“Anneal” softening effect of 2219-T8 aluminum alloy joint during welding and its influence on prediction of welding residual stresses

Prediction of welding residual stresses (WRS) could be unreliable if mechanical property model of the material is inaccurate in finite element model. For TIG welding of 2219-T8 aluminum alloy, mechanical properties change with welding thermal process in a complex pattern. To build complete mechanical property model, influence of temperature, working hardening and “anneal” softening during welding must be considered. Gleeble and DIC system were used in this study to acquire tensile properties in different thermal process. Working hardening and “anneal” softening were studied by tensile curves. It was found that working hardening of 2219-T8 aluminum alloy would be eliminated at 200°C–300°C, which was called “anneal” softening. Then, fined mechanical property model was built for welding simulation. Results showed that “anneal” temperature had a great influence on longitudinal residual stress (LRS) in welding zone (WZ), partly melted zone (PMZ), over aged zone (OAZ) and part of heat affected zone (HAZ in this study) where maximum temperature was higher than 380°C. With correct consideration of “anneal” softening, LRS in these regions could be 100–150 MPa lower than that without “anneal” softening. Yield strength in these regions was greatly reduced due to “anneal” softening. However, for the regions with maximum temperature below 380°C, like other part of HAZ, “anneal” softening had little effect on WRS.