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Number of results: 16
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Abstract

Directionally solidified sample of Fe-Fe3C eutectic alloy were produced under an argon atmosphere in a vacuum Bridgman-type furnace to

study the eutectic growth with v = 167 μm/s pulling rate and constant temperature gradient G = 33.5 K/mm. Since how the growth texture

of eutectic cementite is related to its growth morphology remains unclear, the current study aims to examine this relationship. The technique

such as X-ray diffraction, have been used for the crystallographic analysis of carbide particles in white cast irons.

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Authors and Affiliations

M. Trepczyńska-Łent
T. Szykowny
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Abstract

It is well-known that the better the control of the liquid aluminium allows obtaining of better properties. One of the most important defects

that is held responsible for lower properties has been the presence of porosity. Porosity has always been associated with the amount of

dissolved hydrogen in the liquid. However, it was shown that hydrogen was not the major source but only a contributor the porosity. The

most important defect that causes porosity is the presence of bifilms. These defects are surface entrained mainly due to turbulence and

uncontrolled melt transfer. In this work, a cylindrical mould was designed (Ø30 x 300 mm) both from sand and die. Moulds were produced

both from sand and die. Water cooled copper chill was placed at the bottom of the mould in order to generate a directional solidification.

After the melt was prepared, prior to casting of the DC cast samples, reduced pressure test sample was taken to measure the melt quality

(i.e. bifilm index). The cast parts were then sectioned into regions and longitudinal and transverse areas were investigated

metallographically. Pore size, shape and distribution was measured by image analysis. The formation of porosity was evaluated by means

of bifilm content, size and distribution in A356 alloy.

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Authors and Affiliations

M. Uludağ
D. Dişpinar
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Abstract

A eutectic reaction is a basic liquid-solid transformation, which can be used in the fabrication of high-strength in situ composites.

In this study an attempt was made to ensure directional solidification of Fe-C-V alloy with hypereutectic microstructure. In this alloy, the

crystallisation of regular fibrous eutectic and primary carbides with the shape of non-faceted dendrites takes place. According to the data

given in technical literature, this type of eutectic is suitable for the fabrication of in-situ composites, owing to the fact that a flat

solidification front is formed accompanied by the presence of two phases, where one of the phases can crystallise in the form of elongated

fibres.

In the present study an attempt was also made to produce directionally solidifying vanadium eutectic using an apparatus with a very high

temperature gradient amounting to 380 W/cm at a rate of 3 mm/h. Alloy microstructure was examined in both the initial state and after

directional solidification. It was demonstrated that the resulting microstructure is of a non-homogeneous character, and the process of

directional solidification leads to an oriented arrangement of both the eutectic fibres and primary carbides.

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Authors and Affiliations

M. Górny
M. Kawalec
G. Sikora
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Abstract

Directional solidification of the Fe - 4,3 wt % C alloy was performed with the pulling rate equal to v=83 μm/s. Sample was frozen during

solidification to reveal the shape of the solid/liquid interface. Structures eutectic pyramid and spherolitic eutectic were observed. The

solidification front of ledeburite eutectic was revealed. The leading phase was identified and defined.

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Authors and Affiliations

M. Trepczyńska-Łent
E. Olejnik
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Abstract

Directional solidification of ledeburite was realised out using a Bridgman’s device. The growth rate for movement sample v=83.3 μm/s

was used. In one sample the solidification front was freezing. The value of temperature gradient in liquid at the solidification front was

determined. Interfacial distance λ on the samples was measured with NIS-Elements application for image analysis.

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Authors and Affiliations

M. Trepczyńska-Łent
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Abstract

In a vacuum Bridgman-type furnace, under an argon atmosphere, directionally solidified sample of Fe - C alloy was produced. The pulling

rate was v = 83 μm/s (300 mm/h) and constant temperature gradient G = 33,5 K/mm. The microstructure of the sample was examined on

the longitudinal section using an Optical Microscope and Scanning Electron Microscope. The X-ray diffraction and electron backscatter

diffraction technique (EBSD) have been used for the crystallographic analysis of carbide particles in carbide eutectic. The

X-ray diffraction was made parallel and perpendicular to the axis of the goniometer. The EBSD shows the existence of iron carbide Fe3C

with orthorhombic and hexagonal structure. Rapid solidification may cause a deformation of the lattice plane which is indicated by

different values of the lattice parameters. Such deformation could also be the result of directional solidification. Not all of the peaks in

X–ray diffractograms were identified. They may come from other iron carbides. These unrecognized peaks may also be a result of the

residual impurity of alloy.

