Aging kinetics of friction stir welded Al-Cu-Li-Mg-Ag and Al-Cu-Li-Mg alloys

Friction stir welding under ambient cooling conditions, using tool rotation rate of 800 rpm and welding speed of 200 mm per minute was carried out on 2195 and 2199 Al-Li alloys. Underwater welding was also performed on both the alloys using a pool on the top of workpiece. Post weld heat treatment for various durations was conducted to study the effect of alloy chemistry on aging kinetics in various metallurgical zones developed during welding. Vickers microhardness, differential scanning calorimetry, and transmission electron microscopy results showed that low dislocation density after recrystallization in weld nugget results in delayed aging kinetics for both the alloys. Ag containing alloy 2195 showed faster aging response compared to Ag-free alloy 2199. Coarse precipitates at grain boundary and in the grain interior were found responsible for loss of non-recoverable strength in heat affected zone for both the alloys. (C) 2016 Elsevier Ltd. All rights reserved.