Effect Of Cooling Rate Research Articles

Effect of Carbon Equivalent and Cooling Rate on Chilling Tendency and Mechanical Properties in Flake Graphite Cast Iron with different Mn contents

Effect of Carbon Equivalent and Cooling Rate on Chilling Tendency and Mechanical Properties in Flake Graphite Cast Iron with different Mn contents

Developing 1000 MPa Grade LCLA Steels Through Continuous Cooling: Effects of Cr and Cooling Rate on Bainitic and Martensitic Transformations

Developing 1000 MPa Grade LCLA Steels Through Continuous Cooling: Effects of Cr and Cooling Rate on Bainitic and Martensitic Transformations

Effects of Stirring Time and Cooling Rate on the Rheocast Microstructure and Mechanical Properties of Magnesium Alloy MRI 230D

Abstract Semisolid state processing is a methodology that transforms dendritic as-cast microstructure into globular non-dendritic microstructure with optimized mechanical properties. Rheocasting process involves mechanically stirring metals in a semisolid state and its benefits are associated with processing parameters. In order to evaluate stirring time effects, magnesium alloy MRI 230D (Mg–Al6.45–Ca2.25–Mn0.27–Sr0.25–Sn0.84) was melted and cooled down to semisolid processing temperature (595oC). Moreover, isothermal stirring was executed for 1, 2, 4 and 8 minutes. In each experiment, cylindrical samples with different diameters (6 and 12 mm) were collected to evaluate cooling rates effects. The microstructure was analyzed through optical and electron microscopes. The results showed that in the longest stirring times, the primary α-Mg phase got coarser and the interglobular region became more refined. Although shape factor initially increased, subsequently there was a tendency to stabilize. Regarding cooling conditions, it was found that the interglobular region became more refined at higher cooling rates. Mechanical tests revealed an initial decrease in ultimate tensile strength (UTS) and ductility, but afterwards increased due to a more regular microstructure and superior shape factor. The 8-minutes stirring sample achieved the best results: an increase of 12% in UTS and 16% in ductility.

Effect of Cooling Rate and Austenite Deformation on Hardness and Microstructure of 960MPa High Strength Steel

Abstract In order to develop 960MPa grade high strength steel, the effects of cooling rate and austenite deformation on the hardness and the microstructure of high strength steel has been studied by Scanning Electron microscope (SEM), Transmission Electron Microscope (TEM), Gleeble-3500 thermal simulation testing machine and T2500 Vickers hardness tester. The results show that only when the cooling rate was higher than 10∘C/s and the final cooling temperature was lower than 250∘C, the microstructure mainly consists of martensite, and the strength of high strength steel could be above 960MPa; and austenite deformation could effectively refine the width of martensite lath, thus improving the strength and toughness.

Effect of Temperature, Time, and Cooling Rate on the Mineralogy, Morphology, and Reducibility of Iron Ore Sinter Analogues

Analogue sinter tablets were produced at temperatures between 1250°C and 1320°C, with a range of hold times and cooling rates. Platy silico-ferrite of calcium and aluminum (SFCA) morphology was identified in samples produced at 1250°C using reflected light microscopy; however, quantitative x-ray diffraction (XRD) identified the presence of the SFCA phase, with no SFCA-I detected. This proves that the platy SFCA morphology common in analysis by reflected light microscopy cannot be attributed to the SFCA-I mineral without further analysis. Micro-XRD and electron probe micro-analysis (EPMA) were carried out on an area of platy SFCA confirming this result. The sinter analogue tablets were reduced in a 30% CO, 70% N2 gas mixture at 900°C in a tube furnace thermo-gravimetric analyzer. The degree of reduction of the tablets in this study was found to be controlled by the porosity of the samples, rather than by the morphology or mineralogy of the bonding phase.

