Liquidus Point Research Articles

The lithium oxide solubility in molten fluoride system CeF3 - FLiNaK

Molten systems based on alkali metal halides with lithium oxide additives are promising as a working medium on pyrochemical reprocessing of nuclear waste. A mixture of alkali metal fluorides of eutectic composition (FLiNaK) is a suggesting solvent due to the high solubility of actinide oxides, low viscosity, high boiling points, low vapor pressure, and resistance to radiation damage. Thermal analysis, XRD, Raman spectroscopy and thermodynamic simulations were used to obtain evidences on the phase equilibria and liquidus points of the system (0.85 FLiNaK - 0.15 CeF3) - Li2O, containing up to 8.8 mol % lithium oxide. The solubility of lithium oxide in the fluoride melt FLiNaK - CeF3 and the thermodynamic parameters of dissolution were obtained. The eutectic point (the Li2O content is 3.1 mol %, Tm = 489??) and two peritectic points (lithium oxide content are 3.2 and 4.2 mol %, and liquidus points are 497 and 549??, respectively) were found. Thermodynamic simulation results show an exothermic effect due to interaction between lithium oxide and fluoride melt. The interaction product oxyfluoride CeOF was detected by XRD analysis and Raman spectroscopy.

Certain investigation on feasibility of developing riser less ductile iron castings

The solidification mechanism of ductile iron is a bit complex due to the precipitation of graphite and silicon. These elements change the solidification pattern of cast iron. Density of these elements is less than iron leads to occupying more volume consequently increase the overall metal volume. There are two aspects on this increase in metal volume. One is, reducing this volume increase to reduce the creation of porosities at the earlier stage of solidification and second is, using this volume increase to remove porosity at the later stage of solidification. Proper understanding of this graphite expansion in cast iron solidification will bring insights on reducing or removing of the risers. The current study focus on correlating the net contraction and austenitic liquidus point with shrinkage. The average contraction found through this study is 1.36 % which is more than the net expansion of 0.25 % (without riser) reported in literature. The study found that properly balancing graphite precipitation, pouring temperature and mold strength can enable riserless casting of ductile iron by compensating for liquid contraction through graphite expansion.

Parametric analysis of a PCM-based heat sink for electronic device thermal management

Integrating conventional Heat Sinks with Phase Change Materials (HS-PCM) is a novel strategy for the thermal management of electronic devices. Although various studies attempted to investigate the impact of PCM on the operating temperature of electronic devices, the influence of PCM properties on the performance of the HS-PCM system remained unknown. Therefore, in the present study, an accurate three-dimensional HS-PCM system is designed and simulated to evaluate the effect of PCM properties, including thermal conductivity, enthalpy, specific heat capacity, and liquidus temperature, on the operating temperature of this system. In this order, the HS-PCM system is simulated at multiple operating conditions during both the working and cooling phases. Notably, an experimental setup is fabricated to compare the numerical outputs against the experimental data. Additionally, the Support Vector Regression with Hybrid (HSVR) kernels is used to predict the performance of the HS-PCM system. The hyperparameters of this machine learning model are optimized by implementing Grey Wolf Optimizer (GWO). It is found that raising the liquidus temperature of the PCM can have a minor impact on the working duration of the chipset while it dramatically impacts the cooling process of the system. Also, increasing the enthalpy and heat capacity of the PCM has a favorable effect on the working time of the chipset but extends the cooling process. Thermal conductivity is the only parameter which its enhancement has a positive impact on both the working and cooling duration of the chipset. Raising the thermal conductivity of the PCM from 0.05 W/(m·K) to 0.8 W/(m·K) improves the working duration of the chipset from 22 min to 24 min. Based on the outcomes, the most effective factor on the working time of the chipset is the enthalpy, followed by heat capacity, thermal conductivity, and the liquidus point of the PCM. According to the findings, the GWO-HSVR model can accurately forecast the outcomes of the HS-PCM system at the both working and cooling phases. In the testing process of the model, the values of R2 for the working and cooling phases are calculated to be 0.99174 and 0.99775, respectively.

