Novel AlCu solute cluster precipitates in the Al–Cu alloy by elevated aging and the effect on the tensile properties

• Published in: Materials science & engineering. A, Structural materials : properties, microstructure and processing Vol. 862; p. 144454
• Main Authors: Dong, Xiongbo, Guo, Yongchun, Wang, Jianli, Xia, Feng, Ma, Kaidi, Duan, Hongbo, Yang, Zhong, Wang, Ping, Liang, Minxian, Li, Jianping
• Format: Journal Article
• Language: English
• Published: Lausanne Elsevier B.V 18.01.2023; Elsevier BV
• Subjects: Aging; Aging (metallurgy); Alloys; Aluminum alloys; Aluminum base alloys; Atomic clusters; Copper; Electron microscopes; Heat treatment; High resolution; High resolution electron microscopy; High temperature; L12; Microstructure; Precipitates; Re-aging; Scanning electron microscopy; Scanning transmission electron microscopy; Solute clustering strengthening; Tensile properties; Tensile strength; Transmission electron microscopy; Transmission electron microscopy (TEM); Solute clustering strengthening; Aluminum alloys; L12; Re-aging; Transmission electron microscopy (TEM)
• ISSN: 0921-5093; 1873-4936
• DOI: 10.1016/j.msea.2022.144454

This study examines the precipitation of AlCu solute clusters by re-aging at high temperatures for a long time. It provides evidence for their long-term stable existence in the range of 25–450 °C. In this study, T6 heat-treated Al–4Cu alloys were aged at 350 and 420 °C for 100 h, respectively. The microstructure characteristics of the alloys, corresponding to three kinds of treatments were examined using scanning electron microscopy, high-resolution transmission electron microscopy, and high-resolution scanning transmission electron microscopy. Two types of AlCu solute atomic clusters precipitate during the two re-aging processes. One is disordered clusters precipitated by aging at 350 °C for 100 h, and the other is L12 ordered clusters precipitated by aging at 420 °C for 100 h. Face centered cubic (Al)+L12(AlCu cluster) microstructure was successfully prepared by re-aging at 420 °C for 100 h. Owing to this microstructure, the tensile strength and yield strength of the re-aged alloy at 420 °C was higher than that of the re-aged alloy at 350 °C. The structure and composition of the L12 AlCu solute clusters were studied using transmission electron microscopy and its energy-dispersive X-ray spectrometry. The atoms belonging to the cluster mostly adapt to the Al lattice positions, and few atoms are located in the interstitial position of FCC Al. In this study, utilizing AlCu solute clusters is proposed as a novel and promising approach for designing heat-resistant Al–Cu system alloys.