MORPHOLOGICAL EVOLUTION DURING DIFFUSIVE HEALING OF INTERNAL CRACKS WITHIN GRAINS OF α-IRON

• 来源期刊: 力学学报（英文版）
• 学科: 物理学
• 年，卷（期）: 2002,（5）
• 页码范围: 516-527
• 页数: 12页
• 分类号: O3
• 语种: 英文

摘要

Micron-sized internal cracks were introduced into rounded bars ofpure iron by low cycle fatigue, and the cracks had irregular penny-shaped morphologywith the critical diameter of about 30μm and the thickness of 0.5～1.5μm. The initi-ation and propagation of the cracks were investigated quantitatively as well as theirlocation and geometry. After vacuum annealing of the samples fatigued, the mor-phology in a two-dimensional longitudinal section of cracks within grains had evolvedfrom initially elliptical one into arrays of spherical voids controlled by surface diffu-sion. Furthermore, a typical morphology for a broken crack with a center sphericalvoid surrounded by outer doughnut-like cavities was observed along a perpendicu-lar section of the specimen. Subsequently the spherical voids shrink and diminishgradually dominated by bulk diffusion. A physical model to heal an internal micro-crack was proposed, in particular for the various healing stages controlled by therelated dominant diffusion mechanism and their dependencies upon the morphologyand geometry of an original micro-crack in materials.