Effects of thermomechanical treatment on grain refinement, second-phase particle dissolution, and mechanical properties of 2219 Al alloy

摘要

An improved thermomechanical treatment, which included 50% hot deformation at 440 degrees C, 10% cold pre-deformation at 25 degrees C, and a subsequent heat treatment (solution, 2.5% cold deformation and aging treatment), was performed on 2219 Al alloy forgings. For comparison, a 2219 Al alloy forging was also manufactured using the conventional process, which involved 50% hot deformation at 440 degrees C and a subsequent heat treatment. The evolution of the microstructures of the forgings during the treatments and their final mechanical properties were evaluated. A large number of Al2Cu particles were formed during the hot-deformation process. Further, tangled dislocation structures were formed around these particles after 10% cold deformation in the forging manufactured by the improved process, resulting in a significant grain refinement during the solution treatment because of particle stimulated nucleation as well as a weakened texture. In addition, more coarse Al2Cu particles dissolved into the Al matrix during the solution treatment in the case of the forging subjected to the improved treatment, because the tangled dislocation structures promoted the dissolution of these particles, thus increasing the density of the precipitates after T8-aging. The forging manufactured by the improved treatment exhibited a higher ultimate tensile strength (by 34.3 MPa), higher yield strength (by 43.2 MPa), and significantly lower anisotropy, as well as improved elongations in the axial and radial directions (lower-performance directions).