Growth rate of intermetallic compounds in Al/Cu bimetal produced by cold roll welding process

The aim of this article is to study the growth rate of intermetallic compounds at the interface of cold roll bonded Al/Cu bimetal at 250 degreesC and compare the results with a similar study performed on friction welding of Al to Cu. Samples of tri-layered Cu-Al-Cu composite were produced by the cold roll welding process and heat treated at constant temperature of 250 degreesC for 1 to 1000 h. The thickness, morphology and composition of the intermetallic compound at the interface of Cu and Al were studied by optical and scanning electron microscope and EDX analyzer. The presence of various intermetallic compounds (Cu3Al, Cu4Al3, CuAl and CuAl2) was detected and the priority of formation of each compound was studied. The bond strength and electrical resistivity of different samples were measured by peeling test and a high precision micro-ohmmeter, respectively. The variations of resistivity and bond strength versus thickness of intermetallic compound were plotted. It was observed that the strength and electrical conductivity are greatly reduced by increasing the thickness of intermetallic compounds. Moreover, the growth rate of intermetallic compounds in roll welded bimetal composite is lower compared with that reported for similar friction welded specimens. (C) 2001 Elsevier Science B.V. All rights reserved.