Effects of embedded spherical pore on the tensile properties of a selective laser melted Ti6Al4V alloy

Abstract

Selective laser melting (SLM) is one of the most promising additive manufacturing (AM) technologies in recent years. However, some sub-millimeter defects often appear accidently in SLM specimens, resulting in deterioration of mechanical properties. Therefore, the effects of these defects on the mechanical properties of the SLM materials are significantly important. In this study, the effect of a single spherical defect on the tensile properties was investigated by embedding a spherical pore inside the SLM Ti6Al4V specimens. Different combinations of pore diameters (Ф100 μm, Ф300 μm, Ф500 μm, Ф1000 μm) and locations (center, sub-surface, near-surface) were designed to mimic the sub-millimeter printing defects. The results demonstrated that these embedded pores had negligible influence on the elastic modulus and tensile strength but had a noticeable influence on the tensile elongation. With the increase of pore size, the elongation to failure of the specimens tended to be stochastic, stably high and stably low in sequence, which could be related to different fracture modes. The tensile specimens fractured at the embedded pore when the embedded pore size was increased to a critical diameter (approximately Ф1000 μm). Concurrently, the location of the embedded pore started to have an obvious influence on ductility, namely, the elongation to failure decreased as the embedded pore became closer to free surface.