Dynamic observation of the FCC to 9R shear transformation in a copper {Sigma} = 3 incoherent twin boundary
- Lawrence Livermore National Lab., CA (United States). Chemistry and Materials Science Directorate
- Sandia National Labs., Livermore, CA (United States). Surface and Microstructure Research Dept.
- Univ. of Minnesota, Minneapolis, MN (United States). Dept. of Chemical Engineering and Materials Science
The {Sigma} = 3 (2{ovr 11}) incoherent twin boundary in gold, silver and copper has been observed to have a dissociated structure that can be described as a narrow slab of 9R-stacked material, on the order of 1 nm thick, between two blocks of FCC material. The 9R stacking serves as an intermediate stacking arrangement that reverses the ABC stacking to CBA and is equivalent to an FCC stacking of {l_brace}111{r_brace} planes with an intrinsic stacking fault inserted at every third plane. It has been thought that the 9R structure is stabilized at these interfaces because of the low stacking fault energies of these materials (Au: 32 mJ/m{sup 2}; Cu: 45 mJ/m{sup 2}; Ag: 16 mJ/m{sup 2}); in aluminum, which has a much higher stacking fault energy (Al: 166 mJ/m{sup 2}), the boundary is more compact. Nevertheless, questions remain as to the significance of the width of the boundary dissociation, and in particular, the degree to which this width depends upon factors other than the stacking fault energy. Recent atomistic simulations have predicted that the width of the 9R phase at the incoherent twin boundary should depend quite sensitively upon the state of shear loading parallel to the interface. In this paper the authors present high-resolution transmission electron microscopy (HRTEM) observations of such a shearing process in a copper {Sigma} = 3 bicrystal. These observations provide insight into the dynamics and structural stability of the 9R interfacial phase.
- Research Organization:
- Sandia National Laboratories (SNL), Albuquerque, NM, and Livermore, CA (United States)
- DOE Contract Number:
- AC04-94AL85000; W-7405-ENG-48
- OSTI ID:
- 382484
- Journal Information:
- Scripta Materialia, Vol. 35, Issue 7; Other Information: PBD: 1 Oct 1996
- Country of Publication:
- United States
- Language:
- English
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