Cooling Rate Research Articles

Effects of Cooling Rate and Emulsifier Combination on the Colloidal Stability of Crystalline Dispersions Stabilized by Phospholipids and β-Lactoglobulin

A lot of applications for (semi-)crystalline triacylglycerol (TAG)-in-water dispersions exist in the life science and pharmaceutical industries. Unfortunately, during storage, these dispersions are often prone to changes in particle size due to unforeseen crystallization and recrystallization events. This results in the alterations of important product properties, such as viscosity and mouthfeel, or the premature release of encapsulated material. In this study, we investigated the effects and interplay of formulation, i.e., emulsifier combination, and processing parameters, i.e., cooling rate, on the colloidal stability of dispersed TAGs and aimed to improve their colloidal stability. We chose phospholipids (PLs) and β-lactoglobulin (β-lg) as the emulsifiers for our model systems, which are commonly applied in many food systems. When dispersions were characterized directly after cooling, we obtained smaller particles and narrower size distributions after fast cooling. Over the course of eleven weeks, the creaming behavior, particle size, melting behavior and polymorphism were characterized. The dispersions stabilized with solely β-lg exhibited a slight increase in particle size, whereas a decrease in size was found when PLs were added. Our results indicate that mass transport phenomena between TAG droplets and particles took place during storage. This migration of TAG molecules changed the composition and size distribution of the dispersed phase, especially at higher PL concentration (0.1 wt%). In our case, this could be prevented by using a lower concentration of PLs, i.e., 0.05 wt%.

Effect of Cooling Rates on Solidification Microstructures and Tensile Property of a Novel Wrought Superalloy

Effect of Cooling Rates on Solidification Microstructures and Tensile Property of a Novel Wrought Superalloy

The Effect of Cooling Rate on Crystallographic Features of Phase Transformations in Zr-2.5Nb.

Zirconium (Zr) alloys are utilized as structural components for the cores of nuclear reactors due to the excellent combination of their mechanical properties and corrosion resistance under intense neutron irradiation conditions in water. The characteristics of microstructures formed during heat treatments play a crucial role in obtaining the operational performance of parts made from Zr alloys. This study investigates the morphological features of (α + β)-microstructures in the Zr-2.5Nb alloy, as well as the crystallographic relationships between α- and β-phases. These relationships are induced by the β→α(α″) displacive transformation that occurs during water quenching (WQ) and the diffusion-eutectoid transformation that takes place during furnace cooling (FC). To conduct this analysis, samples solution treated at 920 °C were examined using EBSD and TEM. The experimental distribution of α/β-misorientations for both cooling regimes deviates from the Burgers orientation relationship (BOR) at a discrete set of angles close to 0, 29, 35, and 43°. The experimental α/β-misorientation spectra are confirmed by crystallographic calculations for the β→α→β-transformation path based on the BOR. Similar spectra of misorientation angle distribution in α-phase and between α and β phases in Zr-2.5Nb after WQ and FC point to similar transformation mechanisms and the significant role of shear and shuffle in β→α-transformation.

Achieving High Strength and High Conductivity of Cu-6 wt%Ag Sheets by Controlling the Aging Cooling Rate.

In this paper, Cu-6 wt%Ag alloy sheets were prepared using vacuum induction melting, heat treatment, and cold working rolling. We investigated the influence of the aging cooling rate on the microstructure and properties of Cu-6 wt%Ag alloy sheets. By reducing the cooling rate of the aging treatment, the mechanical properties of the cold-rolled Cu-6 wt%Ag alloy sheets were improved. The cold-rolled Cu-6 wt%Ag alloy sheet achieves a tensile strength of 1003 MPa and an electrical conductivity of 75% IACS (International Annealing Copper Standard), which is superior to the alloy fabricated with other methods. SEM characterization shows that the change in properties of the Cu-6 wt%Ag alloy sheets with the same deformation is due to a precipitation of the nano-Ag phase. The high-performance Cu-Ag sheets are expected to be used as Bitter disks for water-cooled high-field magnets.

Effects of cutaneous administration of an over-the-counter menthol cream during temperate-water immersion for exercise-induced hyperthermia in men.

