Abstract

Additive manufacturing (AM) of metallic components offers a number of technological advantages such as near-net shape forming using a single processing step, flexible and on-demand manufacturing, near-zero material loss during fabrication, etc. Additionally, alloys made with AM techniques such as laser powder bed fusion (LPBF) have substantially finer microstructures (due to rapid solidification) and distinct mesoscale features. A synergetic interplay between these micro- and meso-structural features leads to high strength – toughness combinations. However, certain other intrinsic features such as microporosity can adversely affect the fatigue resistance in AM alloys. In contrast, the fatigue strength (σf) of binder jet printed 316L austenitic stainless steel, which contain significant amounts of pores, are surprisingly comparable to those of the conventionally manufactured 316L whereas the LPBF specimens are far inferior in terms of σf although the porosity in them is relatively smaller. All these results are rationalized by recourse to the distinct microstructures of AM alloys and how they affect plasticity and crack growth. Implications of these results in terms of possible directions for designing AM alloys with high mechanical performance will be discussed.