid slurries, in which non-dendritic solid particles are dispersed in a liquid matrix. The solid volume fraction could vary between 0·1–0·5 with apparent viscosity close to that of liquid state. The slurry flows easily under pressure and makes complicated shapes with high degree of die filling and integrity. There are different ways to prepare SSM slurries including the application of direct or indirect mechanical stirring, chemical treatments of the melt, and manipulation of pouring temperature.One of the important parameters controlling the mechanical and flow characteristics of SSM billets is the morphology of the primary solid phase, e.g. α-Al for Al–Si alloys. The morphological evolution of primary α-Al particles of SSM processed A356 Al–Si billets is studied with variant soaking times, 0–480 s, at 595°C, i.e. 0·33 fraction solid before the applied compression force. The effect of applied compression force of 33 kgf on the evolution of dendritic morphology was also investigated at the same temperature and within the same holding time range. The microstructure was characterised quantitatively and showed that spheroidisation and coarsening are active during the course of treatment with the application of compressive forces bringing about further refinement.Le traitement de métal à l’état semi-solide (SSM) est une technologie relativement nouvelle de formage des métaux, différente des technologies conventionnelles de façonnage des métaux qui utilisent des métaux soit à l’état solide ou liquide comme matériel de départ. Le traitement SSM traite des coulis à l’état semi-solide, dans lesquels des particules solides non-dendritiques sont dispersées dans une matrice liquide. La fraction volumique du solide peut varier entre 0·1 et 0·5, avec une viscosité apparente proche de celle de l’état liquide. Le coulis s’écoule facilement sous pression en des formes compliquées avec un haut degré de remplissage du moule et d’intégrité. Il existe différentes façons de préparer les coulis de SSM, incluant l’application d’agitation mécanique directe ou indirecte, les traitements chimiques du bain et la manipulation de la température de coulage.L’un des paramètres importants contrôlant les caractéristiques mécaniques et d’écoulement des billettes de SSM est la morphologie de la phase solide primaire, par exemple Al-α dans les alliages d’Al–Si. On a étudié l’évolution morphologique des particules primaires d’Al-α de billettes traitées en SSM d’Al–Si A356, avec des temps d’incubation variant de 0 à 480 s, à 595°C – c’est-à-dire fraction solide de 0·33 avant la force appliquée en compression. On a également examiné l’effet de la force de compression appliquée de 33 kgf sur l’évolution de la morphologie dendritique, à la même température et dans la même gamme de temps de rétention. On a caractérisé quantitativement la microstructure et l’on montre que la sphéroïdisation et le grossissement sont actifs tout au long du traitement, l’application de forces compressives amenant davantage d’affinement.

Liquid phase separation, solidification and phase transformations of Gd–Ti and Gd–Ti–Al–Cu alloys

Abstract Phase equilibria of the quaternary Gd–Ti–Al–Cu system have been studied with particular respect to solidification and phase separation phenomena in metallic glasses. Along the section Gd 55− x Ti x Al 25 Cu 20 the primary solidifying phase changes from Gd 2 CuAl ( x =0) toward α-Ti ( x ≥10) with rising Ti-fraction x . This is accompanied by an upturn of the liquidus temperature from T L =745 °C to T L >1100 °C. The miscibility gap predicted from thermodynamic calculations for Gd 55− x Ti x Al 25 Cu 20 melts at intermediate Ti-fractions was not verified experimentally. Unlike binary Gd–Ti melts, levitated Gd–Ti–Al–Cu droplets do not exhibit liquid phase separation features after quenching from different holding temperatures, even at high melt undercooling up to 200 K prior to solidification.

Liquidus Projection of the Ternary Bi-Sb-Te Thermoelectric Material System

The ternary Bi-Sb-Te system is important for thermoelectric applications. Its liquidus projection is determined, except for the Bi-rich corner with various unconfirmed binary Bi-Te compounds. Fifty Bi-Sb-Te ternary alloys are prepared. Primary solidification phases are identified using metallographic observations and X-ray diffraction techniques. Phase transformation temperatures are determined using differential thermal analysis. No ternary compound is found. (Bi,Sb)2Te3 and (Bi,Sb) are continuous solid solutions. The Bi2Te3 and Sb2Te3 phases form a pseudo-binary section. Alloys of the primary solidification phases of Te, (Bi,Sb)2Te3, γ, δ, and (Bi,Sb) are determined and the boundaries of various primary solidification phases are delineated. The Bi-Sb-Te liquidus projection is also calculated with the CALPHAD method using preliminary thermodynamic models, and the calculated results are qualitatively in agreement with the experimental determinations.

The microstructure, liquidus projection and thermodynamic modeling of thermoelectric Ag–Pb–Te system

Ag–Pb–Te is an important system in thermoelectric applications. Various Ag–Pb–Te alloys are prepared and their microstructures are examined. The liquidus projection of ternary Ag–Pb–Te system is determined both by experimental investigations and Calphad calculations, and the results are in good agreement. There are eight primary solidification phases, Ag, γ-Ag2Te, β-Ag2Te, Ag1.9Te, Ag5Te3, Te, PbTe and Pb, including a miscibility gap extended from the Ag–Te side. A ternary-eutectic reaction, L = PbTe + Te + Ag5Te3, was determined with a liquid composition of Ag-4.3at%Pb-62.6at%Te at 337 °C. A nanoscale microstructure containing a dotted PbTe and a lamellar matrix of Ag5Te3 and Te phases results from the ternary eutectic reaction. The solidification paths of selective ternary Ag–Pb–Te alloys are calculated using the Scheil model with the optimized interaction parameters obtained in this study, and the results are consistent with the experimental observations.