Coexistence of Intermetallic Complexions and Bulk Particles in Grain Boundaries in the ZEK100 Alloy

Magnesium-based alloys are highly sought after in the industry due to their lightweight and reliable strength. However, the hexagonal crystal structure of magnesium results in the mechanical properties’ anisotropy. This anisotropy is effectively addressed by alloying magnesium with elements like zirconium, zinc, and rare earth metals (REM). The addition of these elements promotes rapid seed formation, yielding small grains with a uniform orientation distribution, thereby reducing anisotropy. Despite these benefits, the formation of intermetallic phases (IP) containing Zn, Zr, and REM within the microstructure can be a concern. Some of these IP phases can be exceedingly hard and brittle, thus weakening the material by providing easy pathways for crack propagation along grain boundaries (GBs). This issue becomes particularly significant if intermetallic phases form continuous layers along the entire GB between two neighboring GB triple junctions, a phenomenon known as complete GB wetting. To mitigate the risks associated with complete GB wetting and prevent the weakening of the alloy’s structure, understanding the potential occurrence of a GB wetting phase transition and how to control continuous GB layers of IP phases becomes crucial. In the investigation of a commercial magnesium alloy, ZEK100, the GB wetting phase transition (i.e., between complete and partial GB wetting) was successfully studied and confirmed. Notably, complete GB wetting was observed at temperatures near the liquidus point of the alloy. However, at lower temperatures, a coexistence of a nano-scaled precipitate film and bulk particles with nonzero contact angles within the same GB was observed. This insight into the wetting transition characteristics holds potential to expand the range of applications for the present alloy in the industry. By understanding and controlling GB wetting phenomena, the alloy’s mechanical properties and structural integrity can be enhanced, paving the way for its wider utilization in various industrial applications.

Исследование формы ванны расплава при лазерном воздействии на сталь AISI 316L с учетом конвекции Марангони

The paper considers the two-phase physical and mathematical model of the AISI 316L stainless steel melting and its numerical implementation by the finite volume method in the ANSYS CFX software based on the well-known concepts of simulating the thermocapillary convection. Approximation functions are proposed to take into account the effective specific heat and dynamic viscosity in the transition process from a solid to the liquid state to minimize the numerical error in the vicinity of the liquidus and solidus temperature points. The molten pool formation process was considered under the action of laser radiation with the Gaussian intensity profile taking into account boundary conditions of the Marangoni convection, convective heat transfer and radiative heat transfer. Influence of the thermocapillary convection on the shape of the molten pool wetted surface is shown. An approach is proposed to control flows on the free surface of the molten pool by changing the laser intensity profile.

Partial pressure of Cd in equilibrium with stochiometric melt and solid of (Cd0.8Zn0.2)Te between 300 °C and 1250 °C for melt growth

The partial pressures over Cd0.8Zn0.2Te solid and melt were measured by the optical absorption technique on five optical cells loaded with four homogenized samples and one with as-grown crystal. From the measured partials pressures, the three-phase loops with five solidus and four liquidus points were established together with the Cd partial pressure over the melts. A series of crystal growth experiments by directional solidification of Cd0.8Zn0.2Te with controlled Cd overpressure, provided by Cd reservoir temperatures from 750 to 935 °C, were conducted. From the Te precipitates content observed by the IR micrographs, the correlation between the Cd reservoir temperature and the Cd0.8Zn0.2Te melt temperature, which resulted in the lowest precipitate density, was established. From the calculated masses of the elements in the vapor phase, the compositions of the condensed phases for each set of partial pressure data were derived. The correlation between the temperature of the Cd reservoir and the temperature of a stoichiometric Cd0.8Zn0.2Te sample, such that the equilibrium Cd overpressure is coexisted, have been established for the Cd0.8Zn0.2Te melt and the solid between 300 and 1250 °C. Using this information, the temperatures of the Cd reservoir and the Cd0.8Zn0.2Te sample can be programed during the melt growth to process intrinsic/stochiometric crystals. Additionally, the correlation on the equilibrium Cd overpressure environment for the Cd0.8Zn0.2Te solid can also be employed for the heat treatment of post-growth annealing to adjust the composition of the grown crystals toward stoichiometry.

Characterization, propagation, and sensitivity analysis of uncertainties in the directed energy deposition process using a deep learning-based surrogate model

Uncertainties raised from process parameters, material properties, and environmental conditions significantly impact the quality of the printed parts in the directed energy deposition (DED) process. In this study, we perform the characterization, propagation, and sensitivity analysis of the uncertainties in the DED process using deep learning (DL)-based surrogate model to investigate the influence of the uncertain input parameters on the quality of the final printed product. A DL-based surrogate model is first constructed using the offline data obtained from a finite element (FE) model, which was validated against experiments. Sources of uncertainties are characterized using the probabilistic method and are propagated using the Monte-Carlo (MC) simulation. Moreover, we perform the sensitivity analysis (SA) to determine the most influential sources of uncertainty and two potential use cases based on uncertainty quantification results Owing to the fast execution time of the surrogate model, the MC simulation is significantly efficient in terms of computational resources as compared to the simulation that is solely based on the FE model. It is shown that the investigated sources of uncertainty contribute substantially to the inconsistency of the final product quality as they induce variations in temperature field, cooling rate at the liquidus point, and melting pool sizes. These quantities are also strongly dependent on the clad height. Based on the SA results, the laser power, the scanning speed, the heat convection, and the thermal conductivity induce the most uncertainties to the melting pool sizes. Two potential use cases are assessed to further demonstrate the usefulness of UQ results (i.e., uncertainty reduction). In general, these findings provide valuable insights for the process parameter optimization of the DED under uncertainty to improve the quality of the final printed parts.

