Effect of pre-rolling and aging temperature on the microstructure and mechanical properties of creep-aged 2050 Al–Li alloy

The influences of aging temperatures (160-200 °C) and 8% pre-rolling on the mechanical properties, and microstructures of the creep-aged AA2050 alloys were investigated. The results show that for the solid-solutioned alloys after the creep aging, the strength increased with an increase of aging temperatures. The ultimate tensile strength (UTS) and yield strength (YS) reached the highest value of 527 and 484 MPa at 200 °C, respectively, although the elongation (EL) reduced to 10.8%. At expense of σ phases, the temperature increase promoted the dislocation accumulation and the dense precipitation of θ′ and T1 phases, which increased the strength. It is noted that the strong oriented precipitation at 200 °C lost some strengthening effect. After the 8% pre-rolling, the strength of creep-aged alloys increased firstly and then decreased with the increase of temperature. The high strength (UTS=574 MPa, YS=535 MPa) at 180 °C was attributed to the dense precipitation of T1 phases under the action of diffusion kinetic and thermodynamic driving force. When the temperature reached 200 °C, the activated ledge mechanism significantly thickened T1 phases, thus decreasing the strength. The work revealed the critical roles of aging temperature and pre-rolling in tailoring precipitation behaviors and mechanical performance of Al-Li alloys, paving a way in designing creep-aged Al-Li alloys with the superb mechanical properties.