Introduction: Hyperthermia impairs various physiological functions and physical performance. We examined the effects of cutaneous administration with an over-the-counter (OTC) analgesic cream containing 20% methyl salicylate and 6% L-menthol during temperate-water immersion (TWI) for exercise-induced hyperthermia. Methods: In a randomized crossover design, twelve healthy males participated in both of two experiments. Firstly, participants underwent a 15-min TWI at 20°C with (CREAM) or without (CON) cutaneous application of an analgesic cream. Cutaneous vascular conductance (CVC) was measured using laser doppler flowmetry during TWI. In a subsequent experiment, same participants performed a 30-min strenuous interval exercise in a heated (35°C) environment to induce hyperthermia (~39°C), which was followed by 15min of TWI. Results: Core body temperature, as measured by an ingestible telemetry sensor, and mean arterial pressure (MAP) were measured. CVC and %CVC (% baseline) were higher during TWI in CREAM than in CON (Condition effect: p = 0.0053 and p = 0.0010). An additional experiment revealed that core body heat loss during TWI was greater in CREAM than in CON (Cooling rate: CON 0.070 ± 0.020 vs. CREAM 0.084°C ± 0.026°C/min, p = 0.0039). A more attenuated MAP response was observed during TWI in CREAM than in CON (Condition effect: p = 0.0007). Conclusion: An OTC analgesic cream containing L-menthol and MS augmented cooling effects when cutaneously applied during TWI in exercise-induced hyperthermia. This was, at least in part, due to the counteractive vasodilatory effect of the analgesic cream. The cutaneous application of OTC analgesic cream may therefore provide a safe, accessible, and affordable means of enhancing the cooling effects of TWI.

A Systematic Review of Post-Work Core Temperature Cooling Rates Conferred by Passive Rest.

Physical work increases energy expenditure, requiring a considerable elevation of metabolic rate, which causes body heat production that can cause heat stress, heat strain, and hyperthermia in the absence of adequate cooling. Given that passive rest is often used for cooling, a systematic search of literature databases was conducted to identify studies that reported post-work core temperature cooling rates conferred by passive rest, across a range of environmental conditions. Data regarding cooling rates and environmental conditions were extracted, and the validity of key measures was assessed for each study. Forty-four eligible studies were included, providing 50 datasets. Eight datasets indicated a stable or rising core temperature in participants (range 0.000 to +0.028 °C min-1), and forty-two datasets reported reducing core temperature (-0.002 to -0.070 °C min-1) during passive rest, across a range of Wet-Bulb Globe Temperatures (WBGT). For 13 datasets where occupational or similarly insulative clothing was worn, passive rest resulted in a mean core temperature decrease of -0.004 °C min-1 (-0.032 to +0.013 °C min-1). These findings indicate passive rest does not reverse the elevated core temperatures of heat-exposed workers in a timely manner. Climate projections of higher WBGT are anticipated to further marginalise the passive rest cooling rates of heat-exposed workers, particularly when undertaken in occupational attire.

Correlation Between Cooling Rate and γ' Precipitate Size in Rene 95 Alloy Fabricated Through a Powder Metallurgy Process

Correlation Between Cooling Rate and γ' Precipitate Size in Rene 95 Alloy Fabricated Through a Powder Metallurgy Process

Optimizing a Solution Heat Treatment by Increasing the Cooling Rate of Directional Solidification for Ni-Based Superalloys.

The solution heat treatment (SHT) of the third generation of single crystal (SC) Ni-based superalloys required up to 45 h and was expensive. In this study, SHT based on liquid metal cooling (LMC) was optimized to greatly reduce processing time. The experimental and simulation results showed that residual segregation was evidently reduced, e.g., from 2.12 to 1.22 for the most heavily segregated Re. This led to a 16.7% increase in creep life, more uniform microstructures, and a decrease in solidification and homogenization porosity by a factor of 3.4. Structural refinement, approximately 0.32 times, served as the underlying mechanism for this optimization, which reduced diffusion distance and increased homogenization efficiency during SHT.

Effect of Crystallization on Mechanical Properties of Zr85Cu15 Metallic Glasses with Different Cooling Rates

Effect of Crystallization on Mechanical Properties of Zr85Cu15 Metallic Glasses with Different Cooling Rates

Effect of Cooling Rate and Remelting Temperature on the Solidification Structure of Al-5Zr Master Alloy

