Quantitative study of geometric characteristics and formation mechanism of porosity defects in selective laser melted Ti6Al4V alloy by micro-computed tomography

The defects formed inside the additive manufactured (AM) part have a detrimental effect on the mechanical performance of the printed component. The effect of defects on the performance of parts varies with their geometry features. The characteristics of porosity defects in 36 bulk Ti6Al4V specimens with different printing parameters were investigated via X-ray computed tomography (XCT). The porosity defects are classified into four types: spherical shaped, elliptical-shaped, elongated-shaped and irregularly-shaped pores, based on their geometric characteristics. Elongated-shaped defects account for the largest proportion of defects with all printing parameters, and the proportion of irregularly-shaped defects enhances with the increase of scanning speed. The characteristics of gradual accumulation of defects in single-track and multi-track samples were also analyzed. Porosity may gradually accumulate with the overlay of layers, while the appropriate overlapping rate may melt the pores between the tracks. The formation of defects is greatly influenced by surface roughness and pool wetting.

Automated summary

Defects formed in additive manufactured parts have a negative impact on the mechanical performance. The effect of defects varies depending on their geometry. X-ray computed tomography was used to investigate the characteristics of porosity defects in Ti6Al4V specimens with different printing parameters. The defects were classified into four types based on their geometric characteristics. The proportion of elongated-shaped defects was the highest with all printing parameters, and the proportion of irregularly-shaped defects increased with the increase of scanning speed. The accumulation of defects in single-track and multi-track samples was also analyzed. Porosity may accumulate with layered printing, but the appropriate overlapping rate can melt the pore between tracks. The formation of defects is greatly influenced by surface roughness and pool wetting.