The importance of viscoplastic strain rate in the formation of center cracks during the start-up phase of direct-chill cast aluminum extrusion ingots

M’Hamdi, M.; Benum, Steinar; Mortensen, Dag; Fjær, Hallvard G.; Drezet, Jean‐Marie

doi:10.1007/s11661-003-0159-0

Cited by 29 publications

(27 citation statements)

References 16 publications

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“…Influence of solidification behaviors It has been suggested that the generation and history of interdendritic strain can be related to some straining criteria such as strain rate and accumulated strain that are subjected to the material when it is still in mush zone. [35] To check the validity of these criteria, Fig. 3-Carbon concentrations during phase transformations, (a) mode 1, (b) mode 2, and (c) mode 3 of Fe-C alloys.…”

Section: Sensitivity Of Results and Discussionmentioning

confidence: 99%

A Mathematical Model of Interdendritic Thermometallurgical Strain for Dendritic Solidification Processes

El-Bealy¹

2011

Metall Mater Trans B

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A mathematical model of interdendritic thermometallurgical strain (ITM) generated during dendritic solidification of steel alloys has been developed. The model consists of two main parts in which the first part represents the derivation of ITM strain based on the concept of thermal storage energy. Consequently, the second one represents the volume changes associated with dendritic solidification phenomena during the interdendritic coherent region in the mushy zone. Calculations for Fe-C binary alloys show that the straining criteria such as strain rate and accumulated strain are sensitive to the solidification behavior of different steel alloys. The results also point out that good predications of different phases, accurate alloy properties (especially thermal expansion coefficient), and precise enthalpy functions during dendritic solidification are extremely necessary. Also, the predications show that the dendrite coherency criterion is considered an essential parameter to define ITM strain of particularly long solidification interval alloys. Model predications of ITM strain are compared and discussed with other established theoretical approaches and previous modeling work.

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Section: Sensitivity Of Results and Discussionmentioning

confidence: 99%

A Mathematical Model of Interdendritic Thermometallurgical Strain for Dendritic Solidification Processes

El-Bealy¹

2011

Metall Mater Trans B

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“…Prediction of hot tearing during DC casting is based on two steps, namely modeling of the thermomechanical behavior during solidification [2][3][4] and the implementing of hot-tearing criteria into this model. [5][6][7][8][9][10] The first step uses constitutive equations to describe the thermomechanical modeling, to calculate stresses and strains in the billet. Computed stresses or strains indicate the hot-tearing tendency.…”

Section: Introductionmentioning

confidence: 99%

Integrated Approach for Prediction of Hot Tearing

Suyitno

Kool

Katgerman

2009

Metall Mater Trans A

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Shrinkage, imposed strain rate, and (lack of) feeding are considered the main factors that determine cavity formation or the formation of hot tears. A hot-tearing model is proposed that will combine a macroscopic description of the casting process and a microscopic model. The micromodel predicts whether porosity will form or a hot tear will develop. Results for an Al-4.5 pct Cu alloy are presented as a function of the constant strain rate and cooling rate. Also, incorporation of the model in a finite element method (FEM) simulation of the direct-chill (DC) casting process is reported. The model shows features well known from literature such as increasing hot-tearing sensitivity with increasing deformation rate, cooling rate, and grain size. Similar trends are found for the porosity formation as well. The model also predicts a beneficial effect of applying a ramping procedure during the start-up phase, which is an improvement in comparison with earlier findings obtained with alternative models. In principle, the model does not contain adjustable parameters, but several parameters are not well known. A full quanti-tative validation not only requires detailed casting trials but also independent determination of some thermophysical parameters of the semisolid mush. DOI: 10.1007/s11661-009-9941-y The Author(s) 2009. This article is published with open access at Springerlink.co

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“…Furthermore, hot cracks are mostly formed in the start-up period of the DC casting process of extrusion ingots. [3] So, the start-up levels will also have an effect on the formation of cracks. However, few works reported the influence of start-up levels on cracks in DC casting process.…”

Section: Introductionmentioning

confidence: 99%

“…Several models about stresses, strains, and temperatures field during DC casting have been done generally by using a finite-element method. Hamdi et al [3] studied the casting process of AA6060 alloy using a finite element model ALSIM, and found the viscoplastic strain rate played an important role for the center cracks. Pokorny et al [4] used a viscoplastic stress model to simulate the stresses during the casting of binary magnesiumaluminum alloys, and the simulation results were reasonably good agreement with the measurements.…”

Section: Introductionmentioning

confidence: 99%

Effect of Start‐Up Levels on the Stress–Strain Field and Cracking Tendency during Direct‐Chill Casting of Magnesium Alloy AZ80

Bai

Wei

et al. 2016

Adv Eng Mater

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The stress field of magnesium alloy AZ80 billets at different start-up levels in direct-chill (DC) casting is calculated, including equivalent stresses, equivalent strains, sump depth, and temperature fields. The equivalent stresses and strains are highest in the center of the billet for all start-up levels considered. A new criterion called cracking damage index (CDI) is used to predict the cracking susceptibility of the billets. At dangerous position of the billets, increasing start-up levels is benefit for the decrease of CDI, equivalent stresses, and equivalent strains. Consequently, reasonably increasing start-up levels can reduce the risk of cracks in the billets.

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The importance of viscoplastic strain rate in the formation of center cracks during the start-up phase of direct-chill cast aluminum extrusion ingots

Cited by 29 publications

References 16 publications

A Mathematical Model of Interdendritic Thermometallurgical Strain for Dendritic Solidification Processes

A Mathematical Model of Interdendritic Thermometallurgical Strain for Dendritic Solidification Processes

Integrated Approach for Prediction of Hot Tearing

Effect of Start‐Up Levels on the Stress–Strain Field and Cracking Tendency during Direct‐Chill Casting of Magnesium Alloy AZ80

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