Favorable Environment for a Nondendritic Morphology in Controlled Diffusion Solidification

Khalaf, Abbas A.; Shankar, Sumanth

doi:10.1007/s11661-011-0641-z

Cited by 29 publications

(8 citation statements)

References 16 publications

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“…CDS technology employs a combination of solute and thermal fields to enable non-dendritic morphology of the casting [63]. The works of Saha et al [76], Symeonidis et al [77], and Khalaf et al [78][79][80] have resulted in a sound basis for successful CDS processing.…”

Section: Controlled Diffusion Solidification (Cds) Processmentioning

confidence: 99%

“…In this process, two precursor alloy melts with different thermal masses (temperature and mass) are mixed in such a way that the higher thermal mass melt is undercooled by the other . Numerous nucleation of solid nuclei within the undercooled melt, uniform distribution of the nuclei throughout the melt by the forced convection resulting from the mixing process and diffusion of alloying elements toward the solidifying front, leading to a negligible and diminishing chemical undercooling at the solid/liquid interface, prevent instability of the interface and thereby ensure the globular morphology .…”

Section: Controlled Diffusion Solidification (Cds) Processmentioning

confidence: 99%

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The role of indium in the activation of aluminum alloy galvanic anodes

Pourgharibshahi

Lambert

2015

Materials & Corrosion

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Despite six decades use of aluminum as a galvanic (sacrificial) anode, there remains a need for a better understanding of the underlying mechanisms for enhancing its efficient performance in cathodic protection systems. A few mechanisms have been proposed for the role of indium in the activation of Al‐Zn‐In anodes and there appears to be no general agreement on whether this element plays its depassivating role by modifying the bulk microstructure of the anode, chemical composition of its surrounding electrolyte or directly through doping the structure of the passive oxide film. These mechanisms have been critically reviewed to achieve a more comprehensive understanding of the role of indium in such applications. Moreover, the novel solidification processing called controlled diffusion solidification (CDS) has been introduced as an efficient way to surmount the poor castability of the anode alloy without any need for the addition of elements with detrimental effects on the electrochemical properties of the anode.

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Section: Controlled Diffusion Solidification (Cds) Processmentioning

confidence: 99%

Section: Controlled Diffusion Solidification (Cds) Processmentioning

confidence: 99%

The role of indium in the activation of aluminum alloy galvanic anodes

Pourgharibshahi

Lambert

2015

Materials & Corrosion

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“…The average grain size was 930 µm. The smaller average grain size creates in the Ex1 and Ex2 microstructure, establishing from copious nucleation taking place in the mixture [6,8,10,11,[17][18][19].…”

Section: Simulation Of Mixing Stepmentioning

confidence: 99%

“…Aluminum wrought alloys could not be easily cast by conventional casting processes because they are prone to make hot tearing during solidi cation, where the inter-dendritic liquid at the end of the solidi cation process cannot effectively feed the shrinkage cavities created during solidi cation of the primary, secondary, and ternary branches of the dendrites because of creating a large and complex dendritic network [3,4]. The CDS process is a casting process depending on mixing two precursor alloys that have different masses and temperatures to make copious nucleation that results in improving the mechanical properties by changing the microstructure from dendritic to small size nondendrites that leads to minimizing the hot tearing tendencies [5][6][7][8][9][10][11].…”

Section: Introductionmentioning

confidence: 99%

Temperature, density, and velocity distribution in the mixture prepared by controlled diffusion solidification process

Khalaf

2022

Int J Adv Manuf Technol

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Controlled diffusion solidi cation (CDS) is a new casting process that depends on mixing two precursor alloys. The two precursor alloys have precisely controlled temperature and content to make a required resultant alloy. The CDS process can change the microstructure to non-dendritic happening from copious nucleation, resulting in minimizing the tendency toward the hot tearing. Contrary to the conventional casting in which the dendritic microstructure forms the entire microstructure of the product. In the present study, Pure aluminum and Al-33wt%Cu have been used to make Al-4.7wt%Cu by using the CDS technique, where the pure aluminum was mixed into Al-33wt%Cu through funnels that have 9 and 6mm diameter. The events such as the nucleation and heat transfer to the environment have been studied with aid of the temperature, density, and velocity distribution taking place during the mixing step of the CDS process. The results show that the thermal curves give better indications to predict the periods of nucleation and the heat transferring to the environment. Further, the copious nucleation that occurs in the CDS process can be improved by controlling the agitation during the mixing step by decreasing the velocity of the mixture near the crucible wall and increasing the velocity in the middle of the mixture. Ansys software was employed to simulate the temperature, density, and velocity distribution in the mixture during the mixing step. The experimental results were supported by simulation results and an optical microscopy test.

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“…The controlled diffusion solidi cation (CDS) process depends on mixing two precursor alloys in a liquid state innovated to enable casting of aluminum wrought alloys to near-net-shape resulting to form a nondendritic microstructure similar to that forming in the semi-solid processes [5][6][7][8][9][10]. Khalaf [11] mixed pure aluminum into Al-Si eutectic alloy to make Al-1.8 wt%Si as a resultant alloy.…”

Section: Introductionmentioning

confidence: 99%

Microstructure evolution of Al-Si hypoeutectic alloys prepared by controlled diffusion solidification

Khalaf

2022

Int J Adv Manuf Technol

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The possibility of changing the dendritic microstructure associated with the conventional casting processes of hypoeutectic Al-Si alloys to non-dendritic microstructure by using the controlled diffusion solidi cation process (CDS) has been investigated. The successful CDS process depends on mixing two precursor alloys heated at a superheat condition near their respective liquidus temperature. Experimental work and simulation work using Ansys software was carried out in the present study by employing Al-Si and Al-Cu systems. This study investigates the effect of the content of the two precursor alloys, the mass ratio changing from 2.6 to 8.3, and the superheat of the rst precursor alloy on changing the microstructure. The experimental results show that the pure aluminum used as the rst precursor alloy needs more undercooling and agitation during the mixing to form the non-dendritic microstructure compared with hypoeutectic Al-Si alloys. Further, mixing pure aluminum with hypereutectic alloy can change the microstructure of hypoeutectic alloys leading to extending the possibility to choose the second precursor alloy. The results also show that a higher mass ratio is preferred when mixing pure aluminum with hypoeutectic alloy. Furthermore, the microstructure of the alloy Al-6.45Si-4Cu-0.5Mg-0.66Fe-0.66 wt%Zn was successfully changed via the CDS process by mixing Al-7.75Si-0.79Fe-0.78Zn-0.6 wt%Mg at 2°C superheat into Al-24 wt%Cu at around 5°C superheat. The simulation results show that lower air bubbles and better distribution of the two precursor alloys happen during the mixing step when using the Al-Cu system.

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Favorable Environment for a Nondendritic Morphology in Controlled Diffusion Solidification

Cited by 29 publications

References 16 publications

The role of indium in the activation of aluminum alloy galvanic anodes

The role of indium in the activation of aluminum alloy galvanic anodes

Temperature, density, and velocity distribution in the mixture prepared by controlled diffusion solidification process

Microstructure evolution of Al-Si hypoeutectic alloys prepared by controlled diffusion solidification

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