Columnar grain morphology and mechanical anisotropy of face-centered cubic metals and alloys

The columnar grain morphology (grain shape and orientation) in polycrystalline metals is generally considered to contribute to mechanical anisotropy due to the interaction of dislocations with grain boundaries. However, past investigations have failed to reach a consensus on the role of grain morphology on property anisotropy. In this study, the influence of columnar morphology as a potential source for anisotropy is investigated for directed energy deposited (DED) stainless steel 316L (SS 316L). Macroscopic stress-strain behaviors and microscopic slip band evolution of DED SS 316L specimens were obtained under uniaxial tensile testing. The stress-strain behaviors show that the influence of grain morphology on anisotropy is negligible. The characteristics of slip band evolution reveal that the influence of grain morphology on anisotropy depends on the outcome of two competing choices for slip selection: the least resistant glide path versus the one that offers the greatest compatibility with the intergranular deformation.