Density and surface tension of liquid ternary Ni–Cu–Fe alloys

Abstract Density and surface tension of liquid Ni –Cu –Fe alloys have been measured over a wide temperature range, including the undercooled regime. A non-contact technique was used, consisting of an electromagnetic levitator, an optical densitometer, and an oscillating drop tensiometer. At temperatures above and below the liquidus point, density and surface tension are linear functions of temperature. The concentration dependence of the density is significantly influenced by a third-order (ternary) parameter in the volume, while the surface tensions can be derived from the thermodynamic potentials E G of the binary phases alone.

Effect of melt superheating treatment on corrosion resistance of Al2CoCrCuFeNi high entropy alloy in 0.5 M HNO3 solution

Al2CoCrCuFeNi high-entropy alloy (HEA) was heated by vacuum arc furnace at different powers (5.26kW, 6.15 kW, 7.28 kW, 8.26 kW) to different temperatures above the liquidus point (labeled as T1, T2, T3 and T4). The structure and corrosion resistance were investigated by means of X-ray diffraction, scanning electron microscopy with spectroscopy (SEM/EDS), transmission electron microscopy (TEM), and electrochemical workstation. It was found that the HEAs with different superheating temperatures were all simple face-centered cubic (FCC) and body-centered cubic (BCC) solid solutions without complex phases. As the superheating temperature increased, the structure of HEAs became dense, the segregation decreased, and some fine-scale precipitations were formed at T4. When the heating temperature reached T3 or higher, the corrosion current density of the alloy decreased by more than 1/2, and the range of the passivation zone also became wider, indicating that the corrosion resistance was significantly improved. It was found that the pitting potential Eb ranked: T1<T2<T4<T3, indicating that the alloys labeled as T3 and T4 had better pitting resistance than those labeled as T1 and T2. The potential range of the stable passivation region △E ranked: T1<T2<T3<T4, which proved that the passivation film on the surface of HEA became more and more stable as the superheating temperature increased.

Comment on the paper “Physical characterization of Bis(2,2-dinitropropyl) acetal and Bis(2,2-dinitropropyl) formal” by Alexander Edgar, Justine Yang, Manuel Chavez, Michelle Yang & Dali Yang

ABSTRACT Errors are noted in the construction of the binary phase diagram in the paper “Physical characterization of Bis(2,2-dinitropropyl) acetal and Bis(2,2-dinitropropyl) formal” by Alexander Edgar, Justine Yang, Manuel Chavez, Michelle Yang & Dali Yang. The authors of that paper misinterpret differential scanning calorimetry (DSC) thermal features. All of the DSC data show features consistent with samples that are supercooled during testing. Such samples do not show solidus points and may not show liquidus points, rendering the constructed phase diagram invalid.

Interrelation of CCM (Steel Billet Continuous Casting Machine) Tube Steel Casting Parameters and Hot-Rolled Plate Quality

The quality of the hot-rolled plate up to 36 mm thick was estimated by the percentage of rolled products, sorted due to the presence of a surface defect "Non-metallic inclusions", and internal defects, detected by ultrasonic plate control. The analysis of the data on the total sorting of hot-rolled plates demonstrated that the amount of sorting differs significantly on the melting from which each series of tubular metal casting commenced, compared to all the other melting in the series. The sorting of the sheets rolled from the metal of the first in a series of melting proved to be 1.9 times higher than that of the metal of all other melts. The main reason (in 68% of cases) of sorting is the presence of non-metallic inclusions on the surface of the plates. The effect of sorting of hot-rolled plates on non-metallic inclusions of various parameters has been studied: the duration of the intermediate ladle-heating; the length of time from the end of the heating of the intermediate ladle, prior to the beginning of the casting; lining temperatures of the intermediate ladle before the beginning of casting; duration of filling the intermediate ladle; the filling rate of the intermediate ladle with metal; mass of metal in the intermediate ladle before the beginning of casting into the crystallizer; chemical composition of metal; overheating of the metal over the liquidus point at the beginning, middle and end of the casting. On the sorting of flat products for non-metallic inclusions, of all the parameters considered, a statistically significant effect is due only to the overheating of the metal above the liquidus point, which varies in the range from 19 to 35 ° C. In order to obtain an acceptable quality of both the surface of slabs and the surface of hot-rolled plates for non-metallic inclusions, the first in a series of melts recommends overheating of the metal in the intermediate ladle above the liquidus temperature of 30-35 ° C.

