Abstract
This work on the Al-1 to 4%Cu alloys was made mainly by means of electric resistivity and hardness measurements. All the alloys have a region in which electric resistivity is unchanged on the resistivity-aging time curves (flat-region). The electric resistivity in this region (flat-value, ρflat) depends on aging temperature. This can be explained as; ρflat = contribution of solute concentration, ρM + contribution of G.P. zone, ρG.P.. Alloys with various solute concentrations have peculiar constant flat-values above certain temperatures, which are considered to be the limit-temperature for G.P. zone formation (Tlimit)and are respectively 90°C for 1%Cu, 150°C for 2%Cu, 220°C for 3%Cu and 270°C for 4%Cu alloys.
