New Concepts for the Enhancement of High Strength Aluminum Alloy Properties.
DUKE UNIV DURHAM NC DEPT OF MECHANICAL ENGINEERING AND MATERIALS SCIENCE
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The precipitation processes in aluminum alloys are well understood and the identification and analysis of those precipitates primarily responsible for the strengthening effects during precipitation heat treatment is reasonably complete. Less well understood, however, are the roles played by the minor alloying elements involved in the formation of metalloids, dispersoids, and insolubles which are important in controlling, among other things, fineness of grain structure, and the formation of precipitate free zones around grain boundaries. Previously, the study of most of these compounds has been necessarily performed through in situ methods, although anodic dissolution of aluminum alloys in strong acids, or simple dissolution in solutions of iodated methanol have been tried. In addition, extraction-replica techniques have been used to produce small samples of extracted phases for electron microscopy. While a great variety of both chemical and electrochemical methods have been developed for the extraction of secondary phases from steels and nickel-base alloys, until recently, no equivalent anodic dissolution techniques using a relatively inactive electrolyte have been available for aluminum alloys. It has lately been found, however, that methanolic solutions of benzoic acid, oxine and chloroform can be used to selectively remove the aluminum alloy matrix by galvanostatic anodic dissolution, while leaving second phase particles intact.
- Metallurgy and Metallography