Investigation of plastic flow in constrained copper crystals
- Stony Brook Univ., NY (United States)
Comparative studies of the changes in microstructure and micro- relaxation parameters were made between high-purity copper single crystals and identical single crystals which had a surface modification. The latter specimens had a fine-grain polycrystalline surface zone 20 to 40 microns thick, which was produced by controlled deformation and subsequent recrystallization. Such a zone meets the requirements of interface cohesion and is identical to the substrate in chemical composition and elastic parameters. Crystals with the surface zone exhibit a tripling of the yield stress and a Stage I work-hardening rate not much lower than that of Stage II. Relaxation data for modified crystals showed large recovered strains (about an order of magnitude larger than that for single crystals) up to prestrains of 10/sup -3/. Above this prestrain the recovered strain was essentially the same as for copper single crystals in Stage I. Results of forest dislocation etch pit studies in conjunction with the findings indicate that for constrained crystals, dislocations tend to be blocked below the coating/ substrate interface. These dislocations cause stress concentrations (mostly due to screw dislocations), thereby playing a major role in producing an observed forest dislocation build-up. Some comparative studies were also made on copper plated single crystals.
- Research Organization:
- Stony Brook Univ., NY (United States)
- Sponsoring Organization:
- US Atomic Energy Commission (AEC)
- NSA Number:
- NSA-29-004741
- OSTI ID:
- 4408799
- Report Number(s):
- COO--3476-5
- Country of Publication:
- United States
- Language:
- English
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