Effect of Size, Location, and Aspect Ratio of Internal Pores on Failure Behavior of Laser Powder Bed Fusion Ti-6Al-4V

Notched tension Ti-6Al-4V samples were fabricated using laser powder bed fusion additive manufacturing. During the fabrication of each sample, a single internal pore was included, and its size, aspect ratio, and location were varied. The presence of pores significantly reduced the ductility of the samples, where the size and location of the pores were the most critical factors, in that order, and the aspect ratio was not impactful. The severity of the internal pore was quantified with the J-integral, revealing that fracture occurred at a critical value of 23 kN/m. Ductile fracture models were calibrated with the experimentally measured displacements to failure and used to quantify the location-dependent rate of damage accumulation. Although damage initiated near the surface (meaning that near-surface pores were critical in early deformation), the increased stress triaxiality at the center of the sample led to higher damage accumulation with respect to applied displacement for centrally-located pores.