Cooling Rate Research Articles

Impact of Differential Cooling Rates on Wire Arc Additive Manufactured HSLA Steel Component

Impact of Differential Cooling Rates on Wire Arc Additive Manufactured HSLA Steel Component

Influence of Cooling Rate on Primary Silicon Size in Hypereutectic Al–Si Alloy Fabricated by Laser Powder Bed Fusion

Herein, the effects of cooling rate on primary silicon (Si) phases in laser powder bed fusion (PBF‐LB/M) processed hypereutectic Al–Si alloy are investigated. These alloys are particularly in demand for automotive and electronic applications, thanks to their excellent wear and thermal properties. Nevertheless, when processed by conventional methods like casting with comparatively lower cooling rates, the coarse primary Si phases are responsible for increasing brittleness and inducing crack propagation. The refinement of the primary silicon phases is aimed to be achieved through the PBF‐LB/M process, which offers a high cooling rate. The primary Si phases are observed under three different thermal substrate plate conditions—untempered, with cooling and heating, and additionally with varying volume energy density. Furthermore, the impact of primary Si size on the hardness of the fabricated samples is evaluated. The findings show that a faster cooling rate has a notable effect on refining the primary Si size. Then, hardness is directly affected by the primary Si size, with larger Si resulting in decreased hardness.

Enhancing Silicon Refinement in an Al-25Si Hypereutectic Alloy by High Cooling Rate and La–Ce–Y Modifiers

Enhancing Silicon Refinement in an Al-25Si Hypereutectic Alloy by High Cooling Rate and La–Ce–Y Modifiers

Effect of Cooling Rate on Properties of Beeswax and Stearic Acid Oleogel Based on Rice Bran Oil and Sesame Oil

This study aimed to investigate how varying cooling rate impacts the characteristics of oleogels prepared using a sesame oil and rice bran oil blend (5:6, w/w) using a combination of beeswax and stearic acid (3:1, w/w at 12%, w/w) as the oleogelators. The study assessed three different cooling rates—0.5, 1.5, and 5 °C/min—with a focus on the attributes of the oleogels. The study revealed that the cooling rate had a substantial impact on the strength of the gel network. The cooling rate of 0.5 °C/min resulted in a higher oil-binding capacity and a stronger gel structure than fast cooling. The thermal properties and molecular interactions of the oleogels were not influenced by the cooling rate. The findings of this study indicated that the characteristics of beeswax and stearic acid oleogel prepared using sesame oil and rice bran oil blend could be tailored by manipulating the cooling rate.

The Effect of Cooling Rate on Solidification Characteristics and Grain Structure of Al-9Si Cast Alloy

A thermal analysis study is essential before the semisolid metal processing of a particular alloy. The surrounding environment, especially the cooling rate is also an important factor. This study investigated the influence of different cooling rates on the solidification characteristics and microstructure evolution of the Al-9Si cast alloy. Four cooling mediums were designed, and their cooling rates are 0.16 ℃/s, 1.0 ℃/s, 1.3 ℃/s, and 1.9 ℃/s, respectively. The results show that the primary dendrite size of the Al-9Si alloy was reduced from 162.61 μm to 86.86 μm as the cooling rate increased from 0.16 ℃/s to 1.9 ℃/s. Significant grain refinement was observed, however, the external cooling has a negligible impact on solid fraction. The optimal temperature range of the Al-9Si cast alloy for the semisolid metal processing at a solid fraction of 0.5 to 0.7 is between 554 ℃ and 563 ℃. With these thermal profiles provided, the relationship between the solid fraction and the solidification time could be expressed using the polynomial equation, which is also useful for point prediction in the subsequent semisolid metal processing.

