No abstract

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The threshold fatigue crack gzo-vtrr "e L L havior of Inconel 718 forging was investigated from room temperature to lOOOF. For a fine grain condition (ASTM 10 or finer), the measured thresholds were insensitive to prior forging processing history, For a given florging/heat treat practice, the nec%ured threshold stress intensities increased with increasing temperature. This temperature effect bsceme more prlonounced with decreasing grain size. The measured threshold stress intensities appear to be related to grain site (or strength level); at a given temperature, the largest value of threshold stress intensity was obtained for the coerse grain materiel (ASTM grain size 3). This grain size (or strength level) effect was greatest at low temperature, and dtiinlshed with increasing temperature.