Abstract
The effect of grain size and shape on low cycle fatigue of a nickel-based superalloy at elevated temperature was investigated. Fatigue testing was performed using GH4742 specimens having fine, coarse, and irregular grains. The fine-grained material exhibits a transition strain separating the fatigue life diagram into two regimes with distinct slopes while the other two do not. A piecewise log-linear model was proposed to incorporate the transition strain, yielding more accurate predictions. Crack initiation modes and cyclic deformations at half-life were investigated to explain the observed difference and fatigue behavior characteristics of the three grain types.
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