Abstract:
The influence of a stress-relief treatment on impact and fatigue properties of Ti6Al4V ELI samples manufactured
by laser powder bed fusion was analyzed. The heat treatment resulted in removal of residual stresses, coarsening
of needles and formation of precipitations between needles. In both, impact and fatigue tests, crack development
was correlated to microstructural features. Fracture analysis was carried out by means of optical and electron
microscopy to reveal the influence of microstructure on crack development. Ductile fracture was the dominating
fracture mode at impact testing. Pore formation and coalescence were the main crack formation mechanisms.
The microstructural changes led to a decrease in impact toughness after heat treatment. Presumably, this was a
result of the precipitations between needles. Fatigue results showed multiple crack nucleation at the surface in
both, as-built and stress-relieved material. The crack propagation rate was slightly higher and the crack was less
deflected in the stress-relieved material due to the stress relief and coarsening of the microstructure.
