Thermal Profiles and Fraction Solid of Aluminium 7075 at Different Cooling Rate Conditions

2013 ◽  
Vol 554-557 ◽  
pp. 582-595 ◽  
Author(s):  
Asnul Hadi Ahmad ◽  
Sumsun Naher ◽  
Dermot Brabazon
Keyword(s):  
Cooling Rate ◽  
Air Flow ◽  
Phase Changes ◽  
Crucible Wall ◽  
Cooling Curves ◽  
Cooling Rates ◽  
Labview Software ◽  
Fraction Solid ◽  
Forced Air ◽  
Semi Solid

In order to determine suitable processing conditions for semi-solid aluminium 7075 thermal analysis (TA) was performed in order to obtain the relationship between fraction solid and temperature. During experimental work, the alloy was heated to 750°C by induction furnace and solidified at various cooling rates. Cooling curves for the metal were recorded with two thermocouples, one at the centre of the melt volume and one beside the containing crucible wall. A specially designed chamber with kaowool blanket was used to achieve the slowest cooling rate. The faster cooling rate was achieved with the crucible in open atmosphere with a set air flow rate over the crucible. A Data Acquisition (DAQ) system controlled by LabVIEW software was used to record the temperature-time profiles. From these cooling curves, the phase change at any corresponding time and temperature was estimated. The temperature difference between centre and wall of crucible was used to determine dendritic coherency point (DCP). Results show that, the slowest cooling rate with the kaowool blanket was at 0.03°C/s. An intermediate cooling rate of 0.21°C/s was achieved by leaving the melt to cool without kaowool blanket or forced air flow, and the fastest cooling rate was 0.43°C/s. The change in cooling rate altered the temperatures at which phase changes occurred, including those for eutectic and solidus. It was found that for lower the cooling rates that the DCP occurred at lower temperatures. The DCP for the cooling rate of 0.03 °C/s was found to be 574°C (corresponding to 0.85 fraction solid) whereas the DCP for 0.43 °C/s was found to be 623°C (corresponding to 0.55 fraction solid).

Cooling Rates of Brake Drums and Discs

1965 ◽  
Vol 180 (1) ◽  
pp. 191-205 ◽  
Author(s):  
T.P. Newcomb ◽  
N. Millner
Keyword(s):  
Cooling Rate ◽  
Air Flow ◽  
Vehicle Speed ◽  
Uniform Temperature ◽  
Cooling Rates ◽  
Size And Shape ◽  
Slip Ring ◽  
Disc Brakes ◽  
Shape And Size ◽  
Time Plot

An investigation has been made of the rates of cooling of vehicle brake drums and discs. Thermocouples were inserted in the drums and discs and in the wheel hubs and their outputs fed via slip ring units to meters mounted inside the vehicle. The drums or discs were heated to a uniform temperature of 300°-400°C by drag braking and the rate at which they cooled measured while the vehicle was driven at constant speed. Measurements were made at various speeds in the range 0 to 90 mile/h. From the log (temperature) against time plot a cooling coefficient bv was determined. It is shown that at a vehicle speed v the quantity bv can be expressed in the form bv = b0 +Kv0·8 where b0 represents the loss of heat to the hub and K is a constant depending on the size and shape of the drum or disc. Values of these constants have been determined on a variety of cars having discs and drums varying from 7 in to 11 in diameter and on a lorry fitted with 16·75 in diameter drums. Cooling rates are shown to depend on shape and size of the disc or drum. Results show that the cooling rates of front brakes are about 20 per cent higher than the rear brakes and that front discs cool about 25 per cent more quickly than the corresponding drum size recommended for the same vehicle. The cooling rate of front discs did not change when wire wheels were fitted instead of solid wheels. Ventilated discs and solid discs were also compared. The effect of fitting dust shields on disc brakes is shown to reduce the cooling rates by about 30 per cent. The effect of otherwise disturbing the air flow was studied.

