Supercooling Process Research Articles

Investigation of effects of aluminum additions on microstructural evolution and mechanical properties of ultra-high strength and vanadium bearing dual-phase steels

The effects of aluminum (Al) additions (0.04, 0.4, and 0.8 wt%) on the microstructural evolution, tensile properties, and sheared-edge ductility of dual phase (DP) steels were investigated. The DP steels were processed with distinct coiling temperatures after finish rolling, cold rolled, and subjected to two continuous galvanizing line (CGL) simulations: standard galvanizing (GI) and supercooling process (SC). Al expanded both the ɑ-ferrite and (ɑ+γ) phase fields at the expense of the γ-austenite region. Continuous cooling transformation (CCT) diagrams showed that Al increased ferrite start temperatures, broadened the ferrite transformation zone, and reduced austenite stability. Austenite growth kinetics during intercritical annealing, quantified using a modified Johnson-Mehl-Avrami-Kolmogorov (JMAK) model, revealed Avrami exponents ranging from 0.72 to 0.81 and apparent activation energies increasing from 422.9 to 496.7 kJ mol−1 with Al additions. Microstructural characterization revealed larger ferrite grain sizes and higher ferrite volume fractions with higher Al levels. Ultimate tensile strength (UTS) was influenced by Al contents, coiling temperatures, and CGL simulation methods. Global ductility (total elongation, TE) was highest for the 0.8Al Steel with a high coiling temperature and GI annealing, while local ductility (hole expansion ratio, HER) was maximized for the 0.04 Al Steel with a low coiling temperature and SC annealing. The majority of the CGL simulated DP steels exhibited good strength-ductility combinations, with the 0.8Al Steels demonstrating superior properties compared to current automotive advanced high-strength steel (AHSS) grades.

Effects of Heat Treatment on Microstructures and Mechanical Properties of a Low-Alloy Cylinder Liner.

Cylinder liners, considered a crucial component of internal combustion (IC) engines, often require excellent mechanical properties to ensure optimal engine performance under elevated temperatures, pressures, and varying loads. In this work, a new low-alloy cylinder liner, incorporating a low content of molybdenum, copper, and chromium into gray cast iron, was fabricated using a centrifugal casting process. Subsequently, the heat treatment processes were designed to achieve bainite microstructures in the cylinder liner through rapid air cooling, isothermal transformation, and tempering. The effects of different air-cooling rates and tempering temperatures on the microstructure evolution and mechanical properties of cylinder liner were investigated. The results revealed that during the supercooled austenite transformation process, rapid air cooling at a rate of 14.5-23.3 °C/s can effectively bypass the formation of pearlitic structures and directly induce the formation of bainite structures. Once the temperature exceeded 480-520 °C, hardness and tensile strength increased with the temperature increase owing to the enhancement of the lower bainite content, the reduction of residual austenite, and the precipitation of the fine hard carbides in the matrix. With temperatures above 520-550 °C, the carbide and lower bainite organization coarsened, thereby reducing the hardness and tensile strength of the material. Therefore, the optimal heat treatment parameters were rapid cooling at 14.5-23.3 °C/s rate to obtain bainite, and tempering of 480-520 °C for finer and more uniform bainite. In addition, the results of the characterization of the mechanical properties of the cylinder liner after heat treatment showed that the hardness, tensile strength, and wear resistance were improved with the refinement of the bainite.

Improvement of natural gas liquefaction and supercooling process in horizontal channels of printed circuit heat exchangers: Buoyancy analysis

Improvement of natural gas liquefaction and supercooling process in horizontal channels of printed circuit heat exchangers: Buoyancy analysis

Experimental investigation of the effect of stable magnetic field on droplet freezing

