Laser directed energy deposition of Ti-1Al-8V-5Fe alloy: From zero to significant tensile plasticity

Titanium alloy Ti-1Al-8V-5Fe (Ti-185) has essentially remained an experimental alloy since its invention because of the formation of iron-stabilized beta-flecks in conventional manufacturing. Laser directed energy deposition (L-DED) has the potential to avoid this issue while realizing in-situ ageing. This work investigates the L-DED fabrication of Ti-185 alloy. We show that the precipitate phases along the build height of the Ti-185 plate sample have a decisive influence on its tensile properties. Due to the formation of the embrittling isothermal omegaphase (omega iso), the top region of the Ti-185 plate sample exhibited zero plasticity, while the middle region, which is free of the omega-phase (omega), demonstrated significant tensile ductility (20 +/- 2 %) and strength (1042 +/- 13 MPa). The formation of each phase is elucidated using simulated temperature evolution profiles in the plate sample. Furthermore, we show that converting the isothermal omega-phase into the athermal omega-phase (omega ath) through beta-annealing and water quenching restores tensile ductility.

Automated summary

In this study, the fabrication of Ti-1Al-8V-5Fe (Ti-185) alloy using laser directed energy deposition (L-DED) was investigated. The precipitate phases along the build height were found to have a significant influence on the tensile properties of the alloy. The formation of the embrittling isothermal omega-phase (omega iso) was found to result in zero plasticity in the top region of the sample, while the middle region without the omega-phase exhibited significant tensile ductility and strength. Furthermore, it was demonstrated that converting the isothermal omega-phase to the athermal omega-phase (omega ath) restored the tensile ductility of the alloy.