Studies on softening of heat-affected zone of pulsed-current GMA welded Al–Zn–Mg alloy

Studies on the softening behavior of the 7005 alloy by means of real welding experiments and heat-affected zone (HAZ) simulation have been conducted. Softening in the HAZ is found to occur above a peak temperature of about 200 °C. It was found that the heat-affected zone of the alloys can be divided into two sub-zones according to their different mechanism of softening: the dissolution zone and the overageing zone. The dissolution zone is characterised by dissolution of precipitates and covers the peak temperature range above 380 °C. The overageing zone is characterised by growth of precipitates and covers the peak temperature range between 230 and 380 °C. The hardness in the heat-affected zone can be recovered by post-weld heat treatment, especially in the dissolution zone. Artificial ageing is more effective than natural ageing considering the recovery of the hardness.