Heat-resistant performance of an underaged Al-Cu-Mg-Ag alloy

The effects of thermal exposure and high temperature lasting on microstructure and mechanical properties of an underaged (165 degrees C, 2 h)Al-Cu-Mg-Ag-Zr alloy have been investigated, The results show that with prolonging of lasting time, the residual stress of underageing samples appears to be increase first but then decrease, and the peaking stress is obtained when lasting for 20 h. The variation. of ductility of the underageing samples has the same tendency with the variation of residual stress. Compared with underageing condition, the mechanical properties has no obvious variation after lasting for 100 h, which represents a superior heat-resistance ability. The fine and uniform distribution of Omega phase within the matrix grow and coarsen with prolonging of lasting time, and theta'competitive precipitate and precipitate-free zone (PFZ) width increase. Compared with the high temperature lasting condition, the variation of strength of the underageing samples in exposure 200 degrees C has the same tendency, and the ductility decreases with prolonging of exposure time.