The Aging Behavior of Aluminum-Lithium Alloy 2A97

The evolution of microstructures and properties of aged 2A97 alloy at 165 degrees C after quenching, and at 135 degrees C after quenching and 4% plastic deformation for various times were investigated. The results show that theta ''/theta' and delta' phases are the main strengthening phases of aged alloy at 165 degrees C for 18 h after quenching, which shows high tensile strength and ductility resulting from increasing amount of T-1 phase distributed heterogeneously in matrix. With increasing aging time at 165 degrees C, the number density of theta ''/theta', T-1, and delta' increase, and the length of T-1 decreases, while the length of theta ''/theta' increases. Stretch before aging fines the size of theta ''/theta' and T-1, and stimulates the precipitation and uniform distribution of them, so it yields higher strength for the alloy aged at 135 degrees C for 36 h after quenching and stretch, which is 441 MPa, 519 MPa, and 7.4% for sigma(0.2), sigma(b), and sigma(5), respectively, than the alloy aged at 165 degrees C after quenching.