An Investigation on the Anisotropic Plastic Behavior and Forming Limits of an Al-Mg-Li Alloy Sheet

For the Al-Mg-Li alloy sheet with significant anisotropy, the uniaxial and cruciform biaxial tension tests and the Nakazima test are firstly performed to systematically determine the mechanical properties (including strength coefficient, strain hardening exponent, normal anisotropy coefficient, experimental yielding points and forming limits) of this sheet. Afterward, the widely used Hill’s 48 and Yld2000-2d yield criteria are, respectively, identified to describe the yield locus of this sheet and compared with the experimental yielding points. Comparison shows that the identified Yld2000-2d yield function provides a better description of the yield locus for the Al-Mg-Li alloy sheet. Finally, the forming limits of this sheet are predicted by the modified M-K (Marciniak–Kuczyński) model with the Yld2000-2d yield criterion identified in this work. The results show that the predicted forming limits correspond well with the experimental ones within the whole range of strain paths.