Diffusion-controlled growth of hydrogen pores in aluminium–silicon castings: in situ observation and modelling

Atwood, Robert C.; Sridhar, Seetharaman; Zhang, W.; Lee, Peter

doi:10.1016/s1359-6454(99)00363-8

Cited by 133 publications

(91 citation statements)

References 12 publications

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“…Porosity in aluminum is caused by the precipitation of hydrogen from the melt or by shrinkage during solidification, and most often by a combination of these defects. Atwood et al 4) pointed out that the amount of hydrogen in the aluminum melt is the key factor determining the pore growth rate and its distribution in the end product after directional solidification. The pore growth rate increases as the initial hydrogen content in the melt increases and the pore size decreases as the velocity of the solid/liquid interface in the aluminum casting increases.…”

Section: Introductionmentioning

confidence: 99%

Relationship between Ultrasonic Characteristics and Relative Porosity in Al and Al-XSi Alloys

Chen

2009

Mater. Trans.

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Pores form readily in aluminum alloy castings. The percentage of porosity is often used to quantitatively evaluate the quality of aluminum alloy castings. In this study, the relative porosity, as represented by the percentage of porosity in Al and Al-XSi alloys is evaluated. Nondestructive ultrasonic techniques are adopted to investigate the relative porosity of Al and Al-XSi alloys. The relationship between the relative porosity and ultrasonic characteristics, including the ultrasonic velocity and the attenuation coefficient, are determined and compared, and the pore formation in the alloys is also discussed.

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Section: Introductionmentioning

confidence: 99%

Relationship between Ultrasonic Characteristics and Relative Porosity in Al and Al-XSi Alloys

Chen

2009

Mater. Trans.

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“…Based on the experimental observations of Lee et al [6,8], the finite rate of hydrogen diffusion in the liquid is assumed to govern the growth kinetics of the pore 2 . This has been taken into account in the model through a hydrogen conservation equation, neglecting any hydrogen concentration gradient in the gas phase and any hydrogen transport in the liquid due to convection:…”

Section: Modelmentioning

confidence: 99%

“…In order to better characterize and more importantly minimize this defect, a considerable effort has been dedicated to the modeling of pore formation. These models, which range from very simple criteria functions [2] to sophisticated computational solutions of conservation and state equations, provide quantitative information on the effect of the processing conditions and alloy chemistry on microporosity [3][4][5][6][7][8][9][10].…”

Section: Introductionmentioning

confidence: 99%

“…high eutectic fraction. They proposed a pore growth model based on the finite-rate diffusion of hydrogen, a concept that was further developed by Atwood et al [7,8] and applied to Al-Si alloys. A more comprehensive model accounting for both finite-rate hydrogen diffusion and limited flow in the mushy zone of aluminum alloys was proposed recently by Carlson et al [9].…”

Section: Introductionmentioning

confidence: 99%

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Three-dimensional phase-field simulation of micropore formation during solidification: Morphological analysis and pinching effect

et al. 2012

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A three-dimensional (3-D) multiphase-field model has been developed in order to study the formation of a micropore constrained to grow in a solid network (i.e. pinching effect). The model accounts for the pressure difference due to capillarity between liquid and gas, the equilibrium condition at triple (solid-liquid-pore) lines, and the partitioning and diffusion of dissolved gases such as hydrogen. From the predicted 3-D morphology of the pore, entities such as the interfacial shape distribution are plotted and analyzed. It is shown that the mean curvature of the pore-liquid surface, and thus also the pressure inside the pore, is uniform. The results are then compared with analytical pinching models. While predicting a similar trend, analytical models tend to underestimate the pore curvature at high solid fractions. Despite the complex morphology of pores reconstructed using high-resolution X-ray tomography, the present phase-field results suggest that a simple pinching model based on a spherical tip growing in between remaining liquid channels is a fairly good approximation.

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“…[1] Most advanced models of microporosity formation solve at the scale of the process average conservation equations for the evolution of the solid fraction, the flow of interdendritic liquid, and the partitioning and diffusion of gases during solidification. [2][3][4][5][6][7] During its growth, the pressure inside the pore exceeds that of the surrounding liquid due to capillarity forces between liquid and gas. Therefore, to close the problem mathematically, a so-called pinching model, i.e., a mathematical expression relating the radius of curvature of the pore-liquid interface to a microstructural parameter (e.g., solid fraction) is required.…”

mentioning

confidence: 99%

Multiphase-Field Modeling of Micropore Formation in Metallic Alloys

Meidani

Rappaz

Jacot

2013

Volume 2B: Advanced Manufacturing

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A 3D phase-field (PhF) model has been developed to study the formation of micropores constrained to grow within a well-developed solid network. The model accounts for the equilibrium condition at triple (solidliquid-pore) lines and the partitioning of dissolved gases. Growth of a micropore in a representative volume element taken from X-ray tomography was simulated, which offered the possibility to study the pore evolution in temporal and spatial resolutions that are not possible in experiments.

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Diffusion-controlled growth of hydrogen pores in aluminium–silicon castings: in situ observation and modelling

Cited by 133 publications

References 12 publications

Relationship between Ultrasonic Characteristics and Relative Porosity in Al and Al-XSi Alloys

Relationship between Ultrasonic Characteristics and Relative Porosity in Al and Al-XSi Alloys

Three-dimensional phase-field simulation of micropore formation during solidification: Morphological analysis and pinching effect

Multiphase-Field Modeling of Micropore Formation in Metallic Alloys

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