Effect Of Cooling Rate Research Articles

Cooling rate effect on tensile strength of laser deposited Inconel 718

The thermal history generated by the additive manufacturing process influences the resulting material properties. Although trends exist between solidification rate and microstructure, solidification rate is not enough to predict final microstructure and thus mechanical properties. The purpose of this study is to relate the combined effects of solidification time and cooling time of the built material to its final ultimate tensile strength. Cooling time was defined as the time from when the location of interest last passes through 1,200 °C to when it reaches 400 °C. Nine locations on a laser deposited IN718 thin wall were studied in detail to understand the effect of cooling rate on tensile strength. Tensile samples were machined at these locations. The thermal histories of the locations of interest were compared with build geometry and the ultimate tensile strength of that location. An inverse proportional relationship was seen between the distance of the location of interest from the substrate and the cooling time. A trend was also seen linking increased surface temperature and increased solidification time. Weighted Cooling And Solidification Time (WCAST) was defined as the sum of weighted normalized solidification time and the normalized cooling time. Ultimate tensile strength was seen to decrease as WCAST increased. Optical microscopy images of the build microstructure confirm that longer cooling and solidification times lead to coarser microstructures, which may cause the lower tensile strengths measured.

Effects of Shear and Cooling Rate on the Crystallization Behavior and Structure of Cocoa Butter: Shear Applied During the Early Stages of Nucleation

Here we investigated the effects of applied shear and temperature during the early stages of nucleation on the isothermal crystallization behavior and microstructure of cocoa butter (CB). Results showed that the composition of nucleating triacylglycerols (TAGs) as well as crystalline microstructure and polymorphism of CB were affected by mixing and temperature gradients while still in the molten state. The initial crystalline material isolated from CB after it had been subjected to shear had a similar TAG composition as native CB. However, in the absence of shear, high melting TAGs such as trisaturates (SSS) along with lower amounts of monounsaturated TAGs (SUS) were present, possibly due to fractionation. After subjecting CB to shear in its molten state, crystallization rates were faster due to the cocrystallization of different TAGs into a mixed crystal; however, the polymorphic transition into the more stable β-V form was found to be slower due to inherent complexity in TAG composition. Under static co...

Effect of Cooling Rate on the Microstructure and Mechanical Properties of Fe-Mn-Al-C Light-Weight Steels

Effect of Cooling Rate on the Microstructure and Mechanical Properties of Fe-Mn-Al-C Light-Weight Steels

Effect of Cooling Rate on the Microstructure and Mechanical Properties of Cu/Al Bimetal Fabricated by Compound Casting

Cu/Al bimetal was fabricated successfully by compound casting at different cooling rates in the range from 0.8 K/s to 1.83 K/s (0.8 °C/s to 1.83 °C/s). Interfacial cooling curve, microstructure evolution, bonding strength, and interfacial formation mechanism of Cu/Al bimetal were investigated simultaneously. Results show that the transition zone consists of the intermetallic compounds (IMCs) and the remelting zone. The IMCs are identified as Al4Cu9, AlCu, and Al2Cu, types of which are not affected by the cooling rate. The cooling rate primarily influences the thickness of IMCs, the microstructure of the remelting zone, and the morphology of the remelting zone/Al interface. The Cu/Al bimetal produced at the cooling rate of 1.02 K/s (1.02 °C/s) has relatively higher bonding strength than those at the cooling rates of 0.8 K/s and 1.83 K/s (0.8 °C/s and 1.83 °C/s). Shear fracture primarily occurs on the hard brittle IMCs rather than on the remelting zone. Based on the cooling curve and diffusion analysis, a new bonding mechanism of Cu/Al bimetal is proposed.

Effect of Cooling Rate on the Mechanical Properties of AA365 Aluminum Alloy Heat-Treated Under T4, T5, and T6 Conditions

The mechanical properties of AA365, an Al–Si–Mn–Mg alloy used in high-pressure die-casting of automotive parts, can be optimized for a proper application using different heat treatments. During a die-casting process including heat treatment, aluminum alloy cast components experience considerable changes in their mechanical properties due to the non-uniform cooling phenomena. The mechanical properties of AA365 with different cooling rates during T4, T5, and T6 heat treatments were investigated and analyzed by a statistical method using a design of experiments protocol to see which factor is most significant for mechanical properties. The factors used in this study are the type of heat treatment and cooling rate of each step. The microstructural analysis was conducted to observe the mechanism of mechanical property changes. The combination of heat treatment type and cooling rate enabled the control of ductility and strength properties in AA365.

