Effect of service temperature on cyclic mechanical behavior of magnesium with fine grained structure

To explore the effect of operational service temperatures on the fatigue properties of fine-grained magnesium, we processed magnesium using multi-pass rolling at about 200 o C and then tested the samples under a cyclic tension-tension loading at various temperatures. The selected testing temperatures are room temperature, 0 o C, and −60 o C. The loading condition is almost the same for all selected temperatures. The tested samples were prepared for microstructural characterization and observed using the electron backscatter diffraction technique. The fatigue testing and microstructural observation results were analyzed to obtain the stress-strain curves, the fatigue lives, the orientation information of grains, the 0001 and 10-10 pole figures, the inverse pole figures, the misorientation angles of boundaries, the kernel average misorientation distributions and geometrically necessary dislocation density distributions for all studied testing conditions. The fatigue life at room temperature is the longest and that at 0 o C is the shortest among all testing temperatures. The geometrically necessary dislocation density distributions indicate that dislocation activities were substantial for the sample tested at 0 o C and moderate for the samples tested at room temperature and −60 o C. The misorientation angle distribution curves show that very limited tensile twins are in the samples tested at room temperature and 0 o C, and an extensive number of tensile twins are in the sample tested at −60 o C. Thus, tensile twinning is a critical deformation mode for the testing at −60 o C, and this mode is not active for the testing at room temperature and 0 o C.