Cyclic deformation behavior of Cu-30% Zn single crystals oriented for single slip. 2: Dislocation structures
- Univ. of Toronto, Ontario (Canada). Dept. of Metallurgy and Materials Science
- Chinese Academy of Science, Shenyang (China)
The dislocation structures of Cu-30% Zn single crystals cyclically deformed at {gamma}{sub pi} = 3.8 {times} 10{sup {minus}5}--6.4 {times} 10{sup {minus}3} were studied through transmission electron microscopy in order to understand the cyclic deformation mechanisms of the material. It has been shown that the fatigue dislocation structures have two basic configurations depending on the strain amplitude applied. At low strain amplitudes ({gamma}{sub pi} < 3 {times} 10{sup {minus}4}), the dislocation structure is characterized by dislocation segments and multipoles, very similar to that formed in stage 1 of tensile deformation in the same material. At high strain amplitudes ({gamma}{sub pi} > 3.0 {times} 10{sup {minus}4}), however, the dislocation structure is dominated by planar dislocation loops and tangles, in this case a small amount of dislocation multipoles and a special zigzagged structure are also detected. Secondary slips were found to be activated from a very low strain amplitude ({gamma}{sub pi} = 3.8 {times} 10{sup {minus}5}). This behavior is attributed to (1) the lower stress for dislocation generation compared with cyclic flow stresses and (2) heterogeneous deformation at low strain amplitudes that results in a weak effect of local latent hardening. Cyclic deformation mechanisms at low and high strain amplitudes have been discussed in terms of the motion of dislocation multipoles and the dislocation reactions between the primary and secondary slip systems. The critical strain amplitude for the transition of the deformation mechanisms has been also theoretically determined to be 3 {times} 10{sup {minus}4}, in good agreement with results on the cyclic deformation response and the features of dislocation structures. The formation of specific dislocation structures such as the zigzagged structure has been discussed with detailed dislocation mechanisms.
- OSTI ID:
- 328289
- Journal Information:
- Acta Materialia, Vol. 47, Issue 1; Other Information: PBD: 11 Dec 1998
- Country of Publication:
- United States
- Language:
- English
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