Research Article Effects of Rolling Reduction and Strength of Composed Layers on Bond Strength of Pure Copper and Aluminium Alloy Clad Sheets Fabricated by Cold Roll Bonding Yoji Miyajima, Kotaro Iguchi, Susumu Onaka, and Masaharu Kato Department of Materials Science and Engineering, Graduate School of Science and Engineering, Tokyo Institute of Technology, 4250-J2-63 Nagatsuta-cho, Midori-ku, Yokohama 226-8502, Japan Correspondence should be addressed to Yoji Miyajima; miyajima.y.ab@m.titech.ac.jp Received 18 January 2014; Accepted 12 March 2014; Published 17 April 2014 Academic Editor: Roohollah Jamaati Copyright © 2014 Yoji Miyajima et al. Tis is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Tree types of clad sheets, Cu/Al, Cu/AA5052, and Cu/AA5083, were produced by cold roll bonding with the rolling reduction of 50% and 75%. Tensile shear tests which give tensile shear strength were performed in order to assess the bond strength. Scanning electron microscopy was performed on the fractured interface produced by the tensile shear tests, which suggests that the fracture occurs within the Al alloy layer. Te tensile shear strengths considering the area fraction of deposit of Al alloy on Cu side were compared with the shear stress converting from the ultimate tensile strengths. As a result, the tensile shear strength of the clad sheets is attributed to the shear strength of Al alloy layer close to the well bonded interface. A simple model was proposed that explains the efects of the rolling reduction and area fraction of deposit of Al alloy. 1. Introduction Composite materials which have superior characteristics compared with each composed material are widely used, and metals can be used as the composed materials. For instance, Cu/Al composites have smaller density than Cu and higher thermal and electrical conductivities than Al [1]; therefore, they are used as light weight electric wires. Such metallic composites can be fabricated by mechanical alloying, difu- sion bonding, and roll bonding. Especially, roll bonding can produce large amount of metallic sheet-shaped composites, which are also called clad sheets, faster than other methods such as difusion welding. Tere are two types of roll bonding: one is hot roll bond- ing and the other is cold roll bonding, of which defnition is that the former and the latter are carried out above and below recrystallization temperature, respectively. During hot rolling, intermetallic layers are ofen formed at the interfaces of clad sheets. Such intermetallic layers would reduce the bond strength for Cu/Al composites [1]. On the other hand, it is possible to form the bonding without intermetallic layers by cold roll bonding since the critical difusion does not occur at the low process temperature. Li et al. reviewed the bond strength of clad sheets formed by cold roll bonding for several combinations of fcc composed layers and concluded that the sufcient bonding could be achieved rather easily between fcc metallic layers [2]; Manesh prepared Al/Fe clad sheets using roll bonding and measured the bond strength by peeling tests [3]. Pozuelo et al. measured the bond strength of ultrahigh carbon steel/mild steel clad sheets by Charpy impact tests and three points bending tests. It has been reported that the higher rolling reduction and the higher surface roughness of the unrolled composed layers produce higher bond strength [4]. Tere are a few related models and theories for the bond- ing and the bond strength of clad sheets. Jamaati and Torogh- inejad suggest that the faced and contaminated surface layers of metals are destroyed during roll bonding and virgin sur- faces appear from the crack at the contaminated surfaces [5, 6]. Once the virgin surfaces are contacted, bonding between two metals is achieved [5, 6]. However, the relationship between the rolling reduction and the bond strength was not Hindawi Publishing Corporation Advances in Materials Science and Engineering Volume 2014, Article ID 614821, 11 pages http://dx.doi.org/10.1155/2014/614821