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The processability and final mechanical properties of Al-Li alloys are strongly affected by the uniformity of solute element and the degree of recrystallization, which can be improved via homogenization treatments. It is essential to control the microstructure to achieve the desired properties. In this work, the optimal double-step homogenization (DH) parameters for as-cast 2195 Al-Li alloy were first determined as 460 °C/16 h + 515 °C/20 h according to the comparative analysis, which fitted well with the results predicted by the corresponding kinetics modeling. Compared with the conventional single-step homogenization (SH), DH not only prevented the occurrence of overburning but also provided a more favorable condition for Al 3 Zr dispersoids to precipitate uniformly. The size and number density of Al 3 Zr dispersoids in the DH sample are finer and higher than those in the SH sample based on quantitative statistics. Due to the sufficient driving force for nucleation, the precipitate free zone (PFZ) of Al 3 Zr dispersoids was much narrower after DH. As a result, the DH sample possessed a higher Zener drag pressure, leading to a remarkable inhibition on the continuous evolution of substructures. Therefore, the recrystallization behavior in the DH sample was impeded effectively during the subsequent solution treatment. These findings are expected to provide reliable theoretical guidance for the industrial processing of as-cast 2195 Al-Li alloy. • Optimal double-step homogenization parameters were determined according to the microstructure and kinetics analysis. • Effect of homogenization on the precipitation and recrystallization behavior were quantified by HAADF-STEM and EBSD. • Fine, dense and well-distributed Al 3 Zr dispersoids with narrower PFZ were obtained via double-step homogenization. • The recrystallization resistance of 2195 Al-Li alloy can be effectively enhanced via double-step homogenization. [ABSTRACT FROM AUTHOR]

• The influences of Cu content on microstructure evolutions and fatigue crack propagation behaviors of Al-Cu-Li alloys were firstly investigated. • The influences of secondary particle and recrystallized grain structure on the crack initiation has been discussed. • The relationship between crystal orientation and crack path deflection and its influences on the fatigue crack propagation has been discussed in detail. The fatigue crack propagation (FCP) behaviors of Al-Cu-Li cold-rolled sheets with different Cu contents were assessed systematically. The increase of Cu contents significantly reduces the threshold value of fatigue crack growth as secondary particles induce the initiation of microcracks, and provides more opportunities for crack deflection due to finer recrystallized grains. Moreover, Brass-orientated grains with low Schmid factor force the crack to change the direction of propagation, which prevents further crack propagation. Compared to Goss-orientated grains with small tilt and twist angle, cracks prone to deflect at its boundaries with large tilt angles difference between the adjacent grains. [ABSTRACT FROM AUTHOR]

• TTP and TTT diagrams of 2050 Al-Li alloy have been established. • The microstructure evolutions during interrupted quenching have been in-depth investigated. • The effects of microstructure evolution on tensile properties under different cooling rates has been investigated using cold-rolled thin sheets. The quench sensitivity of 2050 Al-Cu-Li alloy was determined by the time-temperature-transformation (TTT) curves and time-temperature-property (TTP) curves based on conductivity and hardness. Additionally, a novel end quenching test was used to investigate the quench sensitivity of cold-rolled sheets with a thickness of 2 mm which cannot be tested by conventional methods. The microstructure evolution during interrupted quenching (IQ) treatment and end quenching test was studied by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The precipitation and coarsening of Cu-rich phases during quenching are the main factors affecting the quench sensitivity of the alloy. Meanwhile, these Cu-rich phases lead to the uneven distribution of precipitates (T 1 and θ′), which results in the decreased tensile properties. The influence of precipitate free zones (PFZs) on elongation during end quenching test was clarified and the high quench sensitive temperature zone was found to be 260 ~440 °C. This work can help to optimize the quenching process and improve the mechanical properties of the 2050 Al-Cu-Li alloy. [ABSTRACT FROM AUTHOR]