Evaluating the microstructural formation in Mo added Ti6Al4V alloy fabricated by direct energy deposition using a laser-stop strategy

The microstructure formation in the Ti64 alloy with the addition of different alloying elements is extensively researched to enhance the mechanical properties of the alloy, especially fabricated using additive manufacturing processes. In this work, the effect of Mo (0, 1, 2, 4 wt.%) addition on the microstructure and mechanical properties of the direct energy deposited (DED) Ti64 alloy was evaluated in detail. As the Mo content increases, a remarkable refinement in the α-laths morphology was observed, with the average width decreasing from ~1.12 μm to ~0.39 μm, and an anomalous increase in the volume fraction of the α phase was noted in the Ti64-1Mo alloy. Further increase of the Mo content results in the attenuation of the variant dominance of the α-laths until virtually eliminated. Notice that the tensile strength and elongation increased by 7.3% and 37.5% with 1 wt.% addition of Mo, respectively. A Laser-Stop (LS) strategy was employed to preserve the formed metastable phases during the DED process. Such LS strategy provides necessary insights into microstructural evolution and elucidates the mechanisms behind the formation of a refined microstructure and in turn its mechanical properties.