Properties and Mechanism of Al/St Bimetal Tube Bonding Produced by Cold Spin-Bonding (CSB) Process

摘要

Spin-bonding is a novel tube cladding method for fabrication of bilayer tubes based on flow-forming process. The bimetal Al/St tubular components have extensive application in different industries. In this paper, an Al/St bimetal tube was successfully produced at different thickness reductions from 35 to 65% and mechanical and metallurgical aspects of the joint were investigated. Peeling tests were done to investigate the strength of the bond. The results showed that an increase in the thickness reduction led to a significant increase in the bond strength. Besides, the bonding mechanism between Al as inner tube to St as an outer one resulting from spin-bonding process was investigated. The results showed that an excellent bonding of Al and St tubes could be achieved from this process. The results showed that the bonding process consisted of three stages. First, removal of surface layers resulting in contact between the virgin metals of two bond surfaces and then an unstable bond was formed that stabilized as deformation proceeded. Finally the bond strengthening occurred. The SEM micrographs of the peeled surfaces showed that removing surface films in aluminum and steel in the first stage was based on different mechanisms. Also, SEM back-scatter images of bond interface showed that no intermetallic phases were formed.