Friction stir welding of advanced Al-Cu-Mg alloy

Abstract

This study investigated the influence of friction stir welding (FSW) conditions on microstructure and mechanical properties of an advanced Al-Cu-Mg alloy AA2624 (according to the Aluminum Association classification). For this study, alloy plates were solution annealed, water quenched, rolled to a 20% reduction at room temperature, and then artificially aged at 190°C for 1 hour (T820 treatment). After thermomechanical treatment, the plates were butt-welded under various regimes. The regimes were selected by varying the rotational speed and feed rate of the tool. The rotational speed of the tool was in the range of 500-1100 rpm, and the feed rate varied from 127 to 380 mm/min. An increase in the rotational speed of the tool from 500 rpm to 1100 rpm resulted in a transformation of the stir zone shape from a bowl-shaped to an elliptical one. This reflected substantial changes in the character of material flow during FSW. It was found that FSW significantly reduced the strength properties of welds compared to the base material. The joint efficiency ranged from 51 to 61%. It was shown that weld failure occurred in the heat-affected zone. Consequently, the feed rate of the tool is a key factor determining weld strength.