The microstructure and properties evolution of Al-Si/Al-Mn clad sheet during plastic deformation
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e microstructure evolution and diffusion of silicon during heat-treatment and plastic deformation process were studied on the clad plates of Al–Mn/Al–Si aluminum composite fabricated by continuous casting. The results show that when the clad slab is homogenized and hot rolled, silicon diffuses across the interface from the Al–Si alloy (4004) side to the Al–Mn alloy (3003) side and dissolves into the 3003 matrix forming a solid solution. However, after deformation by cold-rolling, the increased driving force for precipitation of the solute elements in the core alloy side along with the abundant defects introduced by the severe deformation promotes the precipitation. Some Mg2Si particles precipitate from the solid solutions to form a transition region close to the interface of the two components. The presented transition area not only benefits the microstructure of the clad sheet but also improves the distribution of the microhardness across the interface, a tendency of gradient transition. I. INTRODUCTION
Cladding materials have been used for many years to impart a combination of certain physical properties (e.g., mechanical and corrosion) to the clad sheet that cannot be achieved by a monolithic material. Clad aluminum sheet is produced commercially by the roll bonding process; typical applications are brazing sheet in which a brazeable, usually, an Al–Mn 3 series alloy, is clad with a lowmelting-point Al–Si 4 series alloy and an aerospace sheet in which a high-strength, but low-corrosion-resistant Al–Mg–Cu 2 or Al–Zn–Mg–Cu 7 series alloy is clad with a more corrosion-resistant dilute 1 or 2 alloy.1 Roll bonding is a well-established process, but it is relatively expensive, less efficient and has limited combinations of alloys that can be roll bonded successfully. In addition to these problems, the roll bonding process is difficult to use for some products, particularly packages with varying surface friction characteristics that cause processing difficulties during rolling.2 Continuous casting is an ideal method for producing bimetal slab or sandwich ingot with a clean metallurgically bonded interface that can be further deformed to obtain the clad sheet. This process has few restrictions with regard to the combination of alloys that can be cast, and it allows clad sheet to be produced by essentially the same hot and cold rolling routes used for conventional, monolithic alloys. Numbers of studies have been focused on the rolling process and the deformation mechanism of the clad aluminum sheet fabricated by roll-bonding.3 Some fundamental work has also been carried out about the optimized exper-
II. EXPERIMENTS
The present study was performed using 3003/4004 alloy clad ingot produced by continuous casting.8 The nominal chemical composition in mass fraction of the as-cast clad slab is shown in Table I. With the thickness of 40 mm and
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Address all correspondence to this author. e-mail: [email protected] DOI: 10.1557/jmr.2013.140 J. Mater. Res., Vol. 28, No. 12, Jun 28, 2013
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