Zr is an important element to improve the heat resistance of aluminum alloys, which is usually added to alloys using the Al-Zr master alloys. The microstructure of Al-Zr master alloys has a significant impact on the properties of Zr-bearing aluminum alloys. In this paper, the microstructure of commercial Al-5Zr master alloys was examined, and the effect of the remelting temperature and cooling rate on the solidification structure of the remelted Al-5Zr master alloys was investigated, aiming to develop a feasible way for quality improvement of Al-5Zr master alloys. The results showed that the microstructure of the remelted Al-5Zr master alloy could be regulated effectively by controlling the remelting temperature and cooling rate. When the remelting temperature was 1320 °C, the primary Al3Zr phase in the remelted Al-5Zr master alloy was mainly precipitated as coarse plate-like or fine long needle-like. Higher cooling rate increased nucleation density and refined microstructure. The average length of the primary Al3Zr phase was 178.2, 87.4, and 61.3 μm when the cooling rate was 4.6, 30.8, and 43.9 °C/s, respectively. Lower remelting temperature was generally conducive to refinement of primary Al3Zr phase. When the remelting temperature was 920 °C, the primary Al3Zr phase in the remelted Al-5Zr master alloy was mainly precipitated as block-like, fine needle-like, and petal-like. When the cooling rate was 4.6 °C, coarse plate-like Al3Zr phase precipitated. With increasing cooling rate to 25.3 °C, the coarse plate-like Al3Zr phase disappeared and the block-like and fine needle-like Al3Zr phase precipitated followed by a large number of fine petal-like Al3Zr phase precipitated after cooling rate to 45.6 °C. The optimized remelting process can improve the microstructure of the commercial Al-5Zr master alloy.

Analysis of Critical Cooling Rate and Glass Forming Ability of Amorphous Alloys in Perspective of Bulk Metallic Glasses

Analysis of Critical Cooling Rate and Glass Forming Ability of Amorphous Alloys in Perspective of Bulk Metallic Glasses

Microstructures of Austenitic Stainless Steel 56Fe25Ni16.6Cr0.9Si0.5Mn Solid-treated with Different Cooling Rates

Microstructures of Austenitic Stainless Steel 56Fe25Ni16.6Cr0.9Si0.5Mn Solid-treated with Different Cooling Rates

Formation of Alpha-Case Layer during Oxidation of Ti6Al4V Surface by Annealing at 1050 °C and Change of Microstructure after Different Cooling Rates

The two-phase titanium alloy Ti6Al4V (often referred to as GRADE 5 or Ti64) is currently probably the most widely used type of Ti alloy. It is characterized by an excellent combination of strength - toughness - chemical stability. However, at temperatures above 500 - 800 °C it is prone to the diffusion of oxygen into surface layers, where the increased oxygen content creates the so-called “alpha-case” layer. The formation of this layer is associated with a reduction mainly in the deformation characteristics of the alloy. The paper focuses on the metallographic analysis of the "alpha-case" layer after annealing at 1050 °C with a holding time of 3 hours and cooling at different cooling rates (500 °C/s, 1 °C/s and 0.08 °C/s). Microstructure changes were observed by light microscopy using polarized light – PL, dark field – DF and phases were identified by SEM methods. The influence of changes in the microstructure on the mechanical properties was determined by measuring the microhardness HV0.2 /10 (STN EN ISO 6507) with Zwick / Roell ZHµ and measuring the resistance to impact stress KU (Charpy system STN EN 10045-1). Based on the microhardness measurement, an increase in the microhardness of the surface layers was observed at all cooling rates and at the same time, a decrease in the impact resistance was observed compared to the initial state.

Examination of the Effect of Cooling Rate after Extrusion to Formability of 6061 Automotive Profiles

As part of the present project, an inquiry is being conducted into the impact of the cooling rate subsequent to extrusion on both the mechanical characteristics and microstructure of 6061 alloy extruded profiles tailored for application in the automotive industry. Water quenching, air cooling, and step-cooling (combination of air cooling and water quenching) were performed after a solution heat treatment for simulating different cooling processes on the exit of the extrusion press. Microstructure examination was performed after artificial aging for every cooling method accompanied by three-point bending and tensile testing for investigation of differences in formability characteristics in each one of the three cases. Electron fractography, texture, and grain boundary misorientation analysis consisted the main analytical techniques, allowing the correlation between grains orientation resulting from the extrusion process with cracking initiation behavior in mechanical testing and for the determination of the regions which were more prone to cracking. From the examination, the positive role of rapid cooling for improved formability was highlighted. Through the grain boundary misorientation analysis and the formation of Taylor factor maps, it was shown that crack initiation preferably took place at subsurface regions even though “roughening” of the bent surface was obvious and expected to lead to crack initiation in the more ductile samples. Considerable amounts of LAGBs (Low Angle Grain Boundaries) (14.7%) and SGBs (Subgrain Boundaries) (4.5%) were detected in the sample which was subjected to step cooling accompanied by an outer and inner surface layers (surface zone) of 200–250 μm thicknesses exhibiting different orientations. The results of this project will be used for optimization of the automotive extruded profiles production process, ensuring improved mechanical performance and resistance to premature fracture.

