Experimental investigation of nickel alloy 600 strain hardening recovery

Prediction of residual stresses in welds is essential in order to evaluate the integrity of a component subject to degradation mechanisms such as Stress Corrosion Cracking. During welding operations, complex thermo-mechanical and metallurgical processes take place and lead to microstructural changes such as dynamic recovery and dynamic recrystallization. These microstructural changes induce a modification of hardening behavior that should be taken into account to accurately evaluate residual stresses through numerical simulations. A large test campaign was carried out in order to measure the recovery and recrystallization kinetics of Ni base alloy 600. Tests consisted in introducing 20% of plastic-strain at room temperature and then applying a thermal cycle with a Gleeble heat treatment simulator under stress release conditions. The comparison of mechanical properties prior to heat treatment and after heat treatment allows the evaluation of the recovery parameter that could be considered during welding numerical simulations. During this test campaign, various thermal cycles were applied. Experimental results show that the whole data points can be described as a function of Larson-Miller parameter. Mechanical results, metallurgical investigations and first numerical simulations are also presented in this paper.