Characterizing precipitate evolution of an Al–Zn–Mg–Cu-based commercial alloy during artificial aging and non-isothermal heat treatments by in situ electrical resistivity monitoring

In situ electrical resistivity monitoring technique was employed to continuously evaluate the precipitate evolution of an Al–Zn–Mg–Cu-based commercial alloy during typical artificial aging treatments. The effects of artificial aging on the precipitates stability during non-isothermal heat treatments were also explored. Conventional hardness test, transmission electron microscopy and differential scanning calorimetry were also adopted to verify the electrical resistivity results. The results indicated that both the precipitation process and its timely rate could be followed by the monitored electrical resistivity during artificial aging treatments. The electrical resistivity results gave overall information on continuous precipitation and dissolution processes, especially under high heating rates. Samples artificial aging heat treated at 120°C for 24h followed by aging at 150°C for 24h presented more stable state and coarser precipitates than the samples only artificial aging heat treated at 120°C for 24h or triple artificial aging heat treated at 120°C/24h+195°C/15min+120°/24h. While the incoherent η precipitates in the samples artificial aging heat treated at 120°C for 24h followed by aging at 150°C for 24h were more easiness to coarsening and dissolve during non-isothermal heat treatments as well. •In situ electrical resistivity monitoring technique was employed on an Al-Zn-Mg-Cu alloy.•The precipitate evolution during typical artificial aging treatments was studied.•The precipitate stability during non-isothermal heat treatments was explored.•The electrical resistivity wonderfully monitored continuous precipitation and dissolution.•The alloy submitted to a T7 treatment presents a more stable state during heating due to incoherent η precipitates.