Low-cycle dwell-time fatigue in Ti-6242

Ambient-temperature, low-cycle dwell-time and conventional low-cycle fatigue tests were performed on Ti-6Al-2Sn-4Zr-2Mo-0.1Si (Ti-6242). Specimens were solution annealed at various temperatures below the beta transus to control the volume fraction of primary alpha phase and were subsequently shot-peened. The influence of the changes in primary alpha phase on the low-cycle dwell-time fatigue life (LCDF) were determined and compared to the conventional low-cycle fatigue (LCF) properties of the alloy. A 120-second dwell significantly decreased the number of cycles to failure, although the factor decrease of LCF from a dwell, in general, diminished with decreasing stress. The Increasing primary alpha phase associated with lower solution temperatures appears to increase susceptibility to low-cycle dwell-time fatigue. It also appears that the susceptibility to dwell fatigue may be associated with ambient-temperature, time-dependent, cyclic (creep) plasticity.