Precipitation of Al<inf>3</inf>Zr 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.