Influence of Cooling Rate on Microsegregation Behavior of Magnesium Alloys

Khan, Md. Imran; Mostafa, Ahmad; Aljarrah, M.; Essadiqi, E.; Medraj, Mamoun

doi:10.1155/2014/657647

Cited by 23 publications

(16 citation statements)

References 37 publications

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“…The retrograde solubility phenomenon occurs during solidification and originates from a miscibility gap in the free energy of mixing [ 30 ]. Impurity concentration in the melt varies with the fraction of melt solidified and the value of the impurity distribution coefficient, K o , which is also known as the segregation or partition coefficient [ 31 ]. K o of group IIIA and group VA dopants in Si is less than one, as listed in Table 1 [ 28 , 32 ].…”

Section: Impurity Atoms From Groups Iiia and Vamentioning

confidence: 99%

Binary Phase Diagrams and Thermodynamic Properties of Silicon and Essential Doping Elements (Al, As, B, Bi, Ga, In, N, P, Sb and Tl)

Mostafa

Medraj

2017

Materials

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Fabrication of solar and electronic silicon wafers involves direct contact between solid, liquid and gas phases at near equilibrium conditions. Understanding of the phase diagrams and thermochemical properties of the Si-dopant binary systems is essential for providing processing conditions and for understanding the phase formation and transformation. In this work, ten Si-based binary phase diagrams, including Si with group IIIA elements (Al, B, Ga, In and Tl) and with group VA elements (As, Bi, N, P and Sb), have been reviewed. Each of these systems has been critically discussed on both aspects of phase diagram and thermodynamic properties. The available experimental data and thermodynamic parameters in the literature have been summarized and assessed thoroughly to provide consistent understanding of each system. Some systems were re-calculated to obtain a combination of the best evaluated phase diagram and a set of optimized thermodynamic parameters. As doping levels of solar and electronic silicon are of high technological importance, diffusion data has been presented to serve as a useful reference on the properties, behavior and quantities of metal impurities in silicon. This paper is meant to bridge the theoretical understanding of phase diagrams with the research and development of solar-grade silicon production, relying on the available information in the literature and our own analysis.

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Section: Impurity Atoms From Groups Iiia and Vamentioning

confidence: 99%

Binary Phase Diagrams and Thermodynamic Properties of Silicon and Essential Doping Elements (Al, As, B, Bi, Ga, In, N, P, Sb and Tl)

Mostafa

Medraj

2017

Materials

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“…High pressure die casting (HPDC) is an important and cost effective manufacturing method for many automotive components including body structural applications [2], and more than 95% of all Mg alloy components are fabricated by HPDC [3]. The cooling rates for HPDC components are in the range of 10-1000 °C/s [4,5], which is far greater than those of conventional casting processes such as sand or permanent mold castings [6][7][8][9][10][11][12]. The fast cooling rate present during HPDC affects microstructural characteristics such as microsegregation and cell size, etc.…”

Section: Introductionmentioning

confidence: 99%

“…The fast cooling rate present during HPDC affects microstructural characteristics such as microsegregation and cell size, etc. [9,13]. The redistribution of solute also affects the as-cast volume fraction of the second phase (Mg 17 Al 12 -β phase) in the Mg-Al binary alloys.…”

Section: Introductionmentioning

confidence: 99%

An ICME Method for Predicting Phase Dissolution During Solution Treatment in Advanced Super Vacuum Die Cast Magnesium Alloys

