Floating Grain Formation and Macrosegregation in a 2024 Al Alloy Prepared by Hot-Top DC Casting with a 2024 Al Alloy Insert

In this experimental study, Al-Ti-B powders were ground in planetary ball mill to produce AlxTiyBz where x, y and z stands for the relative molar ratios of elements for the compilation of grain refiner compound. Powder size distribution, phase formation (XRD) and particle morphology was investigated by means of SEM and XRD. The fabrication of AlTiB phases and the grain refinement of Al alloys by adding this phase were aimed. For this purpose, the powders were fed to planetary ball mill to be milled at a speed of 600 rpm. The powders were also milled at different milling times as 30 min and 150 min either in metallic form or compound form of Al, Ti and B powders. The powders were dried after each milling to be characterized by SEM and XRD. The phases and morphology-elemental analysis were also conducted by XRD and SEM, respectively. Moreover, the powders were added to Al alloy castings avoiding the breaking through alloy series which are mainly used in aluminum industry. The Al alloy series were examined for grain refinement by Brinell hardness and optical microscopy for mechanical properties and grain formation as well as by SEM (EDS) for grain formation, morphology and elemental distribution analysis.

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Simulation of Low Frequency Electromagnetic DC Casting

Materials Science Forum ◽

10.4028/www.scientific.net/msf.790-791.390 ◽

2014 ◽

Vol 790-791 ◽

pp. 390-395 ◽

Cited By ~ 4

Author(s):

Nejc Kosnik ◽

Robert Vertnik ◽

Božidar Šarler

Keyword(s):

Solid Phase ◽

Low Frequency ◽

Casting Process ◽

Direct Chill ◽

Temperature Fields ◽

Step Method ◽

Fractional Step Method ◽

Hot Top ◽

Induction Equation ◽

Dc Casting

A comprehensive multiphysics model has been developed to describe the effect of the low frequency electromagnetic field (LFEM) [1, on solidification in the hot-top Direct-Chill (DC) casting [ of round aluminium alloy billets. The volume averaged equations and the rigid solid phase assumption are assumed for fluid flow and heat transfer [. The electromagnetic induction equation for the field imposed by the coil is solved using the diffuse approximate method (DAM), structured in axial symmetry with Gaussian weight function, 6 polynomial basis and 9 nodded domains. The heat, mass, and momentum transfer equations are solved in primitive variables by meshless [ method using 5 nodded domains of influence and 5 scaled multiquadrics radial basis functions, using collocation. Explicit time stepping is used. Pressure-velocity coupling is performed by the fractional step method. The effects of intensity and frequency of the LFEM [ on the velocity and temperature fields is investigated. A comparison of the calculated results with different LFEM field process variables with that of the conventional hot-top DC casting process indicates that the velocity patterns, the temperature profiles, and the shape of the sump could be modified remarkably.

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Study on Multi-Alloy Ingots Produced Using Hot-Top DC Casting Approach

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.1095.199 ◽

2015 ◽

Vol 1095 ◽

pp. 199-204

Author(s):

Xing Han ◽

Jian Zhong Cui

Keyword(s):

Casting Process ◽

Element Distribution ◽

Interface Zone ◽

New Approach ◽

Hot Top ◽

Layer Composite ◽

Supporting Layer ◽

Dc Casting ◽

The Impact ◽

Interface Bonding Strength

In this paper, a new approach that using hot-top DC casting process to produce multi-alloy ingots is present. The different type and size of composite and cladding ingots (4045/3004/4045 three-layer composite ingots with section 630mm by 1500mm and 4045/3003 cladding ingot with Φ140mm/Φ110mm in diameter) are fabricated by this approach. The macro-morphologies and microstructures of the ingots, the temperature distribution and the element distribution in the interface zone were investigated, and the interface bonding strength was measured. The results show that the solid supporting layer formed on the cooling plates plays a key role in the casting process of composite ingots. The solid supporting layer can prevent the blending of two melts by resisting the impact of alloy melt, which ensures the stable casting process and casting high quality composite ingots, because the contact height is increased using hot-top DC casting. In addition, fabrication and properties of 4045/3004/4045 three-layer composite ingots with section 630mm by 1500mm are reported in detail.

