Controlling martensitic decomposition during selective laser melting to achieve best ductility in high strength Ti-6Al-4V

Abstract

Systematic variations of the exposure time and point distance of the pulsed laser used in selective laser melting (SLM) of Ti-6Al-4V resulted in three representative microstructures: the fully martensitic α’ the near-α’ containing a small amount of isolated β and the fully lamellar α/β. The energy density in SLM determines the steady-state temperature in a deposited layer reached by balance between heat input from the subsequent layers and heat loss into the previous ones. A critical energy density was revealed below which no in-situ α’ decomposition occurred. On the other hand, the in-situ formation of fully lamellar α/β was obtained using energy density higher than this critical value, lea..