Microstructural evolution of Al2Cu phase and mechanical properties of the large-scale Al alloy components under different consecutive manufacturing processes

The large-scale Al alloy components are usually manufactured based on the ultra-large Al ingots through different manufacturing processes, i.e. direct-chill (DC) ultrasonic casting, multidirectional forging (MF), and solution-aging treatment (SAT). The Al2Cu particles with different microstructural features significantly affect the mechanical properties of such large-scale Al alloy components. In the present work, an ultra-large cylindrical 2219 Al alloy ingot (with a diameter of 1380 mm and a length of 3700 mm) was cast using ultrasonic casting technology. Then, the ingot experienced a MF process, followed by a slight SAT. The continuous microstructural variation across DC casting, MF process and SAT was examined regarding this ultra-large ingot, particularly for different types of (theta, theta' and theta '') Al2Cu particles. Al2Cu particles mainly developed from solidification, precipitation and the MF-stimulated fragmentation. Most of the Al2Cu particles fragmented from theta-Al2Cu/alpha-Al eutectic networks still retained after SAT, but with partial dissolution. Other types of theta'- and/or theta ''-Al2Cu particles were nearly dissolved into the alpha-Al matrix. SAT improved the ultimate tensile strength and the yield strength while MF evidently increased elongation. However, casting generated very low tensile strength. Further, the correlation between Al2Cu particles and mechanical properties was accordingly discussed. (C) 2019 Elsevier B.V. All rights reserved.