Effect of Sintering Temperature and Cooling Rate on the Microstructure and Hardness of Fe-Cr-Mo-V-W-C Sintered Steel added with MoS2

In this work, the Fe-Cr-Mo-V-W-C sintered steels added with MoS2 (1, 3 and 5 wt.%) were produced by powder metallurgy process. The specimens were prepared by mixing, compacting and sintering at temperatures of 1150, 1200 and 1250°C for 45 min in vacuum furnace. After sintering, the specimens were cooled down with N2 at the different cooling rate (0.1 and 5.2°C/s). The density, hardness and microstructure of the sintered Fe-Cr-Mo-V-W-C steels were investigated. The experimental results indicated that the density and hardness of sintered steel could be improved by increase MoS2 addition, cooling rate and sintering temperature. The sintering mechanism was varied from solid state sintering to liquid phase sintering depend on sintering temperatures and MoS2 content. The presence of liquid phases and the increasing of cooling rate resulted in the amount of carbide precipitated decreased in the steel grain but increased precipitation at grain boundaries. The solidified of liquid and eutectic phases were found rising by increased cooling rate. Carbide precipitation in steel grain could be improved by added MoS2 and sintered at low temperature. From the results, it was indicated that the addition of MoS2, increase sintering temperature and cooling rate resulted in the precipitation of carbide, solidified liquid and eutectic phases, and grain growth in the sintered Fe-Cr-Mo-V-W-C steel.

Experimental test of the cooling rate effect on blocking temperatures in stepwise thermal demagnetization

SUMMARYUpon cooling, most rocks acquire a thermoremanent magnetization (TRM); the cooling rate at which this happens not only affects palaeointensity estimates, but also their unblocking temperatures in stepwise thermal demagnetization experiments, which is important, for example, to estimate volcanic emplacement temperatures. Traditional single-domain (SD) theory of magnetic remanence relates relaxation times to blocking temperatures— the blocking temperature is the temperature at which the relaxation time becomes shorter than the experimental timescale—and therefore strictly only applies to remanence acquisition mechanisms at constant temperatures (i.e. viscous remanent magnetizations, VRMs). A theoretical framework to relate (constant) blocking temperatures to (time-varying) cooling rates exists, but this theory has very limited experimental verification—partly due to the difficulty of accurately knowing the cooling rates of geological materials. Here we present an experimental test of this ‘cooling rate effect on blocking temperatures’ through a series of demagnetization experiments of laboratory-induced TRMs with controlled cooling rates. The tested cooling rates span about 1 order of magnitude and are made possible through (1) extremely accurate demagnetization experiments using a low-temperature magnetic properties measurement system (MPMS) and (2) the use of a ‘1-step-only’ stepwise thermal demagnetization protocol where the relaxation process is measured over time. In this way the relaxation time corresponding to the blocking temperature is measured, which can be done to much higher accuracy than measuring the blocking temperature directly as done in traditional stepwise thermal demagnetization experiments. Our experiments confirm that the cooling rate relationship holds to high accuracy for ideal magnetic recorders, as shown for a synthetic weakly interacting SD magnetoferritin sample. A SD-dominated low-Ti titanomagnetite Tiva Canyon Tuff sample, however, showed that natural samples are unlikely to be sufficiently ‘ideal’ to meet the theoretical predictions to high accuracy—the experimental data agrees only approximately with the theoretical predictions, which may potentially affect blocking temperature estimates in stepwise thermal demagnetization experiments. Moreover, we find a strongly enhanced cooling rate effect on palaeointensities for even marginally non-ideal samples (up to 43 per cent increase in pTRM for a halving of the cooling rate).

Effect of Cooling Rate on Precipitation during Homogenization Cooling in Balanced Al–Mg<sub>2</sub>Si Alloy

Effect of Cooling Rate on Precipitation during Homogenization Cooling in Balanced Al–Mg<sub>2</sub>Si Alloy

First archeomagnetic data from Kenya and Chad: Analysis of iron furnaces from Mount Kenya and Guéra Massif

The variation of the Earth's magnetic field over the last millennia is poorly known in Africa, especially in Sub-Saharan Africa that represents less than 1% of the global archeomagnetic dataset. Fourteen iron furnaces from Kenya and Chad have been studied here for archeomagnetic purposes. These structures were dated by 14C from the 14th century in Kenya and from the 18-19th centuries in Chad. Samples, oriented with the plaster cap technique, have been subjected to thermal and alternating field demagnetization, rock magnetic analysis and paleointensity experiment, with the classical Thellier-Thellier technique corrected for anisotropy and cooling rate effects. New directional data (4 from Kenya and 10 from Chad) and one new paleointensity estimate from Kenya (43.5 ± 1.8 μT) were obtained. The Kenyan declinations are in good agreement with the geomagnetic global models, but the inclinations are lower and the intensity higher than predicted. For Chad, the new results prove the efficiency of the archeomagnetic dating, with a precision that is better than radiocarbon for the 18–19th centuries.