Phase Transformation of M2 High Speed Steel during Semi-Solid Cooling and Conventional Cooling

2022 ◽  
Vol 327 ◽  
pp. 105-110
Author(s):  
Ting Sun ◽  
Yong Jin Wang ◽  
Ren Bo Song ◽  
Ya Zheng Liu ◽  
Jun Yanagimoto ◽  
...  
Keyword(s):  
Cooling Rate ◽  
Microstructure Evolution ◽  
High Speed ◽  
High Speed Steel ◽  
Solid Particles ◽  
Controlled Cooling ◽  
Cooling Rates ◽  
M2 High Speed Steel ◽  
Conventional Cooling ◽  
Semi Solid

In this paper, the fundamental microstructure evolution of M2 high speed steel was investigated during semi-solid controlled cooling and conventional cooling, respectively. Semi-solid controlled cooling was conducted at 1260 °C with cooling rates from 0.1 to 10 °C/s, while conventional cooling was conducted at 1200 °C and 890 °C with different cooling rates. The continuous cooling transformation curves were plot according to the microstructure evolution. The results showed that microstructure transformation behavior of cooling structure in semi-solid temperature range was different from that of conventional process. For semi-solid specimen, the solid austenite dissolved more alloy elements, and the austenite stability was increased. The solid matrix was pearlite structure in the samples with cooling rate of 0.1 °C /s. When the cooling rate reached 1 °C/s, the granular pearlite disappeared and martensite lath was formed. The structure was relatively uniform, on which there were large carbide with regular shape. The solidified liquid phase showed a network shape surrounding the solid particles. The size of solid particles showed a decreasing trend with the increase of cooling rates. For conventional cooling process, the large eutectic M6C carbide and the small precipitated MC carbide could not be dissolved by austenitized at 890 °C. Increasing the austenitization temperature helped dissolving part of the carbides. The hardenability of M2 steel was high. The hardness has increased to a high level for both semi-solid and conventional specimens when cooling rate reached 1 °C/s. No obvious increase happened when cooling rate continued increasing.

Validation of a Simple Two-Point Method To Assess Restaurant Compliance with Food Code Cooling Rates

2020 ◽  
Vol 84 (1) ◽  
pp. 6-13
Author(s):  
MATTHEW J. IGO ◽  
NICOLE HEDEEN ◽  
DONALD W. SCHAFFNER
Keyword(s):  
Cooling Rate ◽  
Screening Tool ◽  
Point Method ◽  
Cooling Curves ◽  
Simple Linear Regression ◽  
Point Model ◽  
Slow Cooling ◽  
Cooling Rates ◽  
Novel Method ◽  
Almost All

ABSTRACT Outbreaks from improperly cooled foods continue to occur despite clearly described Food Code cooling guidelines. It is difficult for regulators to enforce these guidelines because they are typically in an establishment for less than the 6 h needed to document proper cooling. Prior research proposed using a novel method to estimate cooling rates based on two time-temperature points, but this method has not yet been validated. Time-temperature profiles of 29 different foods were collected in 25 different restaurants during cooling. Cooling curves were divided into two categories: typical (21 foods) and atypical (eight foods) prior to further analysis. Analysis of the typical cooling curves used simple linear regression to calculate cooling rates. The atypical cooling profiles were studied using Monte Carlo simulations of the cooling rate. Almost all linearized typical cooling curves had high (>0.90) R2 values. Six foods with typical cooling profiles that did not pass Food Code cooling times were correctly identified by the two-point model as having slow cooling rates. Three foods that did not pass Food Code cooling times were identified by the two-point model as having marginal cooling rates. Ten of 12 foods identified by the two-point model as having acceptable cooling rates met Food Code cooling times. Most (six of eight) foods that were considered to have atypical cooling curves failed to meet the Food Code cooling times. The two-point model was also able to determine whether these foods would fail based on Food Code guidelines depending upon the simulation criteria used. Our data show that food depth has a strong influence on cooling rate. Containers with a food depth ≥7.6 cm (3 in.) were more likely to have cooling rates slower than the U.S. Food and Drug Administration Model Food Code cooling rate. This analysis shows that the two-point method can be a useful screening tool to identify potential cooling rate problems during a routine restaurant inspection visit. HIGHLIGHTS

scholarly journals Effect of Cooling Rates on the Microstructure and Mechanical Property of La Modified Al7SiMg Alloys Processed by Gravity Die Casting and Semi-Solid Die Casting

