No abstract

In the present work, AA5052 sheets with thickness of 1 mm were successfully welded by protrusion friction stir spot welding as a low cost single-step method with a simple design that produces the no-keyhole joints with special mechanical properties at short dwell time and low tool rotation speed. By using suitable process parameters, the process is able to produce welds with superior mechanical performance in items of peak load and energy absorption compared to other techniques. The plunging depth and dwell time in this method were set as 0.2 mm and 6 s, respectively. The tool rotation speed was changed as 500, 800, 1250, and 1600 r/min to determine the optimum condition based on the microstructural and mechanical properties. Welds strength produced by the protrusion friction stir spot welding was directly related to the joint thickness, and the effective thickness of the upper sheet was maximum at 500 r/min. Protrusion friction stir spot welding joints presented circumferential failure mode after tensile shear testing. Regarding the sheets thickness used in this study, the joints produced by the current work presented high load bearing ability at dwell time of 6 s and tool rotation speed of 500 r/min compared to other techniques.

Pressure pulsation is notable for improving diffusion bonding process by breaking oxide layer present at the faying metal surfaces while an increased bonding pressure is envisaged to produce more compressive deformation (squeezing effect) on the reaction layer. This work aims at improving inter-atomic intersperse and mechanical properties of Al/Cu joint via the control of the bonding-compressive pressure. The bonding temperature (600°C) and time (60 min) were kept constant while the bonding pressure was varied between 5 and 12.5 MPa. The metallurgical and mechanical properties of the joint were studied. The results revealed that an oxide-free bond interface was produced in a pressure range of 5-12.5 MPa. The rise in the bonding pressure (5-12.5 MPa) increases the bond strength (78.39-108.47 MPa) and the diffusion depth (11.32-20.87 lm) between the Al/Cu interfaces. Five (5) distinctive regions having CuAl 2.