To give a further research on strengthening mechanism of binary Fe-Cu alloys dur- ing the aging process, the compositions, size distributions and volume fractions of precipitates were investigated by carbon extraction replicas. Both the size and the volume fraction of precipitates increase with the aging time prolonged. The precip- itate sizes are corresponding with Weibull distribution. The stability of the sample aged for 35 rain is worse than that aged for 1800 min and 18000 min. The precipi- tate is Cu-rich phase in the early aging process, and Cu content increases with the prolonging aging time. Before aging peak, the precipitation of Cu-rich phase plays a dominant role in strengthening. The growth and the change in crystal structure of the precipitate particles are the main factors leading to the decrease in strengthening after the aging peak.
Nickel shaped-charge liners with nano-sized grains were prepared by the electroforming technique, and the deformation at ultrahigh strain rate was performed by explosive detonation. The as-formed and post-deformed microstructures of electroformed nickel shaped-charge liners with nano-sized grains were observed by means of transmission electron microscopy, and the orientation distribution of the grains was analyzed by the electron backscattering pattern （EBSP） technique. The melting phenomenon in the jet fragment and the recovery and recrystallization in the slug after plastic deformation at ultrahigh-strain rate were observed in the ultrafine-grained nickel shaped-charge liners. The research evidence shows that dynamic recovery and recrystallization play an important role in plastic deformation at ultrahigh strain rate.
Feng Yang Chun-hua Li Sheng-wei Cheng Lei Wang Wen-huai Tian
