INFLUENCE OF TOOL ROTATIONAL SPEED AND AXIAL LOAD IN FRICTION STIR WELDING (FSW) OF HIGH STRENGTH ALUMINUM ALLOYS

M. S. Mahany, Reham Reda Abbas, M. M. Z. Ahmed, Hoda Abdelkader

Abstract: The aim of the present work was to study the effect of tool rotating speed, and axial load on microstructure, tensile properties, and hardness distribution of FSW butt joints of AA2024-T3 and AA7075-T6 Al- alloys. The joints consists of two plates of different thickness (4 and 5mm). Threaded conical pin and concave surface tool shoulder was manufactured from tool steel H13. Specially designed FSW machine was used to weld the joints. AA2024-T3 was put at the advancing side (AS), while AA7075-T6 was set at the retreating side (RS). Tool axis was tilted by angle 3 ??without offset. Single FSW pass was applied to produce the joints. FSW process was performed at steady feed rate 50 mm/min. Rotational speed ranges between 400 and 1600 rpm, and axial force ranges between 1000 and 1450 Kg were used in the present study. Constant plunging rate and dwell time of 3 mm/min, and 15 second respectively, were used for all conditions. Microstructure changes indicated that stir zone size increased gradually with excess tool rotary speed, and axial load. Increasing of both tool rotary speed, and axial load resulted in increasing the average value of grain size in stir zone, which was attributed to high amount of heat generation between the tool and workpiece. Mechanical investigation indicated that the maximum tensile strength about 378.6 Mpa was achieved at 1200 rpm, and axial load 1300 Kg. Hardness increased in SZ proportionally with tool rotary speed, and axial load due to the better mixing structure, whereas it reached the minimum value at heat affected zone (HAZ) of AA2024-T3 Al-alloy due to the grain growth caused by temperature raising.

Keywords: Friction Stir Welding (FSW), AA2024-T3, AA7075-T6, Rotational Speed, Axial Load, High Strength Al-Alloys

DOI: https://doi.org/10.15623/ijret.2017.0602019