Mechanism of Anomalous Grain Formation During Controlled Diffusion Solidification

Khalaf, Abbas A.; Shankar, Sumanth

doi:10.1007/s11837-020-04198-1

Cited by 10 publications

(10 citation statements)

References 18 publications

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“…Two kinds of nucleation (Heterogeneous and spontaneous nucleations) can occur during the mixing step. The heterogeneous nucleation happens at the crucible wall when the mixture is free of grain re ner [6,8,16,17]. The spontaneous nucleation happens from the undercooled alloy when supersaturation solution forms in the mixture [12,18,19].…”

Section: Enthalpy Of Fusionmentioning

confidence: 99%

“…These equations were numerically solved in the simulation. In Eq.1, Cp=1179 [20] and 953.9 J kg−1 K−1 [17] are the speci c heat for Alloy1 and Alloy2, respectively [16−18], K=95 w.m−1. K−1 [21].…”

Section: Simulation Of Mixing Stepmentioning

confidence: 99%

“…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%

“…Point (E) represents the starting of the thermal recalescence in the thermal curve. The thermal recalescence happens from the latent heat issued from the nucleation that occurs during the mixing step [16, 17,19]. Figure 4(e) shows the temperature distribution at the points (D), (E), and (f) taken at the line X-Y shown in Fig.…”

Section: Simulation Of Mixing Stepmentioning

confidence: 99%

“…The results achieved from the successful CDS process are small size globular morphologies forming from copious nucleation occurring during the CDS steps without needing to add a grain re ner [6,8,11,14,15]. Khalaf [16,17] used Al-Cu and Al-Zn binary alloys system to study the microstructure formed by the CDS process experimentally and by simulation, the results exhibited that globular, rosette, and dendrites coexist in the entire microstructure, even though all the morphologies were exposed to the same thermal environment during growth, further, anomalous morphologies form in the microstructure when using pure aluminum as a rst precursor alloy that has a higher liquidus temperature. Recently, Khalaf [18] employed the concept of the two steps nucleation theory along with the mixing of two alloys to predict the transition temperature at which the metastable zone changes to the labile zone for undercooled Al-Si hypereutectic alloys.…”

Section: Introductionmentioning

confidence: 99%

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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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Section: Enthalpy Of Fusionmentioning

confidence: 99%

Section: Simulation Of Mixing Stepmentioning

confidence: 99%

Section: Simulation Of Mixing Stepmentioning

confidence: 99%

Section: Simulation Of Mixing Stepmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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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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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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Mixing process and nucleation of an Al-Si alloy during controlled diffusion solidification with simultaneous mixing and effect of mixing rate

et al. 2022

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Mechanism of Anomalous Grain Formation During Controlled Diffusion Solidification

Cited by 10 publications

References 18 publications

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

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

Mixing process and nucleation of an Al-Si alloy during controlled diffusion solidification with simultaneous mixing and effect of mixing rate

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