Abstract: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 1 h (T6 condition), then thermal exposed at 250 ℃ for 100 h with and without a tensile stress (130 MPa), respectively. The results indicate that Ω precipitates uniformly disperse in the matrix as a major precipitate after artificially aging at 200 ℃ for 1 h (T6 condition). Exposed at 250 ℃ for 100 h 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.

Key words: Al-Cu-Mg-Ag alloy; Ω phase; thermal exposure; tensile stress