In-situ microstructural control of A6082 alloy to modify second phase particles by melt conditioned direct chill (MC-DC) casting process - A novel approach

The aim of this work is to investigate the effect of different casting speed in DC casting process and solution heat treatment of in situ Al-13.9%Mg2Si composite. The increasing of DC casting speed not only makes primary Mg2Si distribute more uniform and restricts segregation of primary Mg2Si particles, but also it reduces primary Mg2Si particle size. The DC casting speed significantly alter the eutectic Mg2Si phase from fibrous to fine dot-like and eutectic phase refines effectively. The results obtained from mechanical testing demonstrated that the increasing of DC casting speed intensifies both hardness and tensile strength values. Then, the billet were subjected to solutionizing at 500oC for holding time of 4h followed by quenching. The results indicate that the morphology of both primary and eutectic Mg2Si changes after heat treatment. Solutionizing leads to the dissolution of the Mg2Si particles and changes morphology from sharp edges to round shape. After solution heat treatment, tensile strength and elongation increase to 238.8MPa and 13.5%.

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Role of Second-Phase Particles on In Situ Deformation of an AZ80 Mg Alloy

Applications of Microscopy in Materials and Life Sciences - Springer Proceedings in Materials ◽

10.1007/978-981-16-2982-2_6 ◽

2021 ◽

pp. 55-64

Author(s):

R. Sarvesha ◽

W. Alam ◽

J. Jain ◽

S. S. Singh

Keyword(s):

Mg Alloy ◽

Second Phase ◽

Second Phase Particles ◽

In Situ Deformation

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Modelling of the Metal/Mould Interactions in the DC Casting Process for Aluminium and Magnesium

Materials Science Forum ◽

10.4028/www.scientific.net/msf.654-656.783 ◽

2010 ◽

Vol 654-656 ◽

pp. 783-786 ◽

Cited By ~ 1

Author(s):

Arvin Prasad ◽

Ian F. Bainbridge

Keyword(s):

Heat Transfer ◽

Casting Process ◽

Direct Chill ◽

Heat Extraction ◽

Small Scale ◽

Wall Region ◽

Wall Heat Transfer ◽

Mould Wall ◽

Dc Casting ◽

Basic Features

The process of direct chill (DC) casting of aluminium and magnesium alloys is regarded as a mature technology. The thrust of more recent work to understand and upgrade the technology has been centred on developing models of the process, the most advanced of which (e.g., Alsim and Calcasoft) have been used to examine what may be considered macro-features of the process (macro-segregation, hot cracking, etc.). These models, being macroscopic, rarely elaborate on the role of mould-wall heat transfer in the DC casting process. As part of the work on DC casting being conducted at CAST, for the investigation of small scale features of the process (e.g. heat extraction through the mould wall), a 2D finite Difference model of the process near the mould-wall region has been developed. The basic features of the model are described and initial results outlined.In particular, the effect of mould-wall heat transfer on the solid shell formed during the steady state regime of DC casting will be presented.

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Application Research of a New Coupling Stirring on DC Casting Process for Large-Sized Aluminum Ingots

Materials Science Forum ◽

10.4028/www.scientific.net/msf.817.48 ◽

2015 ◽

Vol 817 ◽

pp. 48-54 ◽

Cited By ~ 1

Author(s):

Hai Jun Wang ◽

Jun Xu ◽

Zhi Feng Zhang ◽

Bo Liang ◽

Ming Wei Gao

Keyword(s):

