2013 Volume 54 Issue 10 Pages 1898-1904
The characteristic age-hardening response of Al–3.0Mg–1.0Cu (mass%) alloys with and without Ag addition has been investigated by the hardness measurement, differential scanning calorimetry (DSC) and electrical resistivity measurement. The alloy compositions locating in the (α+S+T) phase field of the Al–Mg–Cu phase diagram are known to be effective to harden in two stages separated by a distinct and often prolonged hardness plateau. The first stage of hardening occurs very rapidly (e.g., within 60 s at 443 K) and contributes to increase hardness as much as 50% of the total age-hardening. After the first stage of hardening, a clear plateau stage is observed in the hardness curve. In the low temperature aging, the characteristic incubation stage at which no clear hardness increase and electrical resistivity increase appears for a long time before the first stage of hardening. The origin of the both incubation and plateau stages is discussed based on the nanocluster formation and vacancies. The influence of the Ag addition on the precipitation behavior is also discussed in terms of the atom-atom interaction.
