Reducing arc heat input and obtaining equiaxed grains by hot-wire method during arc additive manufacturing titanium alloy

Arc additive manufacturing technology has high deposition efficiencies and material utilization rates. However, the large heat input and high temperature gradient during arc additive manufacturing process lead to the formation of the coarse columnar grains. Due to the presence of the coarse columnar grains, the mechanical properties of the part have great anisotropy which limits the application of it. In this experiment, a method named hot-wire arc additive manufacturing was adopted to reduce the arc heat input and refine the columnar grains, and four thin-walled samples with the material of Ti-6.5Al-3.5Mo-1.5Zr-0.3Si were manufactured. It is interesting to find that the coarse columnar grains have been greatly refined, and finally a part consisting of equiaxed grains and short columnar grains was obtained. At the same time, the width of the α-lath has also been refined. The mechanical properties are in accordance with the grain changes and the anisotropy almost disappeared. And it seems that a part with comprehensive mechanical properties can be obtained by the hot-wire arc additive manufacturing.