Hardening Behavior in Aged Al-4%Cu-0.3%Mg Alloys with 0.5 and 2%Ag Additions

Abstract

The precipitation characterization of Al-4 mass% Cu-0.3 mass% Mg alloy with additions of 0.5 and 2 mass% Ag during aging treatments was carried out by transmission electron microscopy (TEM) and microhardness measurements. TEM observation of aged samples showed that thephase is the dominant phase and it is in coexistence with the � 0 phase. Additionally, thephase has the morphology of polygonal prism (almost hexagonal) with flat interfaces and a thin thickness. The variation of the cube of mean radius of precipitates, r 3 , followed a linear relationship, as predicted by the Lifshitz, Slyosov and Wagner (LSW) theory for diffusion-controlled coarsening in both alloys. The coarsening process of thephase was slower in the aged Al-4 mass% Cu-0.3 mass% Mg-2 mass% Ag alloy. The decrease in hardness seems to be related to the coarsening of thephase and the loss of coherency. (doi:10.2320/matertrans.M2009233)