Tetragonal-prism-like Guinier–Preston–Bagaryatsky zones in an AlCuMg alloy

In high-performance AlCu(Li)Mg aluminum alloys, Guinier–Preston–Bagaryatsky zones frequently form upon thermal ageing and play an important role in hardening the alloys. Here we report a novel type of highly-symmetric Guinier–Preston–Bagaryatsky zones formed in a high Cu-content AlCuMg alloy. Using atomic-resolution electron microscopy and first-principles calculations, we precisely characterized their morphology and structures. It is shown that these precipitates undergo three stages of structural and compositional evolution, leading to formation of these tetragonal-prism-like one-dimensional precipitated crystals and their early-stage precursors.