Effects of initial {10-12} twins on cyclic deformation and fatigue of magnesium alloy at low strain amplitudes.

Abstract An extruded AZ31B (Mg-3Al-1Zn-0.5Mn) magnesium alloy with a twin volume fraction of 60% was subjected to fully reversed strain-controlled tension-compression along the extrusion direction at strain amplitudes ranging from 0.23% to 0.45%. Dislocation slips were the dominant plastic deformation mechanisms without involving persistent twinning-detwinning. At an identical strain amplitude, the fatigue life of the pre-twinned alloy was much lower than that of the as-extruded alloy. Fatigue cracks were mainly initiated on the prismatic or prismatic-basal slip bands in the parent grains. The material volume reduction of the parent grains in the pre-twinned alloy enhanced fatigue damage. Twin cracks were not observed. Graphical Abstract Unlabelled Image Highlights • We investigate fatigue behaviors of pre-twinned Mg alloy at low train amplitudes without involving twinning-detwinning. • The fatigue life of pre-twinned alloy is much shorter than twin-free alloy. • Prismatic slip is more likely to cause fatigue microcracks than basal slip. • Fatigue damage was enhanced due to the volume reduction of the parent grains in twinned alloy. [ABSTRACT FROM AUTHOR]