DISLOCATIONS AND PERSISTENT SLIP BANDS IN COPPER SINGLE CRYSTALS FATIGUED AT LOW STRESS AMPLITUDE

Persistent slip bands in fatigued copper single crystals are studied by means of transmission electron microscopy of surface thin foils, both parallel and nonparallel to the surface. Comparing the observations from the different nonparallel sections a three‐dimensional model of the internal structure may be constructed. Dislocations with all six possible Burgers vectors of the type 1/2 〈0011〉 are found in the structure. This demonstrates the microscopic action of the secondary slip systems during the low stress fatigue. The macroscopic action of the secondary systems, which is connected with the cell structure formation, is typical for the high stress fatigue. Surface extrusions are found to be related to the dislocation structure below the surface. Copyright © 1968 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim