Metal flow mechanisms during alternating current arc welding and additive manufacturing of aluminium alloy

Abstract Alternating current (AC) arc melting technology has been developed for the manufacturing of lightweight materials and provides a potential heat source in welding and additive manufacturing. However, metal flow and the corresponding effects of AC arc melting remain unclear. Here, 3D internal and surface flows in an aluminium alloy during AC tungsten arc melting are studied via in situ/operando 4D X-ray radiography and laser high-speed imaging. The molten flow velocity under positive polarity is much greater than that under negative polarity. We find that liquid metal flow is mainly influenced by the cathode spot motion at the molten pool surface in the electrode positive stage. This information can be used to guide process optimization in the manufacturing of light metals via AC arc melting.