Yao

Berman

Allison

2020

Integr Mater Manuf Innov

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An integrated computational materials engineering (ICME) methodology was applied in this study to systematically and quantitatively study the second phase dissolution kinetics during the solution treatment process of a high pressure die cast magnesium sample. The study was conducted on Mg-9 wt% Al, Mg-5 wt% Al, and Mg-11 wt% Al binary alloys after isothermal solution treatments ranging from 380 to 420 °C. The experimental measurements revealed an exponential decrease of the volume fraction of the second β-phase (Mg 17 Al 12) during the solution treatment. A CALPHAD-based computational tool (Thermocalc DICTRA Diffusion Module) was used to simulate the dissolution process. In this study, measurements from as-cast samples were used as input parameters to improve the accuracy of the predicted results. An analytical, physics-based micro-model, based on the Johnson-Mehl-Avrami type equation, was also applied to study the dissolution kinetics. Both the simulation and micro-model quantitatively agree with the experimental results at all solution treatment temperatures. Calibration and verification of a few input parameters help to understand the assumptions made in the modeling, improve the accuracy of the prediction, and can be applicable in different Mg-Al binary alloys. Adopting such an ICME methodology for modeling development and verification in predicting the dissolution kinetics during solution treatment will allow for more rapid optimization of solution treatments procedures to be used in industrial applications.

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“…The development of the microstructure and the segregation of solute during this phase transformation are controlled by phenomena occurring over a wide range of space and time scales. Studies have shown that the significant variables for solidification control are: solidification velocity (V S ), thermal gradient ahead of the solid/liquid interface (T G ), cooling rate (C R ) and concentration and redistribution of solute, which are interconnected through constitutional supercooling 8 . These variables can be correlated with the microstructure obtained with the use of metallography techniques.…”

Section: Introductionmentioning

confidence: 99%

“…When a fast solidification process occurs, the velocity of the solidification front is not low enough to allow the homogenization of the liquid and, therefore, a solute rich layer will be formed in the solidification front. The solute concentration will go through an initial transient and, then, a permanent regime will occur in which the rejection rate of the solute will be equal to the diffusion velocity from the solidification front 3,8 . It should be emphasized that, since the rejected solute is strongly dependent on the solidification velocity and the solute diffusion is affected by the concentration gradient, it is expected that solute concentration in the formed solid becomes a function of the solidification velocity 3,8 .…”

Section: Introductionmentioning

confidence: 99%

Analysis of Microsegregation in Al-Si-Cu Ternary Alloys: Interdependence of Solute Composition at the Solubility Limit during Non-Equilibrium Solidification

et al. 2020

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Virtually all metals used industrially undergo a solidification process during their production. Depending on the material and its manufacturing process, its physical/mechanical properties are affected to a greater or lesser extent by the microstructure and microsegregation obtained during the phase change. Aluminum casting alloys are good examples of products where this microstructure is vital for obtaining the desired properties. A sequence of experiments to analyze the upward vertical unidirectional solidification with transient heat transfer conditions in Al-Si-Cu ternary alloys was developed in the present work. The experimental results obtained were compared with classical microsegregation models. Discrepancies related to their use for ternary alloys were raised. Since the calculated results by these models do not take into account the influence of one alloying element on the solubility of the other element, disparities were founded between experimental and numerical results. A microsegregation model was proposed based on the solubility limits of the Si in the alloy as a function of the Cu concentration present in the liquid. The model, combined with the concepts of classical microsegregation theory, allows a realistic description of the microsegregation phenomenon. The model showed an excellent agreement between microsegregation profiles of solute experimentally measured and calculated.

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Influence of Cooling Rate on Microsegregation Behavior of Magnesium Alloys

Cited by 23 publications

References 37 publications

Binary Phase Diagrams and Thermodynamic Properties of Silicon and Essential Doping Elements (Al, As, B, Bi, Ga, In, N, P, Sb and Tl)

Binary Phase Diagrams and Thermodynamic Properties of Silicon and Essential Doping Elements (Al, As, B, Bi, Ga, In, N, P, Sb and Tl)

An ICME Method for Predicting Phase Dissolution During Solution Treatment in Advanced Super Vacuum Die Cast Magnesium Alloys

Analysis of Microsegregation in Al-Si-Cu Ternary Alloys: Interdependence of Solute Composition at the Solubility Limit during Non-Equilibrium Solidification

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