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Possible Effects and Mechanisms of Ultrasonic Cavitation on Oxide Inclusions during Direct-Chill Casting of an Al Alloy

Metals ◽

10.3390/met8100814 ◽

2018 ◽

Vol 8 (10) ◽

pp. 814 ◽

Cited By ~ 7

Author(s):

Yun Zhang ◽

Ruiqing Li ◽

Xiaoqian Li ◽

Yilong Yang ◽

Pinghu Chen ◽

...

Keyword(s):

Aluminum Alloy ◽

Large Scale ◽

Flow Behavior ◽

Direct Chill ◽

Al Alloy ◽

Aluminum Alloy Casting ◽

Hot Top ◽

Alloy Casting ◽

Continuous Ingot ◽

Ultrasonic Assisted

Oxide films or inclusions can reduce the continuity and integrity of materials and they always lead to a significant reduction in the mechanical properties of an aluminum alloy. They can greatly reduce the plastic flow behavior of materials, thus affecting the subsequent processing performance. Therefore, an effective ultrasonic assisted preparation technology has been applied to industrial manufacturing of large-scale aluminum alloy ingots (with diameter: Φ = 1250 mm and height: h = 3750 mm). However, the mechanisms of ultrasonic purification on the large-scale ingots are not clear. Therefore, a number of aluminum alloy casting experiments were carried out to produce a conventional hot top semi-continuous ingot (CHTI) and an ultrasonic hot top semi-continuous ingot (UHTI) in this work. The microstructures of CHTI and UHTI were analyzed by optical microscopy (OM) and scanning electron microscopy (SEM). The results indicated that there were some oxide film defects in the CHTI but some finely dispersed inclusion particles were discovered in the UHTI. The X-ray diffraction (XRD) data showed that the component of inclusion was Al2O3. According to the different cavitation effects of the different areas of the molten aluminum, the process of ultrasonic purification was divided into three periods and the mechanisms in each period were separately studied.

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Role of Acoustic Streaming in Formation of Unsteady Flow in Billet Sump during Ultrasonic DC Casting of Aluminum Alloys

Materials ◽

10.3390/ma12213532 ◽

2019 ◽

Vol 12 (21) ◽

pp. 3532 ◽

Cited By ~ 3

Author(s):

Sergey Komarov ◽

Takuya Yamamoto

Keyword(s):

Temperature Distribution ◽

Unsteady Flow ◽

Mushy Zone ◽

Flow Pattern ◽

Acoustic Streaming ◽

Ultrasound Irradiation ◽

Numerical Code ◽

Melt Flow ◽

Hot Top ◽

Dc Casting

The present work investigated melt flow pattern and temperature distribution in the sump of aluminum billets produced in a hot-top equipped direct chilling (DC) caster conventionally and with ultrasonic irradiation. The main emphasis was placed on clarifying the effects of acoustic streaming and hot-top unit type. Acoustic streaming characteristics were investigated first by using the earlier developed numerical model and water model experiments. Then, the acoustic streaming model was applied to develop a numerical code capable of simulating unsteady flow phenomena in the sump during the DC casting process. The results revealed that the introduction of ultrasonic vibrations into the melt in the hot-top unit had little or no effect on the temperature distribution and sump profile, but had a considerable effect on the melt flow pattern in the sump. Our results showed that ultrasound irradiation makes the flow velocity faster and produces a lot of relatively small eddies in the sump bulk and near the mushy zone. The latter causes frequently repeated thinning of the mushy zone layer. The numerical predictions were verified against measurements performed on a pilot DC caster producing 203 mm billets of Al-17%Si alloy. The verification revealed approximately the same sump depth and shape as those in the numerical simulations, and confirms the frequent and large fluctuations of the melt temperature during ultrasound irradiation. However, the measured temperature distribution in the sump significantly differed from that predicted numerically. This suggests that the present mathematical model should be further improved, particularly in terms of more accurate descriptions of boundary conditions and mushy zone characteristics.

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

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.1019.90 ◽

2014 ◽

Vol 1019 ◽

pp. 90-95 ◽

Cited By ~ 2

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.

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