scholarly journals Features of the influence of thermal modes of cooling on processes of nonequilibrium crystallization of materials from the liquid state

2018 ◽  
Vol 26 (2) ◽  
pp. 45-48
Author(s):  
V. F. Bashev ◽  
S. I. Ryabtsev ◽  
S. N. Antropov ◽  
N. A. Kutseva ◽  
O. I. Kushnerev ◽  
...  
Keyword(s):  
Cast Iron ◽  
Liquid State ◽  
Quantitative Estimation ◽  
Amorphous State ◽  
Maximum Level ◽  
Cooling Rates ◽  
Splat Quenching ◽  
Glass Insulation ◽  
Amorphous Substrate ◽  
Nonequilibrium Crystallization

The quantitative estimation of maximum level of cooling rates in the process of casting microwires in glass insulation is given. The shown possibility of nonequilibrium formation of microwire substance is due to the influence of an amorphous substrate in the form of glass insulation. The amorphous state in the case of thin microwires with cast iron vein Fe‒20 at.% C confirms the implementation of an increased (compared to splat-quenching) level of nonequilibrium formation of microwires in combination with updated rates of cooling and increased degree of supercooling of liquid microwire vein.

Non-Equilibrium Crystallization of a Eutectic Alloy - Mathematical Model

2019 ◽  
Vol 946 ◽  
pp. 417-422
Author(s):  
Alexander D. Drozin ◽  
Maxim V. Dudorov ◽  
Natalia M. Yaparova
Keyword(s):  
Mathematical Model ◽  
Eutectic Alloy ◽  
Liquid State ◽  
Transformation Temperature ◽  
Amorphous State ◽  
Eutectic Alloys ◽  
Equilibrium Crystallization ◽  
Eutectic Transformation ◽  
Solid Phases ◽  
The Mathematical Model

The process of a eutectic alloy crystallization is considered when the eutectic alloy is instantly cooled from the liquid state to below the eutectic transformation temperature. The features of such crystallization are considered. The mathematical model of the process is constructed that takes into account the nucleation of new phases particles, their growth and the associated change the concentrations of the melt components. The nuclei of new phases are supposed be spherical. As they grow, they come into contact and become lamellar. The developed approach was applied to the amorphization process of the eutectic alloys. An amorphous state has been reached if the clusters of solid phases can’t grow above nanosize. The model allows researching the necessary amorphization conditions.

scholarly journals Influence of Liquid Quenching on Phase Composition and Properties of Be-Si Eutectic Alloy

2020 ◽  
Keyword(s):  
Solid Solution ◽  
Solid Solutions ◽  
Eutectic Alloy ◽  
Electrical Resistance ◽  
Liquid State ◽  
Foil Thickness ◽  
Continuous Heating ◽  
Cooling Rates ◽  
Liquid Quenching ◽  
Substitutional Solid Solutions

By the method of quenching from the liquid state (splat-quenching), it is first revealed the formation of mixture of metastable supersaturated substitutional solid solutions in the eutectic alloy Be-33at.% Si. Cast samples are obtained by pouring melt into a copper mold. High cooling rates during liquid quenching are achieved throw the well-known splat-cooling technique by spreading a drop of melt on the inner surface of a rapidly rotating, heat-conducting copper cylinder. The maximum cooling rates are estimated by the foil thickness. The melt cooling rates (up to 108К/s), used in the work, are sufficient to form amorphous phases in some eutectic alloys with similar phase diagrams, but it is found those rates are insufficient to obtain them in the Be-Si eutectic alloy. The X-ray diffraction analysis is carried out on a diffractometer in filtered Cobalt Ka radiation. Microhardness is measured on a micro-durometer at a load of 50 g. The electrical properties, namely the temperature dependences of relative electrical resistance, are studied by the traditional 4-probe method of heating in vacuum. The accuracy of determining the crystal lattice period of the alloy, taking into account extrapolation of the reflection angle by 900, is ± 3•10-4 nm. It is found that even at extremely high rate of quenching from the melt, instead of the amorphous phase formation, the occurrence of two supersaturated substitutional solid solutions, based on Beryllium and Silicon, is revealed. This fact is established by the obtained dependences of their lattice periods values on the alloying element content. So, during the formation of metastable eutectic structure, a supersaturated with Beryllium solid solution of Silicon has period a = 0.5416 nm, and a supersaturated with Silicon solid solution of low-temperature hexagonal Beryllium has periods a = 0.2298 nm, c = 0.3631 nm. The positive role of the liquid quenching method in increasing the level of mechanical characteristics (microhardness and microstresses) in rapidly cooled Be-Si films is shown. It has been demonstrated that the difference in the atomic radii of the elements significantly affects the distortion of crystal lattices of the formed supersaturated solid solutions, and a significant value of microstresses (second-order stresses) in the Silicon lattice supersaturated with Beryllium is estimated, which, of course, leads to a significant increase in the microhardness, namely: there is an increase in microhardness in the Be-Si alloy under the conditions of applied method of quenching from the liquid state by more than 1.7 times compared to cast eutectic alloy and more than 6 times higher in comparison with the eutectoid cast Iron-Carbon alloy. The obtained polytherm of electrical resistance of the alloy under conditions of continuous heating in vacuum confirms the metastable nature of obtained new phases during quenching from the liquid state.

