Effects of FSW parameters and pin geometry on the weldability of EN AW 2024 alloy

Abstract

Abstract Fusion welding techniques are not recommended for the welding of EN AW 2024 aluminum alloy due to its dendritic structure, porosity, slug inclusion and distortion, etc. To prevent a decrease in weld joint strength, solid state welding techniques represent a more suitable alternative. Friction stir welding is commonly used for welding of aluminum alloys due to the welding temperature which is below melting point. The aim of the present study is to determine the optimal friction stir welding parameters using Taguchi-based Grey relational analysis. The tool pin shape, tool rotational speed and welding speed were considered as process parameters, while the ultimate tensile strength and percentage of elongation were considered as performance characteristics. The optimal level of each welding parameter was determined by the highest mean Grey relational grade of each parameter. The predicted optimal welding condition was confirmed by experiments. The effect of each parameter on the Grey relational grade was investigated using the probability value and the percentage contribution obtained from the analysis of variance. The results of the Grey relational analysis showed that the optimal friction stir welding parameter combination was the pin shape at first level with tool rotational speed of 500 rpm and welding speed of 80 mm × min−1 (PS1TRS1WS2). The evaluation of analysis of variance results indicated that the parameter with the highest contribution to the Grey relational grade value was the tool rotational speed, 39.79 %, and also, it has a large effect, at a 90 % significance level. An investigation of the macrostructure of each welded joint exhibited a sound weld joint for the triangular shaped pin. The tool rotational speed of 800 and 1000 rpm produced the lowest quality in welded joints due to a range of defects in the nugget zone.