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 compou nds 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 A l to Cu. Samples of tri-layered Cu-Al-Cu composite were produced by the col d roll welding process and heat treated at constant temperature of 250 degr eesC for 1 to 1000 h. The thickness, morphology and composition of the inte rmetallic compound at the interface of Cu and Al were studied by optical an d scanning electron microscope and EDX analyzer. The presence of various in termetallic compounds (Cu3Al, Cu4Al3, CuAl and CuAl2) was detected and the priority of formation of each compound was studied. The bond strength and e lectrical resistivity of different samples were measured by peeling test an d a high precision micro-ohmmeter, respectively. The variations of resistiv ity and bond strength versus thickness of intermetallic compound were plott ed. It was observed that the strength and electrical conductivity are great ly reduced by increasing the thickness of intermetallic compounds. Moreover , the growth rate of intermetallic compounds in roll welded bimetal composi te is lower compared with that reported for similar friction welded specime ns. (C) 2001 Elsevier Science B.V. All rights reserved.