The onset of instabilities and finite amplitude waves in a model of aluminum reduction cells with nonuniform cathode current

In aluminum reduction cells, the electric current density at the cathode is seldom uniform. This may be due to a variety of reasons. One of the reasons is that a mass of undissolved alumina may get enrobed by the cryolitic bath, and this mix freezes due to the decrease in temperature below the liquidus point. Thus, an electrically resistive solid layer (“mud”) is formed at a part of the cathode. This leads to horizontal electric currents in the liquid aluminum layer, and their magnetohydrodynamic (MHD) interaction with the vertical magnetic field induces a rotating flow of aluminum. This may cause undesirable MHD instabilities. A quasi-two-dimensional model for the laboratory facility has been presented. The results show that the dominating feature of the flow is a depression of the free surface of the liquid metal above the mud spot. This is due to strong rotation of the liquid metal around the mud spot, which causes the centrifugal force. Other effects may include superimposed conventional MHD instability, which manifests itself in a rotating interface, modulated waves, reflection of the waves from the corners of the domain, sloshing, etc. It has been shown that small mud spots do not affect the cell stability, while the large ones may cause such deep depressions that the centrifugal force completely removes the liquid metal above the spot.

Структура и свойства листов из нового сплава В-1381 системы Al – Mg – Si

The results of the development of a new alloy of the Al – Mg – Si system of the 6xxx series, which received the V-1381 grade, are presented. The influence of the composition and modes of heat treatment on the mechanical and corrosion properties of sheets with a thickness of 1,0 and 3,0 mm, manufactured under the conditions of FSUE “VIAM”, was investigated. Average level of sheet properties: UTS = 410 MPa, YTS = 360 MPa, El = 11.5 %; fatigue crack growth (dl/dN) = 0,59 mm/kcycle at ΔK = 18,6 MPa·m1/2, intergranular corrosion ≤ 0,15 mm, exfoliation corrosion 4 points. It was found that the structure of the sheets is recrystallized, the main strengthening phase is the coherent matrix β’(Mg2Si)-phase evenly distributed in the volume of grains with a high density. There is also a heterogeneous origin of β′-phase on dislocations and dispersoids. At grain boundaries there are zones free from emissions with a width of 15 – 20 nm. Dispersoids of various morphologies are observed in the tested samples. Temperature and heat values of phase transformations in ingots and sheets are determined and established liquidus and solidus points. The sheet weldability was evaluated by automatic argon-arc welding and the critical rate of deformation of the weld metal during crystallization was determined, at which no cracks were formed in it. Laser welding mode has been developed to ensure optimal formation of geometric parameters of the weld.

A selective multiple fit method of the point of inflection for the large-area HTFP melting plateau curve

National Institute of Metrology (NIM) has set up a new large-area tungsten carbide–carbon (WC-C) high-temperature fixed-point (HTFP) blackbody system as the direct radiation source for measuring spectral irradiance. The point of inflection (POI) of the HTFP melting plateau curve was important to determine the liquidus point and applied as the reference point in temperature calibration. This paper presented a selective multiple fit method. The maximum discrepancy of different factors for the new method and traditional methods were 0.001 K and 0.633 K which led to 0.0003% and 0.20% spectral irradiance errors at 500 nm. In addition, when used to calculate POIs of WC-C and Re-C small-area HTFPs, the maximum deviation between the new method and the average value of traditional methods were −0.004 K and −0.03 K. This method was verified to be insensitive to the influencing factors and more effective for large-area HTFPs applications.

Thermophysical properties of the liquid eutectic K-Pb alloy

Using the laser flash method and the drop method, the thermal conductivity and the enthalpy increment of the eutectic K-Pb alloy (with a Pb content of 90.7 at.%) were measured in the temperature range from the liquidus point up to 1077–1175 K. The specific heat capacity and thermal diffusivity of the alloy were calculated. Approximation equations for the studied properties were obtained, and a table of reference data was developed. It was shown that the thermal conductivity of the liquid eutectic is less than that of pure lead and increases with temperature.

Thermal conductivity of Rb73Bi27 alloy in liquid state

Using the laser flash method the thermal conductivity of the Rb-Bi liquid alloy with a bismuth content of 27 at. % was measured in the temperature range from the liquidus point to 1173 K. Approximation equations for thermal conductivity and thermal diffusivity have been obtained, and a table of reference data has been developed. An analysis of the measurement results confirms the existing assumption of the presence of intermetallic complexes with a partially ionic nature of the interatomic interaction in Rb-Bi melts.