Effects of Silver Content and Cooling Rate on Electrical Conductivity and Tensile Properties of Al-Si(-Ag) Alloys

In recent years, new designing of components provided by electronics and automotive industries has required higher mechanical properties and electrical conductivity. Some of the examples are mobile phone frames, automotive powertrain components and new aluminum (Al) housing components. Silver (Ag) and Al have similarities in terms of crystal lattices and atoms diameters. Consequently, the addition of Ag in Al alloys may result in improved properties. The present research focuses on better understanding of the effects of Ag additions and cooling rate variations on the length scale of the dendritic microstructure constituting a Al-5 wt.% Si alloy. One of the factors to be considered during examination of as-cast Al-Si(-Ag) alloys microstructures is the interdendritic spacing. This factor, in combination with the second phases and solid solution, is able to control the application properties. In the present investigation, the ultimate tensile strength increases from 142 MPa for the Al-5 wt.% Si-0.1 wt.% Ag alloy to 154 MPa for the Al-5 wt.% Si-2.0 wt.% Ag alloy. This difference is not observed for ductility, which is preserved essentially unchanged into an improved value of 22% for both Ag-containing alloys. The less Ag-modified alloy samples (0.1 Ag) enhanced electrical conductivity by about 2% and 4% IACS as compared to those of the Al-5 wt.% Si and the Al-5 wt.% Si-2.0 wt.% Ag alloys samples, respectively.

Effects of Cooling Rate during Quenching and Tempering Conditions on Microstructures and Mechanical Properties of Carbon Steel Flange.

This study investigated the mechanical properties of steel in flanges, with the goal of obtaining high strength and high toughness. Quenching was applied alone or in combination with tempering at one of nine combinations of three temperatures TTEM and durations tTEM. Cooling rates at various flange locations during quenching were first estimated using finite element method simulation, and the three locations were selected for mechanical testing in terms of cooling rate. Microstructures of specimens were observed at each condition. Tensile test and hardness test were performed at room temperature, and a Charpy impact test was performed at −46 °C. All specimens had a multiphase microstructure composed of matrix and secondary phases, which decomposed under the various tempering conditions. Decrease in cooling rate (CR) during quenching caused reduction in hardness and strength but did not affect low-temperature toughness significantly. After tempering, hardness and strength were reduced and low-temperature toughness was increased. Microstructures and mechanical properties under the various tempering conditions and CRs during quenching were discussed. This work was based on the properties directly obtained from flanges under industrial processes and is thus expected to be useful for practical applications.

Simulation of the Composition and Cooling Rate Effects on the Solidification Path of Casting Aluminum Alloys

Solidification simulations were carried out for casting aluminum alloy A356 using PanSolidification module of Pandat software which enables consideration of back diffusion in the solid during solidification. The casting microstructure features including the solidified phases, phase fractions, and secondary dendrite arm spacing (SDAS) were simulated. The simulated results explain the experimental observations reasonably well. High throughput calculation was performed to understand the effects of alloy composition and cooling rate on the formation of the intermetallic phases and SDAS in the casting microstructure. The role of Mn in eliminating the formation of detrimental β-AlFeSi phase was also simulated and discussed.

