scholarly journals Effect of Cooling Rate and Modification by Strontium on the Thermal Conductivity of Al-8Si Alloy

Metals ◽  
2021 ◽  
Vol 11 (9) ◽  
pp. 1334
Author(s):  
Guanyi Wang ◽  
Zhiping Guan ◽  
Jinguo Wang ◽  
Mingwen Ren ◽  
Ruifang Yan ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Heat Treatment ◽  
Cooling Rate ◽  
Eutectic Silicon ◽  
Critical Role ◽  
Design Strategy ◽  
Cooling Rates ◽  
Secondary Dendrite Arm Spacing ◽  
Sr Modification ◽  
The Relationship

Cooling rate plays a critical role in determining the thermal conductivity of Al-Si alloys. Although the effect of morphology and size of Si (changed by heat treatment) on its thermal conductivity has been investigated, the effect of cooling rates on thermal conductivity has not been well studied. In this study, we investigated the microstructure of an Al-8Si (with and without modification by Strontium (Sr)) alloy with cooling rates from 46.2 °C/s to 234 °C/s. It was found that the effect of cooling rate on thermal conductivity of Sr modification and Sr-free samples are opposite from each other. As a result, while the cooling rate increased from 46.2 °C/s to 234 °C/s, the calculated thermal conductivity increased from 145.3 MS/m to 151.5 MS/m for Sr-free Al-8Si alloy, and the calculated thermal conductivity was reduced from 187.5 MS/m to 176.7 MS/m for the Sr-modified Al-8Si alloy. By discussing how thermal conductivity correlates with eutectic silicon morphology and secondary dendrite arm spacing, the relationship between cooling rate and thermal conductivity were explained. This work suggests a new design strategy for improving the thermal conductivity of Al-Si hypoeutectic alloys.

Effects of Modification and Heat Treatment on Microstructure and Mechanical Property of Two-Step Foamed ZL111 Alloy Foam

2018 ◽  
Vol 933 ◽  
pp. 68-77
Author(s):  
Yu Yuan Jiang ◽  
Xiao Xu Luo ◽  
Qing Chen ◽  
Ming Wei Zhao ◽  
Jian Sheng Lu ◽  
...  
Keyword(s):  
Heat Treatment ◽  
Mechanical Property ◽  
Eutectic Silicon ◽  
Absorption Capacity ◽  
Compressive Property ◽  
Average Pore ◽  
T6 Heat Treatment ◽  
Sr Modification ◽  
Average Size ◽  
Microstructure And Mechanical Property

ZL111 alloy foams with a porosity of 80% and an average pore diameter of 3.5 mm were fabricated using a two-step foaming process, and the effects of modification and heat treatment on their microstructure and mechanical property were studied. The results indicates that by Y&Sr modification, most of the eutectic silicon in the ZL111 alloy foam is transformed from plate-like into dot-like forms, and the average size of evenly distributed α-Al grain is reduced from 80~100μm to 30~40μm, which is more efficient than separate Y or Sr modifications. By combining Y and Sr modification and T6 heat treatment, the α-Al grain size of ZL111 alloy foam maintains its previous modified effect, eutectic silicon remains spherical and well-distributed, and CuAl2and Al9FeMg3Si5are dispersed homogeneously at the α-Al grain boundary. The Y&Sr modification and T6 heat treatment also significantly improved the compressive property of ZL111 alloy foam, when we compared them with the untreated ZL111 alloy foam. The compressive strength rises from 13.3 MPa to 22.6 MPa, the densification strain improves from 59.3% to 76.9%, and the energy absorption capacity increases from 4.87 MJ/m3to 13.77 MJ/m3.

scholarly journals Development of Precipitation Hardening Parameters for High Strength Alloy AA 7068

Materials ◽  
2020 ◽  
Vol 13 (4) ◽  
pp. 918
Author(s):  
Julia Osten ◽  
Benjamin Milkereit ◽  
Michael Reich ◽  
Bin Yang ◽  
Armin Springer ◽  
...  
Keyword(s):  
Heat Treatment ◽  
Cooling Rate ◽  
Maximum Yield ◽  
High Strength ◽  
Tensile Tests ◽  
Age Hardening ◽  
Scanning Calorimetry ◽  
Cooling Rates ◽  
Critical Cooling Rate ◽  
Kinetics Of