In this study, the effect of magnetic field on droplet freezing was investigated based on a visualization system. Possible influencing factors on droplet freezing, such as magnetic field intensity, cold surface temperature, and droplet volume, were considered in this study. During the two stages of droplet supercooling and freezing process, the changes of the droplet internal temperature, the formation of initial crystal nucleus, and the freezing time were observed. Experimental results show that in comparison with the non-magnetic surface, the supercooling degree of droplets was increased in the range of 150–300 mT magnetic field intensity, thereby prolonging the freezing time of droplets. Particularly, the droplet was best suppressed on a cold surface with 250 mT magnetic field intensity. The freezing time of droplets was prolonged by 132.0 %. However, the droplets were accelerated to freeze on the cold surface with magnetic field intensities of 350 mT and 400 mT. Droplet freezing on cold surfaces was also affected by surface temperature and droplet volume. As the surface temperature of magnetic cooling dropped from −10 °C to −20 °C, the ability of the magnetic field to inhibit droplet freezing would be gradually weakened. With the increase of droplet volume from 20 μL to 50 μL, the initial freezing time of droplets was shortened. These results are related to the influence of magnetic field on the nucleation process and hydrogen bond in the water molecular cluster.

Experimental investigation and multi-objective optimization of ice thermal storage device with multichannel flat tube

A novel plate-shaped ice thermal storage device is constructed with multichannel flat tube. The different temperatures and flow rates of heat transfer fluid (HTF) on the variations in the internal temperature and the store/release power are experimentally investigated. Results indicate that the reduction in temperature of cold HTF from −3 °C to −4 °C is notably to shorten the super-cooling process, reduced the freezing time by 35.04% and increased the average storage power by 24.9%, its effect gradually weaken with decrease in temperature. Furthermore, numerical simulation and response surface method are adopted to gain predictive models of four response indices for estimating the behavior of the device in terms of five different design parameters, and the interaction effects of design parameters on responses are investigated. Finally, the multi-objective joint optimization is developed based on an efficient storage device with goals of excellent thermal performance and thermodynamic perfection, while its manufacturing cost is low. The optimization results recommend the fin height, number and thickness are 30.1 mm, 10, and 0.5 mm, respectively, temperature and flow rate of cold HTF are −4.01 °C and 0.2 m3/h, respectively, to maximize ice formation rate, exergy efficiency, and fin efficiency and minimize the metal consumption.

A new insight into the interaction of hydroxyl radical with supercooled nanodroplet in the atmosphere

Fallstreak clouds are types of clouds with supercooled water droplets, meaning that they are still liquid at sub-freezing temperatures. In the atmosphere, hydroxyl radicals serve as an important source of oxidants. The reactivity of the hydroxyl radicals in ice environments is significant, affecting other atmospheric reactions. However, the interaction between OH radical with supercooled water nanodroplet remains unknown. This work presents a comprehensive computational study of OH radicals at the air-ice interface. Ab initio molecular dynamics simulation showed that despite previous assumptions, the hemibond could also exist in large OH*-nanodroplet systems under supercooling process. Two hydrogen-bonded water molecules along with the hemibond have been found to be the reason for OH* stability. There is a significant correlation between our RDF and ring analysis results and the structural information from X-ray crystallography, confirming LDA ice for supercooled nanodroplets. The hydrogen bond analysis revealed that there is no radical effect on the hydrogen bond formation of water nanodroplets at 250 K. Moreover, the time evolution of critical bonds based on distances revealed that the OH* could be a movable and reactive radical during the supercooling process. Results from this research contribute to a better understanding of natural phenomena and rational design of anti-icing systems for aviation, wind energy, and infrastructures along with cryopreservation.

Occurrence of Warm Freezing Rain: Observation and Modeling Study

AbstractFreezing rain has been normally considered to be composed of supercooled raindrops when the 2 m air temperature (hereafter ) is below freezing. However, according to a statistical survey of freezing rain observations in China from 2000 to 2019, we find that there were 656 events that occurred at greater than 0°C (hereafter warm freezing rain and denoted by WFR), which account for 7% of the total freezing rain observations. Additionally, nearly 3% (266 observations) of freezing rain events occurred when the near‐surface wet‐bulb temperature was greater than 0°C. The modeling and sensitivity experiments on the nonequilibrium raindrop temperature (hereafter ) show that the temperature difference between raindrops and the atmosphere is the main cause of WFR. The magnitudes of the (difference between raindrop temperature and air temperature ) and (difference between and wet‐bulb temperature ) are determined by the raindrop diameter D, temperature lapse rate Г, and relative humidity RH. Increases of D and Г, and a decrease of RH enhance and and thus the occurrence of WFR. Further simulations of 4 idealized and 370 real sounding profiles reveal that either the or the cannot properly distinguish the WFR events. When considering the temperature difference between raindrops and the atmosphere, the WFR can form by the “melting of solid hydrometeors” or “supercooled warm rain process.” This study can also deepen our understanding of the conditions of WFR and freezing rain formation at different altitudes.

