Friction Stir Welded Al-5052 Strengthened by the Hybrid Interlayers and Pin-Eccentric Stir Tool

The hybrid interlayers combined with Zn- and Cu-foil are employed in order to strengthen the mechanical properties of Al-5052 friction stir welded joint. During friction stir welding (FSW), the Zn-foil partly melts and dissolves into Al matrix; meanwhile, the Cu-foil gets broken into small detached particles. Compared with the conventional joint, the grains in the nugget zone of interlayer-added joint become finer due to both the decreased FSW temperature and the elevated pinning press. Moreover, the annealing softening and the recrystallization in the heat‐affected zone are inhibited by inserting the hybrid interlayers. Consequently, the hardness and tensile strength of interlayer-added joint are improved in comparison with the conventional joint. In addition, both the stir behavior and the material flow in the nugget zone are enhanced by the application of pin-eccentric stir tool, thus refining and homogenizing the microstructures of nugget zone further.