Yield surface characterization of GRX-810: Linking texture, microstructure, and anisotropic behavior

Additively manufactured (AM) alloys exhibit pronounced direction-dependent mechanical behavior arising from process-induced microstructures; however, the extent of their influence on multiaxial yielding remains insufficiently quantified. In this work, the anisotropic yield surface of L-PBF GRX-810, a NiCoCr-based medium-entropy alloy, is experimentally constructed using proportional axial–torsional loading of tubular specimens fabricated in vertical and diagonal orientations, under both as-built (AB) and hot isostatically pressed (HIP) conditions. Yield stresses are determined using a 0.2% offset criterion, with stress corrections based on surface roughness and X-ray computed tomography to account for the effective load-bearing area. The measured yield loci reveal pronounced anisotropy and tension–compression asymmetry. Vertical specimens exhibit enhanced shear strength relative to isotropic predictions, whereas diagonal specimens, characterized by a ∼ 45 ° -tilted texture, show increased axial strength and reduced shear strength. These trends are consistent with Schmid factor analysis, which links the behavior to texture-driven variations in slip-system activation under different loading modes. Comparison with established yield criteria shows that the von Mises model underperforms in capturing anisotropy and strength asymmetry, while the Hill criterion is only adequate when the yield surface approaches a quadratic form. In contrast, the adopted CPB06 formulation accurately captures the non-quadratic distortions and orientation-dependent asymmetry across all conditions. Although such advanced models typically require extensive calibration, the present framework extracts all required parameters from a single axial–torsional testing configuration, significantly reducing experimental complexity. This study establishes a transferable methodology for characterizing multiaxial anisotropic behavior in AM alloys and provides a direct link between AM processing, microstructure, and yield-surface evolution, with implications for the design and certification of AM components under complex loading conditions.