Multi-physical modelling of alloy element transportation in wire arc additive manufacturing of a ?-TiAl alloy*

How to obtain homogeneous element distribution is a challenging research in wire arc additive manufacturing (WAAM) of gamma-TiAl alloys, and the wire transfer has a great influence on it. A multi-physical numerical model considering the dissimilar wire feeding and melting, and element mixing is developed, and a high-speed video camera is adopted to investigate the wire transfer behaviors in WAAM of a gamma-TiAl alloy. The Ti and Al elements can be transferred to the molten pool through a liquid TiAl bridge. However, the liquid TiAl bridge is not very stable, and the breakup between the Al wire and liquid TiAl bridge can be observed. The wetting ability (wetting angle) of the liquid TiAl metal on the Ti wire surface can be used to predict the possibility of the liquid TiAl bridge breakup. The surface tension causes backward flow and growth of a liquid TiAl droplet, and thus suppresses the droplet transfer.