M. Abbasi, Karaj Islamic Azad University, Karaj, Iran; A. K. Taheri, Sharif University of Technology, Tehran, Iran
ABSTRACT
The aim of this article is to study the growth rate of Intermetallic compounds at interface of cold roll bonded Al/Cu bimetal at 250 oC 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 cold roll welding process and heat treated at constant temperature of 250 oC for 1 to 1000 hours. The thickness, morphology and composition of intermetallic compound at interface of Cu and Al were studied by optical and scanning electron microscopes and EDX analyzer. The presence of various intermetallic compounds (Cu3Al, Cu2Al, 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 is 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.
Keywords: Aluminum; copper; roll welding; Intermetallic growth; bond strength; bimetal resistivity.
Summary: The aim of this article is to study the growth rate of Intermetallic compounds at interface of cold roll bonded Al/Cu bimetal at 250 oC 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 cold roll welding process and heat treated at constant temperature of 250 oC for 1 to 1000 hours. The thickness, morphology and composition of intermetallic compound at interface of Cu and Al were studied by optical and scanning electron microscopes and EDX analyzer. The presence of various intermetallic compounds (Cu3Al, Cu2Al, 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 electrical resistivity and bond strength versus thickness of intermetallic compound were plotted. It was observed that the strength and electrical conductivity is greatly reduced by increasing the thickness of intermetallic compounds at interface. Moreover, the growth rate of intermetallic compounds in roll welded bimetal composite is at least ten times lower compared with that reported for similar friction welded specimens.