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Authors and Affiliations

M. Trepczyńska-Łent
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Abstract

Twinned dendrites in Al-Zn alloy with high Zn content (40% wt.%) were successfully prepared by directional solidification. At different directional solidification rates (1000 and 1500 μm/s), microstructures and growth orientation variations of Al twinned dendrite and non-twinned dendrite were characterized. By using the inverted trapezoidal graphite sleeve at 1000 μm/s, Al twinned dendrite were formed to developed feather crystal structures in longitudinal section. Its primary and secondary twinned dendrite were grew along [110] direction. Moreover the deviation angle between [110] direction of Al twinned dendrite and the heat flow direction was about 27.15°. While not using the inverted trapezoidal graphite sleeve at 1000 and 1500 μm/s, Al dendrite was the non-twinned dendrite and the twinned dendrite was not appeared. The experimental results showed that the higher temperature gradient, a certain pulling rate and convection environment were the formation conditions of twinned dendrites.

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Authors and Affiliations

K. Gao
W. Song
L. Fan
Y. Ding
X. Guo
R. Zhang
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Abstract

In order to determine the leading phase of the Fe - 4.25% C eutectic alloy, the method of directional crystallization, which allows to study the character of the solid / liquid growth front, was used. Examined eutectic was directionally solidified with a constant temperature gradient of G = 33,5 K/mm and growth rate of v = 125 μm/s (450 mm/h). The Bridgman technique was used for the solidification process. The sample was grown by pulling it downwards up to 30 mm in length. The alloy quenched by rapid pulling down into the Ga-In-Sn liquid metal. The sample was examined on the longitudinal section using a light microscope and scanning electron microscope. The shape of the solid/liquid interface and particularly the leading phase protrusion were revealed. The formation of the concave – convex interface has been identified in the quasi-regular eutectic growth arrested by quenching. The cementite phase was determined to be a leading phase. The total protrusion d is marked in the adequate figure.

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Authors and Affiliations

M. Trepczyńska-Łent
ORCID: ORCID

Authors and Affiliations

Małgorzata Perek-Nowak
1
Grzegorz Boczkal
1
ORCID: ORCID
Paweł Pałka
1
ORCID: ORCID
Piotr Kuropatwa
1

  1. Faculty of Non-Ferrous Metals, AGH University of Science and Technology, al. Mickiewicza 30, 30-059 Kraków, Poland
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Abstract

The current work is dedicated to the mathematical description of a protrusion of the leading phase (cementite) over the wetting phase (austenite) observed during the author’s experiments in previous articles. A cementite protrusion is confirmed in the directionally solidified Fe-4.25% C eutectic alloy. The protrusion is defined due to the mass balance fulfilment. A coordinate system is attached to the solid/liquid interface, which is moving with the constant growth rate v.
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Bibliography