Metals ◽  
2020 ◽  
Vol 10 (4) ◽  
pp. 549
Author(s):  
Longfei Li ◽  
Daquan Li ◽  
Jian Feng ◽  
Yongzhong Zhang ◽  
Yonglin Kang
Keyword(s):  
Mechanical Properties ◽  
Cooling Rate ◽  
Die Casting ◽  
Casting Process ◽  
Cooling Rates ◽  
Eutectic Si ◽  
Fibrous Morphology ◽  
La Addition ◽  
Semi Solid ◽  
Re Elements

Rare earth (RE) additions are capable of refining the α-Al phase as well as modifying the eutectic Si particles of alloys. The cooling rate in casting process should be carefully concerned when the Al-Si alloys are refined and modified by adding RE elements. In this study, the effect of cooling rates on the microstructure and mechanical properties of La modified Al-7.0Si-0.3Mg alloys was studied in gravity die casting and semi-solid die casting. It is found that in La modified Al-7.0Si-0.3Mg alloys, with increasing the cooling rate from 0.2 to 9 K/s in gravity die casting, the α-Al grains are greatly refined and the Si particles are modified to branching morphology, which evidently increases the UTS and elongation of alloys. In addition, when increasing the cooling rate from 30 to 130 K/s in semi-solid die casting, the α-Al grains are refined from 140 to 47 μm, and the Si particles are modified to fibrous morphology, which increases the UTS from 190 to 230 MPa and elongation from 10% to 11%. However, the 0.4 wt.% La addition results to La-rich phases formed in microstructure, which impairs the mechanical properties of Al-7.0Si-0.3Mg alloys in semi-solid die casting.

scholarly journals Study of the Effect of Cooling Rate on Eutectic Modification in A356 Aluminium Alloys

2013 ◽  
Vol 765 ◽  
pp. 130-134 ◽  
Author(s):  
Deni Ferdian ◽  
Jacques Lacaze ◽  
Ibon Lizarralde ◽  
Andrea Niklas ◽  
Ana Isabel Fernandez-Calvo
Keyword(s):  
Thermal Analysis ◽  
Differential Thermal Analysis ◽  
Cooling Rate ◽  
Melting Temperature ◽  
Aluminium Alloys ◽  
A356 Alloy ◽  
Cooling Curves ◽  
Eutectic Melting ◽  
Cooling Rates ◽  
Eutectic Modification

In this present work, an assessment of eutectic modification based on thermal analysis was performed on modified A356 alloy. The effect of various cooling rates which were achieved by means of casting samples with various moduli in sand and metallic moulds was investigated. Cooling curves recorded from thermocouples inserted in the centre of the samples showed characteristic undercooling and recalescence associated with (Al)-Si eutectic modification. The results showed that cooling rate has a role in observed modification level. Furthermore, differential thermal analysis was included to determine the eutectic melting temperature.

Effect of Cooling Rate on the Microstructure of Al-5.17Cu-2.63Si Cast Alloy

2013 ◽  
Vol 813 ◽  
pp. 157-160
Author(s):  
Guang Wei Zhao ◽  
Xi Cong Ye ◽  
Zeng Min Shi ◽  
Wen Jun Liu
Keyword(s):  
Cooling Rate ◽  
Volume Fraction ◽  
Cast Alloy ◽  
Eutectic Phase ◽  
Cooling Curves ◽  
Cooling Rates ◽  
Dendrite Arm Spacing

The effect of cooling rate on the solicitation microstructure of a ternary cast Al-5.17Cu-2.63Si alloy is investigated. To create widely different cooling rates for the investigated alloy, the melts were cast into four molds made of different materials: aluminum, graphite, sand, and alumina-silicate-fiber felt (a thermal insulated material), respectively. The cooling curves for each mold specimen were simultaneously measured using calibrated K-type thermocouples, which are linked to a PC computer. The microstructures are characterized in terms of eutectic volume fraction and second dendrite arm spacing. The experiment result shows that increasing the cooling rate increases the amount of eutectic phase and decreases significantly the second dendrite arm spacing.

