Precipitation Thermodynamics and Kinetics of the Second Phase of Al–Zn–Mg–Cu–Sc–Zr–Ti Aluminum Alloy

The precipitation thermodynamics and kinetics of the second-phase of the as-quenched Al–Zn–Mg–Cu–Sc–Zr–Ti alloy was investigated by hardness measurements, electrical conductivity, differential scanning calorimetry (DSC) and transmission electron microscopy (TEM). The results show that: 1) Both the GP zone and η′ phases are strengthening phases, and the strengthening effect of the η′ phase is dominant. The η phase decrease the hardness but increase the electrical electrical conductivity at high temperature. 2) The activation energy of GP zone, η′ phase and η phase are 118.80 kJ· mol−1, 105.74 kJ· mol−1 and 273.78 kJ· mol−1 respectively. The precipitation formulas are simulated and the precise equations are obtained, which match with experimental values well.