A Resistometric study of zone Formation in Al-Cu-Mg alloys

The kinetics of zone formation in Al-3wt% Cu-1wt% Mg alloy, with or without trace impurities like Si and Fe and trace addition of Ag, has been studied by resistivity technique. In these alloys an undercooling of 10-15°C below zone solvus temperature is necessary for homogenous nucleation of zones. Strong solute-vacancy interactions are present in these alloys. At temperatures above 130°C, clustering mechanism does not change with temperature. Si influence zone formation possibly by being present in the zones. Further addition of 0.23% Ag alters the ageing response totally. The mechanism of action of Ag is to some extent similar to that of Si. (Shri S.K. Pabi, Lecturer, Materials Science Centre, I.I.T., Kharagpur)