Prediction of hardness minimum locations during natural aging in an aluminum alloy 6061-T6 friction stir weld
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This study describes a method that can predict the hardness minimum location as a function of natural aging time in a heat-treatable 6061-T6 Al alloy plate subjected to friction stir welding (FSW). First, temperature distributions were simulated in the FSW plate by finite element modeling. Second, to determine the natural aging kinetics, hardness changes were measured as a function of natural aging time from a number of Al specimens that had been isothermally heat treated at different peak temperatures. Finally, the simulated temperature profiles and the natural aging kinetics were correlated to predict the hardness profiles in the FSW plate. The predicted hardness minimum locations are consistent with the measured hardness profiles in that the hardness moves away from the weld centerline as the aging time increases. Moreover, the predicted hardness minimum is located at the similar position of failure in cross-weld tensile samples.
KeywordsFriction Stir Welding Friction Stir Welding Natural Aging Hardness Profile Tool Shoulder
This work was supported by the NSF International Materials Institutes (IMI) Program under contract DMR-0231320. This research was sponsored by the Laboratory Directed Research and Development program of Oak Ridge National Laboratory (ORNL), managed by UT-Battelle, LLC for the U.S. Department of Energy under Contract No. DE-AC05-00OR22725. WW was supported by Nuclear Research and Development Program of the Korea Science and Engineering Foundation funded by the Korean government. PJW is grateful to the EPSRC Lightweight alloys portfolio grant for financial support. The authors would like to thank B. Lovell, S. A. David, C. J. Rawn, and A. Frederick for their help. WW is especially grateful to David Richards for help with the modeling during his visit to Manchester.