Effects of the scanning strategy on the microstructure and mechanical properties of a TiAl6V4 alloy produced by electron beam additive manufacturing

Ti6Al4V specimens were produced using electron beam melting (EBM) with the goal of studying the effects of the scanning strategies on the surface morphology, microstructure, and mechanical properties. As the factory condition consists in the use of different parameters for scanning the hatch and the contour, additional processing conditions were investigated using the hatch and contour strategies separately, oriented from the center to the border, and vice versa. Due to material anisotropy, the samples were fabricated in both the vertical and planar directions. This work demonstrates that the scanning strategies affect several features of EBMed TiAl4V samples, like the relative density of the specimens, the surface morphology, and the microstructure and mechanical properties. In details, pure contour can increase the relative density, due to the use of pulses instead of continuous electron beam emission, while the hatch scanning produces smoother and more uniform surface morphology. As different thermal histories can be associated with the variation of the scanning strategy, the microstructure can be varied in terms of grain growth. Finally, the tensile behavior of the specimens, evaluated in both the principal orientations, can be correlated to the relative density and surface irregularity.