Research on strain rate effects of AZ31B magnesium alloy of different orientation samples

Dynamic mechanical properties of the samples with compression axis 90°, 45° or 0° from the normal direction of the AZ31B plate were tested using split Hopkinson bar. The microstructure evolutions were analyzed using optical microscope and transmission electron microscope. The analyzed results indicate that the twinned area fraction increases gradually with the increment of the strain, the twinning is main deformation mechanism, its stress-strain curve is concave, for the sample with 90° angle between compression axis and normal direction at a strain rate 1200 s^-1; the main plastic deformations are dislocation and slip, their stress-strain curves are approximate line and convex respectively, for the samples with the angles of 45°, 0° between compression axis and normal direction at a strain rate of 1200 s^-1; the curves change from concave to convex for 90° sample at a strain rate of 2800 s^-1, due to rapidly increasing twinned area fraction, which changes the orientations of most grains and makes slipping more easily.