Experimental Comparison of Three Characterization Methods for Two Phase Change Materials Suitable for Domestic Hot Water Storage

This study presents an experimental comparison of three characterization methods for phase change materials (PCM). Two methods were carried out with a calorimeter, the first with direct scanning (DSC) and the second with step scanning (STEP). The third method is a fluxmetric (FM) characterization performed using a fluxmeter bench. For the three methods, paraffin RT58 and polymer PEG6000, two PCM suitable for domestic hot water (DHW) storage, were characterized. For each PCM, no significant difference was observed on the latent heat and the total energy exchanged between the three characterization methods. However, DSC and STEP methods did not enable the accurate characterization of the supercooling process observed with the FM method for polymer PEG6000. For PEG6000, the shape of the enthalpy curve of melting also differed between the experiments on the calorimeter—DSC and STEP—methods, and the FM method. Concerning the PCM comparison, RT58 and PEG6000 appeared to have an equivalent energy density but, as the mass density of PEG6000 is greater, more energy is stored inside the same volume for PEG6000. However, as PEG6000 experienced supercooling, the discharging temperature was lower than for RT58 and the material is therefore less adapted to DHW storage operating with partial phase change cycles where the PCM temperature does not decrease below 52 °C.

Characterization of the Fe-6.5wt%Si Strip with Rapid Cooling Coupling Deep Supercooled Solidification.

The phase transition law between ordered and disordered phases, second phase reinforcement, microstructure, and mechanical properties were systematically studied in the rapid cooling coupling deep supercooled solidification process through an arc melting furnace, electromagnetic induction heating, and high-speed cooling single-roll technology. The results show that uniform nucleation and grain refinement are promoted under rapid cooling coupling deep supercooled solidification, and the phase transition from the disordered phase (A2) to the ordered phase (B2 and DO3) is also effectively suppressed. The decreased crystalline grain size and optimized microstructure morphology improved the plasticity and magnetic property. The Fe-6.5wt%Si steel strip at 42 m/s has a good phase composition of Fe (predominant), Fe2Si, and SiC. The sample showed an equiaxed ferrite crystal structure, and the saturation magnetizations were 302.5 and 356.6 emu/g in the parallel magnetic direction and the vertical magnetic direction, respectively. This phase transition behavior contributed to the exceptional magnetic property of the Fe-6.5wt%Si steel.

Isochoric supercooled preservation and revival of human cardiac microtissues

Low-temperature biopreservation and 3D tissue engineering present two differing routes towards eventual on-demand access to transplantable biologics, but recent advances in both fields present critical new opportunities for crossover between them. In this work, we demonstrate sub-zero centigrade preservation and revival of autonomously beating three-dimensional human induced pluripotent stem cell (hiPSC)-derived cardiac microtissues via isochoric supercooling, without the use of chemical cryoprotectants. We show that these tissues can cease autonomous beating during preservation and resume it after warming, that the supercooling process does not affect sarcomere structural integrity, and that the tissues maintain responsiveness to drug exposure following revival. Our work suggests both that functional three dimensional (3D) engineered tissues may provide an excellent high-content, low-risk testbed to study complex tissue biopreservation in a genetically human context, and that isochoric supercooling may provide a robust method for preserving and reviving engineered tissues themselves.