The mechanical properties after age hardening heat treatment and the kinetics of related phase transformations of high strength AlZnMgCu alloy AA 7068 were investigated. The experimental work includes differential scanning calorimetry (DSC), differential fast scanning calorimetry (DFSC), sophisticated differential dilatometry (DIL), scanning electron microscopy (SEM), as well as hardness and tensile tests. For the kinetic analysis of quench induced precipitation by dilatometry new metrological methods and evaluation procedures were established. Using DSC, dissolution behaviour during heating to solution annealing temperature was investigated. These experiments allowed for identification of the appropriate temperature and duration for the solution heat treatment. Continuous cooling experiments in DSC, DFSC, and DIL determined the kinetics of quench induced precipitation. DSC and DIL revealed several overlapping precipitation reactions. The critical cooling rate for a complete supersaturation of the solid solution has been identified to be 600 to 800 K/s. At slightly subcritical cooling rates quench induced precipitation results in a direct hardening effect resulting in a technological critical cooling rate of about 100 K/s, i.e., the hardness after ageing reaches a saturation level for cooling rates faster than 100 K/s. Maximum yield strength of above 600 MPa and tensile strength of up to 650 MPa were attained.

scholarly journals Statistical Relationship Between Strontium Content and Cooling Rate on A356 Alloy by Using Regression Analysis

2021 ◽  
pp. 31-37
Author(s):  
Batuhan Dogdu ◽  
Onur Ertugrul
Keyword(s):  
Cooling Rate ◽  
Eutectic Silicon ◽  
A356 Alloy ◽  
Chemical Modifier ◽  
Statistical Relationship ◽  
Silicon Phase ◽  
Strontium Content ◽  
Cooling Rates ◽  
Cast Part ◽  
Eutectic Modification

Eutectic silicon modification is an important casting parameter on Al-Si alloys on the aspect of mechanical capability and energy absorption of the cast part. Chemical modifier element strontium has been used to obtain eutectic modification on Al-Si alloy commercially. On the other hand, high cooling rate on Al-Si alloys both refine dendrites and silicon phase which enhances mechanical characteristic. In order to find a statistical relationship between strontium amount and cooling rate, a special mold was designed in order to obtain different range of cooling rates in same cast part, then tensile test data of A356 alloy were analyzed in Minitab software. Therefore, after regression and analysis of variance tests have been proceeded, it was found that strontium amount is only dominant for lower cooling rates of < 0.9 oC.

scholarly journals The Effect of Cooling Rate on Mechanical Properties of Carbon Steel (St 35)

2014 ◽  
Vol 7 (1) ◽  
pp. 109-118
Author(s):  
Jenan Mohammed Nagie
Keyword(s):  
Mechanical Properties ◽  
Heat Treatment ◽  
Grain Size ◽  
Carbon Steel ◽  
Cooling Rate ◽  
Experimental Results ◽  
Heat Treated ◽  
Before And After ◽  
Water Media ◽  
The Relationship

This paper is aimed to study the effect of cooling rate on mechanical properties of Steel 35. Specimens prepared to apply tensile, torsion, impact and hardness tests.Many prepared specimens heat treated at (850ºC) for one hour and subsequently were cooled by three different media [Water-Air-furnace] to show the effect of Medias cooling rate on mechanical properties. Microstructures of all specimens examined before and after heat treatment by an optical microscopy.To figure the phases obtained after heat treatment and its effect on the mechanical properties Experimental results have shown that the microstructure of steel can be changed and significantly improved by varying line cooling rate thus, improving one property will effect on the others because of the relationship between all properties.In water media tensile, torsion and hardness improved while impact results reduced. Air media contributed in improving most of the mechanical properties because of grain size homogeneity. At furnace media ductility and impact improved

Thermal conductivity of metallic glassy alloys and its relationship to the glass forming ability and the observed cooling rates

