Development and validation of a thermal model of the direct chill casting of AZ31 magnesium billets

Hai, Hong; Maijer, Daan M.; Wells, Mary A.; Cockcroft, S. L.; Sediako, D.; Hibbins, Stephen G.

doi:10.1007/s11661-004-0290-6

Cited by 43 publications

(31 citation statements)

References 8 publications

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“…Hot tears are thought to occur as a result of the development of tensile strains in the casting at high fraction solid (fs) due to temperature gradients and/or mechanical constraints [3], in combination with limited liquid feeding [4] and low ductility [5]. In recent years, a number of mathematical models [6][7][8] have been developed to quantify the influence of casting parameters on the development of semi-solid thermal stresses and strains, in an effort to reduce solidification defects. These models require prior knowledge of the magnesium constitutive behaviour in the as-cast state over a wide range of temperatures and strain rates.…”

Section: Paper Textmentioning

confidence: 99%

Constitutive behavior of as-cast magnesium alloy Mg–Al3–Zn1 in the semi-solid state

Phillion

Maijer

et al. 2009

Scripta Materialia

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Abstract:The first reported tensile semi-solid stress/strain data for as-cast magnesium alloy Mg-Al3-Zn1 are provided. The results show that the maximum tensile stress at the solidus temperature (460°C) was 13 MPa. Furthermore, this alloy has no ductility above 540°C, and cannot sustain tensile stresses above 560°C. Based on these tests, an equation relating the maximum tensile stress with temperature was derived. The microstructure of the tested specimens was also examined to link the tensile properties to fraction solid and microstructure. Paper Text:Having the highest strength-to-weight ratio of common structural metals, magnesium alloys offer many benefits in terms of reduced weight and energy savings for both the automotive and aerospace industries, in spite of their higher cost. These benefits have lead to a significant increase in the demand for cast and wrought magnesium products over the past few years [1].One of the most common commercial magnesium alloys for wrought products is AZ31, due to its good mechanical properties. As compared to both aluminum and steel, the use of AZ31 provides a significant mass reduction for applications with large surface area. The Direct Chill (DC) casting process, which is utilized to produce the starting material for this alloy, is receiving more attention for the sake of process optimization [2] and defect reduction.The DC casting process has been used to cast magnesium alloys for approximately 50 years.Although much work has been done to minimize solidification defects, hot tearing, cold cracks and dimensional control remain serious issues. Hot tears are thought to occur as a result of the development of tensile strains in the casting at high fraction solid (fs) due to temperature gradients and/or mechanical constraints [3], in combination with limited liquid feeding [4] and low ductility [5]. In recent years, a number of mathematical models [6][7][8] have been developed to quantify the influence of casting parameters on the development of semi-solid thermal stresses and strains, in an effort to reduce solidification defects. These models require prior knowledge of the magnesium constitutive behaviour in the as-cast state over a wide range of temperatures and strain rates. While prior research has been performed to characterize AZ31 under compressive

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Section: Paper Textmentioning

confidence: 99%

Constitutive behavior of as-cast magnesium alloy Mg–Al3–Zn1 in the semi-solid state

Phillion

Maijer

et al. 2009

Scripta Materialia

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“…The application of the heat transfer model was based on the following assumptions [7][8][9] : 1) Some properties depend on temperature. The values of conductivity and specific heat and other properties are independent on the space.…”

Section: Methodsmentioning

confidence: 99%

Thermal-stress simulation of direct-chill casting of AZ31 magnesium alloy billets

Huang

Pan

Yang

2009

J. Wuhan Univ. Technol.-Mat. Sci. Edit.

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Two-dimensional (2D) transient coupled finite element model was developed to compute the temperature and stress field in cast billets, so as to predict the defects of the I-type billets made from AZ31 magnesium alloy and find the causes and solutions for surface cracks and shrinkages during direct-chill (DC) casting process. Method of equivalent specific heat was used in the heat conduction equation. The boundary and initial conditions used for primary and secondary cooling were elucidated on the basis of the heat transfer during the solidification of the billet. The temperature and the thermal-stress fields were simulated with the thermal-structural coupled module of ANSYS software. The influences of casting parameters on the distributions of temperature and stress were studied, which helped optimize the parameters (at pouring temperature of 680 ℃, casting speed of 2 mm/s, heat-transfer coefficient of the second cooling equals to 5 000 W/m 2 ·℃ -1 ). The simulation results of thermal stress and strain fields reveal the formation mechanism of some casting defects, which is favourable for optimizing the casting parameters and obtain high quality billets. Some measures of controlling processes were taken to prevent the defects for direct-chill casting billets.

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“…Tests on the casting of magnesium-based alloys [20] showed that casting speed has a large impact on the pool depth. As casting velocity is increased, the metal pool deepens.…”

Section: Casting Velocitymentioning

confidence: 99%

Depicting Aluminium DC Casting by Means of Dimensionless Numbers

Méndez¹,

Ambriz²,

Jaramillo³

et al. 2018

Advanced Casting Technologies

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DC casting of aluminium and its alloys is a controlled heat removal solidification process. The rate of heat extraction has strong effects on the microstructure and mechanical properties of the solidified alloy ingots. In view of this strict temperature, control over the ingot as it solidifies should be implemented in order to achieve metal with the best possible properties. In situ direct temperature measurements are complicated; so in this report, the use of dimensionless analysis to predict temperature distributions on the ingots as they are casted is proposed. It is reported that the dimensionless groups that better represent the impact of process variables on the solidification of aluminium and its alloys are the Péclet (Pe) and Biot (Bi) numbers.

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Development and validation of a thermal model of the direct chill casting of AZ31 magnesium billets

Cited by 43 publications

References 8 publications

Constitutive behavior of as-cast magnesium alloy Mg–Al3–Zn1 in the semi-solid state

Constitutive behavior of as-cast magnesium alloy Mg–Al3–Zn1 in the semi-solid state

Thermal-stress simulation of direct-chill casting of AZ31 magnesium alloy billets

Depicting Aluminium DC Casting by Means of Dimensionless Numbers

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