Mechanical Properties ◽

Grain Size ◽

Casting Process ◽

Direct Chill ◽

Application Research ◽

Center Position ◽

Composition Segregation ◽

Dc Casting ◽

The Difference ◽

7075 Alloy

A new coupling stirring technology was proposed and used to prepare direct chill (DC) ingots. Ingots of 7075 alloy were produced by a process of normal direct chill (NDC) casting and coupling-stirring direct chill (CDC) casting, respectively. The effect of the technology on the microstructures, composition segregation and mechanical properties of the ingots was investigated. The results showed that the temperature variation in the CDC casting process was more uniform than that in the NDC casting process. The grain of the CDC ingots was finer and more spherical than the grain of NDC ingots. The grain size at the edge, 1/2 radius, and center position in CDC ingot decrease by 28%, 22%, and 24% comparing with the grain size of the corresponding positions of NDC ingot, respectively. The billets with higher performance and lower macro-segregation were obtained in case of CDC. The flow stresses and the difference in different positions of DC ingots measured at Gleeble-1500D thermo-mechanical simulator decreased obviously when the coupling stirring technology is used in the casting process.

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Preparation of Nano Ti3SiC2/MoSi2 Composite by SPS Process

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.284-286.2414 ◽

2011 ◽

Vol 284-286 ◽

pp. 2414-2419 ◽

Cited By ~ 1

Author(s):

Jun Cai Zhang ◽

Cheng Chang Jia

Keyword(s):

Mechanical Activation ◽

Particle Diameter ◽

Second Phase ◽

Strong Restriction ◽

Matrix Surface ◽

Second Phase Particles ◽

The Matrix ◽

Strong Repulsion

In this paper, nano-Ti3SiC2/MoSi2 composite, whose second phase was 20-150nm, was in situ prepared by mechanical activation (MA) and SPS process with the quaternary powers of Mo, Si, Ti, and C. The results showed that: (1) matrix MoSi2 has strong repulsion to other elements, which leads to more second-phase particles inside the matrix rather than on the matrix surface; (2) matrix MoSi2 has strong restriction on the growing of the second phase, which makes the particle diameter of the second phase inside the matrix only in 200 nm around, while that over the surface reaches to 800 nm around.

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Microstructures of DC Cast Light Alloys under the Influence of Intensive Melt Shearing

Materials Science Forum ◽

10.4028/www.scientific.net/msf.690.137 ◽

2011 ◽

Vol 690 ◽

pp. 137-140 ◽

Cited By ~ 12

Author(s):

Yu Bo Zuo ◽

Bo Jiang ◽

Zhong Yun Fan

Keyword(s):

Grain Refinement ◽

Heterogeneous Nucleation ◽

Solidification Process ◽

Casting Process ◽

Direct Chill ◽

Light Alloy ◽

High Quality ◽

Light Alloys ◽

Refined Microstructure ◽

Dc Casting

A new direct chill (DC) casting process, melt conditioned DC (MC-DC) process has been developed for production of high quality ingots and billets of light alloys. In the MC-DC casting process, intensive melt shearing provided by a newly developed rotor-stator unit is used to control the solidification process during the DC casting with a conventional DC caster. Experimental results of DC casting of Al- and Mg-alloys with and without intensive melt shearing have demonstrated that the MC-DC casting process can produce light alloy billets with significantly refined microstructure and substantially reduced cast defects. The effect of intensive melt shearing on grain refinement has been mainly attributed to the enhanced heterogeneous nucleation on well dispersed oxides occurring naturally in the alloy melt.

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A Comparison Between 3-D Thermal Model and 3-D CFD Model for Vertical DC Casting of Rolling Ingots of Aluminum Alloy 7050

Volume 8B: Heat Transfer and Thermal Engineering ◽

10.1115/imece2014-36763 ◽

2014 ◽

Author(s):

Mainul Hasan ◽

Latifa Begum

Keyword(s):

