The rheological properties and hot tearing behaviour of an Al-Cu alloy

Zhao, Liangyi; Baoyin,; Wang, Na; Sahajwalla, Veena; Pehlke, Robert D.

doi:10.1080/13640461.2000.11819399

Cited by 23 publications

(11 citation statements)

References 4 publications

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“…The former type of criteria deals with the vulnerable temperature range, phase diagram, and process parameters, and is represented by the criteria of Clyne and Davies, [6] Feurer, [43] and Katgerman. [38] The latter type of criteria involves critical stress, [9,29,33,34,48] critical strain, [9,31,53] or critical strain rate. [25,[40][41][42]54,55] Different casting processes impose specific requirements on the application of hot tearing criteria.…”

Section: Current Hot Tearing Criteria and Their Applicability To mentioning

confidence: 99%

A Quest for a New Hot Tearing Criterion

Eskin¹,

Katgerman

2007

Metall Mater Trans A

229

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Hot tearing remains a major problem of casting technology despite decades-long efforts to develop working hot tearing criteria and to implement those into casting process computer simulation. Existing models allow one to calculate the stress-strain and temperature situation in a casting (ingot, billet) and to compare those with the chosen hot tearing criterion. In most successful cases, the simulation shows the relative probability of hot tearing and the sensitivity of this probability to such process parameters as casting speed, casting dimensions, and casting recipe. None of the existing criteria, however, can give the answer on whether the hot crack will appear or not and what will be the extent of hot cracking (position, length, shape). This article outlines the requirements for a modern hot tearing model and a criterion based on this model as well as the future development of hot tearing research in terms of mechanisms of hot crack nucleation and propagation. It is suggested that the new model and criterion should take into account different mechanisms of hot tearing that are operational at different stages of solidification and be based on fracture mechanics, i.e., include the mechanisms of nucleation and propagation of a crack.

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Section: Current Hot Tearing Criteria and Their Applicability To mentioning

confidence: 99%

A Quest for a New Hot Tearing Criterion

Eskin¹,

Katgerman

2007

Metall Mater Trans A

229

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“…Investigations on hot tears have been reported in many previous studies [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19] and it is concluded that when tensile stress or strain exceeds the fracture strength or fracture strain of the solidifying material, a crack can be generated. Values of fracture strain and fracture strength, however, are considerably different by measurement technique used and experimental condition applied.…”

Section: Introductionmentioning

confidence: 99%

Mechanical Properties of High Strength Al-Mg-Si Alloy during Solidification

et al. 2006

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Mechanical properties of high strength Al-Mg-Si alloy during solidification have been investigated. Tensile strength and ductility have been measured by using an electromagnetic induction heating tensile machine. The relation between solid fraction and temperature was calculated by the Gulliver-Scheil model applied with the thermodynamic data-base Thermo-Calc for multi-component system, and its validity was confirmed, comparing with the experiment. Zero Strength Temperature (ZST) and Zero Ductility Temperature (ZDT) were evaluated and correlated with the corresponding solid fraction. Furthermore, the capability of the high temperature tensile test to apply to the break-out of direct chill (DC) casting was examined, comparing the breaking section of the tensile test sample with that of DC billet. Main conclusions are as follows: (1) ZST and ZDT were 893 and 883 K at which the corresponding solid fraction were 0.69 and 0.77, respectively. (2) Breaking sections of the tensile testing sample and DC billet had a similar rupture structure where intergranular fracture was observed. Consequently, it was considered that breaking elongation and breaking strength that were obtained by the present tensile test can be used as one of the criteria of Direct-Chill casting crack formation.

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“…Based on the tensile test observations on the Al-Cu alloys, the theoretical analysis gives a global relationship between stress, strain, strain rate and temperature, which involves both rheological and mechanical behaviors, and generally follows a power law [57,66,67,68,89,90,91]:…”

Section: Experimental Results From Experimentsmentioning

confidence: 99%

“…increasing. This phenomenon was explained by Liangyi Zhao et al [66], who suggested the maximum strain occurs after hot tearing and the stress related to the maximum strain causes hot tearing, is extensive in the solid state.…”

Section: Stress -Strain Curvesmentioning

confidence: 99%

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modeling of hot tearing in aluminium alloy /

Wu¹

2003

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Hot tearing is one of the "universal" defects in many aluminium casting products. The formation of hot tearing involves complex solidification phenomena and processing conditions. During the DC casting process, it often initiates at the surface and propagates towards centre. In the present work, a coupled solidification model (microstructure) and hot tearing model has been developed in order to predict the hot tearing susceptibility of aluminium alloys and thus to better control its occurrence.The microstructure modeling in this project was progressed from two-dimensional simulation of Al-4.5%Cu binary alloy solidification, and the modeling results were compared with the experimental data. The information provided by the microstructural model, such as temperature field, evolution of solid fraction, the final grain size and the microstructure morphology, is essential for the further study of hot tearing.In order to predict the hot tearing susceptibility during solidification, two hot tearing criteria with different aspects have been implemented into the microstructural model. The Lahaie Bouchard (LB) criterion is based on the mechanical response of the semi-solid body, while the Rappaz Drezet Grenaud (RDG) criterion considers the pressure drop from both thermal deformation and solidification shrinkage through the mushy zone.In the microstructure -hot tearing model using LB criterion, by combining the constitutive law that reflected the viscous behaviour and the critical fracture based on the capillary force, a critical strain can be calculated to identify when and where hot tearing 11 could occur. The critical strain is influenced by cooling condition, strain rate, solid fraction and alloy composition. The modeling results give an overall indication of the appearance of hot tearing, and can be used to investigate the susceptibility of hot tearing tendency influencing by the solidification parameters and the thermal properties of the Al-Cu alloys.To valid the coupled microstructure-hot tearing model, some experiments have been carried out on the Direct Chill Ingot Surface Simulator (DCSS). The displacements under applied tensile loads were measured and the occurrence of the hot tearing was observed.The results from modeling and experiments were compared and discussed. The complete microstructure -hot tearing model (with the LB criterion), corresponds with the facture stress range found in the experimental data. By further correction based on a recently modified constitutive model, the critical strain range between the modeling and experiment can give better agreement to identify the appropriate condition for the susceptibility of hot tearing.The modeling results from the RDG criterion showed that it is more suitable for the central type of hot tearing. It needs to be studied further to know whether this criterion is applicable for the surface hot tearing as in the case of DC cast sheet ingots. Ill ACKNOWLEDGEMENTSIt is with great pleasure that I acknowledge all those who were involved directly or indirectl...

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The rheological properties and hot tearing behaviour of an Al-Cu alloy

Cited by 23 publications

References 4 publications

A Quest for a New Hot Tearing Criterion

A Quest for a New Hot Tearing Criterion

Mechanical Properties of High Strength Al-Mg-Si Alloy during Solidification

modeling of hot tearing in aluminium alloy /

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