Prediction model of ultimate tensile strength and investigation on microstructural characterization of friction stir welded AA2024-T3

The main goal of this study is the modeling of ultimate tensile strength produced by friction stir welding of AA2024-T3 aluminum alloy using Taguchi and surface response methodologies. The considered process parameters are tool rotation speed, tool traverse speed, and wiper™ tool geometry (shoulder diameter). Analysis of variance, signal to noise ratio, and main effects plot used to check which process parameters were statistically significant and have better quality characteristics. Linear regression model was used to predict the ultimate tensile strength of the welded joints by incorporating process parameters. By using sensitivity analysis, the effectiveness of process parameters and the most significant parameter have been shown. From this research, the optimal experimental condition which gives the maximum ultimate tensile strength was obtained with a tool rotation speed of 750 rpm, a tool traverse speed of 100 mm/min, and a tool shoulder diameter of 12 mm which is 84% of joint efficiency of the base metal. The ultimate tensile strength increased to a maximum value and could be decreased with increasing tool rotation speed. Moreover, increasing the tool traverse speed or the tool shoulder diameter also make it decreased. Microscopic analysis showed that the increasing of the tool rotation speed or tool shoulder diameter results in an increase of average grain size in the nugget zone while it decreased slightly as tool traverse speed increases.