Effect of Cooling Rate on Dopant Spatial Localization and Phase Transformation in Cu‐Doped Y‐Stabilized ZrO2 Nanopowders

The effect of calcination temperature (TC = 500–1000 °C) and cooling rate on the dopant distribution in Cu‐doped Y‐stabilized ZrO2 nanopowders is studied. The powders are produced by co‐precipitation technique and investigated by attenuated total reflection, UV‐vis diffuse reflectance, electron paramagnetic resonance, and transmission electron microscopy methods. The cooling rate is found to affect the amount of Cu substances on grain surface, the powders subjected to fast cooling (quenching) showed higher amount of Cu‐related complexes on the grains’ surface than their counterparts cooled with furnace after calcination. It is observed that Cu impurities diffuse inside ZrO2 grains from Cu‐related surface substances when TC < 800 °C. This process is accompanied by the enhancement of 275‐nm absorption band caused by oxygen vacancies formation. For TC > 800 °C, outward migration of Cu dopants takes place. Simultaneously, the intensity of 275‐nm absorption band decreases, the monoclinic ZrO2 phase forms and its contribution rises with TC. It is proposed that monoclinic phase formation is caused by the replacement of Cu atoms from lattice sites to interstitials leading to an appearance of the channels for Y out‐diffusion via cation vacancies and destabilization of ZrO2 tetragonal phase.

Rapid geomagnetic field intensity variations in the Near East during the 6th millennium BC: New archeointensity data from Halafian site Yarim Tepe II (Northern Iraq)

We present new archeointensity results from a series of groups of pottery fragments that were collected from the multi-layered archeological site Yarim Tepe II in Northern Iraq (Northern Mesopotamia) dated to the 6th millennium BC. This site comprises a 7-m-thick sequence of archeological deposits encompassing the Middle Halaf, Late Halaf and the Halaf-Ubaid Transitional (HUT), between ∼5750 and ∼5000 BC according to the chronology currently considered for the Halafian archeological period. Three new radiocarbon dates obtained from bone fragments confirm that Yarim Tepe II was likely not occupied before the Middle Halaf, as was independently established from archeological constraints. Archeointensity determinations were carried out using the protocol developed for the Triaxe magnetometer. This procedure takes into account thermoremanent magnetization anisotropy and cooling rate effects. 114 fragments fulfilled our set of archeointensity selection criteria, with intensity data obtained from at least two but most often three specimens per fragment. Mean archeointensity values were estimated for 23 groups of fragments well distributed across the entire stratigraphic sequence from the averaging of the data obtained from a minimum of three fragments per group. These values were dated using a bootstrap procedure relying on the stratigraphic position of the different groups of fragments and on the different age constraints available inside the Yarim Tepe II sequence. The new data show a significant decrease in geomagnetic field intensity by ∼12 μT between the Middle Halaf and the Late Halaf–HUT time interval. This decrease was accompanied by a short intensity peak, which may have lasted only a few decades, around the Middle Halaf–Late Halaf boundary, at ∼5500 BC. This evolution is quite similar to that observed from Syrian and Bulgarian archeointensity data, even though the precise duration of the intensity peak is presently questionable. The Bulgarian data set further suggests that the intensity secular variation in the Near East and in Eastern Europe during the 6th millennium BC was in fact principally punctuated by two successive short-lasting intensity peaks, the first around 5800 BC and the second around 5500 BC. The scarcity of the intensity data available worldwide, however, prevents us constraining the geomagnetic dipole or non-dipole origin of these features. The variation rates associated with the rapid intensity fluctuations observed in Yarim Tepe II are of ∼0.15–0.25 μT/yr. This range of values appears similar to that of rapid intensity variations that sporadically occurred in more recent times, such as in Western Europe around 700 BC and 1000 AD. In contrast, it is lower than the variation rates that were proposed for geomagnetic spikes. Our results also have interesting implications on Halafian archeology; in particular, they suggest that the Late Halaf–HUT boundary was older by ∼ one century than previously considered.

