L Journal of Alloys and Compounds 361 (2003) 138–143 www.elsevier.com / locate / jallcom Bond strength and formability of an aluminum-clad steel sheet * H. Danesh Manesh , A. Karimi Taheri Materials Science and Engineering Department, Sharif University of Technology, Azadi Ave., P .O. Box 11365-9466, Tehran, Iran Received 6 January 2003; received in revised form 18 March 2003; accepted 18 March 2003 Abstract The production of an aluminum-clad steel sheet by the cold rolling process is a more efficient and economical approach compared with the other types of processes utilized for the production of such sheets. In this process, high plastic deformation of two metals, aluminum and steel, is necessary to create the cold bonding between the intermediate surfaces. Therefore, the work-hardened sheet must be annealed in order to obtain a high formability. Heat treatment of the sheet is, however, difficult due to the formation of a brittle intermetallic compound of aluminum and iron at the interface between the layers during heat treatment. In this investigation, the formability of these sheets was measured using the Erichsen cupping test technique. Also, the bond strength was evaluated by macroscopic examination of the surfaces of Erichsen cup specimens. The results indicate that there is an optimum annealing temperature and time leading to a high bonding strength as well as enhanced formability.  2003 Elsevier B.V. All rights reserved. Keywords: Metals; Roll welding; Intermetallics 1. Introduction or peel off when the sheet is deformed [2]. Consequently, the aluminum clad steel method is one of the most The aluminum-clad steel sheet successfully combines desirable means of aluminum coating, since it increases the the surface properties of an aluminum alloy coating with corrosion resistance and improves the formability of the the satisfactory mechanical properties of the steel sub- surface layer [2]. strate. The sheet possesses a high reflectivity and high The cold-welding process includes typical metal-form- electrical and thermal conductivity, making it a chosen ing processes such as rolling, extrusion, explosive forming, material for specific applications in automobile manufac- and drawing [3]. The production of Al-clad steel sheets by turing, the appliances industry and, to a lesser extent, the rolling, however, is a more efficient and economical building industry. The main application for the material is approach compared with the other type of processes [3,4]. in automotive exhaust systems [1]. In the cold roll bonding process, high plastic deformation There are two main technologies to produce aluminized of two metals, for example aluminum and steel, is neces- steel sheets: (1) the hot dip method, and (2) the aluminum sary to create a cold bond between the layers [5,6]. clad method (cold welding process) [1,2]. The hot dip Therefore, a roll bonded and work-hardened strip compo- method is most widely used in producing aluminum-coated site must be heat treated in order to obtain a composite of steel. However, the aluminum-coated steel manufactured high formability. The heat treatment process used for the by this method is believed to be inferior to an aluminum composite strip is, however, difficult, because it is likely to sheet with respect to surface appearance, corrosion resist- produce undesirable characteristics, such as a reduction in ance and formability of the coated metal. This is because bond strength, due to the formation of a brittle inter- the corrosion resistance of these materials depends on the metallic compound of aluminum and iron at the interface thickness of the coating layer. An increase in coating between these metals [1,2,7–10]. This is because the thickness, however, results in deterioration of the surface recrystallization temperature of the steel substrate is very layer formability, i.e. the aluminum coating tends to crack close to the temperature at which the brittle intermetallic compounds are formed [2,7]. Generally speaking, the bonding strength is not reduced *Corresponding author. E-mail address: daneshma@mehr.sharif.edu (H.D. Manesh). in the case where the thickness of an intermetallic com- 0925-8388 / 03 / $ – see front matter  2003 Elsevier B.V. All rights reserved. doi:10.1016 / S0925-8388(03)00392-X