Analytical modelling of PCM supercooling including recalescence for complete and partial heating/cooling cycles

Abstract Phase change material (PCM) experiencing supercooling and phase change hysteresis are widely reported in the literature. However, only few studies model analytically such PCM, and they mostly focus on either supercooling or phase change hysteresis, but rarely on both phenomena. Moreover, partial phase change cycles, with an incomplete melting or solidification, are rarely considered even if these processes occur frequently in latent heat thermal energy storage (LHTES) systems. The objective of this study is to model analytically the thermal behaviour of a PCM experiencing supercooling and phase change hysteresis, for complete and partial phase change cycles. The developed method, based on a heat source term, enables to model the recalescence process during the solidification. Currently rarely considered, the influence of the cooling rate on the supercooling degree and the recalescence process is evaluated with a phenomenological approach. For partial cycles, the different behavior between heating and cooling is modelled with the hysteresis model “curve scale” already validated in literature. The experimental validation is carried out on a PCM brick sample, monitoring both the heat flux and the PCM temperature, which enables to characterize a greater mass of PCM compared to direct scanning calorimeter (DSC) analysis. The selected PCM undergoing supercooling during solidification is PEG6000, a polymer suitable for domestic hot water (DHW) storage. Results show a good agreement between experimental and numerical results for complete heating and cooling cycles. The behavior laws used to model the solidification with the supercooling and recalescence processes are validated for the cooling rate range tested. The modelling is also satisfactory concerning the experiments on partial solidification for different temperature plateaus. However, the model fails to correctly represent the thermal behavior for a cooling process after a partial melting of the PCM. To conclude, the developed model enables to represent accurately the thermal behaviour of a PCM experiencing supercooling and phase change hysteresis for most of the phase change processes studied. Investigations on the thermal conditions influencing the crystalline structure and the effect on the phase change dynamic are suggested to improve supercooling modelling. The developed model needs to be validated for PCM having a higher supercooling degree, such as sugar alcohols or salt hydrates.

Unfrozen state by the supercooling of chuño for traditional agriculture in altiplano andes

Abstract The freezing point and supercooling process are discussed for their impact on the traditional Andean freeze-dried potatoes called chuno. The freezing point depends on potato species, but typically it is slightly below zero to −3 ​°C; supercooling always occurs before the potatoes freeze, and the lowest supercooling point (LSP) can reach −4.3 ​°C. Recently many of the potato fields near Lake Titicaca are not cold enough to freeze tubers for chuno, and the loss of this food source will be critical in the future.

Investigation of effects of processing on stretch-flangeability of the ultra-high strength, vanadium-bearing dual-phase steels

The purpose of this paper was to gain a better insight into the sheared-edge ductility of high strength dual-phase steels for the purpose of helping improve the hole expansion behavior of such steels. A candidate dual-phase (DP) steel in this study was designed and processed with distinct coiling temperatures after conventional finish rolling, and then further processed with two continuous galvanizing line (CGL) simulations. Two CGL simulations with slightly different thermal paths were conducted on a Gleeble 3800 machine; one was to replicate standard galvanizing (GI), where the intercritically annealed steels were cooled to the zinc pot temperature, and the other one was a supercooling process (SC) where the intercritically annealed steels were first cooled to the M90 temperature of the intercritically formed austenite, then up-quenched to the zinc pot temperature. The findings indicated that the combination of a low coiling temperature and GI anneal can obtain the microstructures characterized by a high-volume-percentage of martensite and fine-grained ferrite with a high tensile strength (UTS) of 1092.8 MPa and a good total elongation (TE) of 20.8%. A large amount of fresh martensite was replaced by tempered martensite caused by the changes in CGL thermal paths from GI to SC anneals, resulting in the considerable increase in sheared-edge ductility properties, although with a loss of UTS. Additionally, the damages caused by hole punching were examined by electron backscattered diffraction (EBSD) - kernel average misorientation (KAM) and nanoindentation technologies. These results showed that the micro-voids or micro-cracks in the initial punched hole surfaces and plastic internal strains near the initial punched hole sheared edges introduced by hole punching will severely influence stretch-flangeability.