High thermoelectric performance of GeTe–Ag8GeTe6 eutectic composites

The (GeTe)1−x(Ag8GeTe6)x composites with x=0.02, 0.05, 0.08 and 0.11 were prepared by melting, ball milling and spark plasma sintering techniques. The thermoelectric properties of the composites were investigated. The experimental results show that all samples are composites consisting of the primary solidification phase GeTe and eutectic microstructures with GeTe and Ag8GeTe6 phases. The composites are p-type semiconductors. As compared to the pure compound GeTe, the existence of Ag8GeTe6 compound in the GeTe phase enhances its electrical resistivity at low temperatures while reduces its electrical resistivity at high temperatures. Also, the Seebeck coefficient of the composite is slightly decreased due to the Ag8GeTe6 compound, but its thermal conductivities are reduced significantly. As a result, the figure of merit ZT for the materials can be enhanced. The maximum figure of merit ZT was obtained as 1.15 in the sample (GeTe)0.89(Ag8GeTe6)0.11 at 673K. This value is much higher than that for the pure GeTe, leading to a substantial improvement in the thermoelectric performance of the material.

Thermodynamic properties and microstructural characteristics of binary Ag-Sn alloys

The liquidus and solidus temperatures and enthalpy of fusion for Ag-Sn alloys are systematically measured within the whole composition range by differential scanning calorimetry (DSC). The measured enthalpy of fusion is related to Sn content by polynomial functions, which exhibit one maximum value at 52 wt%Sn and two minimum values around 21 wt%Sn and 96.5 wt%Sn, respectively. The liquidus slope, the solidification temperature interval, the solute partition coefficient and the entropy of fusion are calculated on the basis of the measured results. The undercoolability of those liquid Ag-Sn alloys solidifying with primary (Ag) solid solution phase is stronger than the other alloys with the preferential nucleation of ζ and ɛ intermetallic compounds. Morphological observations reveal that peritectic reactions can rarely be completed, and the peritectic microstructures are always composed of both primary and peritectic phases.

Directional Solidification and Liquidus Projection of the Sn-Co-Cu System

This study investigates the Sn-Co-Cu ternary system, which is of interest to the electronics industry. Ternary Sn-Co-Cu alloys were prepared, their as-solidified microstructures were examined, and their primary solidification phases were determined. The primary solidification phases observed were Cu, Co, Co3Sn2, CoSn, CoSn2, Cu6Sn5, Co3Sn2, γ, and β phases. Although there are ternary compounds reported in this ternary system, no ternary compound was found as the primary solidification phase. The directional solidification technique was applied when difficulties were encountered using the conventional quenching method to distinguish the primary solidification phases, such as Cu6Sn5, Cu3Sn, and γ phases. Of all the primary solidification phases, the Co3Sn2 and Co phases have the largest compositional regimes in which alloys display them as the primary solidification phases. There are four class II reactions and four class III reactions. The reactions with the highest and lowest reaction temperatures are both class III reactions, and are L + CoSn2 + Cu6Sn5 = CoSn3 at 621.5 K (348.3 °C) and L + Co3Sn2 + CoSn = Cu6Sn5 at 1157.8 K (884.6 °C), respectively.

Modeling of Two-Stage Solidification: Part I Model Development

Abstract The paper presents a new numerical model of solidification processes in hypoeutectic alloys. The model combines stochastic elements, such as e.g. random nucleation sites and orientation of dendritic grains, as well as deterministic methods e.g. to compute velocity of dendritic tips and eutectic grains. The model can be used to determine the temperature and the size of structure constituents (of both, the primary solid phase and eutectics) and the arrangement of individual dendritic and eutectic grains in the consecutive stages of solidification. Two eutectic transformation modes, typical to modified and unmodified hypoeutectic alloys, have been included in the model. To achieve this, cellular automata and Voronoi diagrams have been utilized.

Liquidus projection and phase equilibria isothermal section of Se–Sn–Te system

Ternary Se–Sn–Te alloys have important applications in thermoelectricity, optical recording and infrared devices. Air-cooled and 250°C-equilibrated ternary Se–Sn–Te alloys were prepared in this study. The primary solidification phases were determined for the air-cooled alloys and these were used to construct the liquidus projection. The liquidus projection contains seven primary phase regions and three ternary invariant reactions. The temperatures of the invariant reaction were determined by thermal analysis as occurring at 230°C, 400°C and 420°C, respectively. Using the equilibrium phases of the thermally equilibrated ternary alloys determined in this study and the phase diagram information of the three binary constituent systems, the 250°C isothermal section of the Se–Sn–Te ternary system was constructed. The equilibrated solubility of Se in SnTe is about 4at%Se and is less than that of Te in SnSe, which is about 10at%Te. No ternary compound was found in either the liquidus projection or the isothermal section.