The Influence of Cooling Rate on the Damping Characteristics of the ZnAl27Cu2 Alloy

The Influence of Cooling Rate on the Damping Characteristics of the ZnAl27Cu2 Alloy

La Palma 2021 Eruption (Canary Islands): Measurements and Modelling of Lava Flow Cooling Rates and Applications for Infrastructure Reconstruction and Risk Mitigation

La Palma 2021 Eruption (Canary Islands): Measurements and Modelling of Lava Flow Cooling Rates and Applications for Infrastructure Reconstruction and Risk Mitigation

Critical Cooling Rate of Fast-Crystallizing Polyesters: The Example of Poly(alkylene trans-1,4-cyclohexanedicarboxylate)

Controlling the cooling rate experienced by a material during a manufacturing process is a challenge and a major issue. Industrial processing techniques are very diverse and may involve a whole range of cooling rates, which are sometimes extremely high for small and/or thin manufactured parts. For polymers, the cooling rate has consequences on both the microstructure and the time-dependent properties. The common cooling rates associated with conventional calorimetric measurements are generally limited to a few tens of degrees per minute. This work combines several calorimetric techniques (DSC, modulated-temperature DSC, stochastically-modulated DSC and Fast Scanning Calorimetry) to estimate the critical cooling rate required to melt-quench fast-crystallizing polyesters to their fully amorphous state, based on the example of a series of poly(alkylene trans-1,4-cyclohexanedicarboxylate) (PCHs) with a number of methylene groups in the main structure of the repeating unit nCH2 varying from 3 to 6. The even-numbered ones require faster cooling rates (about 3000 K s−1 for nCH2 = 4, between 500 and 1000 K s−1 for nCH2 = 6) compared to the odd-numbered ones (between 50 K min−1 and 100 K s−1 for nCH2 = 3, between 10 and 30 K min−1 for nCH2 = 5).

Formation of Bainite in a Low‐Carbon Steel at Slow Cooling Rate – Experimental Observations and Thermodynamic Validation

Bainitic microstructures in high‐strength steels are obtained either by continuous cooling or isothermal holding. Both scenarios necessitate faster cooling to keep the parent austenite phase untransformed till the bainite‐start temperature. The present study reports the development of bainitic microstructure in a low‐carbon steel with minimal alloying additions, under continuous cooling at very slow rates, similar to furnace cooling. For understanding the related transformation pathways, samples from the forged‐steel ingot are austenitized and cooled at different rates, viz. water quenching, air cooling, and furnace cooling. Microstructural characterization reveals development of acicular microstructures in all samples including the forged one, with gross absence of carbides. X‐ray diffraction confirms the ferritic nature of acicular plates and also indicated retained austenite present in some samples, the content of which could be correlated to the extent of bainitic transformation. Thermodynamic calculations together with microstructural observations (e.g., ferrite plate size) and hardness data established the development of fully martensitic microstructure on water quenching, while that of a mixed microstructure comprising predominantly of bainite in the forged, air cooled, and furnace‐cooled condition. The aforementioned findings could have wider implications in developing fully bainitic microstructures in large components, where uniform rapid cooling is not practically feasible.

In Situ Observation of Microstructure and Precipitate Phase Transformation during the Solidification of Mg‐Containing GH3625 Alloy at Different Cooling Rates

In practical applications, intermetallic compounds like Laves phase and metal carbides adversely affect the performance of nickel‐based superalloys. Using a high‐temperature confocal laser scanning microscope, the solidification process of as‐cast GH3625 alloy containing Mg at different cooling rates (−20, −35, and −50 °C min−1) is studied. Fitting curves of the volume fraction of the solid phase with solidification temperature before and after Mg treatment are obtained. Trends of solid phase transformation rates with solidification temperature are determined. Differential scanning calorimetry is employed to analyze and statistically evaluate the melting temperature range and enthalpy of each phase during the melting process. Experimental results demonstrate that Mg treatment significantly accelerates the alloy solidification at the cooling rates of −20 and −35 °C min−1, while reducing the area of residual liquid phase at the same solidification temperature, disrupting the Laves/NbC eutectic relationship, and regularizing NbC morphology, transitioning its distribution from aggregation to dispersion. After Mg treatment, the precipitation of the Laves phase is significantly reduced. As a result, the influence mechanism of Mg treatment on the phase transformation and microstructure of GH3625 is clarified based on homogeneous nucleation theory.

Preparation of Metallized Pellets for Steelmaking by Hydrogen Cooling Reduction with Different Cooling Rates.

