Microstructural evolution after creep in aluminum alloy 2618

• Published in: Journal of materials science 2012-03, Vol.47 (6), p.2541-2547
• Main Authors: Du, Z. W., Wang, G. J., Han, X. L., Li, Z. H., Zhu, B. H., Fu, X., Zhang, Y. A., Xiong, B. Q.
• Format: Article
• Language: English
• Subjects: Aging; Aging (metallurgy); Alloys; Aluminum; Aluminum base alloys; Characterization and Evaluation of Materials; Chemical precipitation; Chemistry and Materials Science; Classical Mechanics; Clusters; Copper; Creep (materials); Crystallography and Scattering Methods; Dislocations; Evolution; Heat treating; High resolution electron microscopy; Magnesium; Materials Science; Microscopy; Microstructure; Nickel; Phases; Polymer Sciences; Precipitates; Precipitation; Solid Mechanics; Specialty metals industry; Transmission electron microscopy
• ISSN: 0022-2461; 1573-4803
• DOI: 10.1007/s10853-011-6077-4

The microstructural evolution of Al–2.24 Cu–1.42 Mg–0.9 Fe–0.9 Ni (AA2618) alloy after 195 °C/18 h aging, as well as after 180 and 240 °C/100 h creep, has been studied by transmission electron microscopy and high resolution electron microscopy (HREM). The Guinier–Preston–Bagaryatsky (GPB) zones/co-clusters, S″, S, and Al 9 FeNi phases co-exist in the alloys after the 195 °C/18 h aging. After creep, precipitates become coarser and the transformation of GPB zones/co-clusters and S″ to S phase take place. A large number of GPB zones/co-clusters as those in aging state exist after 180 °C/100 h creep which possibly dynamically precipitates during the creep process. After the 240 °C/100 h creep, most of the precipitates are S variants with a few GPB zones and S″ phase. More dislocations appear upon which precipitate colonies form after creep. HREM images show that most of the early precipitates less than about 5 nm cannot exhibit perfect lattice image for the existence of stress. However, certain GPB/co-clusters possessing coherent relationship with the matrix can also be observed. HREM demonstrates that certain S particles viewed along [100] S and [013] S have classic orientation relationship with the matrix, and that those upon the dislocations depart from the standard orientation.