The effect of Cu addition on the precipitation and redissolution in Al-Zn-Mg alloy by the differential dilatometry

With the aim to determine the effect of the addition of micro-constituents (copper and magnesium, essentially the copper) on the phenomena of phase transformation and kinetic of precipitation in an Al-Zn-Mg alloy we proceeded to study the effect of addition of Cu and Mg by dilatometry and measurements of microhardness. The results show that the addition of copper modifies appreciably the number and perhaps the nature of some phases that precipitate in this alloy system. We showed that the number of the types of the equilibrium eta phase increases and that for the underaged states this equilibrium eta phase seems to precipitate from the eta' intermediate phase. (C) 2009 Elsevier B.V. All rights reserved.