To utilize the sensible heat of hot roasted iron ore pellets with no CO2 emission in the production of metallized pellets for direct steelmaking, the pellets were reduced in H2 during their cooling process with variable cooling rates. When the cooling rate decreased from 5.2 °C/min to 2.0 °C/min, the total iron content, reduction degree, and iron metallization degree of the pellets increased continuously from 74.0 wt%, 52%, and 31.1% to 84.9 wt%, 93.4%, and 89.2%, respectively. However, the compressive strength of the pellets increased initially from 2100 N/p to 2436 N/p and then decreased considerably to 841 N/p. As the cooling rate decreased, more Fe2O3 was reduced to Fe with diminishing FeO and Fe2SiO4. The porosity of the pellets increased from 23.9% to 54.3%, with higher distribution uniformity of pores. The morphology of metallic iron particles also transited from a layered form to a spherical form and lastly to a porous reticular form. Meanwhile, the metallic iron particles in the pellets grew evidently with more uniform distributions. When the cooling rate was 3.7 °C/min, the resulting metallized pellets had the reduction degree of 74.2%, iron metallization degree of 66.9%, and the highest compressive strength of 2436 N/p, in association with the spherical morphology and relatively large size of metallic iron particles.

Effect of glass infiltration and modified cooling rates on color characteristics alteration of monochrome and multilayer high yttrium oxide containing zirconia.

Sintering technique impacted color of zirconia. This study examined the effect of glass infiltration and altering cooling rate on color alteration of monochrome (Mo) and multilayer (Mu) 5 mol% yttria-partially stabilized zirconia (5Y-PSZ). 180 specimens (width, length, thickness = 10, 20, 2 mm) were prepared from Mo and Mu (comprising cervical (C) and incisal (I) zone) 5Y-PSZ shade VITA-A2. Unintentionally categorized samples (n=15/group) were sintered with traditional (T) versus glass infiltrated (G) technique and cooled down with slow (S: 5°C/min), normal (N: 35°C/min), and fast (F: 70°C/min). CIE-L*a*b* color characteristics were determined for translucency parameter (TP), contrast ratio (CR), opalescence parameter (OP), and color difference (∆Ediff). Microstructures were investigated with SEM and XRD. ANOVA and Tamhane's comparisons were determined for significant differences (p<0.05). TP and OP were significantly higher for Mo than MuC and MuI, but no significant difference in CR among them. Comparable ΔEdiff between Mo and MuC were indicated, but both were significantly lesser than MuL. Glass infiltration and raising cooling rate significantly decreased TP and OP, whereas increased CR and ΔEdiff, which amplified color alteration. Glass infiltration sintering and modified cooling rate significantly altered color parameters of 5Y-PSZ. Monochrome demonstrated higher translucency and opalescence than multilayer, possibly due to colorant additives. Glass infiltration decreased translucency and opalescence due to different refractive indices. Increased cooling rate resulted in decreasing translucency and opalescence due to smaller grain size and t→m transformation. Nevertheless, altered sintering and cooling rates still rendered an acceptable color alteration. Key words:Cooling rate, glass infiltration, optical characteristics, translucency.

Effect of Pouring Temperature Variation on Cooling Rate, Hardness and Microstructure of Al-Zn in Aircraft Structures

Al-Zn alloys are widely utilized in industries such as automotive, aircraft manufacturing, and advanced military equipment due to their exceptional strength-to-weight ratio. Among various fabrication methods, metal casting is a commonly used technique for producing structural components from these alloys. However, a significant challenge with metal casting is the reduction in mechanical properties compared to the base material before melting. This reduction highlights the need for research to identify the optimal casting conditions, particularly the casting temperature, which plays a crucial role in maintaining and potentially enhancing the material's mechanical properties. Aluminum alloy 7075, known for its high strength, was selected for investigation. According to the Al-Zn phase diagram, the melting point of aluminum alloy 7075, based on the weight percentage specified by the Standard Aluminum Association, is approximately 660°C. Experiments were conducted by varying the pouring temperature during casting in 30°C increments above this melting point. Specifically, the alloy was melted and cast at three different temperatures: 690°C, 720°C, and 750°C. The mold temperature was consistently maintained at 220°C to isolate the effects of the pouring temperature. Results indicate that increasing the casting temperature significantly affects the alloy's microstructure and mechanical properties. As the casting temperature increases, the cooling rate decreases, leading to a finer grain structure. This finer grain size directly contributes to an increase in hardness, suggesting that higher casting temperatures can enhance the mechanical properties of Al-Zn alloys. These findings emphasize the importance of precise control over casting temperatures to optimize the performance characteristics of aluminum alloy 7075 in high-strength applications.

