Effect of Sample-Build Orientation on the Tensile Deformation and Properties of Ti6Al4V Processed by Laser Powder Bed Fusion

The effect of sample-build orientation on the tensile properties and deformation behavior of Ti6Al4V fabricated by laser powder bed fusion (LPBF) has been investigated by examining the changes in X-ray diffraction spectra, microstructure, and dimension on the longitudinal cross-sections after fracture. The anisotropy in strength is dominated by the difference in martensite (alpha ') lattice distortion, and the highest strength is achieved in the diagonally built sample (Z45) due to its largest alpha ' lattice distortion. The plastic deformation is mainly accommodated by sliding and micro-void formation between alpha ' laths due to the insufficient number of slip systems in hexagonal close-packed alpha ' phase. Therefore, the spatial orientation of alpha ' laths with respect to the loading direction is critical to the ductility. Different deformation mechanisms have been observed in different prior-beta grains due to their different alpha ' crystallographic orientations. The highest elongation is achieved in the vertically built sample (Z) because alpha ' laths in the vertically built sample are spatially at +/- 45 degrees with the loading axis. Ti6Al4V samples fabricated by laser powder bed fusion process at different orientations are characterized by the different distortion of martensite lattices and angle of martensite laths with the loading direction. The former results in the anisotropy in strength and the latter leads to the different ductility in the cylindrical samples built at different angles with the loading axis.image (c) 2024 WILEY-VCH GmbH