Interfacial microstructures and mechanical properties of friction welded Al/steel dissimilar joints

Abstract

A quality joining of Al alloy to steel is difficult to be obtained by fusion welding processes owing to the large difference between melting temperatures and the formation of thick brittle Al/Fe intermetallic compounds (IMCs) layer at the joint interface. In this study, the 6061 Al alloy and 304 austenitic stainless steel were successfully joined by the continuous drive friction welding under different welding parameters. A sound welded joint with joint efficiency of 88 % and bending angle of 80° was obtained at a low friction time and a high upset pressure, where no detect was found at the interface. The IMCs layer was not formed at the interface, but a thin diffusion zone could be observed, indicating the realization of the metallurgical bonding. Under experimental range, a relatively thinner diffusion zone was recommended to ensure higher joint strength and more excellent bend ductility. The IMCs were identified as Fe2Al5, Fe4Al13 and FeAl2 at fracture surface by XRD. The propagation of cracks during tensile testing concentrated on the area where the IMCs existed. The less amount of IMCs was detrimental for joint properties at a low welding parameters. Fracture analysis showed that the dimple fracture predominated the fracture mode for a sound joint.