Dislocation microstructures and surface morphology in fatigued fine-grained copper polycrystals

Abstract

Transmission electron microscopy observations of the dislocation substructure in fine-grained copper polycrystals fatigued at room temperature were carried out to investigate the correlation between surface morphology and the underlying dislocation substructure. The results indicate that samples fatigued under constant plastic strain amplitude well into the saturation region develop a small-scale surface roughness. The volume fraction of persistent slip band (PSB)-type structures is extremely low. PSB structures formed by the dominant slip system are observed only within narrow twin grains and are associated with an extrusion-like surface profile. The results are interpreted in terms of the size effect that allows one dominant slip system to operate in the plane parallel to a coherent twin boundary.

Acknowledgements

It is our privilege to dedicate this article to the late Professor Basinski who encouraged us to work on this problem. He was generous with his time and with his knowledge and experience. We wish to express our gratitude to Ms S.J. Basinski and to the reviewers for very constructive comments on the manuscript. One of the authors (H.K.) would like to thank Professor Takasugi at Osaka Prefectural University for his support in preparing specimens and chemical analysis and to graduate students at Yonago National College of Technology for their effort to improve grain-refining methods in the course of their graduation studies. The financial support of the Natural Sciences and Engineering Research Council (Canada) is also gratefully acknowledged.