Investigation of Cooling Rate Effect of Liquid Vanadium on the Crystallization Process with Molecular Dynamic Simulation Method

Isıtma ve soğutma süreçlerinde vanadyumun mikro yapısal değişimleri ve soğutma hızının kristalizasyon süreci üzerine etkileri gömülü atom metodu kullanılarak moleküler dinamik benzetim yöntemi ile araştırıldı. Soğutma oranın etkisi sekiz farklı soğutma oranı (Q=0.05-10 K/ps) kullanılarak araştırıldı ve sonuçlar çiftler dağılım fonksiyonu, Honeycutt-Andersen ve Voronoi mozaikleme analiz yöntemleri kullanılarak analiz edildi ve ayrıntılı bir şekilde tartışıldı. Erime noktası civarında hesaplanan çiftler dağılım fonksiyonu ve yapı faktörünün deneysel sonuçlarla tutarlı olduğu gözlenmiştir. Daha yavaş soğutma oranları için kristalizasyon sıcaklığından başlayarak ideal bcc kristal yapıyı temsil eden 1441 ve 1661 bağlı çiftlerinin ve <0,6,0,8> kümelerinin ani ve bir o kadar keskin bir artışı izlenmiştir. Daha düşük sıcaklıklarda söz konusu bağlı çiftlerin ve kümelerin dağılımlarının ısıtma sürecinde elde edilen sonuçlarla neredeyse üst üste olduğu gözlenmiştir. Bu sonuçlar yavaş soğutma oranları için sistemin sıvı yapıdan ideal bcc kristal yapıya geçiş yaptığının açık delilidir. Sistem daha hızlı soğutulduğunda, bcc kümelerin yanı sıra başka kristal kümelerin de oluştuğu gözlenmiştir.

Effect of cooling rate on the residual ductility of Post-LOCA Zircaloy-4 cladding

Effects of cooling rates on mechanical behavior of steam-oxidized Zircaloy-4 are systematically investigated with the cladding material oxidized to the current ductility-based regulatory limits (17% ECR at 1204 °C). Three different cooling rates associated with distinctively different quenching environments are tested; ambient air cooled (<7 °C/s), boiling water (∼400–500 °C/s), and room temperature water (∼1600–2000 °C/s). Cooling rates of post-LOCA Zircaloy-4 have (1) limited effects on average cladding residual ductility for non-hydrided cladding, (2) pronounced effects on statistical variation of ring compression test results, and (3) effects on fracture strength reduction on pre-hydrided cladding (765 wppm). The limited effect of cooling rate on average residual ductility of non-hydrided cladding is due to the cooling-rate insensitive resulting phase thicknesses and their oxygen contents, both of which dictate the level of cladding residual ductility. Homogenizing prior-β phase with finer lamellar structures and reduced α incursion, fast cooling (i.e., 25 °C water quenching) effectively reduces statistical variation of RCT results. The presented results support regulatory validity of past experiments conducted irrespective of cooling rates for Zircaloy-4 with no pre-transient hydrogen content. The observed insensitivity of cooling rates on the ECCS criteria for non-hydrided Zircaloy-4 may represent a gap between ductility-based regulation and integral fuel rod behavior. Cooling rate effect is shown to become increasingly important for increasing pre-transient hydrogen embrittlement, as shown by the fracture strength changes.

Effect of Cooling Rate on Glass Forming Ability of Novel Fe-Based Bulk Metallic Glass

Effect of Cooling Rate on Glass Forming Ability of Novel Fe-Based Bulk Metallic Glass

Effect of Cooling Rate on Microstructure of Rejuvenated Fe-Ni Based Superalloys

Fe-Ni based superalloys have been widely used in land-base gas turbine application. The turbine blade was in service for 50,000 h at high temperature and stresses. When subjected to long-term exposure at high temperature, the microstructure lost its best mechanical properties due to the microstructural instability. The aim of this research is to understand the effect of cooling rate on gamma (γ) grain size and gamma prime (γ’) particle size, morphology, and its volume fraction in rejuvenated Fe-Ni based superalloys. The alloys were solutionized above the γ’ solvus temperature at 1125 °C for 2 h for homogenization and cooling to room temperature at different cooling rates. The alloys were experienced with furnace cooling, air cooling, oil quenching, and water quenching. Microstructural analyses were investigated. Grain size, morphology, volume fraction of γ’ precipitates were investigated. Preliminary mechanical properties such as microhardness was conducted.

Effect of Na and Cooling Rate on the Activation of Mg-Ni Alloys for Hydrogen Storage.

