scholarly journals Transient Modeling of Grain Structure and Macrosegregation during Direct Chill Casting of Al-Cu Alloy

Processes ◽  
2019 ◽  
Vol 7 (6) ◽  
pp. 333 ◽  
Author(s):  
Qipeng Chen ◽  
Hongxiang Li ◽  
Houfa Shen
Keyword(s):  
Direct Chill ◽  
Grain Structure ◽  
Fe Model ◽  
Grain Refiner ◽  
Negative Segregation ◽  
Cu Alloy ◽  
Transient Modeling ◽  
Dc Casting ◽  
Columnar Grain

Grain structure and macrosegregation are two important aspects to assess the quality of direct chill (DC) cast billets, and the phenomena responsible for their formation are strongly interacted. Transient modeling of grain structure and macrosegregation during DC casting is achieved with a cellular automaton (CA)–finite element (FE) model, by which the macroscopic transport is coupled with microscopic relations for grain growth. In the CAFE model, a two-dimensional (2D) axisymmetric description is used for cylindrical geometry, and a Lagrangian representation is employed for both FE and CA calculations. This model is applied to the DC casting of two industrial scale Al-6.0 wt % Cu round billets with and without grain refiner. The grain structure and macrosegregation under thermal and solutal convection are studied. It is shown that the grain structure is fully equiaxed in the grain-refined billet, while a fine columnar grain region and a coarse columnar grain region are formed in the non-grain-refined billet. With the increasing casting speed, grains become finer and grow in a direction more perpendicular to the axis, and the positive segregation near the centerline becomes more pronounced. The increasing casting temperature makes grains coarser and the negative segregation near the surface more pronounced.

Effect of Electromagnetic Field on the Macrosegregation Behaviour of Al-Cu Alloy Ingot Prepared with Direct-Chill Casting Process

2016 ◽  
Vol 877 ◽  
pp. 84-89
Author(s):  
Yu Bo Zuo ◽  
Qing Feng Zhu ◽  
Lei Li ◽  
Guang Ming Xu ◽  
Jian Zhong Cui
Keyword(s):  
Electromagnetic Field ◽  
Low Frequency ◽  
Casting Process ◽  
Direct Chill ◽  
Grain Refiner ◽  
Negative Segregation ◽  
Cu Alloy ◽  
Dc Casting ◽  
Positive Segregation ◽  
Direct Chill Casting Process

A low frequency electromagnetic field was introduced into the direct chill (DC) casting process and the ingots of Al-Cu alloy were prepared to study the macrosegregation behaviour of the ingots under the influence of the electromagnetic field. The experimental results showed that there is an obvious positive segregation near to the surface and a negative segregation in the centre area of the ingot. Cu shows the highest segregation tendency among the main elements of Cu, Mg and Mn. Grain refiner element Ti shows a segregation trend opposite to that of Cu. With the application of electromagnetic field, the negative centreline segregation in the centre area of the ingot was evidently reduced although it didn’t show significant effect on the segregation near to the ingot surface. A significant grain refinement was also achieved with the application of electromagnetic field. The mechanism of the reduction of macrosegregation with electromagnetic field was also analyzed in the present work.

Direct Chill Casting of Aluminum Alloys: Modeling and Experiments on Industrial Scale Ingots

2001 ◽  
Author(s):  
Christopher J. Vreeman ◽  
J. David Schloz ◽  
Matthew John M. Krane
Keyword(s):  
Casting Process ◽  
Direct Chill ◽  
Solid Particles ◽  
Direct Chill Casting ◽  
Grain Structure ◽  
Temperature Fields ◽  
Industrial Scale ◽  
Grain Refiner ◽  
Chill Casting ◽  
Continuum Mixture Model

Abstract A continuum mixture model of the direct chill casting process is compared to experimental results from industrial scale aluminum billets. The model, which includes the transport of free-floating solid particles, can simulate the effect of a grain refiner on macrosegregation and fluid flow. It is applied to an Al - 6 wt% Cu alloy and the effect of grain refiner on macrosegregation, sump profile, and temperature fields are presented. Two 45 cm diameter billets were cast under production conditions with and without grain refiner. Temperature and composition measurements and sump profiles are compared to the numerical results. The comparison shows excellent agreement for the grain refined case. It is believed that an incorrect assumption about the grain structure prevents good agreement in the non-grain refined billet.

