Effects of structural anisotropy on deformation and damage of a duplex stainless steel under high strain rate loading

Duplex stainless steel (DSS) with pronounced microstructural anisotropy, is shock-loaded along normal direction, transverse direction and rolling direction to investigate the effects of structural anisotropy on high strain rate deformation and damage. Hugoniot elastic limit (HEL) and spall strength are obtained from free surface velocity histories. The recovered samples are characterized with electron backscatter diffraction and x-ray computed tomography. HEL shows negligible anisotropy and is dominated by the weaker austenite phase. Spall strength shows anisotropy for incipient spallation but not for full spallation. Plastic deformation and damage depend on the mismatch in sound speed and strength between ferrite and austenite. Damage nucleates at phase boundaries, and propagates as cleavage cracks in the textured ferrite; the propagation is blocked by austenite. These factors coupled with different stress states induced by different impact velocities contribute to DSS's anisotropic or isotropic response.