Fatigue Performance of Ti-6Al-4V Processed by Wire-Arc Directed Energy Deposition

Ti-6Al-4V has a wide range of applications, but long lead times and low-efficiency processing of the material leads to limitations. Through additive
manufacturing, such as wire-arc directed energy deposition, higher processing
efficiency, and lower lead times are possible. To fully realize the benefits, an
important parameter for application is the fatigue performance, which needs
to be better documented and performance shortcomings improved. Currently,
available results on fatigue performance of wire-arc directed energy deposition
of Ti-6Al-4V are limited. Therefore, wire-arc directed energy deposition of Ti6Al-4V was used with the following approach. Samples were characterized
using scanning electron microscopy and optical light microscopy, and
mechanically tested for tensile and fatigue performance. Minimal pore density
and a fine a microstructure within coarsened epitaxial columnar b-grains was
observed. Additionally, elemental burn-off and oxygen contamination was
assessed, showing a loss of 0.2 wt.% aluminum during processing and no
oxygen pick-up. Compared to other cold metal transfer-based wire-arc directed
energy deposition results available in the literature, the results present significant improvements. Fractography indicated mixed fracture modes, which
are likely due to the macro-zones of a having varying orientations. Our work
provides an advancement in fatigue performance and processing, further
showing the potential of the technology.