Friction stir welding (FSW) is a solid-state joining technique which can be used for joining not only traditionally weldable aluminum alloys but also high strength aluminum and other metallic alloys that are hard to weld using conventional fusion welding processes. Mechanical strength of FSL welds under static loading is commonly determined using tensile shear testing and fracture strength (σLap) corresponding to the maximum load in a test over the sample width is widely used the strength value. In (friction stir lap welding) FSLW of dissimilar metallic alloys with large differences in melting temperatures, a metallurgical bond is established through the formation of interfacial intermetallics. However, as these intermetallic compounds are generally believed to be brittle with limited ductility, they are commonly viewed to adversely affect σLap. The aim of the present research is to study how the interface structure is affected by FS conditions and how the formation of interface structure affects σLap of Al Steel and Al-Ti FSL welds.

Keywords : Friction stir lap welding, aluminum, steel, titanium, intermetallics, fracture strength.