Effect of Tensile Stress on Microstructure Evolution of Al-Cu-Mg-Ag Alloys

The effect of tensile stress on thermal microstructure evolution of Ω phase in an Al-Cu-Mg-Ag alloy with high Cu/Mg ratio and higher Ag content was investigated by transmission electron microcopy (TEM) The samples were aged at 200℃ for 1h (T6 condition), then thermal exposed at 250℃ for 100h with and without a tensile stress (130MPa), respectively. The results indicate that Ω precipitates uniformly disperse in the matrix as a major precipitate after artificially aging at 200℃ for 1h (T6 condition). Exposed at 250℃ for 100h without stress, Ω precipitates dissolve dramatically. Whereas, during stress exposure they coarsen unexpectedly rather than dissolve into matrix. It can be deduced that the stress retards the redissolution of Ω phase.