Influence of Cooling Rate on Solidification and Segregation Characteristics of Cu-Ni-Si Alloy

Influence of Cooling Rate on Solidification and Segregation Characteristics of Cu-Ni-Si Alloy

Influence of the Cooling Rate on Mechanical and Corrosion Properties of Ferritic Si–Mo Ductile Cast Iron

In this study, the effect of the cooling rate controlled by different castings thickness ranging from 3 to 25 mm on the mechanical and corrosion behavior of Si–Mo ductile iron (DI) castings was investigated. SEM-EBSD investigations demonstrated that the nodule counts, nodularity, and ferrite phase increased while the ferritic grain size decreased with decreasing in the casting wall thickness; this in turn led to improvements in the tensile properties of the DI. The corrosion behavior of Si–Mo DI castings was investigated after different immersion times in a 3.5 wt pct NaCl solution via electrochemical experiments. The electrochemical results showed that the corrosion resistance of Si–Mo DI decreased in the following order: 3 > 5 > 13 > 25 mm. The results indicated that all of the tested DI samples exhibited galvanic corrosion between the nobler carbide and ferritic matrix phases. SEM analysis showed that the dissolution of the ferrite phase with the pearlite phase exposed and accumulated on the DI’s surface, which led to intense corrosion acceleration. The higher corrosion rates that were observed for those samples with higher casting wall thicknesses could be associated with the higher contents of pearlite/carbide.

Primary phase transformation mechanism in a hypereutectic Al-Ce alloy during rapid solidification

Cooling rate plays an important role in determining the microstructure in as-cast aluminum alloys. To obtain a cooling rate gradient, a wedge Cu mould was selected. Here, we found a transition from hypereutectic to hypoeutectic microstructures in a hypereutectic Al-Ce alloy during rapid solidification. There was a distinct interface at a cooling rate of 1598 K/s. When the cooling rate was lower than 1598 K/s, the microstructures were composed of primary Al11Ce3 phases and Al/Al11Ce3 eutectic colonies. As the cooling rate was higher than 1598 K/s, the primary Al11Ce3 phases transformed into α-Al. Compared with the α-Al, the nucleation of Al11Ce3 phases was more favorable because of the lower nucleation energy. The growth rate of α-Al was higher than that of Al11Ce3 phases as the undercooling was larger than 182 K. Primary phase transformation mechanism in the hypereutectic Al-Ce alloy was controlled by nucleation and growth of α-Al and Al11Ce3 phases.

The Effect of Cooling Rates on Thermal, Crystallization, Mechanical and Barrier Properties of Rotational Molding Polyamide 11 as the Liner Material for High-Capacity High-Pressure Vessels

The rapid development of hydrogen fuel cells has been paralleled by increased demand for lightweight type IV hydrogen storage vessels with high hydrogen storage density, which raises the performance requirements of internal plastic liners. An appropriate manufacturing process is important to improve the quality of polymer liners. In this paper, DSC, WAXD, a universal testing machine and a differential pressure gas permeameter were used to investigate the effect of the cooling rate of the rotational molding polyamide 11 on the thermal, crystallization, mechanical and barrier properties. The cooling rate is formulated according to the cooling rate that can be achieved in actual production. The results suggest that two PA11 liner materials initially exhibited two-dimensional (circular) growth under non-isothermal crystallization conditions and shifted to one-dimensional space growth due to spherulite collision and crowding during the secondary crystallization stage. The slower the cooling process, the greater the crystallinity of the specimen. The increase in crystallinity significantly improved the barrier properties of the two PA11 liner materials, and the gas permeability coefficient was 2-3-fold higher than at low crystallinity. Moreover, the tensile strength, the tensile modulus, the flexural strength, and the flexural modulus increased, and the elongation at break decreased as the crystallinity increased.

Damage Effect of Thermal Shock on the Heated Granite at Different Cooling Rates

This study investigates the affecting pattern of cooling rates on the physical and mechanical properties of granite at high temperature. The different cooling rates are realized by cooling the heated granite specimens in the air at room temperature, −60 °C, and −100 °C. Slow cooling in the unplugged furnace is also performed on an additional set of specimens as a reference group. Physical and mechanical tests are performed on the granite specimens after thermal shock treatments. The results indicate a decreasing trend of the dry density, P-wave velocity, strength, and fracture toughness, and an increasing trend of the porosity, as the heating level or the cooling rate ascends. The microscopic observation on the fracture surface of the tested specimens manifests the deteriorating effect of thermal shock with a higher cooling rate, where the transition from trans-granular and intra-granular fracturing to intergranular fracturing serves to explain the variation pattern of the properties obtained in the lab tests.

Effect of Cooling Rate on Microstructure and Mechanical Properties of a Microlaminated Low-Density Steel

Effect of Cooling Rate on Microstructure and Mechanical Properties of a Microlaminated Low-Density Steel