Experimental study on temperature-dependent ratchetting-fatigue interaction of extruded AZ31 magnesium alloy

Abstract

The variations in the plastic deformation mechanisms of extruded AZ31 magnesium (Mg) alloy at elevated temperature and the temperature-dependence of its ratchetting-fatigue interaction were revealed by a series of uniaxial stress-control low-cycle fatigue experiments. The experimental results elucidate that: (1) The tension-compression asymmetry and the S-shaped inflection point in the stress-strain hysteresis loops are gradually attenuated with elevating the temperature, and the evolution of ratchetting is also remarkably affected by the elevated temperature due to the activation of abundant non-basal plane slipping; (2) The fatigue life of the alloy exhibits a pronounced temperature-dependence, and specifically, the fatigue life is greater at 100°C compared to that at room temperature, but sharply decreases at 150°C and 200°C due to the significant ratchetting deformation at these two temperatures. Moreover, the dependence of fatigue life on the applied mean stress is also different at different temperatures; (3) Due to the significant ratchetting deformation in the alloy at elevated temperature, a transition from a brittle fatigue fracture mode to a ductile one also occurs as the temperature increases. This research provides valuable experimental data that serve as an important reference for the practical application of Mg alloys.