[1] E . Cadirli, H. Kaya, M. Gunduz, Materials Research Bulletin 38, 1457-1476 (2003).
[2] G .J. Davies, Solidification and casting, Wiley (1973).
[3] V .L. Davies, Journal of the Institute of Metals 93, 10-14 (1964-65).
[4] M. Hillert, V.V. Subba Rao, Iron and Steel Intitute Publication 110, 204-212 (1968).
[5] D .M. Stefanescu, Eutectic solidification, Science and Engineering of Casting Solidification, Springer 207 (2015).
[6] E . Fraś, Krystalizacja metali, Wydawnictwo Naukowo Techniczne, Warszawa (2003).
[7] M. Trepczyńska-Łent, Archives of Foundry Engineering 13 (3), 101-106 (2013).
[8] M. Trepczyńska-Łent, Archives of Metallurgy and Materials 58 (3), 987-991. (2013). DOI : https://doi.org/10.2478/amm-2013-0116
[9] M. Trepczyńska-Łent, Archives of Foundry Engineering 16 (4), 169-174 (2016). DOI : https://doi.org/10.1515/afe-2016-0104
[10] M. Trepczyńska-Łent, Archives of Metallurgy and Materials 62 (1), 365-368 (2017). DOI : https://doi.org/10.1515/amm-2017-0056
[11] M. Trepczyńska-Łent, Crystal Research and Technology 52 (7), 1600359 (2017). DOI : https://doi.org/10.1002/crat.201600359
[12] M. Trepczyńska-Łent, Archives of Foundry Engineering 19 (4), 113-116 (2019).
[13] E . Guzik, A model of irregular eutectic growth taking as an example the graphite eutectic in Fe-C alloys. Dissertations Monographies 15, AGH Kraków (1994).
[14] P . Magnin, W. Kurz, Acta Metall. 35, 1119 (1987).
[15] J.D Hunt., K.A Jackson, Trans Metall. Soc. AI ME 236, 843-852 (1966).
[16] K .A. Jackson, J.D. Hunt, Transactions of the Metallurgical Society of AI ME 236, 1129-1142 (1966).
[17] W Wołczyński, Defect and Diffusion Forum 272, 123-138 (2007).
[18] W. Wołczyński, Archives of Metallurgy and Materials 63 (1), 65-72 (2018).
[19] G .A Chadwick, Eutectic Alloy Solidification, Chapter 2 in: Progress in Materials Science. Pergamon Press, Headington Hill Hall, Oxford (1964).
[20] W. Wołczyński, Crystal Research and Technology 25 (1), 1303- 1309 (1990).
[21] W. Wołczyński, Archives of Metallurgy and Materials 65 (2), 653-666 (2020). DOI : https://doi.org/10.24425/amm.2020.132804
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Authors and Affiliations

M. Trepczyńska-Łent
1
ORCID: ORCID

  1. UTP University of Science and Technology, Mechanical Engineering Faculty, Bydgoszcz, Poland
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Abstract

Cu-2wt%Ag alloy with diameter of 10 mm was fabricated by induction heating directional solidification (IHDS). The effect of different mold temperatures on microstructure of IHDS Cu-2wt%Ag alloy was investigated. The results show that IHDS ­Cu-2wt%Ag alloy is mainly composed of coarse columnar grains at mold temperature of 1075°C. While the mold temperature is at 1100°C, 1150°C and 1200°C, respectively, the IHDS Cu-2wt%Ag alloy is composed of columnar grains and equiaxed grains and the number of grains increases. Meanwhile, the growth direction of columnar grains in the edge of alloys deviates from the direction of continuous casting to form “V” shape. While the mold temperature is controlled at high temperature, the induced current increases, which leads to the enhancement of eddy current in the mold. Therefore, the dendrites fall off to form new grains under the effect of eddy stirring, resulting in an increasing in the number of grains.

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Authors and Affiliations

Jihui Luo
Yangyang Li
Yanke Huang
Yuehao Huang
Yuling Zheng
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Abstract

Directional solidification technique is an important research instrument to study solidification of metals and alloys. In the paper the model

[6,7,8] of directional solidification in special Artemis-3 facility was presented. The current work aimed to propose the ease and efficient

way in calibrating the facility. The introduced M coefficient allowed effective calibration and implementation of defined thermal

conditions. The specimens of AlSi alloys with Fe-rich intermetallics and especially deleterious β-Al5FeSi were processed by controlled

solidification velocity, temperature gradient and cooling rate.

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Authors and Affiliations

P. Mikołajczak
L. Ratke
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Abstract

Solidification of AlSiFe alloys was studied using a directional solidification facility and the CALPHAD technique was applied to calculate

phase diagrams and to predict occurring phases. The specimens solidified by electromagnetic stirring showed segregation across, and the

measured chemical compositions were transferred into phase diagrams. The ternary phase diagrams presented different solidification paths

caused by segregation in each selected specimen. The property diagrams showed modification in the sequence and precipitation

temperature of the phases. It is proposed in the study to use thermodynamic calculations with Thermo-Calc which enables us to visualize

the mushy zone in directional solidification. 2D maps based on property diagrams show a mushy zone with a liquid channel in the

AlSi7Fe1.0 specimen center, where significant mass fraction (33%) of β-Al5FeSi phases may precipitate before α-Al dendrites form.

