Wetting dynamic characteristics and interfacial structures in CMT welding process of Mg-steel

The wetting characteristics of Mg AZ61 alloy on the surfaces of Q235 steel and galvanized steel were studied, respectively. The interfacial microstructures were also studied by using SEM and EDS. The results show that the final wettability is improved with the increase of wire feeding speed, and the wettability is worsened due to the weakened interfacial reactivity which is caused by the reducing of heat on interface.Two layers (Al-Fe intermetallic layer beneath the brittle Mg-Zn eutectic) are formed which induced the weak bonding.The transition of metal for Mg-Q235 steel is more effective and the effect of Zn coating on wetting dynamics can be negligible under different wire feeding speeds, and the dynamic characteristics both of Mg-Q235 steel and Mg-galvanized steel are related to the temperature depended capillarity.