2008 ◽  
Vol 23 (8) ◽  
pp. 2283-2287 ◽  
Author(s):  
Dmitri V. Louzguine-Luzgin ◽  
Takanobu Saito ◽  
Junji Saida ◽  
Akihisa Inoue
Keyword(s):  
Thermal Conductivity ◽  
Glassy Alloy ◽  
Glass Forming Ability ◽  
Bulk Glass ◽  
Cooling Rates ◽  
Glass Forming ◽  
Glassy Alloys ◽  
Mold Casting ◽  
Cooling Behavior ◽  
The Relationship

In this work, we study the cooling behavior of several typical bulk glassy alloys on casing and present the relationship between the thermal conductivity of a glassy alloy and the cooling rate upon mold casting. The cooling rates obtained for Ti-, Zr-, Pd-, and Cu-based bulk glass forming alloys are found to scale with the thermal conductivities of the studied glassy alloys.

Study of the Boron Distribution and Microstructure of Solidified Al-Si Alloy During the Process of Silicon Purification

2018 ◽  
Vol 37 (1) ◽  
pp. 69-73 ◽  
Author(s):  
Yanlei Li ◽  
Jian Chen ◽  
Songyuan Dai
Keyword(s):  
Cooling Rate ◽  
Transition Layer ◽  
Boron Content ◽  
Eutectic Silicon ◽  
Primary Silicon ◽  
Silicon Phase ◽  
Cooling Rates ◽  
Average Width ◽  
Boron Distribution ◽  
Silicon Purification

AbstractThe Al-Si melts that contain different silicon contents were solidified with a series of cooling rates, and the boron contents in primary silicon phases and eutectic silicon phases were measured and discussed. The results indicate that the boron content in the eutectic silicon phases is higher than that in the primary silicon phases when the cooling rate is constant. When the cooling rate decreases, the boron content in the primary silicon phases decreases, but the boron content in the eutectic silicon phases increases. The microstructure observations of solidified ingots show that there is an interface transition layer beside the primary silicon phase, and the average width of the interface transition layer increases with decreasing cooling rate.

scholarly journals Effect of Modification with Different Contents of Sb and Sr on the Thermal Conductivity of Hypoeutectic Al-Si Alloy

Metals ◽  
2020 ◽  
Vol 10 (12) ◽  
pp. 1637
Author(s):  
Jin Guo ◽  
Zhi-Ping Guan ◽  
Rui-Fang Yan ◽  
Pin-Kui Ma ◽  
Ming-Hui Wang ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Heat Treatment ◽  
Electrical Conductivity ◽  
Electron Transport ◽  
Eutectic Silicon ◽  
Weak Effect ◽  
Microstructure Control ◽  
T6 Heat Treatment

In this paper, the effects of size, morphology and distribution of eutectic silicon on the thermal conductivity of Al-8Si alloy modified by Sr (0.04, 0.08, 0.12 wt.%) and Sb (0.1, 0.3, 0.5 wt.%) elements with T6 heat treatment were investigated. The results show that the modified fibrous eutectic silicon has a significant capability of improvement of thermal conductivity, while the amount of the modifier has a relatively weak effect on thermal conductivity. After T6 treatment, the fracture or spheroidization of the flake eutectic silicon and the disappearance of clustering phenomenon could raise thermal conductivity, but the coarsening of fibrous eutectic silicon is inconducive to thermal conductivity. Finally, the effect of eutectic silicon on electron transport is analyzed in detail, which could provide a reference for enhancing the thermal (or electrical) conductivity of hypoeutectic Al-Si alloy through effective microstructure control.

scholarly journals Effect of cooling rates on T6 Treatment of B390 Aluminium-Silicon Hypereutectic alloys

2019 ◽  
Vol 293 ◽  
pp. 02001
Author(s):  
Porawit Jiandon ◽  
Sukangkana Talangkun
Keyword(s):  
Cooling Rate ◽  
Ageing Time ◽  
Eutectic Silicon ◽  
Primary Silicon ◽  
Peak Hardness ◽  
Pouring Temperature ◽  
Cooling Rates ◽  
Hardness Peak ◽  
3Si2 Phase ◽  
Hardness Values