Otherwise liquid channel occurred almost empty of β in AlSi7Fe0.5 specimen and completely without β in AlSi9Fe0.2. The property

diagrams revealed also possible formation of α–Al8Fe2Si phases.

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Authors and Affiliations

P. Mikołajczak
L. Ratke
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Abstract

Fe - 4,25% C alloy was directionally solidified with a constant temperature gradient of G = 33,5 K/mm and growth rate of v = 83,3 μm/s (300 mm/h) using a vacuum Bridgman-type crystal growing facility with liquid metal cooling technique. To reveal more detailed microstructure, the deep etching was made. This was obtained in the process of electrolytic dissolution. The microstructure of the sample was examined on the longitudinal and transverse sections using an Optical Microscope and Scanning Electron Microscope. Using the Electron Backscattered Diffraction technique, phase map and analysis of phase were made. In this paper the analysis of Fe-C alloy eutectic microstructure is presented. Regular eutectic structure was obtained. The fracture surfaces show lamellar structure. Microscopic observation after electrolytic extraction indicates that the grains of longitudinal shape of eutectic cementite have been obtained. These grains are characterized by layered construction with many rounded discontinuities.

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Authors and Affiliations

M. Trepczyńska-Łent
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Abstract

CM247LC alloy was manufactured by using selective laser melting (SLM) process, one of the laser powder bed fusion ­(L-PBF) methods. The hot isostatic pressing (HIP) process was additionally conducted on the SLM-built CM247LC to control its microstructures and defects. The high temperature oxidation property was investigated, and it was compared with conventional DS247LC sample (reference) prepared via the directional solidification process. The L-PBF HIP sample showed blocky-type MC carbides generated along the grain boundary with average size of about 200 nm. A semi-spherical primary γ' phase of size 0.4-1.0 μm was also observed inside the grains. Moreover, the DS247LC sample displayed a coarse eutectic γ' phase and many script-type MC carbides. Furthermore, cuboidal-type γ' with an average size of about 0.5 μm was detected. High-temperature oxidation tests were conducted at 1000°C and 1100°C for 24 hours. The results at 1100°C oxidation temperature showed that the measured oxidation weight gains for HIP and DS247LC were 1.96 mg/cm2 and 2.26 mg/cm2, respectively, indicating the superior high-temperature oxidation resistance of the L-PBF HIP sample. Based on the above results, a high-temperature oxidation mechanism of the CM247LC alloys manufactured by the SLM process and the directional solidification process has been proposed.
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Authors and Affiliations

Jung-Uk Lee
1
Young-Kyun Kim
2
ORCID: ORCID
Seong-Moon Seo
2
Kee-Ahn Lee
1
ORCID: ORCID

  1. Inha University, Department of Materials Science and Engineering, Incheon 22212, Republic of Korea
  2. Korea Institute of Materials Science, Changwon 51508, Republic of Korea
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Abstract

One of the most important factors directly affecting microstructure and mechanical properties in directional solidification process is secondary dendrite arm spacing (SDAS). It is very important to measure the SDAS and examine the factors that may affect them. To investigate the effect of growth rate on the SDAS, the alloy specimens were directional solidified upward with different growth rates ( V = 8.3-83.0 μm/s) at a constant temperature gradient ( G = 4 K/mm) in a Bridgman-type growth apparatus. After the specimens are directionally solidified, they were exposed to metallographic processes in order to observe the dendritic solidification structure on the longitudinal section of the specimens. Coarsen secondary dendrite arm spacings (λ 2C) were measured excluding the first arms near the tip of the dendrite. Local solidification times ( tf) were calculated by ratio of spacings to growth rates. It was determined that the tf values decreased with increasing V values. The relationships between tf and λ 2C were defined by means of the binary regression analysis. Exponent values of tf were obtained as 0.37, 0.43, 0.46 and 0.47 according to increasing V values, respectively. These exponent values are close to the exponent value (0.33) predicted by the Rappaz-Boettinger theoretical model and good agreement with the exponent values (0.33-0.50) obtained by other experimental studies.
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Authors and Affiliations

Erkan Üstün
1
ORCID: ORCID
Emin Çadirli
1
ORCID: ORCID

  1. Niğde Ömer Halisdemir University, Institute of Science, Department of Physics, Niğde, Turkey

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