Experimental investigation on defrosting of a cold flat plate via ultrasonic vibration under natural convection

The present experimental study examines the effect of ultrasonic vibration on the frost formation under a free convective environment. A stainless steel SS ANSI 316 flat surface is tested under 12–24 °C dry bulb temperature and 58–84% relative humidity. The experiments are conducted with direct contact and non-contact high-frequency ultrasonic source having continuous or intermittent vibrations. The ultrasonic transducer contains 28 ± 0.5 kHz resonance frequency. It is found that increasing the relative humidity will increase the frost thickness and influences the frost property. Imposing ultrasonic vibration under high relative humidity and low ambient temperature increases the droplets' circularity with comparatively sparse distribution. Test results indicate that non-contact vibration has no effect on the frost formation. Intensive intermittent contact vibration is the most effective way to suppress frost growth. Compared to continuous contact vibration, either it is applied after each an hour or after every 30 min as an intensive continuous, intensive intermittent contact vibration shows a reduction in frost thickness as much as 24%. In addition, the ultrasonic vibration should be applied after the supersaturation stage since ultrasonic vibration enhances the supercooled process.

Mathematical modelling of the formation and evolution of surface ice

During the fall season in cold regions when the air temperature drops below freezing levels, it removes heat from the water surface and creates a supercooled surface layer. In weak turbulent flows, the supercooled surface layer initiates the formation of ice particles on the water surface, which could evolve into various types of surface ice runs. In this paper a mathematical model of the formation and evolution of surface ice is presented. A heat balance model at the water surface is applied to calculate the heat loss from the water. The turbulent kinetic energy and the energy dissipation rates are modelled to find the eddy viscosity that affects the mixing rate. The mathematical model is then calibrated and verified using experimental data collected at the Hydraulics Research and Testing Laboratory at the University of Manitoba. The model simulates the supercooling process reasonably well for all surface ice conditions.

Experimental investigation and hygrothermal modelling of freeze-thaw process of saturated fired clay materials including supercooling phenomenon

To investigate the supercooling phenomenon in fired clay materials, low-temperature differential scanning calorimetry (DSC) and a one-dimensional freeze-thaw (FT) experiment were performed on saturated specimens. The rate of increase in ice saturation during freezing was calculated from the DSC result. Rapid ice growth over a relatively narrow temperature range (within about 0.2 K) was observed at a cooling rate of 0.25 K/min. In the FT experiment, the temperature distribution of a specimen was measured with inserted thermocouples. According to the results of the FT experiment, a rapid temperature increase was observed at sub-zero temperatures accompanied by freezing of the supercooled water. When the supercooled water began to freeze, the released latent heat was found to strongly prevent the specimen temperature from dropping even during the cooling period. Finally, a hygrothermal model of freezing and thawing including a non-equilibrium supercooling process was developed. The freezing rate of the supercooled water was modelled based on the DSC result. The validity of the model was verified by comparing the results of the FT experiment and calculations. The model was found to be able to replicate the rapid temperature rise during the cooling period of the FT experiment.

Laboratory study of the properties of frazil ice particles and flocs in water of different salinities

Abstract. Measurements of the size and shape of frazil ice particles and flocs in saline water and of frazil ice flocs in freshwater are limited. This study consisted of a series of laboratory experiments producing frazil ice at salinities of 0 ‰, 15 ‰, 25 ‰ and 35 ‰ to address this lack of data. The experiments were conducted in a large tank in a cold room with bottom-mounted propellers to create turbulence. A high-resolution camera system was used to capture images of frazil ice particles and flocs passing through cross-polarizing lenses. The high-resolution images of the frazil ice were processed using a computer algorithm to differentiate particles from flocs and determine key properties including size, concentration and volume. The size and volume distributions of particles and flocs at all four salinities were found to fit log-normal distributions closely. The concentration, mean size, and standard deviation of flocs and particles were assessed at different times during the supercooling process to determine how these properties evolve with time. Comparisons were made to determine the effect of salinity on the properties of frazil ice particles and flocs. The overall mean size of frazil ice particles in saline water and freshwater was found to range between 0.52 and 0.45 mm, with particles sizes in freshwater ∼13 % larger than in saline water. However, qualitative observations showed that frazil ice particles in saline water tend to be more irregularly shaped. The overall mean size of flocs in freshwater was 2.57 mm compared to a mean size of 1.47 mm for flocs in saline water. The average growth rate of frazil particles was found to be 0.174, 0.070, 0.033, and 0.024 mm min−1 and the average floc growth rate was 0.408, 0.118, 0.089, and 0.072 mm min−1 for the 0 ‰, 15 ‰, 25 ‰, and 35 ‰, respectively. Estimates for the porosity of frazil ice flocs were made by equating the estimated volume of ice produced based on thermodynamic conditions to the estimated volume of ice determined from the digital images. The estimated porosities of frazil ice flocs were determined to be 0.86, 0.82, 0.8 and 0.75 for 0 ‰, 15 ‰, 25 ‰ and 35 ‰ saline water, respectively.

