Fracture characteristic of Mg-Gd-Y alloy in wide stress state: Experiment and modeling

The stress state with the complex loading path substantially impacts the hardening and fracture behaviors of the magnesium-rare earth alloys, creating considerable difficulties for practical engineering implementation. To uncover the complicated deformation behavior from yield to fracture, this research carried out the mechanical experiments of an Mg-Gd-Y alloy under various loading conditions. A constitutive model is established, including the analytical Yoon2014 (A-Yoon2014) yield function, the modified Voce (M-Voce) hardening law and the two-component ductile fracture stress-based (2DFs) fracture criterion. Experimental results indicate that the mechanical strength is with the strain-dependent coupling effect of the anisotropic and strength-differential hardening. The A-Yoon2014+M-Voce model accurately captures the non-proportional evolution characteristic of the anisotropic-asymmetric hardening behavior, and simulates the deformation behavior of all fracture specimens to determine the fracture-related variables. The fracture stress is with a strong sensitivity to the loading path. The loading path-related fracture behavior at wide stress triaxiality is modeled by the 2DFs fracture criterion with a lower prediction error (0.212) than that (0.251) of the DF2016 stress-based fracture criterion. This work proposes a constitutive model from yield to fracture to provide the numerical guidance for the forming and application of magnesium-rare earth alloys.