Friction Stir Brazing: a Novel Process for Fabricating Al/Steel Layered Composite and for Dissimilar Joining of Al to Steel

Abstract

A novel process of friction stir brazing (FSB) for fabricating Al/steel layered composite (by multipass) and for joining Al to steel (by single pass) was proposed to avoid the wear of pin by steel, in which a tool without pin was used. FSB of 1.8-mm-thick Al sheet to steel sheet was conducted using a cylindrical tool with 20-mm diameter but without pin and using 0.1-mm-thick zinc foil as filler metal. For the rotational speed of 1500 rpm, sound joints were reliably obtained at the medium range of traverse speed of 75 to 235 mm/min, which fractured within Al parent sheet during tensile shear test. Furthermore, for peel test on the sound joints, Al and steel parent sheets tended to crack and deform, respectively. Metallographic examination showed that most Zn was extruded and the resultant interfacial structure consisted of several Al-Fe intermetallic compounds (IMCs) with a little Zn, less than 3 at. pct. The thickness of IMCs can be controlled to be less than 10 lm by properly increasing traverse speed (e.g., 150 mm/min). The metallurgical process of FSB was investigated by observing the microstructure of the longitudinal section of a friction stir brazed joint obtained by the suddenly stopping technique.

Inhibition of the formation of intermetallic compounds in aluminum-steel welded joints by friction stir welding

“…Esta técnica permitió la obtención de juntas soldadas con unión metalúrgica y ductilidad adecuada, gracias a la formación de una capa fina y homogénea de CIM, con espesor entre 5 y 10 μm (Zhang et al, 2009;Cao et al, 2013;Lin et al, 2013). Este resultado coincide con la afirmación de algunos autores que sostienen que es necesaria la formación de una capa fina de CIM que garantice la unión metalúrgica de ambos materiales, con un espesor tal que no comprometa substancialmente la ductilidad (Xue, et al, 2010;Zhang et al, 2011).…”

Weldability of Aluminum-Steel Joints Using Continuous Drive Friction Welding Process, Without the Presence of Intermetallic Compounds

“…Girard et al [77] support the need to form a thin layer (< 1 µm) of IMC to guarantee the metallurgical continuity of the welded assembly, proposing for this welding condition the name of friction stir diffusion bonding. Zhang et al [30] go further proposing the friction stir brazing as an alternative method for the formation of metallurgical bonding in solid state, having into account the application of a zinc layer to improve the formation of IMC as it is proposed by Elrefaey [76], but trying to get a thin layer of compound (< 10 µm) as it is stablished by Girard [77].…”

“…This conjecture opens another path in which the IMCs must be controlled but not suppressed in the welded joint. About this subject, the convenience of IMCs in the joint, persists because of authors such as Xue et al [29] and Zhang et al [30] remark the necessity of compound formation to guarantee the metallurgical joining although Wang et al [31] defend the position in which the effect of the IMC is counterproductive, specifically, when these compounds show thicknesses higher than 10 µm.…”

Effect of Steel Galvanization on the Microstructure and Mechanical Performances of Planar Magnetic Pulse Welds of Aluminum and Steel

“…[62] The beneficial effects of a 15 wt pct Cu [59,60,63] or 0.1 wt pct Be [3] addition in liquid Al during steel aluminization have also been reported. A Zn, [56] Ni, [16] Ag, [27,64] Al, Al-Mg, Ni-Zn, Zn-Al, or Ag-Zn [3] coating on steel also hampers the interdiffusion between Fe and Al during arc welding. (3) Using solid-state welding processes.…”