Electron microscopy of an Al-Cu of 1.3 at% obtained by implantation

An Al-Cu alloy of 1.3 at% is obtained by implantation of Cu ions in thin foils of aluminium. The purpose of the electron-microscope study is to determine the ageing reactions of this alloy as compared with those occuring in the quenched solid solution. It has been shown that the implantation temperature is an essential parameter in the unmixing process. After a 77 K implantation 8 months of ageing at 200C are necessary to obtain the first stages of unmixing characterized by the formation of Guinier-Prestion I zones, whereas after an implantation at room-temperature, the THETA'' phase is directly observed. The behaviour of the solid solution obtained at 77 K is similar to the conventional Al-Cu solid solution. On the contrary, during the implantation at room-temperature, the unmixing is already started and this fact can be explained on account of an enhanced diffusion. (orig./R)