This research aimed to study an effect of cooling rates on T6 treatment process of B390 aluminium hypereutectic alloy. B390 casting samples were casted with pouring temperature of 710°C and solidified in three different cooling rates of 33.33, 28.60 and 22.22°C/s, respectively using three metal moulds. After that samples were subjected to T6 treatment: solution treated at 510°C for 30 min and aged at 200°C at various times. However, after ageing, hardness values of as-casted samples reduced with increasing cooling rate. It was found that the specimen cooled with the highest cooling rate exhibited the highest hardness. Peak hardness values of samples cooled with cooling rate of 33.33, 28.60 and 22.22°C/s after ageing obtained from ageing time of 3, 6 and 8 hour, respectively. Furthermore, the result showed that morphology of primary silicon, eutectic silicon and Ali5(Mn, Fe)3Si2 phase presented in the aged specimen cooled with the highest cooling rate exhibited more globular, finer and distributed more evenly compared with the slower cooled samples. It can be concluded that rapid cooling rate increases concentration of a-solid solution resulted in shorter aging time.

Estimation of the Cooling Rate on the Basis of Secondary Dendrite Arm Spacing in Case of Continuous Cast Steel Slab

2006 ◽  
Vol 508 ◽  
pp. 245-250 ◽  
Author(s):  
Csaba Hoó ◽  
Ilona Teleszky ◽  
András Roósz ◽  
Zsolt Csepeli
Keyword(s):  
Cooling Rate ◽  
Cast Steel ◽  
Continuous Cast ◽  
Secondary Dendrite Arm Spacing ◽  
Dendrite Arm Spacing ◽  
Cooling Conditions ◽  
Steel Slab ◽  
Solidification Processes ◽  
Continuous Cast Steel ◽  
The Relationship

The different solidification processes occuring in steels can be well studied by using the microstructure investigation. The microstructure can be observed after the sample preparation by using a special type of Oberhoffer etching. The changes in the cooling rate can be described by determining the secondary dendrite arm spacing. A relative cooling rate can be calculated by applying the relationship between the secondary dendrite arm spacing and the cooling rate which characterises the changes of cooling conditions in the ingot during the solidification..

scholarly journals Development of recommendations on cooling rates of railway wheels with the use of modeling in the software package qform vx 8.2 for the formation of a homogeneous ferritic-perlite structure

2021 ◽  
Vol 3 (134) ◽  
pp. 13-22
Author(s):  
Alexander Babachenko ◽  
Ganna Kononenko ◽  
Evgen Klemeshov ◽  
Rostislav Podolskyi
Keyword(s):  
Mechanical Properties ◽  
Heat Treatment ◽  
Cooling Rate ◽  
Software Package ◽  
Accelerated Cooling ◽  
Cooling Rates ◽  
Permissible Range ◽  
Thermal Section ◽  
High Set ◽  
Railway Wheels

The tests were performed on ER7 steel according to EN 13262. Based on the hardenability test (GOST 5657) by the method of end hardening (Jomen) the distance from the surface from which unilateral cooling was performed, where the hardness met the requirements of regulatory documentation for wheels of test steel, and the distance where the formation of needle structures, including bainite and otmanshtette, no longer took place. Simulation was applied in the software package QForm VX 8.2, as a result, a model was developed, for the adaptation of which the results of the experiment were used. Confirmed the high convergence of the results of the calculation and the experiment. At the same time, the model allowed to obtain an instantaneous cooling rate in a form that is more in line with the physical meaning of the process and to avoid the scatter of actual values associated with the discreteness of data capture. It is established that the instantaneous cooling rate changes in the process of continuous uniform supply of the cooler. The permissible range of cooling rates of the surface and central sections of the wheel rim during accelerated cooling of ER7 steel is determined. The data can be used to improve the heat treatment modes of railway wheels of current production in order to achieve a high set of mechanical properties both with the existing cooling technology and with differentiated cooling on the modernized equipment of the thermal section of the wheel shop. The developed model can be used to build thermokinetic diagrams under continuous cooling and to develop recommendations for heat treatment modes to achieve the specified mechanical properties under a certain structural state.

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