Precipitation of Al3Zr by two-step homogenization and its effect on the recrystallization and mechanical property in 2195 Al–Cu–Li alloys

To improve the recrystallization resistance of 2195 Al–Cu–Li alloys, we proposed a two-step homogenization (TS) to facilitate the homogeneous nucleation of Al₃Zr, and the effect of Al₃Zr precipitate on the recrystallization behavior and on the strength and ductility of 2195 alloys were investigated. It is shown that the first low-temperature homogenization in TS promotes the nucleation of Al₃Zr due to large driving force, and second high-temperature homogenization helps to accelerate diffusion process of Zr, resulting in fine and dense Al₃Zr distribution (radius of 22.6 ± 4.1 nm and number density of 1.94 × 10²⁰/m³). As a result, the recrystallization resistance of 2195 alloys is significantly improved comparing with those treated by the traditional one-step homogenization (OS). The TS alloys exhibits best yield strength (566.7 MPa), tensile strength (598.8 MPa) and elongation of 11.9% comparing with OS alloys. The strength improvement of TS 2195 alloys mainly originates from Orowan mechanism and grain refinement induced by Al₃Zr precipitate. The remained deformed lamellar structure in TS alloys effectively deflectes and zigzags the propagation of cracks, which is beneficial to the energy dissipation, leading to the enhancement of ductility.