INFLUENCE OF HEAT-TREATMENT ON THE MICROSTRUCTURE AND PROPERTIES OF LASER WELDS IN 8090

An investigation into the weldability of the Al-Li-Cu-Mg-Zr alloy 8090 using a CO2 laser indicates that the grain structure and microstructu re of the weld zone are sensitive to the post-weld heat treatment. If a slow heating rate of 1 Kmin(-1) to the solution treatment temperatur e is used the formation of beta' (Al3Zr) dispersoids is promoted which leads to a uniformly small grain size within the fusion zone. If, how ever, faster heating rates are employed massive grains can form in the fusion zone. This is shown to be associated with a virtual absence of beta' precipitates.