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

Abstract

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 α lath coarsening from 0.7 μm up to 3 μm. 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-β columnar and colony size increases with α lath width resulting from increased energy input; however, each grain type appears to respond differently to either beam velocity or hatch space variation. Average α lath width values show greater correlation to energy density, which demonstrates the dependence of grain formation on hatch overlap.

Keywords

• Ti-6Al–4V
• Electron beam melting
• Process parameters
• Microstructure