LAUSR

Abstract Friction stir welding of an underaged Al-Cu-Li alloy, 2050 Al, was conducted to study the effect of welding parameters on microstructure and mechanical properties. The effect of thermal management using different backing plates was also investigated. Microhardness profiling, tensile testing, differential scanning calorimetry, and transmission electron microscopy were used to characterize the microstructure and properties. Among the parameters used, localized transverse joint strength of welds varied from 50% to 75% of peak aged base material strength. Strength recovery in weld nugget after post weld heat treatment was higher for welds made at higher traverse speeds and with higher heat input. Use of different backing plates to manipulate cooling rate during welding was important to obtain the best results. Grain boundary precipitation, coarsening, and absence of strengthening precipitates were responsible for low strength recovery in low peak temperature and slow traverse speed welds.