Cooling rate upon in air heat treatment and magnetic properties of amorphous soft magnetic alloys

Investigation of the cooling rate effect during heat treatment in air of amorphous magnetic alloys of Fe-Ni-Si-B and Co-Fe-Ni-Cr-Mn-Si-B in states with different signs of saturation magnetostriction were performed to optimize the magnetic properties. It is shown that the increase in cooling rate from 15 to 40 °C/min contributes to the magnetic properties improvement in a state with λs > 0 and their deterioration in a state with λs < 0. This is due to the different influence of induced stresses caused by interaction of ribbon surface with atmospheric water vapor, and their value changes affected by cooling rate change.

Experimental Study on the Effect of Cooling Rate on the Secondary Phase in As‐Cast Mg–Gd–Y–Zr Alloy

The effect of cooling rate on the composition, morphology, size, and volume fraction of the secondary phase in as‐cast Mg–Gd–Y–Zr alloy is investigated. In the study, a casting containing five steps with thickness of 10–50 mm is produced, in which cooling rate ranging from 2.6 to 11.0 K s−1 is created. The secondary phase is characterized using optical microscope (OM), scanning electron microscope (SEM), and electron probe micro‐analyzer (EPMA). The volume fraction of the secondary phase is determined using OM and quantitative metallographic analysis, and Vickers hardness test is conducted to verify the analysis results. The effect of the cooling rate on the volume fraction of the secondary phase is discussed in detail. The result shows that with the increase of the cooling rate, the size of the secondary phase decreases. The effect of the cooling rate on the volume fraction of the secondary phase is complicated somewhat. A comprehensive analysis on the experimental data shows that a critical cooling rate may exist, over which the volume fraction of the secondary phase decreases with the increase of the cooling rate, however under which the volume fraction increases with the increase of the cooling rate.

Effect of Cooling Rates on the Transformation Behavior and Mechanical Properties of a Ni-Rich NiTi Alloy

Slightly nickel-rich Ni–Ti alloys (typically 50.5–51% atomic percent nickel) are commonly used to produce devices that are superelastic at body temperature. This excess nickel can be tolerated in the NiTi matrix when its temperature is above the solvus of about 600 °C, but will precipitate out during lower temperatures. Recent work has been done on exploring the effect lower temperatures have on the material properties of NiTi. Findings showed that properties begin to change at temperatures as low as 100 °C. It is because of these results that it was deemed important to better understand what may be happening during the quenching process itself. Through running a combination of DSC and tensile tests on samples cooled at varying rates, it was found that the cooling rate has an effect on properties when heat treated above a specific temperature. Understanding how quickly the alloy must be cooled to fully retain the supersaturated NiTi matrix is important to optimizing processes and anticipating material properties after a heat treatment.

Effects of Heating and Cooling Rates on Phase Transformations in 10 Wt Pct Ni Steel and Their Application to Gas Tungsten Arc Welding

10 wt pct Ni steel is a high-strength steel that possesses good ballistic resistance from the deformation induced transformation of austenite to martensite, known as the transformation-induced-plasticity effect. The effects of rapid heating and cooling rates associated with welding thermal cycles on the phase transformations and microstructures, specifically in the heat-affected zone, were determined using dilatometry, microhardness, and microstructural characterization. Heating rate experiments demonstrate that the Ac3 temperature is dependent on heating rate, varying from 1094 K (821 °C) at a heating rate of 1 °C/s to 1324 K (1051 °C) at a heating rate of 1830 °C/s. A continuous cooling transformation diagram produced for 10 wt pct Ni steel reveals that martensite will form over a wide range of cooling rates, which reflects a very high hardenability of this alloy. These results were applied to a single pass, autogenous, gas tungsten arc weld. The diffusion of nickel from regions of austenite to martensite during the welding thermal cycle manifests itself in a muddled, rod-like lath martensitic microstructure. The results of these studies show that the nickel enrichment of the austenite in 10 wt pct Ni steel plays a critical role in phase transformations during welding.

