Heat treatment of a friction-stir-welded and spin-formed Al-Li alloy

Prototype end domes for cryogenic propellant tanks were fabricated using friction stir welding and spin forming technology. Subsequent heat treatment of a dome to a high strength temper resulted in weldment properties which were below specifications. The microstructural reason for this was identified as abnormal grain growth (AGG) and a modified T8 heat treatment was developed to alleviate the problem. Adoption of this procedure may allow the innovative combination of technologies to be applied to the manufacture of future launch vehicles. In this manuscript, the results of the metallurgical analyses performed to establish why post-forming, pre-solution treatment recovery annealing was effective in suppressing AGG are presented. (C) 2011 Published by Elsevier Ltd. Selection and peer-review under responsibility of ICM11