Effects of pre-annealing conditions on the microstructure and properties of vanadium-bearing dual-phase steels produced using continuous galvanizing line simulations

It is well known that the fracture behavior and weldability of steel often vary inversely with the carbon content. In the case of thin sheet intended for automotive applications, this means spot weldability and tensile ductility. However, the question arises, what is the reasonable maximum strength attainable in a low-carbon dual-phase (DP) steel under the constraints of: (1) with carbon levels at 0.1 wt%, (2) with the product (UTS × % TE) > 18,000 MPa, and (3) with processing on a simulated continuous hot-dipped galvanizing line. This study has focused on experimental compositions intended to meet DP steel grade properties in excess of 780 MPa UTS. This kind of advanced high-strength steel (AHSS) is an integral part of mass reduction programs for the body-in-white for the automotive industry. The family of steels investigated here is based on a low-carbon, aluminum-killed base steel containing Cr and Mo. In this study, the effects of the presence of V were studied. In addition, there were three processing variables investigated in terms of their respective effects on microstructure and mechanical properties: first, hot band coiling temperature; second, % cold reduction; and third, the thermal path through the CGL process. The thermal paths explored included both a standard galvanizing process and a new supercooling process; these were studied using a CGL simulation. This research revealed that all three variables can have a significant effect on the final microstructure and properties.

Supercooling Self-Assembly of Magnetic Shelled Core/Shell Supraparticles.

Molecular self-assembly has emerged as a powerful technique for controlling the structure and properties of core/shell structured supraparticles. However, drug-loading capacities and therapeutic effects of self-assembled magnetic core/shell nanocarriers with magnetic nanoparticles in the core are limited by the intervention of the outer organic or inorganic shell, the aggregation of superparamagnetic nanoparticles, the narrowed inner cavity, etc. Here, we present a self-assembly approach based on rebalancing hydrogen bonds between components under a supercooling process to form a new core/shell nanoscale supraparticle with magnetic nanoparticles as the shell and a polysaccharide as a core. Compared with conventional iron oxide nanoparticles, this magnetic shelled core/shell nanoparticle possesses an optimized inner cavity and a loss-free outer magnetic property. Furthermore, we find that the drug-loaded magnetic shelled nanocarriers showed interesting in vitro release behaviors at different pH conditions, including "swelling-broken", "dissociating-broken", and "bursting-broken" modes. Our experiments demonstrate the novel design of the multifunctional hybrid nanostructure and provide a considerable potential for the biomedical applications.

Formation of chemical short range order and its influences on the dynamic/mechanical heterogeneity in amorphous Zr–Cu–Ag alloys: A molecular dynamics study

The chemical short range order of metallic glasses is expected to be correlated with their mechanical properties. In this article, classic molecular dynamics simulations of amorphous Zr45Cu45Ag10 alloys were carried out to reveal such links in metallic glasses. Our calculations of Warren–Cowley parameter indicate the growth of chemical short range order during supercooling process, which also depends on the effective cooling rates. The chemical short range ordering is related to the energetic stability of the system. Based on the chemical preference or avoidance for different bonds, the model is separated into Cu-rich regions and Ag-rich regions. Simulated structural relaxation and shear loading process were performed to study how chemical bonds affect the distribution of dynamic and mechanical heterogeneity in our systems. The Cu-rich regions exhibit slower dynamics and higher shear resistance, whereas Ag-rich regions have faster dynamics and prefer to be plastically deformed.