Study on the plastic anisotropy of advanced high strength steel sheet: Experiments and microstructure-based crystal plasticity modeling

摘要

For their versatile microstructure controlling techniques, advanced high strength steels (AHSSs) show great potential to be tailored for various application scenarios. The unique microstructure of AHSSs renders their complex plasticity behaviors and mechanical properties. In this work, uniaxial tensile tests combined with a 3D digital image correlation system were carried out to capture the mechanical anisotropy evolution of a cold-rolled dualphase AHSS (DP980) sheet. In contrast to the conventional body centered cubic (BCC) steel sheets, the studied DP980 sheet shows much smaller Lankford coefficients and a mild strength anisotropy. The Lankford coefficients depend significantly on tensile directions and vary obviously with deformation; they increase with deformation first and then decrease after macroscopic strain localization takes place. Postmortem experimental characterizations as well as microstructure based full-field crystal plasticity simulations were employed to uncover the underneath mechanisms. Plasticity heterogeneities and micromechanical interactions between the soft ferrite matrix and hard martensite islands primarily account for the mechanical anisotropy of the studied steel sheet.