Fatigue properties of the hot extruded magnesium alloy AZ31

The fatigue properties of differently extruded magnesium alloy AZ31 and hence different microstructures were investigated during total strain and stress-controlled fatigue tests with different applied strain and stress amplitudes, respectively. Extruded magnesium profiles exhibit a significant asymmetry in the quasi-static mechanical properties under tension and compression, due to the low activation energy for the {1 0 (1) over bar 2} < 1 0 (1) over bar 1 > extension twinning. The asymmetry of the tension-compression yield strength leads to a sigmoidal shape of the hysteresis loops under cyclic loading conditions which is reduced if the tension-compression asymmetry is reduced. Moreover the evolution of stress and strain amplitudes, the plastic strain amplitudes and the mean stress and strain were analyzed. The Manson-Coffin and the Basquin approaches were used to describe the lifetime of the differently extruded products. (C) 2010 Elsevier B.V. All rights reserved.