Surface Segregation of Indium by Heat Treatment of Aluminium
| Periodical | Materials Science Forum (Volumes 519 - 521) |
|---|---|
| Main Theme | Aluminium Alloys 2006 - ICAA10 |
| Edited by | W.J. Poole, M.A. Wells and D.J. Lloyd |
| Pages | 673-678 |
| DOI | 10.4028/www.scientific.net/MSF.519-521.673 |
| Citation | Brit Graver et al., 2006, Materials Science Forum, 519-521, 673 |
| Online since | July, 2006 |
| Authors | Brit Graver, Antonius van Helvoort, John Charles Walmsley, Kemal Nisancioglu |
| Keywords | Depth Profiling, Microstructure, Segregation, Trace Elements |
| Price | US$ 28,- |
High temperature heat treatment of aluminium alloys causes surface enrichment of the trace elements in Group IIIA - VA, specifically the low melting point elements Pb, Bi, In and Sn. The phenomenon has practical significance in promoting certain types of localised corrosion, such as galvanic and filiform corrosion, while mitigating other types, such as pitting corrosion of the bare surface. The purpose of this paper is to investigate the surface enrichment and microstructure of indium relative to the available data for Pb. Model binary AlIn alloys, containing 20-1000 ppm of In, were used after heat treatment at various temperatures. In addition to electrochemical investigations, the microstructures were characterised by field emission scanning electron microscopy (FEG SEM) and field emission transmission electron microscopy (FEG TEM). Heat treatment at temperatures as low as 300ºC gave significant segregation of In as opposed to 600ºC for Pb. As a result of this and yet unresolved oxide film breakdown mechanism on aluminium, In was significantly more effective than Pb in anodically activating aluminium. These results suggest the possibility that significant activation earlier observed on certain commercial alloys as a result of low temperature heat treatment may be due to the trace elements In.
