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1

Effect of Growth Rate on Coarsening of Secondary Dendrite Arm Spacings in Directionally Solidified of Al-8.8La-1.2Ni Ternary Alloy

Üstün Erkan, Çadirli Emin

Archives of Metallurgy and Materials

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2022

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Vol. 67, iss. 3

931--938

EN

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 (λ2C) 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 λ2C 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.

2

Influence of variable casting wall thickness and shell mold material and its thermal properties on secondary dendrite arm spacing in IN 713C superalloy castings

Szczotok A.

Inżynieria Materiałowa

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2016

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Vol. 37, nr 5

217--222

EN

The results of microstructure investigations of IN 713C superalloys obtained as thin walled‚ wedge’ castings from three kinds of shell molds are presented. Light microscopy, scanning electron microscopy observations and secondary dendrite arm spacing (SDAS) measurements were used to determine the differences in the IN 713C castings obtained using three kinds of shell mold materials. The effects of major constituents of the three shell molds: zirconium silicate ZrSiO4, aluminosilicate mAl2O3 . nSiO2 and SiC-based system on the SDAS in the investigated castings of the IN 713C superalloy are described. The results confirm that crystallization conditions (the variable wall thickness of the casting and material of the shell) of the IN 713C castings influence their microstructure. The increased SiC content in the shell molds has an effect on the crystallization process kinetics as indicated by the changes in the observed secondary dendrite arm spacing.

PL

Powszechnie wiadomo, że parametry procesu odlewania mogą wpływać na mikrostrukturę i właściwości mechaniczne nadstopów na osnowie niklu. Zmniejszenie odległości między ramionami wtórnymi dendrytów (SDAS) prowadzi do zredukowania porowatości i obszarów eutektyki w odlewie. Celem przeprowadzonych badań było ustalenie wpływu grubości ścianki odlewu oraz składu materiału i właściwości cieplnych formy ceramicznej na odległości między ramionami wtórnymi dendrytów w odlewach z nadstopu IN 713C.

3

Prediction of Secondary Dendrite Arm Spacing in Squeeze Casting Using Fuzzy Logic Based Approaches

Patel M. G. C., Krishna P., Parappagoudar M. B.

Archives of Foundry Engineering

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2015

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Vol. 15, iss. 1

51--68

EN

The quality of the squeeze castings is significantly affected by secondary dendrite arm spacing, which is influenced by squeeze cast input parameters. The relationships of secondary dendrite arm spacing with the input parameters, namely time delay, pressure duration, squeeze pressure, pouring and die temperatures are complex in nature. The present research work focuses on the development of input-output relationships using fuzzy logic approach. In fuzzy logic approach, squeeze cast process variables are expressed as a function of input parameters and secondary dendrite arm spacing is expressed as an output parameter. It is important to note that two fuzzy logic based approaches have been developed for the said problem. The first approach deals with the manually constructed mamdani based fuzzy system and the second approach deals with automatic evolution of the Takagi and Sugeno’s fuzzy system. It is important to note that the performance of the developed models is tested for both linear and non-linear type membership functions. In addition the developed models were compared with the ten test cases which are different from those of training data. The developed fuzzy systems eliminates the need of a number of trials in selection of most influential squeeze cast process parameters. This will reduce time and cost of trial experimentations. The results showed that, all the developed models can be effectively used for making prediction. Further, the present research work will help foundrymen to select parameters in squeeze casting to obtain the desired quality casting without much of time and resource consuming.

4

The effect of major alloying elements on the size of the secondary dendrite arm spacing in the as-cast Al-Si-Cu alloys

Djurdjevič M. B., Grzinčič M. A.

Archives of Foundry Engineering

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2012

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Vol. 12, iss. 1

19-24

EN

A comprehensive understanding of melt quality is of paramount importance for the control and prediction of actual casting characteristics. Among many phenomenons that occur during the solidification of castings, there are four that control structure and consequently mechanical properties: chemical composition, liquid metal treatment, cooling rate and temperature gradient. The cooling rate and alloy composition are among them most important. This paper investigates the effect of some major alloying elements (silicon and copper) of Al-Si-Cu alloys on the size of the secondary dendrite arm spacing. It has been shown that both alloying elements have reasonable influence on the refinement of this solidification parameter.

5

Evaluation of Superalloy Incomel 713C Dendritic Microstructure of the Turbine Blade Castings

Pieczaba D., Jach A.

