2008 Volume 49 Issue 11 Pages 2591-2596
An annealed AZ31-Mg specimen (AZ31-O) was given a FSP (friction stir process) to obtain a AZ31-FSP specimen, whose tensile and vibration fracture mechanisms are examined in this study. As a result of FSP, the structure of the stirred zone (SZ) separated into two zones: (1) the SZ-top had a finer structure and (2) the grain size of the SZ-bottom was like the AZ31-O specimen. Because the basal plane (0002) had pressed close to the trace surface of the onion structure in the SZ, the recrystallization of FSP increased the elongation of the specimens at room temperature, but the refined grains had no contribution to tensile strength and had an unusual Hall-Petch effect. Notably, the vibration deformed resistance of the AZ31-FSP specimen was higher than that of the AZ31-O specimen. The FSP specimen not only possessed finer structures but also had a preferred orientation in the stirred zone. This led to an increase in the crack tortuosity, which in turn increased the crack propagation resistance and the vibration life.