Fatigue behavior and bilinear Coffin-Manson plots of Ni-based GH4169 alloy with different volume fractions of δ phase

The effect of volume fraction of delta phase, which was changed through changing the heat treatment conditions, on the strain-controlled fatigue behavior of Nickel-based GH4169 alloys at room temperature was investigated. The delta phase had almost no effect on fatigue life at strain amplitude higher than 0.5%. However, the fatigue life increased with increasing volume fraction of (delta phase at the strain amplitude of 0.4%. The alloys with three different volume fractions of delta phase exhibited dual-slope Coffin-Manson relationships, which could be attributed to the changes in the deformation mode from twinning to slip bands as well as the crack initiation mode from transgranular to intergranular with increasing strain amplitude.