Prediction of Hot Tearing Using a Dimensionless Niyama Criterion

Monroe, Charles; Beckermann, C.

doi:10.1007/s11837-014-0999-7

Cited by 30 publications

(22 citation statements)

References 9 publications

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“…Both Monroe and Beckerman's extension of Ny* [17] and the RDG criterion [15] were developed from Eqs. [3] and [4] based on the assumptions that: (1) fluid moves only along the thermal gradient and thus equates to a one-dimensional fluid flow, and (2) the solid deforms only in a direction transverse to the fluid motion/thermal gradient.…”

Section: Model Development 21 Pore Fraction Hot Tearing Modelmentioning

confidence: 99%

“…The permeability K has also been left inside the integrations of , ℎ̇ , and ℎ because many different empirical relations exist for this function, [21,22] such as the Kozeny-Carman relation. [21] Following Monroe and Beckerman [17] , it is assumed that fluid flow ceases once the pressure drop exceeds ΔPcr. Thus, for a given value of ΔPcr, the critical fraction of fluid flcr can be obtained from Eq.…”

Section: Model Development 21 Pore Fraction Hot Tearing Modelmentioning

confidence: 99%

“…Although this criterion has achieved much recognition in the literature, it cannot distinguish between shrinkage porosity and hot tearing, especially for low thermal gradients. [17] The Niyama criterion, Ny, is commonly-used as a qualitative predictor of solidification shrinkage porosity during metal casting processes [18] . Recently, Carlson and Beckermann [9] proposed a dimensionless form of the Niyama criterion, Ny*, that directly predicts shrinkage pore fractions.…”

Section: Introductionmentioning

confidence: 99%

“…Thus, any solidification occurring after liquid feeding has ceased can result in shrinkage porosity. Monroe and Beckermann [17] later modified Ny* by adding a term related to strain rate perpendicular to the thermal gradient into the pressure drop equation. With the same method, i.e.…”

Section: Introductionmentioning

confidence: 99%

“…In this study, a Pore Fraction hot tearing model for predicting the evolution of pore fraction during solidification is presented that follows the method developed by Monroe and Beckermann [17] but additionally considers the effects of deformation parallel with the thermal gradient in the mushy zone. This model is then applied to the DC casting of an Al-Mg alloy, AA5182.…”

Section: Introductionmentioning

confidence: 99%

See 4 more Smart Citations

Application of a Pore Fraction Hot Tearing Model to Directionally Solidified and Direct Chill Cast Aluminum Alloys

Dou

Phillion

2016

Metall Mater Trans A

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Hot tearing is strongly linked with the applied semi-solid strain rate. This defect is commonly qualitatively predicted using a pressure drop equation in the mushy zone that includes the effects of both tensile deformation perpendicular to the thermal gradient and shrinkage feeding. In this study, the effect of strain rate parallel to the thermal gradient is additionally introduced in order to assess its effect on hot tearing predictions. The deformation and shrinkage pore fractions are obtained on the basis of the dimensionless Niyama criterion and a scaling variable method. This Pore Fraction hot tearing model is first applied to the binary Al-Cu system under conditions of directional solidification. It is shown that for the same Niyama criterion, a decrease in the cooling rate increases both the deformation and shrinkage pore fractions because of an increase in the time spent in the brittle temperature region. Then, using a finite element simulation, the pore fraction distributions during Direct Chill casting of the AA5182 aluminum alloy are obtained. It is shown that including the strain rate parallel to the thermal gradient significantly improved the predictive quality of hot tearing criteria based on the pressure drop equation. Further, an increase in the casting speed increases the deformation and shrinkage pore fractions and causes the maximum point of pore fraction to move towards the base of the casting.

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Section: Model Development 21 Pore Fraction Hot Tearing Modelmentioning

confidence: 99%

Section: Model Development 21 Pore Fraction Hot Tearing Modelmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Application of a Pore Fraction Hot Tearing Model to Directionally Solidified and Direct Chill Cast Aluminum Alloys

Dou

Phillion

2016

Metall Mater Trans A

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Prediction of Shrinkage Microporosity in Gravity‐Cast and Low‐Pressure Sand‐Cast Mg–6Gd–3Y–0.5Zr Magnesium Alloys

Zhou

Chen

et al. 2019

Adv Eng Mater

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The Niyama criterion and the dimensionless Niyama criterion are used to predict shrinkage microporosity in Mg–6Gd–3Y–0.5Zr magnesium plates processed by gravity casting and low‐pressure sand casting. Instead of the Niyama evaluation condition recommended by commercial ProCAST software and precious studies, the most appropriate Niyama evaluation condition is suggested as fraction solid of 0.7 for the investigated alloys. With consideration of the actual distribution of shrinkage microporosity and the definition of unsound samples (shrinkage microporosity volume fraction is higher than 1% based on the tensile test), the corresponding threshold Niyama values are qualitatively determined as 0.44 and 0.3 °C0.5 s0.5 mm−1 for gravity‐cast and low‐pressure sand‐cast plates, respectively. It indicates that exerting pressure contributes to the decrease in the threshold Niyama value. In addition, exerting pressure can reduce the amount of shrinkage microporosity. For the dimensionless Niyama criterion, it is capable to quantitatively predict the shrinkage microporosity volume fraction in low microporosity‐containing regions, but not in high microporosity‐containing regions.

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Investigation on the Effect of Cooling Rate on Hot Tearing Susceptibility of Al2024 Alloy Using Thermal Analysis

Shabestari

Ghoncheh

2015

Metall Mater Trans B

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Prediction of Hot Tearing Using a Dimensionless Niyama Criterion

Cited by 30 publications

References 9 publications

Application of a Pore Fraction Hot Tearing Model to Directionally Solidified and Direct Chill Cast Aluminum Alloys

Application of a Pore Fraction Hot Tearing Model to Directionally Solidified and Direct Chill Cast Aluminum Alloys

Prediction of Shrinkage Microporosity in Gravity‐Cast and Low‐Pressure Sand‐Cast Mg–6Gd–3Y–0.5Zr Magnesium Alloys

Investigation on the Effect of Cooling Rate on Hot Tearing Susceptibility of Al2024 Alloy Using Thermal Analysis

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