Influence of melt parameters on the microstructure of electron beam melted Ti-6Al-4V

Additively manufactured, Electron Beam Melted (EBM) specimens of the titanium alloy, Ti-6Al-4V, have been produced using a process window determined through a normalised energy density method. Two batches were manufactured and compared using identical energy density values with differing beam current, power, and beam velocity. A stable process window has been demonstrated with a Vickers hardness range of 360-395 VHN resulting from alpha lath coarsening from 0.7 mu m up to 3 mu m. A range of macro morphologies have been reported and relate to the hatch overlap and beam velocity parameters. Base plate position does not appear to influence microstructure or micro-hardness. Prior-beta columnar and colony size increases with alpha lath width resulting from increased energy input; however, each grain type appears to respond differently to either beam velocity or hatch space variation. Average alpha lath width values show greater correlation to energy density, which demonstrates the dependence of grain formation on hatch overlap.