Heat Transfer ◽

Aluminum Alloy ◽

Thermal Model ◽

Casting Process ◽

Direct Chill ◽

Turbulent Heat Transfer ◽

Mushy Region ◽

Turbulent Heat ◽

Cfd Model ◽

Dc Casting

In this study, first a 3-D thermal model is developed for an open top, vertical direct chill (DC) casting process of rolling slabs (ingots) by taking into account the casting speed in the form of slag flow in the thermal connective-diffusion equation. The mushy region solidification characteristics of the process are accounted for through the implementation of the enthalpy porosity technique. The thermal model is later extended to a 3-D CFD model to account for the coupled turbulent heat transfer and solidification aspect of the process. Both models simulate an industrial-sized, hot-top type vertical Direct Chill (DC) slab caster for high strength aluminum alloy AA-7050. A staggered control volume based finite-difference scheme is used to solve the modeled equations and the associated boundary conditions. In the CFD model, the turbulent aspects of flow and solidification heat transfer are modeled using a low Reynolds number version of the k–ε eddy viscosity approach. Computed results for the steady-state phase of the casting process are presented for four casting speeds varying from 60 to 180 mm/min for a fixed inlet melt superheat of 32°C. Simulation results of the velocity and temperature fields and heat fluxes along the caster surface are presented for the CFD model and the shell thickness and sump depth are compared between the CFD and thermal models.

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Continuous and Discontinuous Recrystallization of 6013 Aluminum Alloy

Materials Science Forum ◽

10.4028/www.scientific.net/msf.753.221 ◽

2013 ◽

Vol 753 ◽

pp. 221-224 ◽

Cited By ~ 4

Author(s):

Krzysztof Sztwiertnia ◽

Magdalena Bieda ◽

Anna Korneva

Keyword(s):

Aluminum Alloy ◽

Grain Boundaries ◽

Second Phase ◽

Sheet Plane ◽

Temperature Range ◽

Orientation Mapping ◽

Second Phase Particles ◽

The Matrix ◽

Continuous Recrystallization

In situ orientation mapping using TEM and calorimetric measurements were carried out to investigate the annealing behavior of cold-rolled 6013 aluminum alloy. The recrystallization of the material can be considered to be a number of processes that correspond to two separate stored energy release peaks. In the temperature range of the peak 1, the deformation zones around the large second-phase particles acted as sites for particle-stimulated nucleation. In the matrix, at the same time, some elongation of grains occurred. The elongated matrix grains appeared because of the reduction of the dislocation density and the annihilation of some low-angle grain boundaries between chains of subgrains lying in layers parallel to the sheet plane. The matrix processes in this temperatures range can be considered forms of continuous recrystallization. The matrix high-angle grain boundaries started to migrate at the temperature range of the peak 2. They moved mostly in the direction normal to the sheet plane. Heating of the sample for an appropriate time at those temperatures resulted in the complete discontinuous recrystallization of the material. The recrystallized microstructure was dominated now by elongated grains, which were a few times thicker than those obtained by annealing at the temperatures of the peak 1.

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Unravelling the characteristics of Al-alloy corrosion at the atomic to nanometre scale by transmission electron microscopy

MATEC Web of Conferences ◽

10.1051/matecconf/202032601007 ◽

2020 ◽

Vol 326 ◽

pp. 01007

Author(s):

Shravan K. Kairy ◽

Nick Birbilis

Keyword(s):

Electron Microscopy ◽

Transmission Electron Microscopy ◽

Al Alloy ◽

Second Phase ◽

Clear Understanding ◽

Transmission Electron ◽

Second Phase Particles ◽

Al Matrix

The localised corrosion associated with Mg2Si in the Al-matrix of an Al-Mg-Si alloy was studied in 0.1 M NaCl at pH 6 by quasi in-situ transmission electron microscopy. Herein, physical imaging of corrosion at the atomic to nanometre scale was performed. Phase transformation and subsequent chemical composition variations associated with the localised corrosion of Mg2Si were studied. It was observed that corrosion initiated upon Mg2Si, often preferentially at the interface with the Al-matrix, and propagated until Mg2Si was completely dealloyed by Mg-dissolution, resulting in an amorphous SiO-rich phase remnant. The SiO-rich remnant became electrochemically inert and did not initiate corrosion in the Al-matrix. This study provides a clear understanding on the localised corrosion of Al-alloys associated with Mg2Si. In addition, the methodology followed in this study can also be applied to understand the role of precipitates and second phase particles in the localised corrosion of Al-alloy systems.

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