Study of the Reaction Layer of Ti and Al Dissimilar Alloys by Wire and Arc Additive Manufacturing

The wire and arc additive manufactured Ti/Al dissimilar alloys can be used in the aerospace and automobile industries. For some parts, Ti alloy was replaced by Al alloy, which reduced the weight and cost. The additive manufactured Ti/Al dissimilar alloys had the advantages of two materials and remedied the each other's shortcomings. In this study, TC4 and ER2319 wires were deposited by direct current cold metal transfer (CMT) and variable polarity-CMT+pulse mode, respectively, to realize the wire and arc additive manufacturing for Ti/Al dissimilar alloys. The arc shape, droplet transfer, voltage and current were captured by high speed camera and electrical signal acquisition system. Microstructure and mechanical properties of Ti/Al component were analyzed by OM, SEM, TEM, EDS, hardness test and tensile test. The results showed that the variable polarity-CMT+pulse welding process included the positive pulse periods and negative CMT periods. During the positive pulse periods, the arc concentrated at the end of welding wire. During the negative CMT periods, the heat input was low, which had a cooling effect on component. The reaction layer in the component included the interface layer and transition layer. The thickness of TiAl3 interfacial layer was 10 pm. The hardness of reaction layer was between that of Ti and Al alloys. The crack was formed in the interface layer. The average tensile strength was approximately 65 MPa. All samples fractured in the interface layer. The fracture mode was brittle fracture.