Stress and deformation evaluation of the subarea scanning effect in direct laser-deposited Ti-6Al-4V

The present work investigated the influence of the subarea scanning pattern on substrate deformation and residual stress distribution in direct laser-deposited Ti-6Al-4V. An island scanning pattern, adopted as a representative subarea scanning pattern, was compared with the successive scanning pattern experimentally. Additionally, different island scanning strategies with islands of different sizes (60 x 60, 40 x 40, and 20 x 20 mm(2)) and different island scanning orders (specified, outside in and inside out) were investigated in large-scale deposition. The results showed that the island scanning pattern reduces the deformation due to successive scanning pattern by 71% and causes a periodically oscillated residual stress distribution on the whole deposit. The island scanning order has a more basic effect than the island size on deformation and residual stress. The newly defined outside-in island scanning order remarkably minimizes deformation, while the randomly specified order induces the smallest residual stress; thus, their combination is appropriate for the fabrication of the large components. Moreover, buckling deformation unexpectedly occurs even if a 5-mm-thick substrate is used primarily due to the small temperature gradient generated by the small island size of 20 x 20 mm(2).