Characterization of the fatigue behaviour of the magnesium alloy AZ91D by means of mechanical hysteresis and temperature measurements

Stress-controlled load increase and constant amplitude tests were performed on the cast magnesium alloy AZ91D. Rather small values of the plastic strain amplitude reflect the very localised plastic deformation predominant in the _I-phase. The cyclic deformation and temperature curves of the load increase tests exhibit cyclic yield strength values which allow a good estimation of the endurance limit. Stress amplitudes above the endurance limit lead to cyclic hardening. As compared to the behaviour under monotonic tensile loading, the alloy exhibits cyclic hardening. Microscopic investigations illustrate the different influences of the - and β-phase in respect to crack initiation.