Ambient Compression–Compression Fatigue Behavior of Magnesium Single Crystal

Abstract

A magnesium single crystal sample with a near \( 1 1 {\bar{{2}}{0}} \) orientation was tested at room temperature under compression–compression cyclic loading, and the microstructure was characterized to disclose the involved deformation mechanisms. No plastic deformation region appeared on the stress–strain curve during the cyclic loading. The stress–strain curve stabilized at the first cycle, the strain range for each cycle fluctuated slightly around a constant value, and the mean strain for each cycle was in a narrow range from 0.0846 to 0.0863 during the whole test. The ratcheting strain rate decreased exponentially from ~0.0003, and reached a relatively small and stable value of about zero. The observed deformation mechanisms were prismatic slip, compression twinning, and tension twinning. The prismatic dislocation slip roughened the cylindrical sample surface by forming extrusions and intrusions, and small cracks were also observed on the surface.