Effect of Cu on Discontinuous Precipitation of a Symmetrical AlZn Alloy
摘要
The effect of Cu additions on discontinuous precipitation of AlZn alloy were studied with optical microscopy, scanning electron microscopy and X-ray diffraction. It is found that the effect of addition of 2 at. pct Cu on cellular nucleation site is not remarkable, while the effect of aging temperature on cellular nucleation site of AlZn and AlZn-2Cu alloys is fairly obvious. The cell growth rate of discontinuous precipitation of AlZn alloy is remarkably accelerated with the addition of 2 at. pct Cu. The discontinuous precipitation microstructure of AlZn alloy is not apparently affected with the addition of 2 at. pct Cu and the cellular front is still fine microstructure of spinodal decomposition. The phase constituents consist of a fcc Al-rich phase, a hcp Zn-rich phase and a CuZn4 phase. The transformation rate of discontinuous precipitation of AlZn alloy is remarkably accelerated with the addition of 2 at. pct Cu.