Cyclic deformation behavior of non-isoaxial copper tricrystals and bicrystals

Journal Article · Fri May 28 04:00:00 EDT 1999 · Acta Materialia

DOI:https://doi.org/10.1016/S1359-6454(99)00074-9· OSTI ID:357930

Jia, W P; Li, S X; Wang, Z G; Li, X W; Li, G Y ^[1]

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1. Chinese Academy of Sciences, Shenyang (China). State Key Lab. for Fatigue and Fracture of Materials

The cyclic hardening and saturation behaviors of copper tricrystals and bicrystals were investigated in strain-controlled multiple step tests. The results show that, for the inclined grain boundary (GB) bicrystal with single slip components, the cyclic stress strain (CSS) curve exhibits a plateau or quasi-plateau region, while the CSS curve of tricrystals shows no plateau. Observations of surface morphologies indicated that owing to the strain incompatibility of three grains, at lower strain amplitude the triple junction (TJ) retards obviously the primary slip in grains and makes deformation near it smaller than that near the bicrystal GB, while at higher strain amplitude slip can be distributed near the TJ homogeneously. The probability of crack initiation at the same TJ is closely related to the loading direction. The saturation dislocation structures of tricrystal specimens under the strain amplitude of the last step were explored by the electron channeling contrast technique in SEM (ECC-SEM). Loop patches with persistent slip band (PSB) ladders embedded were found even in the TJ vicinity for all grains. Dislocation-free zones (DFZ) occurred in the vicinity of TJ and GB, and the difference in shapes between them is due to the difference in internal stress field. Misoriented cell structure and dislocation wall structure were found near the crack tip, and the formation of them is associated with the cooperative action of crack tip, GB, grain orientation and the applied strain amplitude.

• OSTI ID: 357930
• Journal Information: Acta Materialia, Journal Name: Acta Materialia Journal Issue: 7 Vol. 47; ISSN 1359-6454; ISSN ACMAFD
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
COPPER
CRACKS
DEFORMATION
DISLOCATIONS
FATIGUE
POLYCRYSTALS
SLIP
STRAINS
STRESSES