No abstract

The development of persistent slipband topography, crack nucleation, and crack growth in fatigued copper single crystals was studied by an new section technique, which reveals surface topographies with a resolution of 20 nm. Experiments were performed in air, oxygen, hydrogen, water vapor, high vacuum, and ultrahigh vacuum in order to study the influence of the environment on these processes. The development of persistent slipband topography, including intrusions, extrusions, and the protrusion of the whole persistent slipband, does not depend on environment. Crack nucleation and early propagation, however, do strongly depend on the environment. Intrusions can also be distinguished from crack nuclei by their finite vertex angle of approximately 30 deg. Quantitative data of the average protrusion growth as well as crack growth are presented. Chains of large voids were found in high vacuum and ultrahigh vacuum along the trace of the primary slip plane and are interpreted as remnants of rewelded Stage I cracks.

No abstract