Dynamic Coarsening of Austenite Dendrite in Lamellar Cast Iron Part 2 - The Influence of Carbon Composition

2014 ◽  
Vol 790-791 ◽  
pp. 211-216 ◽  
Author(s):  
Vasilios Fourlakidis ◽  
Rubén Lora ◽  
Attila Diószegi
Keyword(s):  
Cast Iron ◽  
Eutectic Composition ◽  
Primary Dendrite ◽  
Cast Irons ◽  
Dendrite Morphology ◽  
Cooling Rates ◽  
Iron Part ◽  
Interdendritic Space ◽  
Wide Range ◽  
The One

Investigation of dynamic coarsening in lamellar cast iron is extended over a wide interval ranging from hypoeutectic to eutectic composition. The dendrite morphology is defined on as-cast samples produced under various cooling rates. The as-cast morphology is considered being close to the one at the end of solidification. The obtained relations describing the coarsening process as a function of local solidification time and fraction austenite are compared to results obtained from interrupted solidification experiments. By using the Modulus of primary dendrite (MPD) and the Hydraulic diameter of the interdendritic space (DHydIP) become possible to characterize the coarseness of a wide range of lamellar cast irons solidified under various cooling rates.

Effect of Cooling Rate on Drop-Tube Processed Commercial Grey Cast Iron

2015 ◽  
Author(s):  
Olamilekan R. Oloyede ◽  
Tim Bigg ◽  
Andrew M. Mullis
Keyword(s):  
Cast Iron ◽  
Cooling Rate ◽  
Volume Fraction ◽  
Microstructural Analysis ◽  
Control Sample ◽  
Grey Cast Iron ◽  
Drop Tube ◽  
Flake Graphite ◽  
Cooling Rates ◽  
Grey Cast

This study focuses on the fundamental of solidification of commercial grey cast iron as a function of the externally applied cooling rate. Grey cast iron powders were prepared using the drop-tube method, which is a good analogue for commercial production via high pressure gas atomization. The as-solidified droplets were collected and sieved into size ranges from > 850 μm to < 53 μm diameter, with estimated cooling rates of 500 K s−1 to 75,000 K s−1, with each sieve fraction being prepared for metallographic characterization. The microstructure and phase composition of the powders were analyzed using XRD, optical and scanning electron microscopy, with the results being compared against a control sample subject to slow cooling in the drop-tube crucible; which has typical grey cast iron microstructure with extensive flake graphite in a largely ferrite matrix. In contrast, flake graphite was absent in virtually all the drop-tube samples, even in those with the most modest cooling rates. Microstructural analysis revealed that as the cooling rate increased there was less fragmentation of the primary austenite/ferrite dendrites and the volume fraction of primary dendritic material increased. Hence, as the particle fractions get smaller (D < 106 μm) there is a distinct microstructural evidence of a martensite phase which is related to its better mechanical properties (microhardness) as the sample sizes decrease.

Thermal analysis of nodular and lamellar eutectic cast iron under different cooling rates

2003 ◽  
Vol 16 (1-3) ◽  
pp. 53-58 ◽  
Author(s):  
José Tinoco ◽  
Pedro Delvasto ◽  
Omar Quintero ◽  
Hasse Fredriksson
Keyword(s):  
Thermal Analysis ◽  
Cast Iron ◽  
Cooling Rates ◽  
Lamellar Eutectic

scholarly journals Determination of Eutectoid Transformation Temperatures in Ductile Cast Iron

2015 ◽  
Vol 15 (4) ◽  
pp. 51-54 ◽  
Author(s):  
A.W. Orłowicz ◽  
A. Trytek ◽  
M. Mróz ◽  
M. Tupaj
Keyword(s):  
Cast Iron ◽  
Cooling Rate ◽  
Ductile Cast Iron ◽  
Eutectoid Transformation ◽  
Heating Rates ◽  
Cooling Rates ◽  
Metallographic Examination ◽  
Transformation Temperatures ◽  
Rate Of Cooling

Abstract The paper proposes a methodology useful in verification of results of dilatometric tests aimed at determination of temperatures defining the start and the end of eutectoid transformation in the course of ductile cast iron cooling, based on quenching techniques and metallographic examination. For an industrial melt of ductile cast iron, the effect of the rate of cooling after austenitization at temperature 900°C carried out for 30 minutes on temperatures TAr1start and TAr1end was determined. The heating rates applied in the study were the same as the cooling rates and equaled 30, 60, 90, 150, and 300°C/h. It has been found that with increasing cooling rate, values of temperatures TAr1start and TAr1end decrease by several dozen degrees.

