The tests are carried out to investigate the effect of the
double-stage ageing treatment on the tensile properties at room
temperature and the distribution of precipitated particles for an Al-1. 9 Li-2. 33 Cu-0. 09 Zr-0. 11Ce alloy. The first-stage ageing temperature has an insignificant effect on the strength and ductility. With a rise in the second-stage ageing temperature, the strength increases and then decreases promptly after over the peak point at 185℃ while the ductility always decreases. With a delay in the second-stage ageing time,the yield strength increases and ultimate tensile strength could almost remain constant after it increases to a certain degree while the elongation has an insignificant variation. Under the conditions of lower first and second-stage ageing temperatures or shorter second-stagen ageing time,δ' particles have an insufficient
precipitation and growth but finer T1 particles conld he promoted to precipitate directly from alpha matrix. The elevated first and secondstage ageing temperature could induce δ' particles to coarsen or to change into T1 phase.Moreover, the elevated first and second-stage temperatures could also induce T1 particles to coarsen or precipitate along the grain boundaries. The longer second-stage ageing time only causes δ' particles,except T1 particles, to coarsen. A suitable processing of double-stage age ing treatment for the alloy could make the microstructures contain more and larger δ' particles with finer T1 particles to result in a more significant effect on precipitation hardening.