Effect of Mould Heating Temperature on Cooling Rate of the Melt upon Bronze Crystallization

2014 ◽  
Vol 682 ◽  
pp. 231-235 ◽  
Author(s):  
Nikita Martyushev ◽  
Yuriy N. Petrenko
Keyword(s):  
Cast Iron ◽  
Cooling Rate ◽  
Heating Temperature ◽  
Numerical Data ◽  
Cooling Curves ◽  
Cooling Rates ◽  
Thermal Electromotive Force ◽  
Alumel Thermocouple ◽  
Melt Cooling ◽  
Graphite Mould

The article presents the cooling curves of the tin-leaded bronze melt (consists of 10% of lead, 10% of tin, and 80% of copper) being poured in the moulds of various thermal conductivities: massive cast iron chill mould (with the 1:8 cast mass to mould mass ratio) and graphite mould. The curves were plotted for the moulds previously heated to the temperatures of 20; 200; 400; 600; 800 °С. Plotting of the curves was performed with the use of the device Thermograph designed at Tomsk Polytechnic University. The device records thermal electromotive force values of the chromel-alumel thermocouple and converts them into temperature values. The cooling curves are used to determine melt cooling rates within the temperature range involving the crystallization range. It is shown that under similar conditions the cooling rate when casting in cast iron mould is 30-40% higher than in the case of casting in graphite mould. The data given in the paper indicate that preheating of the mould enables us to considerably reduce the cast cooling rate and prolong the period of the melt being in liquid state. It is worth mentioning that cooling rate values of the preheated and non-heated casting moulds are most vividly observed at the initial moments after the melt pouring. When decreasing the casts’ cooling to 300-400 °С the cooling rates tend to be identical. In the article, the numerical data of cooling rates for various mould heating temperatures are presented.

The effect of cooling rate on crystallization behavior and tensile properties of CF/PEEK composites

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Guangming Dai ◽  
Lihua Zhan ◽  
Chenglong Guan ◽  
Minghui Huang
Keyword(s):  
Cooling Rate ◽  
Crystallization Temperature ◽  
Crystallization Behavior ◽  
Crystalline Polymer ◽  
Scanning Calorimetry ◽  
Nonisothermal Crystallization ◽  
Cooling Rates ◽  
Control Range ◽  
Temperature Range ◽  
Transverse Tensile

Abstract In this study, the differential scanning calorimetry (DSC) tests were performed to measure the nonisothermal crystallization behavior of carbon fiber reinforced polyether ether ketone (CF/PEEK) composites under different cooling rates. The characteristic parameters of crystallization were obtained, and the nonisothermal crystallization model was established. The crystallization temperature range of the material at different cooling rates was predicted by the model. The unidirectional laminates were fabricated at different cooling rates in the crystallization temperature range. The results showed that the crystallization temperature range shifted to a lower temperature with the increase of cooling rate, the established nonisothermal crystallization model was consistent with the DSC test results. It is feasible to shorten the cooling control range from the whole process to the crystallization range. The crystallinity and transverse tensile strength declined significantly with the increase of the cooling rate in the crystallization temperature range. The research results provided theoretical support for the selection of cooling conditions and temperature control range, which could be applied to the thermoforming process of semi-crystalline polymer matrixed composites to improve the manufacturing efficiency.

Effects of RE on Critical Cooling Rate of Bearing-B Steel

2012 ◽  
Vol 535-537 ◽  
pp. 761-763 ◽  
Author(s):  
Yi Sheng Zhao ◽  
Xin Ming Zhang ◽  
Zhi Guo Gao
Keyword(s):  
Phase Change ◽  
Cooling Rate ◽  
Experimental Results ◽  
Cooling Rates ◽  
Critical Cooling Rate ◽  
The Law

The law of phase change of bearing-B steel during continual cooling was studied by adopting dilatometer. The CCT curves of bearing-B steel were drawn, and the effects of RE on critical cooling rates were studied. The experimental results show that the start temperatures of martensite TM was decreased from 438 to 404°C. The critical cooling rate was simultaneously decreased from 33 to 15°C/s.

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