Interface structure of faceted lath-shaped Cr precipitates in a Cu-0.33 wt% Cr alloy
- Lawrence Berkeley National Lab., CA (United States). National Center for Electron Microscopy
The interface structure of lath-shaped, faceted Cr-rich precipitates in a Cu-0.33 wt% Cr alloy was investigated by transmission electron microscopy using diffraction contrast and weak beam dark field imaging techniques. The lath axis was aligned precisely with the [5{bar 6}1]{sub f} invariant line direction, and its cross-sectional shape was characterized by four distinct facets with different defect contents. The major facet near (335){sub f} appeared defect-free. The (111){sub f} and (552){sub f} facets showed a single set of ledges with a step height of {approximately}1.1 nm and an associated displacement vector along {approximately}[335]{sub f}. The curves {approximately}(44{bar 3}){sub f} side facets contained an array of dislocations spaced {approximately}8.1 nm apart with a Burgers vector that could reasonably be characterized as 1/3[111]{sub f} or 1/2[110]{sub b}, i.e. as d.s.c. lattice dislocations accommodating the misfit in interplanar spacing of the parallel close-packed planes in the two phases. A detailed model of the interface is in excellent agreement with the observed defect structure and the previously determined crystallographic characteristics. The model shows that the major facet near (335){sub f} which appears to be defect free, actually contains a closely spaced array of dislocations in near-screw orientation. The uniform ledge height of {approximately}1.1 nm in all interfaces is the plane spacing of the primary O-lattice planes of Zhang and Purdy.
- Sponsoring Organization:
- USDOE, Washington, DC (United States)
- DOE Contract Number:
- AC03-76SF00098
- OSTI ID:
- 616252
- Journal Information:
- Acta Materialia, Vol. 46, Issue 6; Other Information: PBD: 23 Mar 1998
- Country of Publication:
- United States
- Language:
- English
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