Thermal Parameter Optimization for Enhanced Graphite Nodular Properties in Ductile Cast Iron: A Comprehensive Analysis of Cooling Rates and Its Effect on Microstructure

Thermal Parameter Optimization for Enhanced Graphite Nodular Properties in Ductile Cast Iron: A Comprehensive Analysis of Cooling Rates and Its Effect on Microstructure

Effect of CuO Nanostructure Addition and Cooling Rate on the Microstructure and Mechanical Characteristics of Hypoeutectic Al-2wt.%Si Alloy

Effect of CuO Nanostructure Addition and Cooling Rate on the Microstructure and Mechanical Characteristics of Hypoeutectic Al-2wt.%Si Alloy

Grain Refinement Mechanism in the CGHAZ of Ultra-High-Strength Structural Steel: A Critical Analysis of the Impacts of Prior Austenite Grain and Cooling Rates

Grain Refinement Mechanism in the CGHAZ of Ultra-High-Strength Structural Steel: A Critical Analysis of the Impacts of Prior Austenite Grain and Cooling Rates

Effect of Cooling Rate on Inclusions, Primary Carbides, and Microstructure in Rare-Earth H13 Steel

Effect of Cooling Rate on Inclusions, Primary Carbides, and Microstructure in Rare-Earth H13 Steel

Effects of Cooling Rate and Ti Content on the Solidification Characteristics of Al-Ti Alloys

Effects of Cooling Rate and Ti Content on the Solidification Characteristics of Al-Ti Alloys

Unveiling the Effect of Cooling Rate on Grown-in Defects Concentration in Polycrystalline Perovskite Films for Solar Cells with Improved Stability.

Numerous efforts are devoted to reducing the defects at perovskite surface and/or grain boundary; however, the grown-in defects inside grain is rarely studied. Here, the influence of cooling rate on the point defects concentration in polycrystalline perovskite film during heat treatment processing is investigated. With the combination of theoretical and experimental studies, this work reveals that the supersaturated point defects in perovskite films generate during the cooling process and its concentration improves as the cooling rate increases. The supersaturated point defects can be minimized through slowing the cooling rate. As a result, the optimized FAPbI3 polycrystalline films achieve a superior carrier lifetime of up to 12.6 µs and improved stability. The champion device delivers a 25.47% PCE (certified 24.7%) and retain 90% of their initial value after >1100 h of operation at the maximum power point. These results provide a fundamental understanding of the mechanisms of grown-in defects formation in polycrystalline perovskite film.

Effect of cooling rate on solidification microstructure, microsegregation, and nanoprecipitates in medium carbon CrMo cast steel

Precipitation strengthening is a crucial method for enhancing the mechanical properties of steel. The bridgman directional solidification furnace, optical microscope (OM), scanning electron microscope (SEM), electron probe analyzer (EPMA) and transmission electron microscope (TEM) were used to investigate the effect of solidification cooling rate on the solidification microstructure, microsegregation, and nanoprecipitates in medium carbon CrMo cast steel. The results indicate that as the cooling rate increases, the solidification microstructure is significantly refined. The relationship between the cooling rate (CA) and primary dendrite arm spacing (PDAS, λ1) and secondary dendrite arm spacing (SDAS, λ2) are given by λ1 = 123.74 × C-0.4088A, λ2 = 66.63 × C-0.6532A. Solute elements like Cr, Mo, and V exhibit noticeable positive segregation in the inter-dendritic. When the cooling rate does not exceed 0.47 °C/s, the solute concentrations in the inter-dendritic increase with higher cooling rate, leading to a decrease in the effective solute partition coefficient. This phenomenon is primarily attributed to the back diffusion of solute elements during solidification. Following heat treatment, precipitation of M6C, V(C,N), and M23C6 occurs within the inter-dendritic regions. If the solidification cooling rate does not exceed 0.47 °C/s, the density and volume fraction of nanoprecipitates increase with higher cooling rate. This trend primarily results from the reduction in critical nucleation radius and critical nucleation energy, facilitating easier nucleation of nanoprecipitates.