Laser-inherent porosity defects in additively manufactured Ti–6Al–4V implant: Formation, distribution, and effect on fatigue performance

• Published in: Journal of materials research and technology Vol. 30; pp. 5121 - 5132
• Main Authors: Aliyu, Abdul Azeez Abdu, Puncreobutr, Chedtha, Kuimalee, Surasak, Phetrattanarangsi, Thanawat, Boonchuduang, Thanachai, Taweekitikul, Pariwat, Panwisawas, Chinnapat, Shinjo, Junji, Lohwongwatana, Boonrat
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.05.2024; Elsevier
• Subjects: Additive manufacturing; Defects; Laser; Mechanical properties; Porosity; Titanium; Titanium; Mechanical properties; Porosity; Additive manufacturing; Laser; Defects
• ISSN: 2238-7854
• DOI: 10.1016/j.jmrt.2024.04.225

Porosity defects are inherently present in Ti–6Al–4V (Ti6-4) parts produced using additive manufacturing (AM) methods like laser powder-bed fusion (LPBF). This work aims to investigate different laser-inherent porosity defects at various LPBF parameter settings and assess their impact on the fatigue behaviour of Ti6-4 implants processed by LPBF. The presence of LPBF-inherent porosity defects with different shapes and sizes was established using microstructural examination and X-ray micro-CT analysis. These mostly comprise lack-of-fusion porosity (LoFP), gas-entrapped porosity (GeP), and pores-induced microcracks. Volumetric porosity defects were seen to range from 1.9 × 104 to 9.52 × 105 μm3. The L-1 specimen exhibited the lowest defect, while the L-6 specimen displayed the largest number of defects. While LoFP defects predominate in L-6, there was a notable presence of GeP defects in the specimens processed using the factory default condition (L-D). Upon examination of the majority of specimens, GeP and LoFP coalesced to form clusters, leading to the formation of pores-induced microcracks. This ultimately leads to a decrease in fatigue performance. By maintaining the power at the default setting and increasing the scan speed by 8% of the default value, a specimen (L-1) with minimal porosity defects and superior fatigue performance is achieved. L-6 exhibits defects with significant dimensions and irregular form. Consequently, it displays inferior fatigue characteristics. [Display omitted] •X-ray Computed tomography and Archimedes density approaches were used to evaluate the laser-inherent porosity defects.•The defects were detected at various parameter settings according to their size, quantity, and geometry.•The primary laser-inherent porosity defects influencing fatigue behaviour were identified.•Cracks initiating sites including surface and subsurface regions were ascertained.