Formability, microstructure and mechanical properties of Ti-6Al-4V deposited by wire and arc additive manufacturing with different deposition paths

By means of wire and arc additive manufacturing (WAAM) in an inert environment, the Ti-6Al-4V thin-wall parts were fabricated. To explore the effect of different deposition paths of WAAM on formability, microstructure and mechanical properties, the samples were analyzed by surface profiler, optical microscope (OM), scanning electron microscopy (SEM), X-ray diffraction (XRD), Vickers hardness and universal testing machine. The results indicate that the side surface waviness (SW) of the samples from samples by reciprocating deposition path in both ends are higher than those in the middle, but SW of the samples by co-directional deposition path gradually rise from arc starting to arc stopping. Prior-beta grains from the samples by co-directional deposition path are inclined relative to the building direction, and there are many winding prior-beta grains in the samples by reciprocating deposition path. In the vertical direction, the strength of samples by co-directional deposition path is higher than those by reciprocating deposition path. Furthermore, the microstructure around the white band structure consists of fine basket-weave, colony alpha and coarse basket-weave in sequence from top to bottom. The white band region is a slight hardness drop (similar to 20 HV0.2), but it has almost no effect on tensile strength.