Abstract
Rotating bending fatigue tests were performed at frequency of 30 Hz using four kinds of the extruded AZ31 magnesium alloys, which were processed under different extrusion ratios (10 and 100) and different extrusion temperatures (623 K and 696 K), to determine S-N curves and crack propagation behavior of those materials. Effect of the extrusion ratios and extrusion temperatures on the fatigue lives and crack propagation behavior were discussed in detail. Fatigue processes of those materials were observed by the replica method. It was clarified that cracks initiated early in the fatigue process, and total of fatigue life can be approximated as the crack propagation life. Crack propagation behavior observed in those materials was analyzed using a modified linear elastic fracture mechanics parameter, M. The relation crack propagation rate vs. M parameter was clarified to be useful in predicting fatigue lives and crack propagation curves in those materials.
