Microstructure of In-Situ Friction Stir Processed Al-Cu Transition Zone

Abstract

The majority of literature sources dedicated to dissimilar Al-Cu friction stir welding testifies to the formation of intermetallic compounds (IMC) according to diffusion-controlled reactions, i.e., without liquation on the Al/Cu interfaces. Fewer sources report on revealing Al-Cu eutectics, i.e., that IMCs are formed with the presence of the liquid phase. This work is an attempt to fill the gap in the results and find out the reasons behind such a difference. Structural-phase characteristics of an in-situ friction stir processed (FSP) Al-Cu zone were studied. The single-pass FSPed stir zone (SZ) was characterized by the presence of IMCs such as Al2Cu, Al2Cu3, AlCu3, Al2MgCu, whose distribution in the SZ was extremely inhomogeneous. The advancing side SZ contained large IMC particles as well as Al(Mg,Cu) solid solution (SS) dendrites and Al-Al2Cu eutectics. The retreating side SZ was composed of Al-Cu solid solution layered structures and smaller IMCs. Such a difference may be explained by different levels of heat input with respect to the SZ sides as well as by using lap FSP instead of the butt one.

In Situ Intermetallics-Reinforced Composite Prepared Using Multi-Pass Friction Stir Processing of Copper Powder on a Ti6Al4V Alloy

“…A similar displacive transformation mechanism of solid-state amorphization was reported [ 43 ] when metastable β-Ti grains in a Ti59.1Zr37Cu2.3Fe1.6 system had an amorphous phase during β → α′/α″ martensitic transformation. Shmorgun et al [ 39 ] substantiated the idea that such an amorphization was controlled more by elastic softening and lattice shear according to Born’s criterion [ 44 ] than the vibrational instability of the crystalline lattice, as suggested by Lindemann [ 45 ].…”

“…The Ti/Cu system is a well-known one, as evidenced by many papers having been published on preparing Ti/Cu alloys. The reaction–diffusion mechanism plays a great role in nucleation and growth of IMCs during FSP on metal systems, such as Al/Cu, with a high exothermic effect of interaction and contact melting [ 39 ]. Both Al and Cu have their melting points much below that of titanium and, therefore, contact melting during FSP is easy to observe.…”

Casting and Solidification of Light Alloys

“…The structural phase characteristics of the friction-treated Al-Cu alloy zone were studied in [11]. The presence of Al 2 Cu, Al 2 Cu 3 , AlCu 3 , Al 2 MgCu, etc.…”

Energy-efficient method for developing in-situ Al-Cu metal matrix composites using microwave sintering and friction stir processing

“…Surface/bulk MMC can be fabricated by using FSP either as a primary or secondary process [19]. Zykova et al [20]. conducted a study to reveal the reason for the formation of intermetallic compounds during FSP.…”