Effect of tool/material interface temperature on flow stress and the Zener-Holloman parameter in Al 6082 friction stir butt welds

Abstract

This paper outlines, the temperature around the tool/material interface during friction stir welding (FSW) of Al 6082-T6 alloy. The first section gives a brief overview on temperature measurement around the tool periphery, i.e. trailing edge (TE), leading edge (LE), retreating side (RS), advancing side (AS), and their corners associated with it. The second section was focused on the plasticity behavior of welded material as a function of temperature, governed by flow stress and Zener Holloman (Z)-parameter. Around the tool periphery in a clockwise direction, the critical observations were made from the obtained data. The peak temperature surges with increasing shoulder diameter and it was higher for the weld done with 24mm shoulder diameter tool. It was noted that during every cycle there was asymmetric temperature distribution at tool/material interface, the rate of heat generation was higher in TE to RS-LE zone and lower in RS-LE to TE zone. The calculated flow stress and log Z values were higher on RS and lower in AS to RS-LE zone of the tool shoulder periphery. Flow stress was almost uniform for all the shoulder diameters except on RS of 18mm shoulder tool. The optimum tool shoulder diameter was found to be 21mm, below which the flow stress was high and above which the plasticity at tool shoulder periphery was negligible.