Direct Chill Casting of Aluminum Alloys: Modeling and Experiments on Industrial Scale Ingots

2002 ◽  
Vol 124 (5) ◽  
pp. 947-953 ◽  
Author(s):  
Christopher J. Vreeman ◽  
J. David Schloz ◽  
Matthew John M. Krane
Keyword(s):  
Casting Process ◽  
Direct Chill ◽  
Solid Particles ◽  
Direct Chill Casting ◽  
Grain Structure ◽  
Temperature Fields ◽  
Industrial Scale ◽  
Grain Refiner ◽  
Chill Casting ◽  
Continuum Mixture Model

A continuum mixture model of the direct chill casting process is compared to experimental results from industrial scale aluminum billets. The model, which includes the transport of free-floating solid particles, can simulate the effect of a grain refiner on macrosegregation and fluid flow. It is applied to an Al-6 wt% Cu alloy and the effect of grain refiner on macrosegregation, sump profile, and temperature fields are presented. Two 45 cm diameter billets were cast under production conditions with and without grain refiner. Temperature and composition measurements and sump profiles are compared to the numerical results. The comparison shows some agreement for the grain refined case. It is believed that an incorrect assumption about the actual grain structure prevents good agreement in the non-grain refined billet.

Comparison of Morphological Evolution of Al-7wt%Si-2.5wt%Cu Alloy Produced by Direct Chill Casting/Electromagnetic Stirring and ECAP

2016 ◽  
Vol 256 ◽  
pp. 17-24 ◽  
Author(s):  
Luis Vanderlei Torres ◽  
Cecilia Tereza W. Proni ◽  
Eugênio José Zoqui
Keyword(s):  
Liquid Fraction ◽  
Morphological Evolution ◽  
Metal Flow ◽  
Direct Chill ◽  
Direct Chill Casting ◽  
Electromagnetic Stirring ◽  
Semisolid State ◽  
Grain Refiner ◽  
Chill Casting ◽  
Cu Alloy

In semisolid state forming the thermodynamic control of the solid liquid transition is necessary but not sufficient condition for having a good processing. For thixoforming it is critical to have a refined microstructure that during the heating to the semisolid state, achieve a mixture of small spheres immerse in liquid, which is crucial in order to get the best rheological properties for the slurry. This work compares the morphological evolution at the semisolid state of the Al-7wt%Si-2.5wt%Cu alloy produced by a) direct chill casting under electromagnetic stirring (EMS) combined with grain refinement and b) processed via one single pass in an equal channel angular pressing. EMS introduces metal flow during solidification that allows the better distribution of the nuclei provide by the grain refiner. ECAP has emerged as a promising technique capable of imposing large homogeneous deformations in metals, that could leads to a optimal grain refining. The ECAP deformation occurs in a die that contains two channels of the same cross-sectional area and form an angle of 120°. The raw materials were submitted to a heating treatment in order to reach 60% liquid fraction, at soaking times of 0s, 30s, 90s and 210s and the microstructure was evaluated via B&W and color metalography. Comparing the two production processes, it is observed that the ECAP process is highly efficient: while the traditional EMS method produced grains about 150 μm size, ECAP technique achieved grains of 60 μm, providing a fully globular structure, which exhibit favorable characteristics for the thixoforming process reaching to apparent viscosity about 2*104Pa.s.

Role of Grain Refining in Macrosegregation upon Direct Chill Casting of AA 2024 Round Billet

2006 ◽  
Vol 519-521 ◽  
pp. 1841-1846 ◽  
Author(s):  
Ravi Nadella ◽  
Dmitry G. Eskin ◽  
Laurens Katgerman
Keyword(s):  
Cross Section ◽  
Direct Chill ◽  
Al Alloys ◽  
Grain Refining ◽  
Negative Segregation ◽  
Aa 2024 ◽  
Dc Casting ◽  
Size And Morphology ◽  
Equiaxed Grains

The addition of grain refiners during industrial direct chill (DC) casting of aluminum billets promotes formation of smaller equiaxed grains with obvious advantages. However, the role of grain refining in the extent of macrosegregation in DC cast Al alloys is still unclear. This is particularly evident in the case of commercial aluminum alloys with various alloying elements. In this work, the structure and associated macrosegregation patterns in DC cast AA 2024 (Al–Cu–Mg) aluminum alloy billets were studied at different casting speeds. The concentration profiles of Cu and Mg, measured along the billet diameter, showed an expected negative segregation in the center and close to the surface. The severity of segregation increases at a higher casting speed. On the other hand, grain refining does not seem to have any dramatic effect on the macrosegregation patterns. The experimental results are correlated with microstructural observations such as grain size and morphology and the occurrence of “floating” grains across the cross-section of the billet.