In spite of favourable hydrogen storage properties such as low density, high theoretical capacity (7.6 wt% H/MgH₂) and economics, commercial use of Mg-based alloys is not feasible due to long activation times, slow hydrogen sorption kinetics, and a high temperature for hydrogen release. Mg- Ni alloys have been considered promising materials for hydrogen storage systems as the Mg₂Ni intermetallic phase enhances the kinetics of hydrogen absorption in Mg-Ni alloys through a catalytic effect. It has been suggested that the refinement of eutectic in Mg-Ni alloys can further improve hydrogen absorption kinetics and that this can be achieved through trace Na additions. However, the refinement of the eutectic can also be achieved by increasing the cooling rate during solidification. In this study we investigate the effect of cooling rate and Na additions to Mg-Ni alloys on hydrogen absorption kinetics. Our results indicate that Na additions improve the hydrogen absorption kinetics independent of eutectic refinement and that the effect of the latter is relatively small.

Atom-probe tomographic and dilatometric studies of phase-transformations after inter-critical annealing of a low-carbon dual-phase steel

Phase-transformations and microstructural evolution during and after inter-critical annealing of a low-alloy, dual-phase steel are studied utilizing dilatometric measurements, and microstructural characterization methods, including scanning electron microscopy, synchrotron X-ray diffraction, and atom-probe tomography. Dilatometric measurements reveal that the sample contains ~72% austenite, after annealing for 5-min at 871 °C, which agrees with the water-quenched microstructure, and ~90% after further annealing to 1 h, which agrees with thermodynamic predictions. A continuous-cooling transformation (CCT) diagram is constructed, within the cooling-rate range between 1 °C/s and 70 °C/s. The incubation time for the ferrite-transformation is <1 s, after inter-critical annealing, and the secondary-phases are mainly pearlite for cooling-rates of <5 °C/s, and martensite for cooling-rates >10 °C/s, which is confirmed utilizing scanning electron-microscope observations. The microhardness increases as the cooling rate increases, and an abrupt slope-change is explained by the major secondary-phase changing from martensite to pearlite between 5 °C/s and 10 °C/s. Atom-probe tomography demonstrates the coexistence of martensite and pearlite as secondary-phases for 30 °C/s and a switch in austenite-ferrite transformation mechanisms from para-equilibrium (70 °C/s) to partitioning local-equilibrium (30 °C/s). A microstructural map is constructed to reveal the austenite decomposition products in the cooling-rate range between 1 °C/s and 70 °C/s. Based on composition measurements of the matrix, utilizing APT, the effects of cooling-rates on solid-solution-strengthening are estimated, and the results demonstrate that solid-solution strengthening, especially carbon-redistribution, accounts for the majority of the strength variations due to different cooling-rates.

Post-aging cooling rate effects in Ni45.3Ti34.7Hf15Pd5 shape memory alloys

Effects of post-aging cooling rate (water quenched, WQ, and furnace cooled, FC) on the shape memory properties of polycrystalline Ni45.3Ti34.7Hf15Pd5 alloys were studied. Their functional properties such as transformation temperatures, hysteresis, elastic energy, superelastic behavior and recoverable strain were found to be closely related to the post-aging cooling rate. Martensite start temperature decreased from 77 °C for WQ sample to 22 °C for FC sample. Impressive shape memory effect was observed under a huge compressive stress of 1 GPa with recoverable strains of 2.2 % and 2.5 % for the water quenched and furnace cooled samples, respectively. While both WQ and FC alloys showed perfect superelasticity for a wide temperature range, the WQ sample showed superelasticity at higher temperatures above 100 °C.

Quenching Temperature and Cooling Rate Effects on Thermal Rejuvenation of Metallic Glasses

Thermal rejuvenation was explored when Zr62Cu17Ni13Al8 metallic glass was rapidly heated to at least 100 K higher than its glass transition temperature at a heating rate of 60 K/s and then quenched into copper molds. The effect of the quenching temperature and the cooling rate on rejuvenation was evaluated using transmission electron microscopy images, differential scanning calorimetry, density measurements, and Vickers indents. This study suggests that the density of flow units is mainly affected by the final cooling rate rather than the quenching temperature.