LOW-CYCLE FATIGUE BEHAVIOR OF AN ALPHA-TITANIUM ALLOY - TI6246(BETA)

The present study focused on the cyclic behavior of an alpha + beta ti tanium alloy, Ti6246. Low cycle fatigue tests were carried out between 20-degrees-C and 500-degrees-C under plastic strain control. The expe rimental results show that the 6246 alloy exhibits cyclic softening ir respective of the imposed temperature or strain. Nevertheless, careful analysis of the stress-strain hysteresis loops revealed that the phys ical origins and the underlying physical mechanisms of the softening a re strongly temperature dependent. At room temperature, the softening appears to proceed from a decrease in the kinematic component of stres s; it is governed by the gradual homogenization of the initially heter ogeneous distribution of dislocations (localized slip bands) in the al pha phase in relation to the long-range internal stress field.In contr ast, at high temperatures, the second phase shearing process due to th e homogeneously distributed dislocations, and the occurrence of cross- slip, lower the isotropic contribution and lead to the observed cyclic softening. The mechanical results and the microstructural observation s are therefore fairly consistent with one another.