Microstructure Evolution in Melt Conditioned Direct Chill (MC-DC) Casting of Fe-Rich Al-Alloy

2014 ◽  
Vol 1019 ◽  
pp. 90-95 ◽  
Author(s):  
H.R. Kotadia ◽  
J.B. Patel ◽  
H Tian Li ◽  
F. Gao ◽  
Z. Fan
Keyword(s):  
Grain Refinement ◽  
Microstructure Evolution ◽  
Morphological Evolution ◽  
Casting Process ◽  
Direct Chill ◽  
Al Alloy ◽  
Complete Suppression ◽  
High Quality ◽  
Dc Casting ◽  
Columnar Grain

In order to fabricate high quality aluminium products, it is first essential to produce high quality billets/slabs. One of the key objectives associated with casting processes is to be able to control the as-cast structure. A novel direct chill (DC) casting process, the melt conditioned direct chill (MC-DC) casting process, has been developed for production of high quality aluminium billets. In the MC-DC casting process, a high shear device is submerged in the sump of the DC mould to provide intensive melt shearing, which in turn, disperses potential nucleation particles, creates a macroscopic melt flow to uniformly distribute the dispersed particles, and maintains a uniform temperature and chemical composition throughout the melt in the sump. The effect of intensive shearing on the complex microstructure evolution observed after MC-DC is explained on the basis of nucleation and growth behavior. Complete suppression of typical columnar grain growth and significant equiaxed grain refinement is observed. The solidification mechanisms responsible for the significant grain refinement by intensive shearing and the morphological evolution of Mg2Si and Fe–containing intermetallic phases are discussed.

Preparing Large Sized Billet of High Strength Aluminum Alloy with the Application of Low Frequency Electromagnetic Field

2012 ◽  
Vol 472-475 ◽  
pp. 723-726
Author(s):  
Yu Bo Zuo ◽  
Zhi Hao Zhao ◽  
Qing Feng Zhu ◽  
Xiang Jie Wang ◽  
Jian Zhong Cui
Keyword(s):  
Electromagnetic Field ◽  
Aluminum Alloy ◽  
Large Scale ◽  
Low Frequency ◽  
High Strength ◽  
Direct Chill ◽  
Hot Tearing ◽  
Grain Structure ◽  
Grain Refiner ◽  
7050 Aluminum Alloy

Grain refinement is quite important for producing 7050 alloy billet especially in large scale. Low frequency electromagnetic casting (LFEC) process was used to make 7050 aluminum alloy Φ500 mm billets and study the effect of electromagnetic field on the microstructure. The sound Φ500 mm billets of 7050 alloys without any grain refiner can be successfully prepared by the LFEC process. The results show that low frequency electromagnetic field has a significant grain refining effect on 7050 alloy and can effectively eliminate feather grain structure. The microstructures of LFEC ingot from the border to the center of the cross section are all equiaxed grains and are finer and more uniform than that of conventional direct chill (DC) cast billets. The LFEC process also shows a strong power to eliminate hot tearing during casting large sized billet of high strength aluminium alloy.

