Experimental analysis of bonding strength in shape rolling of Al–Cu bimetallic circular pipes into square tubes

Abstract

In the present research, the intermetallic layer situation and bond strength of square tubes produced by shape rolling of Al–Cu bimetallic pipes has been investigated. The explosive welding process was used for the production of bimetallic circular pipes. The macro- and microscopic features of explosive-welded pipes and shape-rolled specimens at various stages were experimentally measured by using shear and hardness testing and optical metallography. Moreover, scanning electron microscopy was used for fractography of the fracture surfaces after the last stage of forming. The experimental results showed that the shear strength variation is dependent on the intermetallic layer thickness and its continuity. Also, continuity in Al–Cu interfaces that have a thick intermetallic layer intensifies the microcrack propagation, while due to discontinuity in the thin intermetallic layer, the retardation of catastrophic crack propagation was observed in the early passes of the shape-rolling process. However, the results of the present study showed that as the passes proceed in the rolling process, the crack propagation phenomenon, which is the cause of a decrease in shear strength, is expected.