Creep rupture mechanisms of 5083-Al alloy under multiaxial stress states

The high-temperature rupture behavior of the 5083-Al alloy was tested to failure at 548 K under multiaxial stress states of uniaxial tension using smooth bar specimens, biaxial shearing using double shear bar specimens, and triaxial tension using notched bar specimens. Rupture times were compared for uniaxial, biaxial, and triaxial stress states with respect to the maximum principal stress, the von-Mises effective stress, and the principal facet stress. The results indicate that the von Mises effective and principal facet stresses show a good correlation for the investigated material. The success with two parameters implies that the creep rupture of the 5083-Al alloy is dominated by grain boundary cavitation that is constrained by the creep deformation of the surroundings. The experimental results reveal that the creep rupture of this alloy under the testing condition in the present study is controlled by cavitation coupled with the highly localized deformation process such as grain boundary sliding. The failure-mechanism control parameter for the notched triaxial tension specimens confirms that the effective stress primarily controls the rupture of the uniaxial and triaxial tension specimens. A theoretical prediction based on constrained cavity growth and continuous nucleation was found to be in agreement with the experimental rupture data within a factor of three.