Effect of stress state and pores on fracture of additively manufactured metals

The effect of internal pores and stress state on the fracture behavior of relatively high ductility stainless steel 316, and relatively low ductility Ti-6Al-4V, manufactured using laser powder bed fusion (L-PBF) additive manufacturing (AM) was investigated. Cylinders were fabricated using L-PBF, with a single internal pore of varying diameter included inside each cylinder to probe the effect of relative defect size with respect to sample geometry. Uniaxial samples and notched specimens were machined from these cylinders, and samples were tested under tensile loading to probe the effect of pore size and stress triaxiality on the ductility of each of the alloys. Finite element analysis simulations of all tests were performed to identify the evolution of stress state and strain accumulation within samples up to fracture. This presentation will describe the impact of defects on ductility under multiaxial loading for these two disparate alloys.