Microstructure and property of friction stir welded LF21 aluminum sheet

Tests about friction stir butt-welds of LF21 aluminum sheet with 1.4 mm in thickness were made in a single pass. The experimental results show that when rotating speed is 1500 r/min and welding speed is 100-180 mm/min, the good welds can be achieved. The tensile strength of welds is 125-134 MPa, which is between 78% and 83% of that of base metal. It shows that the welding adaptability of LF21 aluminum alloy is good. The micro-hardness result shows that the weld is softened, and the soften zone of weld is about 25 mm in width. The brittle MnAl6 compounds are precipitated along the rolling direction with the heat of welding, so the tensile strength of weld decreases.