PLASTIC BEHAVIOR OF COPPER SHEETS DURING SEQUENTIAL TENSION TESTS

• Type: Article in International Scientific Journal
• Date: 1991

Authors

Schmitt, JH (Author) Other; Fernandes, JV (Author) Other; Gracio, JJ (Author) Other; Vieira, MF (Author) Other; Vieira, MF (Author) FEUP

Journal

The Journal is awaiting validation by the Administrative Services.

Title: MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING

Vol. 147

Pages: 143-154

ISSN: 0921-5093

Indexing

ISI Web of Knowledge - 60 Citations

Scopus - 63 Citations

Other information

Authenticus ID: P-007-5E3

DOI: 10.1016/0921-5093(91)90840-j

Resumo (PT): Sequences of two uniaxial tension tests along different axes were performed on a polycrystalline copper sheet. In order to reach a better understanding of the physical mechanisms occurring during the second deformation, the effect of the strain path change on subsequent yield and flow behaviour has been investigated using optical and transmission electron microscopy. The value of the reloading yield stress is a function of the angle between the two tensile axes. For ? > 15° the requirement of glide of dislocations with a new Burgers vector implies that a very low density of potentially mobile dislocations is available at the beginning of the reloading deformation. This effect is moderated at ? values of about 90° by the inverse activity on some slip systems during reloading. The transient observed in the workhardening behaviour after the path change is concomitant with the disappearance of some dislocation walls developed during the prestrain. A more homogeneous dislocation substructure appears for ? > 15° as a result of the interactions between the mobile dislocations on the new active slip systems and the previous dislocation walls; the dissolution of the previous dislocation arrangement is also promoted by the inversion of the slip direction in some systems, depending on the value of the angle ?. This results in an increase in dynamic recovery rate during the early stage of reloading, particularly when ? approaches 90°.

Abstract (EN): Sequences of two uniaxial tension tests along different axes were performed on a polycrystalline copper sheet. In order to reach a better understanding of the physical mechanisms occurring during the second deformation, the effect of the strain path change on subsequent yield and flow behaviour has been investigated using optical transmission electron microscopy. The value of the reloading yield stress is a function of the angle-PHI between the two tensile axes. For PHI > 15-degrees the requirement of glide of dislocations with a new Burgers vector implies that a very low density of potentially mobile dislocations is available at the beginning of the reloading deformation. This effect is moderated at PHI-values of about 90-degrees by the inverse activity on some slip systems during reloading. The transient observed in the work-hardening behaviour after the path change is concomitant with the disappearance of some dislocation walls developed during the prestrain. A more homogeneous dislocation substructure appears for PHI > 15-degrees as a result of the interactions between the mobile dislocations on the new active slip systems and the previous dislocation walls; the dissolution of the previous dislocation arrangement is also promoted by the inversion of the slip direction in some systems, depending on the value of the angle-PHI. This results in an increase in dynamic recovery rate during the early stage of reloading, particularly when PHI approaches 90-degrees.

Language: English

Type (Professor's evaluation): Scientific

No. of pages: 12