| Abstract Scope |
This research investigates the effect of combining multi-exposure scanning with laser defocus during laser powder bed fusion (LPBF) on the residual stress and properties of Commercially Pure Ti Grade 1 parts. The approach aims to reduce residual stress and distortion while maintaining surface finish and part density. A laser defocus was applied as an additional exposure to mimic in-situ annealing, using four scan strategies: single exposure (SE, control), defocus first (D1), defocus second (D2), and multi-exposure without defocus (ME). Density, porosity, surface roughness, hardness, and residual stress magnitude through distortion were assessed. D1 and ME reduced residual stress, while D2 increased density and minimized porosity (99.9% dense). D2 also improved top surface finish, though D1 and ME increased roughness. Mechanical and microstructural analyses showed no significant differences. Overall, applying laser defocus before the main exposure effectively reduces residual stress while maintaining desirable LPBF part qualities. |