Influence of heat input on microstructure and mechanical properties of wire arc additively manufactured Ti-6Al-4V alloy

In this study, wire arc additive manufacturing (WAAM) was employed to fabricate Ti-6Al-4V alloy components under varying heat input conditions. The influence of heat input on the weld-properties was analyzed in both the longitudinal and build directions. Observations from the deposited material reveal that an increase in heat input results in a greater joint height, while the width remains relatively consistent across all specimens. Microstructural analysis indicates the presence of a fine Widmanstätten structure, characterized by needle-like α colonies within the β grains at the top region. Conversely, the lower section exhibits a coarser Widmanstätten structure with thicker α lamellae. Hardness measurements reveal that the upper region possesses lower hardness compared to the bottom. Furthermore, hardness progressively increases with higher heat input, reaching its peak at the maximum heat input level. Tensile strength follows a similar trend, improving with increasing heat input due to the formation of a well-defined Widmanstätten structure, consisting of interwoven α and β phases. Fractographic analysis of the fractured surfaces indicates a mixed mode of intergranular and transgranular fracture, displaying distinct deposited layers along with fractures propagating through elongated grains.