Effect of Cooling Rate on Precipitation Behavior and Micromechanical Properties of Ferrite in V-N Alloyed Steel During a Simulated Thermomechanical Process

The effect of the cooling rate after finish deformation at 1223 K (950 °C) on the microstructural evolution, V(C,N) precipitation, and micromechanical properties of ferrite in high-N V-alloyed building steel was comparatively investigated using a Gleeble-1500 thermomechanical simulator. Metallographic analysis shows that polygonal ferrite (PF) and pearlite (P) were dominant microconstituents at cooling rates ranging from 0.5 K/s to 3 K/s (0.5 °C/s to 3 °C/s). As the cooling rate increased within this range, the average ferrite grain size decreased from 6.1 ± 0.30 to 4.4 ± 0.25 μm. Besides, the sheet spacing of interphase precipitated V(C,N) particles decreased from 64.0 to 78.7 to 21.9 to 24.5 nm, and the average size of randomly precipitated particles was refined from 8.2 ± 3.24 to 6.3 ± 2.18 nm. The number density of precipitates with a size below and above 10 nm decreased, and the total number density decreased from 2482 ± 430 to 1699 ± 142 μm−2. Moreover, high-resolution transmission electron microscopy (HRTEM) observation revealed that there exists a coherent interface between the nanoscaled V(C,N) particle and the ferrite matrix. This interface lowered the nucleation energy barrier and promoted the V(C,N) particle precipitation in the ferrite matrix. Nanoindentation measurements indicated that the ferrite phase became softer, and the corresponding value of nanohardness and Young’s modulus decreased as the cooling rate increased, which was caused predominantly by the decrease in precipitation hardening due to the lower number density of V(C,N) precipitates.

Effect of Cooling Rate on Microstructure of Two Kinds of High Nb Containing Tial Alloys

In this paper, high Nb-TiAl alloys with Cr and W additions were prepared by Vacuum induction melting method, and then were heat treated under three different cooling rates of slow cooling, furnace cooling and air cooling. The phase composition of the alloy was analyzed by X ray diffraction, and the microstructure of the alloy was observed by optical microscope (OM), scanning electron microscope (SEM) and energy dispersive analyzer. The results show that the microstructure of Ti45Al8Nb0.2Cr and Ti45Al8Nb0.2W are fully lamellar structure with the main phase composition of α+γ after 3 different heat treatment conditions. The grain size of the two alloys decreases with decreasing of cooling rate, and the grain size of the alloyed with Cr alloy is smaller than that of the alloyed with W alloy. Most of the original massive β phase at grain boundaries and lamellar interfaces dissolved after heat treatment, and the transformation of β phase is easier for Ti45Al8Nb0.2Cr.

Cooling rate effects in sodium silicate glasses: Bridging the gap between molecular dynamics simulations and experiments.

Although molecular dynamics (MD) simulations are commonly used to predict the structure and properties of glasses, they are intrinsically limited to short time scales, necessitating the use of fast cooling rates. It is therefore challenging to compare results from MD simulations to experimental results for glasses cooled on typical laboratory time scales. Based on MD simulations of a sodium silicate glass with varying cooling rate (from 0.01 to 100 K/ps), here we show that thermal history primarily affects the medium-range order structure, while the short-range order is largely unaffected over the range of cooling rates simulated. This results in a decoupling between the enthalpy and volume relaxation functions, where the enthalpy quickly plateaus as the cooling rate decreases, whereas density exhibits a slower relaxation. Finally, we show that, using the proper extrapolation method, the outcomes of MD simulations can be meaningfully compared to experimental values when extrapolated to slower cooling rates.