Archives of Metallurgy and Materials

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2010

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Vol. 55, iss. 1

25-35

EN

The influence of the crystallization conditions on microstructure of Inconel 713 C superalloy was presented in the paper. Turbine blades with airfoil section width of 22 and 30 mm and length of 50 mm were casted in investment molds in a vacuum furnace. The secondary dendrite arm spacing was determined through microscopic examinations. On the basis of obtained results it was established that prolonged process of crystallization results in an increase of microstructure constituents dispersion.

PL

W pracy przedstawiono wyniki badań wpływu warunków krystalizacji na mikrostrukturę odlewniczego stopu Inconel 713 C. Łopatki turbin o szerokości pióra 22 i 30 mm i długości pióra 50 mm wykonano metodą wytapianych modeli w piecu próżniowym. Dyspersję składników mikrostruktury określono poprzez pomiar odległości ramion dendrytów wtórnych.

6

The effect of cooling rate on microstructure and mechanical properties of AC AlSi9Cu alloy

Dobrzański L. A., Maniara R., Sokolowski J. H.

Archives of Materials Science and Engineering

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2007

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Vol. 28, nr 2

105-112

EN

Purpose: In this work the effect of cooling rate on the size of the grains, SDAS, size of the β precipitation and thermal characteristic results of AC AlSi9Cu cast alloy have been described. The solidification process was studied using the cooling curve and crystallization curve at solidification rate ranging from 0,16 °Cs -1 up to 1,04 °Cs -1. Design/methodology/approach: The experimental alloy used in this investigation was prepared by mixing in suitable proportion the AC AlSi5Cu1(Mg) commercial alloys and two master alloys AlSi49 and AlCu55. Thermal analysis tests were made using the UMSA Technology Platform. Cooling curve thermal analysis was performed on all samples using high sensitivity thermocouples of K type that were protected in a stainless steel sheath and data were acquired by a high speed data acquisition system linked to a PC computer. Each chilled sample was sectioned horizontally where the tip of the thermocouple was located and it was prepared by standard grinding and polishing procedures. The final stage of polishing was done using commercial silicon oxide slurry. Optical microscopy was used to characterize the microstructure and intermetallic phases. Secondary dendrite arm spacing measurements were carried out using a Leica Q-Win ™ image analyzer. The UTM measurements were carried out using a Zwick testing machine. Findings: Increasing the cooling rate increases significantly the liquidus temperature, nucleation undercooling temperature, solidification range and decreases the recalescence undercooling temperature. Increasing cooling rate refines all microstructural features including secondary dendrite arm spacing (SDAS) and intermetallic compounds and improves silicon modification level. Research limitations/implications: The results presented in this paper show results only for the one alloy - AC AlSi9Cu, and for the assessment of the Silicon Modification Level didn't include the arrangement of a Si crystal in a matrix. Practical implications: The aim of this work is describe in detail the solidification process in a number of AC AlSi9Cu foundry alloy. Cooling rates applied in this experiment occur in cross section of a bloc engine. The results shows the effect of different cooling rates on the microstructural features and the characteristic parameters of the cooling curve of ACAlSi9Cu alloy. Originality/value: Original value of the work is applied the artificial intelligence for the assessment of the Silicon Modification Level.

7

Influence of the crystallization condition on Al-Si-Cu casting alloys structure

Dobrzański L. A., Borek W., Maniara R.

Journal of Achievements in Materials and Manufacturing Engineering

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2006

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Vol. 18, nr 1-2

211--214

EN

Purpose: The purpose of this paper is to show the effect of solidification rate on microstructural features, hardness and microhardness of Al-Si-Cu alloys in as cast state. Design/methodology/approach: The main base of the paper is to compare the properties of aluminium cast alloys of ACAlSi7Cu, ACAlSi7Cu2 and ACAlSi7Cu4. Microstructural features were characterised using light optical microscopy. For rapid determination of the parameters: grains size and Secondary Dendrite Arm Spacing - SDAS were used Leica Q-WinTM computer image analyzer. Findings: Increasing the solidification rate increases refines all microstructural features grain size and SDAS. Increasing the solidification rate have an impact on the hardness and microhardness of investigated aluminium cast alloys. Research limitations/implications: In this paper influence of solidification rate on mechanical properties was described. Further investigations should be concentrate on assessment an influence of silicon contents and solidification rate on microstructural features and mechanical properties. Practical implications: The aim of this work is describe the effect of different solidification conditions on changes of microstructure and mechanical properties of ACAlSi7Cu, ACAlSi7Cu2, ACAlSi7Cu4 alloys used to produce the car engine block. Originality/value: The paper contributes to better understanding and recognition an influence of different solidification condition on microstructure and mechanical properties of aluminium alloys.