MECHANICAL-PROPERTIES OF WELDED-JOINTS IN THIN-WALLED ALUMINUM EXTRUSIONS

The present work describes the tensile properties of weldments in thin walled extruded Al-Mg-Si alloys. Tungsten inert gas (TIG), metal iner t gas (MIG), and friction stir (FS) welding are considered. Properties of joints welded with different filler metals are presented, both mat ching and undermatching the parent materials in strength. The weldment s were tested in both as welded and post-weld aged conditions. It is s hown that silicon rich filler metals (Al-5Si and Al-12Si) were adequat e for the welding of 6063 alloy but did not give welds with strength s ufficient to match that of 6082 alloy. Tungsten inert gas welding resu lted in large heat affected zone (HAZ) widths of 20 mm, compared with HAZ widths of 10 and 8 mm for MIG and FS welding respectively. This re lationship was also seen in tensile tests where FS specimens exhibited the highest strength and TIG specimens exhibited the lowest strength. The post-weld aged materials recovered some strength, with increases in tensile strength of 10-15% for 6063 alloy and of 20% for alloy 6082 compared with the strengths of the as welded specimens. Comparisons b etween experimental data and two design codes, a draft European standa rd and the British standard BS 8118 describes MIG and FS HAZ widths we ll but underestimates the HAZ width for TIG welds. (C) 1997 The Instit ute of Materials.