Abstract
Micron-sized internal cracks were introduced into rounded bars of pure iron by low cycle fatigue, and the cracks had irregular penny-shaped morphology with the critical diameter of about 30μm and the thickness of 0.5–1.5μm. The initiation and propagation of the cracks were investigated quantitatively as well as their location and geometry. After vacuum annealing of the samples fatigued, the morphology in a two-dimensional longitudinal section of cracks within grains had evolved from initially elliptical one into arrays of spherical voids controlled by surface diffusion. Furthermore, a typical morphology for a broken crack with a center spherical void surrounded by outer doughnut-like cavities was observed along a perpendicular section of the specimen. Subsequently the spherical voids shrink and diminish gradually dominated by bulk diffusion. A physical model to heal an internal microcrack was proposed, in particular for the various healing stages controlled by the related dominant diffusion mechanism and their dependencies upon the morphology and geometry of an original micro-crack in materials.
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The project supported by the National Outstanding Young Investigator Grant of China (59925104) and the National Natural Science Foundation of China (59889101)
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Hailong, Z., Jun, S. Morphological evolution during diffusive healing of internal cracks within grains of α-iron. Acta Mech Sinica 18, 516–527 (2002). https://doi.org/10.1007/BF02486576
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DOI: https://doi.org/10.1007/BF02486576