Double-peak age strengthening of cold-worked 2024 aluminum alloy

• Published in: Acta materialia 2013-03, Vol.61 (5), p.1624-1638
• Main Authors: Zhao, Y.L., Yang, Z.Q., Zhang, Z., Su, G.Y., Ma, X.L.
• Format: Article
• Language: English
• Subjects: 2024 Al alloy; Age strengthening; Applied sciences; Ductility; Exact sciences and technology; Mechanical properties and methods of testing. Rheology. Fracture mechanics. Tribology; Metals. Metallurgy; Precipitation; Ω-phase
• ISSN: 1359-6454; 1873-2453
• DOI: 10.1016/j.actamat.2012.11.039

The microstructure and mechanical properties of a 2024 Al alloy subjected to different levels of cold-rolling at room temperature and their evolution upon ageing at 453K were investigated by means of microhardness measurements, tensile tests and transmission electron microscopy. The cold-worked 2024 Al alloy showed double-peak age strengthening behavior. After ageing for 120min, the samples reached the first peak strength with quite low ductility. However, simultaneous high strength and ductility were achieved by prolonged ageing of 720min. The first strengthening peak is due to the precipitation of fine S′ precipitates. The optimized mechanical properties of high strength and suitable ductility are attributed mainly to the precipitation of Ω-phase particles at the expense of S′ precipitates after ageing for 720min. The Ω precipitates are effective in dislocation pinning and accumulation, and they can undergo plastic deformation to some extent, leading to simultaneously improved tensile strength, work-hardening ability and ductility. The present finding sheds light on the development of processing techniques to optimize the mechanical properties of 2024 Al alloy.