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Lawrence Berkeley National Laboratory Recent Work Title HIGH-RESOLUTION OBSERVATIONS OF PENTAGONALLY-TWINNED PRECIPITATE NEEDLES IN ALUMINUM Permalink
| Content Provider | Semantic Scholar |
|---|---|
| Author | Dahmen, Ulrich Westmacott, Kenneth H. |
| Copyright Year | 2013 |
| Abstract | U. Dahmen and K.H. Westmacott National Center for Electron Microscopy Materials and Molecular Research Division Lawrence Berkeley Laboratory University of California Berkeley, CA 94720, U.S.A. Unusual pentagonally-twinned precipitates were observed in a high-resolution transmission electron microscopy (TEM) study of needle-shaped germanium particles in aluminum. Although commonly found in small particles foroed on substrates, such twinning has not been seen before in precipitates grown in the solid state. The morphologies and orientation relationships are consistent with symmetry principles. The morphology of a precipitate forming in a solid matrix is determined by mP-ny factors. Strain energy, interfacial energy, formation temperature and prior history are amongst the most important. The fundamental processes underlying a precipitation reaction have been treated using many different approaches; for example, thermodynamic, mechanistic, kinetic, elastic continuum, all of which illuminate various aspects of the problem. It has recently become more appreciated that considerable understanding of a precipitation process might be deduced from an analysis of the precipitate morphology and orientation relationship in terms of crystal symmetry operations.0-3) The present note gives a striking example of a precipitate morphology found in an Al-Ge alloy and a discussion of a preliminary analysis based on symmetry considerations. The aluminum-rich end of the Al-Ge phase diagram is particularly simple. A decreasing solubility with decreasing temperature gives it characteristics typical of age-hardening systems. In dilute alloys (1.14 at% in the present work) |
| File Format | PDF HTM / HTML |
| Alternate Webpage(s) | https://cloudfront.escholarship.org/dist/prd/content/qt5z52f7p9/qt5z52f7p9.pdf?t=p0gj7j |
| Language | English |
| Access Restriction | Open |
| Content Type | Text |
| Resource Type | Article |