Experimental Study of the Influence of Periodic Boundary Conditions: Effects of Finite Size and Faster Cooling Rates on Dissimilar Polymer–Polymer Interfaces

Building on our recent work that mapped the profile in local glass transition temperature Tg(z) across a single polystyrene (PS)/poly(n-butyl methacrylate) (PnBMA) interface, we explore the impact of limiting domain size and increasing cooling rate. This study is motivated by traditional computational approaches employed to overcome computer-power limitations, extrapolating short time scales and using periodic boundary conditions that introduce repeating interfaces. Using a localized fluorescence method, we find addition of a second PS/PnBMA interface perturbs the local PS Tg(z) at a distance of z = 100 nm from the first interface when the second interface approaches a distance closer than 300 nm. The local Tg(z) profile across a finite PS domain size of 300 nm for a range of cooling rates shows that limiting domain size and increasing cooling rate (faster time scales) diminishes and truncates the broad asymmetric Tg(z) profile, weakening the confinement effect for dissimilar polymer–polymer interfaces, c...

저합금강의 이중 오스테나이징 템퍼링에서 냉각 속도에 따른 미세조직 및 기계적 특성 변화

저합금강의 이중 오스테나이징 템퍼링에서 냉각 속도에 따른 미세조직 및 기계적 특성 변화

Effect of Cooling Rate on Microstructure and Properties ofa Cu-Containing Titanium Alloy

Effect of Cooling Rate on Microstructure and Properties ofa Cu-Containing Titanium Alloy

Erratum to: Effect of Cooling Rate on the Dendrite Coherency Point During Solidification of Al2024 Alloy

Erratum to: Effect of Cooling Rate on the Dendrite Coherency Point During Solidification of Al2024 Alloy

Fast geomagnetic field intensity variations between 1400 and 400 BCE: New archaeointensity data from Germany

Thirty-five mean archaeointensity data were obtained on ceramic sherds dated between 1400 and 400 BCE from sites located near Munich, Germany. The 453 sherds were collected from 52 graves, pits and wells dated by archaeological correlation, radiocarbon and/or dendrochronology. Rock magnetic analyses indicate that the remanent magnetization was mainly carried by magnetite. Data from Thellier-Thellier experiments were corrected for anisotropy and cooling rate effects. Triaxe and multispecimen (MSP-DSC) protocols were also measured on a subset of specimens. Around 60% of the samples provide reliable results when using stringent criteria selection. The 35 average archaeointensity values based on 154 pots are consistent with previous data and triple the Western Europe database between 1400 and 400 BCE. A secular variation curve for central-western Europe, built using a Bayesian approach, shows a double oscillation in geomagnetic field strength with intensity maxima of ∼70µT around 1000-900 BCE and another up to ∼90µT around 600-500 BCE. The maximum rate of variation was ∼0.25µT/yr circa 700 BCE. The secular variation trend in Western Europe is similar to that observed in the Middle East and the Caucasus except that we find no evidence for hyper-rapid field variations (i.e. geomagnetic spikes). Virtual Axial Dipole Moments from Western Europe, the Middle East and central Asia differ by more than 2·1022A·m2 prior to 600 BCE, which signifies a departure from an axial dipole field especially between 1000 and 600 BCE. Our observations suggest that the regional Levantine Iron Age anomaly has been accompanied by an increase of the axial dipole moment together with a tilt of the dipole.

Cooling rate effect on microstructure and mechanical properties of AlxCoCrFeNi high entropy alloys

The AlxCoCrFeNi alloys were prepared by arc-melting (AMx) and suction-casting (SCx) method. Their microstructure and phase constituents were characterized by scanning electron microscope, X-ray diffractometer and electron backscattered diffraction, and the compressive properties were tested as well. It is found that higher cooling rate during suction-casting process could not only refine microstructure but also change the phase morphology and strengthening mechanism. Microstructure refinement should enhance the strength of SCx alloys, but the strength difference between SCx and AMx alloys increases first when the Al content increase from 0.15 to 0.75 and then decreases. For Al0.15CoCrFeNi alloy, the density of 60°〈111〉 deformation twins in the compressive samples prepared by arc-melting is higher than suction-casting. This will offset the strength contribution of microstructure refinement caused by higher cooling rate. For Al0.75CoCrFeNi alloy, the high strength for SC0.75 alloy can be attributed to not only microstructure refinement but also increase in volume fraction of BCC phase with high strength and lattice strain in FCC phase.