Transmission electron microscopy observations on the microstructure of naturally aged Al–Mg–Si alloy AA6022 processed with an electric field
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The influence of an electric field applied during the solution heat treatment and during a short subsequent initial natural aging of AA6022 on the nature of the precipitates which occurred after natural aging for a long time (2–3 years) was determined employing transmission electron microscopy and selected area electron diffraction. The precipitates were spherical in shape ranging from 2 nm to 40 nm in diameter d p with an average of 7.9 nm. Their average size was larger than that (4.9 nm) in a specimen processed without field and their size distribution had a greater number of precipitates with d p>∼3 nm. Moreover, their crystal structure differed from that in specimens processed without a field. The increase in yield stress which occurred with the electric field treatments is attributed to an increase in the interaction force between the precipitates and dislocations, which resulted from the larger size and different crystal structure of the precipitates by the field.
KeywordsHigh Resolution Transmission Electron Microscopy Select Area Electron Diffraction High Resolution Transmission Electron Microscopy Natural Aging Select Area Electron Diffraction Pattern
This research was funded by the U.S. Army Research Laboratories and the U.S. Army Research Office under Award DAA1902-1-0315 with Dr. William Mullins as contract monitor. The authors also wish to thank Dr. R. Ramage, Alcoa Technical Center, for providing the AA6022 material and Dr. D. Lloyd, Novelis Global Technology Center, for the chemical analysis and helpful discussions. We also wish to thank Ms. R. O’Connell for typing the manuscript.
- 1.Jung K, Conrad H (2004) J Mater Sci 39:6481Google Scholar
- 2.Conrad H, Jung K (2004) Z f Matallkde 95:352Google Scholar
- 3.Conrad H, Jung K, Unpublished research North Carolina State University (2004)Google Scholar
- 5.Pashley DW, Rhodes JW, Sendorek A (1966) J Inst Mat 94:41Google Scholar
- 6.Miao E, Laughlin DE (2000) Metall Mater Trans A 31A:361Google Scholar
- 7.Murayama M, Hono K, Miao WF, Laughlin DE (2001) Metall Mater Trans A 32A:239Google Scholar
- 10.Zhuang L, Janse JE, De Smer P, Chen JH, Zandberger HW, in Aluminum 2001: Proc. TMS 2001 Aluminum, Automotive and Joining Sessions, TMS Warrendale, PA (2001), p 77Google Scholar
- 11.Matsuda K, Uetani Y, Sato T, Ikeno S (2001) Matell Mater Trans A 32A:1293Google Scholar
- 14.Weatherly GC, Perovic A, Mukhopadhyay NK, Lloyd DJ, Perovic DD (2001) Metall Mater Trans A 32A:21Google Scholar
- 15.Esmaeili S, Wang X, Lloyd DJ, Poole WJ (2003) Metall Mater Trans A 34A:751Google Scholar
- 17.JCPDS-ICDD data base: PDF-2 Data Base (Sets 1–39) PDF-2 39 6A June 89 (1989)Google Scholar