Statistical techniques have shown that under creep conditions, Nimonic 108 recrystallizes at temperatures as low as 800°C. Longitudinal carbide stringers originally present in the material arrest grain-boundary movement causing preferential grain growth in a longitudinal direction. Electron-microscopical evidenceis now presented to show that under creep conditions the grain boundaries do break away from their original positions,and that these mobile boundaries, being carbide-free, move appreciable distances until they are arrested. Theboundary areas then thicken by accretion of carbide and gamma prime precipitate enabling them to be detected by optical-microscopicaltechniques.
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References
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MayesP. F. and HancockP., Metal Sci J., 1973, 7, 69.
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GibbonsT. B., ibid., 1972, 6, 13.
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