Low Cycle Fatigue of Single Crystal Nickel-based Superalloy DD6 at 1100℃

The total strain-controlled low cycle fatigue(LCF) behaviors of a single crystal superalloy DD6 at 1100℃ for <i>R</i>=-1 and 0.05 were investigated. The results of LCF tests indicated that the cyclic hardening/softening behavior of the alloy not only has the relationship with the microstructure of the material, but also the loading status. The mean stress relaxation occurred under asymmetric straining. The rate of mean stress relaxation increased with the increasing of strain amplitude; when <i>R</i>=-1, the alloy shows tension-compression asymmetry behavior. All the LCF data obtain under various ratios were well correlated by three models for lifetime prediction, the precision rates predicted are fallen into the factor of&#177;2 times scatter band