Density changes of iron during morphological healing evolution of internal fatigue microcracks

作者：Zhang HL^*; Gao L; Sun J

来源：Metallurgical and Materials Transactions A-Physical Metallurgy and Materials Science, 2003, 34A(12): 2925-2933.

DOI：10.1007/s11661-003-0192-z

Plastic-strain-controlled fatigue was performed on pure iron specimens with uniaxial symmetric tension-compression loadings at room temperature. The as-fatigued specimens were then annealed in vacuum at 1173 K from I to 7 hours. The morphologies of internal fatigue microcracks were observed by scanning electron microscopy (SEM) in the as-fatigued and as-annealed specimens. The density of the specimens was measured with an electronic analytical balance. The density of the as-fatigued specimens decreased continuously as the fractional fatigue life increased, and was nearly constant when the specimens were annealed up to 2 hours at 1173 K, but increased gradually after 2 hours of annealing time. The density of some specimens eventually approximates to the value of rho(0), the initial density, at 7 hours of annealing time. This suggests that the initial decrease in density is due to crack initiation and propagation in the as-fatigued specimens. At the early stage of annealing, the specimen density is nearly constant because the crack morphological change is controlled by surface diffusion. At the later stages, the density increases and finally returns to the initial density because the spherical voids evolved from the parent crack are reduced by volume diffusion coupled with grain-boundary diffusion. A combined model is presented to predict the shrinkage of the spherical voids within the specimens, and is in broad agreement with the experimental data.

• 出版日期2003-12
• 单位西安交通大学