Nucleation of persistent slip bands in Cu single crystals under stress controlled cycling
- Univ. of Vienna (Austria)
The study of cyclic stress strain response of Cu-single crystals has been the subject of numerous investigations during the past decade. It was pointed out that the cyclic loading under certain conditions leads to strain localization zones of highly deformable material layers called Persistent Slip Bands (PSB). These PSB`s have been connected with the evolution of a characteristic dislocation substructure (ladder-like structure) and the formation of extrusion/intrusion slip markings on the specimen surface. Under the most frequently applied plastic-strain controlled cycling, a saturation plateau stress in the CSS-curve was observed. The resolved shear stress of this plateau was reported to be 28 MPa for single crystals of Cu oriented for single slip when cycled at room temperature. Kettunen reported results on Cu single crystals cycled under stress control with the desired stress amplitude reached in the first half-cycle. He found that PSB`s formed already at a shear stress amplitude as low as 17 MPa. Recent experiments with Cu-polycrystals showed that an increase in the length of the stress loading ramp resulted in an increase of the nucleating stress for PSB`s. For the case of direct loading a nucleation shear stress was calculated for values between 16 and 21 MPa depending on the constraint factor used to convert the stress values. Based on this knowledge the authors designed experiments on single crystal Cu specimens oriented for single slip under various loading ramp length (1--1,000 cycles) to study the nucleation conditions of PSB`s and the related saturation behavior.
- OSTI ID:
- 474223
- Journal Information:
- Scripta Materialia, Vol. 36, Issue 9; Other Information: PBD: 1 May 1997
- Country of Publication:
- United States
- Language:
- English
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