Investigation on Low-Frequency Electromagnetic DC Casting of AZ91 Magnesium Alloy

2005 ◽  
Vol 488-489 ◽  
pp. 345-348 ◽  
Author(s):  
Q. Le ◽  
J. Cui ◽  
Shi Jie Guo ◽  
Z. Zhao ◽  
F. Yu
Keyword(s):  
Magnesium Alloy ◽  
Low Frequency ◽  
Direct Chill ◽  
Experimental Investigations ◽  
Az91 Magnesium Alloy ◽  
The Past ◽  
Az91 Magnesium ◽  
Dc Casting ◽  
A New Technique

Direct chill (DC) casting is a dominant way of producing aluminum and copper alloy billets. In the past we developed a new technique, namely Low Frequency Electromagnetic Casting (LFEC), in which low-frequency electromagnetic field (LFEF) is incorporated to DC casting processing. In this work, LFEF was introduced to the magnesium DC casting processing. Experimental investigations and numerical simulation indicate that application of LFEF to DC casting magnesium alloy can significantly improve the surface quality of the AZ91 billets, refine microstructure and reduce both macro and micro segregations. It was also found that high casting velocity become possible for magnesium alloys through LFEC processing.

scholarly journals Motion and Distribution of Floating Grain in Direct-Chill Casting of Aluminum Alloys: Experiments and Numerical Modeling

Materials ◽  
2020 ◽  
Vol 13 (23) ◽  
pp. 5379
Author(s):  
Qipeng Dong ◽  
Yanbin Yin ◽  
Zhen Zhu ◽  
Hiromi Nagaumi
Keyword(s):  
Numerical Modeling ◽  
Aluminum Alloys ◽  
Mushy Zone ◽  
Central Region ◽  
Direct Chill ◽  
Direct Chill Casting ◽  
Grain Structure ◽  
Chill Casting ◽  
Centerline Segregation ◽  
Negative Segregation

Sedimentation of free-floating grains is the main origin of the negative centerline segregation in direct-chill casting of aluminum alloys. This study examines the motion and distribution of the floating grains during casting using experimental measurements and numerical modeling. The typical floating grains consisting of interior solute-lean coarse dendrites and periphery fine dendrites were experimentally observed only in the central region of the billet along with the negative segregation. The billet exhibits the strongest segregation at the center where the most floating grains are found. In simulations, under the action of the convection and the underlying forces, the grains floating in the transition region exhibit different motion behaviors, i.e., settling to the mushy zone, floating in the slurry zone, and moving upward to the liquid zone. However, most grains were transported to the central region of the billet and then were captured by the mushy zone and settled. Therefore, the floating grains comprise the largest share of the grain structure at the center of the billet, in agreement with the experimental results. Moreover, the simulation results indicate that the increased size of the grains promotes the sedimentation of the floating grains. These results are important for the future alleviation of negative centerline segregation in direct-chill casting of aluminum alloys.

scholarly journals Homogenization of 7075 and 7049 Aluminium Alloys Intended for Extrusion Welding

Metals ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 338
Author(s):  
Antoni Woźnicki ◽  
Beata Leszczyńska-Madej ◽  
Grzegorz Włoch ◽  
Justyna Grzyb ◽  
Jacek Madura ◽  
...  
Keyword(s):  
Solidus Temperature ◽  
Direct Chill ◽  
Scanning Calorimetry ◽  
Cu Alloy ◽  
Extrusion Welding ◽  
Microstructural Effects ◽  
Chill Cast ◽  
Direct Chill Cast ◽  
Longitudinal Welds

During the extrusion of aluminum alloys profiles using porthole dies, the temperature of the material in the welding chamber is one of crucial parameters determining the quality of longitudinal welds. In order to extend the permissible temperature range, the billets intended for this process should be characterized by the maximum attainable solidus temperature. Within the present work, the homogenization of AlZnMgCu alloys DC-cast (Direct Chill-cast) billets was investigated, with the aim of solidus temperature maximization. Conditions of soaking and cooling stages were analyzed. The materials were homogenized in laboratory conditions, and the microstructural effects were evaluated on the basis of DSC (Differential Scanning Calorimetry) tests and SEM/EDS (Scanning Electron Microscopy/Energy-Dispersive Spectroscopy) investigations. For all examined alloys, the unequilibrium low-melting microstructure components were dissolved during soaking, which led to the significant solidus temperature increase, in comparison to the as-cast state. The values within the range of 525–548 °C were obtained. In the case of alloy with highest Cu concentration, the application of two-step soaking was necessary. In order to take advantage of the high solidus temperature obtained after soaking, the cooling rate from homogenization must be controlled, and the effective cooling manner is strongly dependent on alloy composition. For high-Cu alloy, the solidus decreased, despite the fast cooling and the careful billets preheating being necessary.

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