Realization of the triple point of carbon dioxide evaluated by the ITS–90

We performed a precise temperature measurement of the triple point of carbon dioxide (CO2), which is one of the secondary reference points of the International Temperature Scale of 1990 (ITS–90), using an adiabatic calorimeter with five capsule-type standard platinum resistance thermometers (SPRTs). Impurity analyses showed that the purity of the CO2 sample was 99.999 37%. A thermal treatment process before the realization of the triple point reduced the width of the melting curve of the triple point of CO2 and increased the linearity of the melting curves with respect to the inverse of the melting fraction F. We determined the triple-point temperature of CO2 at the liquidus point by extrapolating the six melting curves obtained after the thermal treatment process. The triple-point temperature of CO2 measured in this work is 216.590 90 K 0.36 mK (k = 1). This result indicates that the triple point of CO2 can potentially be used as a fixed point based on the ITS–90 to replace the triple point of mercury.

Investigation of the Ledge Structure in Aluminum Smelting Cells

In aluminum smelting cells, ledges freeze on to cell walls from the cryolitic bath when the temperature drops below the bath liquidus point. Modern cell design and control cause a suitable ledge profile to form and be maintained, in order to protect the cell walls from corrosive liquids (molten salts and Al metal) and ensure efficient current distribution and cell heat balance. During cell operation, a significant ledge, freezing and melting does occur following heat balance changes due to batch operations. The ledge formation mechanism has been studied at the laboratory scale in our previous work. It shows a linkage between the rate and directional nature of ledge growth and its structure as affected through a superheat change. An open ledge structure can dominate the laboratory ledge material growth or melt it out quickly when the superheat either decreases or increases, respectively. This paper begins the investigation of industrial ledge samples, in terms of structure and composition, primarily to identify whether the same ledge formation mechanism exists in industrial cells. In this study, as expected, the industrial ledge shows more complexity than the laboratory ledge; the open structure is different compared to the laboratory ledge due to the inclusion of carbon dust, a large thermal gradient across the ledge, and sufficient aging of the ledge in the cell. The comparison between the laboratory ledge and the industrial ledge has provided insight into the ledge growth mechanism in aluminum smelting cells.

Development of a Steel Temperature Prediction Model in a Steel Ladle and Tundish in a Casting and Rolling Complex

The paper presents a prediction model for steel temperature in a specified time interval during its overheating over a liquidus point in the tundish of a continuous casting machine (CCM). This depends on the last temperature measurement in a ladle prior to casting with consideration to the ladle’s history and treatment during secondary metallurgical processes in an casting and rolling complex (CRC). The prediction of steel superheat temperature at CRC is based on two modeling stages: the first stage integrates two approaches—a machine-learning algorithm and a probabilistic-graphical model (PGM and Bayesian networks); and the second stage uses a method for evaluating probability distributions. The first approach gives a point estimate of the intermediate and final temperatures of specific heat. The PGM-approach is useful for scenarios with uncertain input data, which is often the case for metallurgical enterprises. The accuracy level in predicting the temperature of the metal in the tundish at the first stage reached 6.0°C. At the second stage, the model integration into the process control system improved prediction accuracy, as well as provided technological parameter control in real time. The model is used as an advisor (master) for the technical team of the ladle furnace and vacuum degasser.

Experimental and theoretical prediction of Copper-Nickel nano-phase diagram

Copper and Nickel alloys form binary isomorphous system with a symmetric lens shaped curve formed by solidus and liquidus. This shape and size of the solidus and liquidus curves are altered by the particle size. This effect is greatly enhanced if the particle size is less than 100 nm. In the present work, phase diagram is predicted for nanoparticles considering Copper and Nickel and is compared with the experimental results. Copper and Nickel nanoparticles were procured and were characterized for the particle morphology and size using TEM, FE-SEM and XRD. The nanoparticles were also subjected to DSC analysis to find the melting point. The nanoparticles were blended in a high energy ball-mill for various compositions. The blending was carried out for different time intervals and was characterized using XRD to find the effective alloying time. The blended nanoparticles after effective alloying were subjected to DSC analysis to experimentally determine the solidus and liquidus points for various compositions. Phase diagram was determined experimentally and was compared with the theoretical prediction. GTE model and E&E models were used to predict the phase diagram for nanoparticles and was compared with the experimental results. It was found that the E&E model acurately predicts the nano phase diagram for Cu–Ni system with an error of 2% for 89 wt% Cu-11 wt% Ni alloy.