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.

scholarly journals Bathroom brake circuits with vermicular graphite

2018 ◽  
pp. 40-49
Author(s):  
L Ivanova ◽  
E Kolotilo
Keyword(s):  
Rare Earth ◽  
Cast Iron ◽  
Cooling Rate ◽  
Rare Earth Metal ◽  
Earth Metal ◽  
Physical And Mechanical Properties ◽  
Cooling Rates ◽  
Highly Effective ◽  
Graphite Inclusions ◽  
The Rare Earth

The processes of structuring in cast iron of different chemical composition in the range of cooling rates of 0.5 ... 5.5 deg / s, which take place in the roll casting mould, are investigated. Scientifically based theoretical and experimental results were obtained, the set of which allowed to develop highly effective technologies of casting of rolling rolls from cast iron with vermicular graphite with increased operational characteristics. Optimum content of rare earth metal (REM) in roller cast iron with vermicular graphite at different cooling rates was experimentally established. In the low sulfur (up to 0,03%) cast iron, the rare earth metal residual (REMres) content is -0,065 ... 0,176 (for a cooling rate of 0,5 deg / s) and 0,01 ... 0,156% (for a cooling rate of 5,5 deg / s) . In the cast iron with high sulfur content (up to 0.10%), at the cooling rates studied, the intervals of concentrations of REMres have been experimentally established to provide the vermicular inclusions of graphite: at a cooling rate of 5.5 deg / c - 0.081-0.129%, and at a speed of 0.5 deg / s - 0.161 ... 0.190%. When modifying melts with a complex modifier based on magnesium KMg9, the Mg content at cooling rates of 5.5 and 0.5 deg / s should be within 0.022 ... 0.03 and 0.019 ... 0.03%, respectively, when treated with the complex KMg9 and FS30RZM30 in the cast iron it is necessary to have 0,0071 ... 0,015% Mg and 0,023 ... 0,025% REMres. With such content of modifiers, the best combinations of microstructure and physical and mechanical properties of castings are obtained. The areas of formation of vermicular graphite inclusions in roll cast irons were determined when processed with a complex modifier based on rare-earth metals and ferrotitanium: at a cooling rate of 5.5 degrees / s and a titanium content of 0.40 ... 0.42%, the concentration range of the rare-earth bridge for stable production of graphite inclusions of vermicular form has expanded and was 0.061 ... 0.169%, and at a cooling rate of 0.5 deg / s –0.129 ... 0.230%. The technological process of casting of bleached roller rolls has been improved due to the application of a highly effective complex modifier (ligature) of optimal composition for the modification of the base metal. The technology for the production of pig iron with vermicular graphite is developed and mastered at casting of rollers with the use of mixtures for modification consisting of two ligatures in the ratio of 1: 3.

INFLUENCE OF METHODS FOR ALTI MASTER ALLOY PRODUCTION ON ITS STRUCTURE AND EFFICIENCY IN ALUMINUM ALLOY MODIFICATION

2018 ◽  
pp. 45-52
Author(s):  
K. V. Nikitin ◽  
I. Yu. Timoshkin ◽  
V. I. Nikitin
Keyword(s):  
Electrical Conductivity ◽  
Cast Iron ◽  
Master Alloy ◽  
Alloy Structure ◽  
Cooling Rates ◽  
Master Alloys ◽  
Chill Mold ◽  
Modifying Effect ◽  
Determination Methods ◽  
Iron Mold

A comparative study on the effect of methods for obtaining AlTi4 modifying master alloys on the sizes of Al3Ti intermetallics is made. It is found that increasing cooling rates at solidification from 10–15 °C/s (crystallization in a hot cast iron mold, a plate 30 mm in thickness) to 60–65 °C/s (crystallization in a cold cast iron chill mold, a rod 20 mm in diameter, 170 mm in length) reduces the length and thickness of needle-shaped intermetallics almost twice (397×23 to 215×13 μm). At the same time, lower electrical conductivity and higher alloy density in a solid state are observed. Melt modification with 0,5 wt.% magnesium addition causes the formation of homogeneous 98×3 μm fine-needle intermetallics. The addition of magnesium slightly reduces electrical conductivity and density compared with the AlTi4 master alloy crystallized at the same cooling rate (60–65 °C/s). Modification of A97 grade aluminum and AK9ch alloy (Al–Si–Mg system) with the specified master alloys at the same amount of titanium added (0,01 wt.%) exerts hereditary influence on the density and electrical conductivity, and macrograin (A97) and dendrites of aluminium (AK9ch). The maximum modifying effect is provided by the AlTi4 master alloy containing 0,5 wt.% magnesium. When introduced into the alloy, it contributes to the formation of 10 μm aluminum dendrites 1427 pcs/mm2 in total in the alloy structure. When the AK9ch alloy is modified with the master alloy crystallized at cooling rates of 10–15 °C/s, 28 μm dendrites 672 pcs/mm2 in total are formed in the alloy structure. It is suggested to use density and electrical conductivity determination methods for express evaluation of master alloy modifying effectiveness.

Sign in / Sign up

Export Citation Format

Share Document