Mechanical properties and microstructural characterization of extrusion welds in AA6082-T4

Microstructural observations of extrusion welds in an A-pillar made of AA6082-T4 revealed that the observed extrusion weld is a composite of a seam weld (longitudinal weld) and a charge weld (transverse weld). To determine the mechanical properties of this weld region, tensile specimens were prepared with the weld located at 0°, 45°, and 90° to the tensile axis. For comparison purposes, specimens from no-weld regions were also prepared in the same orientations and tested. The specimens with 45°-weld exhibited the lowest tensile strength, followed by the specimens with 90°-weld, no-weld and 0°-weld specimens. Comparison of failure strains and fracture modes revealed that weld regions are less ductile than the no-weld regions. Microscopic observations of fractured surfaces and further analysis revealed that Mg2Si precipitates that align along the charge weld cause premature failure at these locations.