Solid-State Joining of Thick-Section Dissimilar Materials Using a New Friction Stir Dovetailing (FSD) Process

Abstract

Solid-state joining of thick section aluminum to steel plate has been achieved using a new process called friction stir dovetailing (FSD). In FSD, a custom designed pin tool is used to flow a lower melting point material (AA6061) into dovetail grooves machined into the surface of an underlying material that has a higher melting point (rolled homogeneous armor [RHA]). Repeating dovetails form a mechanical interlocking structure akin to metallic Velcro. In this study, 38.1 mm (1.5 in.) thick AA6061 was joined to 12.7 mm (0.5 in.) thick RHA plates. The effectiveness of FSD is demonstrated through tensile test data that shows specimens failing in the processed aluminum rather than at the joint interface. Numerical simulations that highlight the importance of optimizing dovetail geometry are presented. The effect of process parameters on joint strength and microstructure also are discussed.