Investigation of microstructure and mechanical performance of Ti6Al4V-ELI components produced by DMLS and EBM additive technologies in different geometries

A comparative study of the microstructural features of Ti6Al4V-ELI alloy components fabricated by Direct Metal Laser Sintering (DMLS) and Electron Beam Melting (EBM) were investigated. Samples had two different shapes, one cylindrical (CYL) and one parallelepiped (PAR). They were characterized in the build plane and in the two orthogonal planes by Optical Microscopy (OM) and Scanning Electron Microscopy (SEM) revealing a Basket-Weave (Widmanstatten) microstructure in each sample. X-ray Diffraction (XRD) spectra confirmed the presence of alpha and beta phases with limited texturing. Quantitative processing of SEM images highlighted the presence of 10% beta phase. All investigated samples satisfied related microhardness (ASTM F136-13) and tensile test (ASTM F2924-14) specifications; however, DMLS samples achieved the most isotropic mechanical properties. CYL-DMLS samples achieved the highest microhardness (404 +/- 4 HV0.5) and ultimate tensile strength (sigma(UTS) = 1155 +/- 50 MPa) maintaining outstanding elongation at 15 +/- 1%. By comparing the microstructure and mechanical behavior, it is evident that mechanical performance is strictly related to the fineness, homogeneity and size distribution of beta domains dispersed in the alpha matrix.