A Critical Assessment on Rotary Friction Welded High Strength Armor Grade Aluminum Alloy Joints

A high strength aluminum alloy has been widely employed in aerospace industry because of its high specific strength to weight ratio. Earlier, the fusion welding of aluminum alloys resulted in solidification cracking and shrinkage defects. To eliminate these drawbacks, the solid-state welding processes have been preferred to join the components of parts of armor grade aluminum alloy. This paper is devoted to the analysis of the mechanical properties and metallurgical characteristics of rotary friction welded aluminum alloy joints produced under optimized conditions. The maximum recorded transverse tensile strength and joint efficiency is of 472 MPa and 86%, respectively. The microstructural features exhibited ultrafine grains in the region of a fully-deformed zone (FDZ) of the alloy. The deformed grains in the thermomechanical affected zone (TMAZ) were recorded to have lower microhardness. Although, the dispersed precipitates revealed from the weld cross section were Al₇Cu₂Fe, Mg₃Cr₂Al₁₈, and MgZn₂. From this investigation, it has been found that most of the weld failures occurred due to grain deformation and subsequent softening during solidification.