ABSTRACT
An annoying feature in aluminium construction is the weakening of the metal around welds, known as HAZ (heat-affected zone) softening (Figure 6.1). With the 6xxx-series alloys, the heat of welding can locally reduce the parent metal strength by nearly half. With 7xxx alloys, the weakening is less severe, but extends further out from the weld. For work-hardened material (5xxx, 3xxx series), the metal in the HAZ becomes locally annealed, with properties falling to the O-condition level. Only for parent metal supplied in the annealed or T4 condition can HAZ effects be ignored.
