Microstructures of Components Synthesized via Electron Beam Selective Melting Using Blended Pre-Alloyed Powders of Ti6Al4V and Ti45Al7Nb

The Ti-based components were synthesized via electron beam selective melting (EBSM) using blended pre-alloyed powders of Ti6Al4V and Ti45Al7Nb with a mass ratio of about 1:1. The microstructures and the chemical compositions of EBSM component samples were investigated by optical microscopy (OM), scanning electronic microscopy (SEM), electron probe micro-analyzer (EPMA) and X-ray diffraction (XRD). The results indicate that an increase of energy density leads to a decrease of fusion defects and an increase of density of the samples. The macro-structure consists of two regions, the martensite phase region and α2+β phase region. The martensite phase is formed due to the rapid solidification, while the reheating cycles have a remarkable effect on the formation of α2+β phase. The micro-hardness of martensite region is significantly higher than that of α2+β phase region. Due to the discontinuous distribution of thick platelet α2 phase along grain boundaries and the high coordinating deformation capability of equiaxial α2 phase, the samples have a tensile strength up to 1214.3 MPa, and a large elongation of 18%.