Interface characteristics and mechanical behavior of aluminum alloy/ ultrahigh-strength steel plasma arc welded joint
Di Wu, Xiaolong Cai, Hongmei Li, Xiaoqi Zhang, DaQian Sun
Abstract
5A06 aluminum alloy and DP1180 ultrahigh-strength steel dissimilar metals were joined by plasma arc welding with AlCu6 welding wire. The interface of AlCu6 weld/steel joint was characterized by SEM, electron backscatter diffraction (EBSD) and focused ion beam-transmission electron microscopy (FIB-TEM). The results revealed that Fe–Al intermetallic compounds (IMCs) layer with double structure was formed at AlCu6 weld/steel interface, which were Fe 4 Al 13 layer with needle-like shape and Fe 2 Al 5 layer with tongue-shape. Fe 2 Al 5 grains exhibited a clear preferential orientation in the [001] crystal direction and a strong silk texture in the <001> direction, but were weaker in Fe 4 Al 13 grains. The average Schmidt factor of the Fe 4 Al 13 and Fe 2 Al 5 grains in the interface zone was 0.269 and 0.287, respectively, corresponding to the high brittleness and hardness of Fe 4 Al 13 and Fe 2 Al 5 . The maximum tensile strength of the joints was 118.0 MPa and the aluminum/steel joints all fractured at the interface zones. The brittle IMCs of Fe 4 Al 13 and Fe 2 Al 5 played a crucial role in contributing to the joint fracture.