Materials Science and Engineering A 527 (2010) 2320–2326 Contents lists available at ScienceDirect Materials Science and Engineering A journal homepage: www.elsevier.com/locate/msea Investigation of the parameters of the cold roll bonding (CRB) process Roohollah Jamaati * , Mohammad Reza Toroghinejad Department of Materials Engineering, Isfahan University of Technology, Isfahan 8415683111, Iran article info Article history: Received 21 August 2009 Received in revised form 26 November 2009 Accepted 30 November 2009 Keywords: Aluminum alloys Cold roll bonding Bond strength abstract In this study, commercial purity aluminum (AA1100) strips were cold roll bonded at ambient temperature. As the main factors, the effects of different amounts of reduction in thickness, initial thickness, rolling speed, and rolling direction on bond strength were evaluated by the peeling test. Also, the effects of pre- and post-rolling annealing treatments were investigated. It was found that higher reductions, lower initial thickness, and rolling speed were the important factors involved in improving bond strength. Also, annealing treatment before and/or after the CRB process increased bond strength, while the effect of pre- rolling annealing was more pronounced. Furthermore, bond strength decreased by increasing the angle of CRB process with respect to the rolling direction of as-received strips. Finally, optical and scanning electron microscopes were used to evaluate the surface conditions of the peeled surfaces. © 2009 Elsevier B.V. All rights reserved. 1. Introduction Aluminum alloys are commonly used in heat exchangers in the automotive industry for their interesting combination of such properties as low density, satisfactory mechanical properties, good thermal conductivity, and relatively good corrosion resistance [1]. It is well known that 46% of aluminum alloys used for various applications comes in sheets and plates [2]. Among the alloy tech- nologies, the cold roll bonding (CRB) process for producing sheets has witnessed rapid growth and development in recent years due to its unique service performance features [3–7]. In comparison with other methods, CRB is simple and can be easily automated. CRB is a solid phase welding process, in which bonding is estab- lished by joint plastic deformation of the metals to be bonded. Bonding is obtained when surface expansion causes the surfaces of virgin metal to be exposed and when pressure reaches a value large enough to extrude the virgin material through the cracks of the fractured layer, resulting in the establishment of contact and bonding between opposing virgin surfaces [7–9]. Many studies have been carried out on the parameters govern- ing the bonding mechanism in order to understand its complex nature so that the conditions of the process have nowadays been well defined. It has been reported that the roll bonding of metals is affected by various factors such as reduction in thickness during rolling [10–12], bonding temperature [7], and annealing treatment [13]. * Corresponding author. Tel.: +98 911 2124023; fax: +98 311 3915726. E-mail addresses: r.jamaatikenari@ma.iut.ac.ir (R. Jamaati), toroghi@cc.iut.ac.ir (M.R. Toroghinejad). Recent applications of CRB to a range of materials prompted the present study to investigate the effects of process parameters on bonding quality. This paper will, therefore, report our findings concerning the effects of process parameters on bonding, including reduction in thickness during rolling, annealing treatment before (pre-rolling annealing) or after (post-rolling annealing) bonding, initial thickness of strips, rolling direction, and rolling speed. Efforts will also be made to provide a brief description of bonding mecha- nisms. 2. Experimental procedure 2.1. Materials Commercial purity aluminum strips (AA1100) with the specifi- cations given in Table 1 were used in this study. Strips 150 mm long, 30 mm wide, and of varying thicknesses (0.5, 1, and 1.5 mm) were cut from a cold rolled sheet, parallel to the original rolling direc- tion, in order to investigate the effect of initial thickness on bond strength. Additionally, some strips were cut parallel to the trans- verse rolling direction to determine the effect of rolling direction on bond strength. 2.2. Surface preparation To produce a satisfactory metallurgical bond by roll bonding, it is essential to remove contamination layers on the surfaces of the metals to be joined. These layers are composed of oxides, adsorbed ions, greases, moisture, and dust particles. A number of authors have stated that the best method of surface preparation is degreas- ing followed by scratch brushing with a rotating steel brush [3]. The 0921-5093/$ – see front matter © 2009 Elsevier B.V. All rights reserved. doi:10.1016/j.msea.2009.11.069