Synthesis of nanocrystallite by mechanical alloying and in situ observation of their combustion phase transformation in Al3Ti

Elemental powders of stoichiometric Al3Ti were mechanically alloyed (MA) in order to investigate the phase formation during the milling process. Furth ermore the stability of MA powders were studied under transmission electron microscopy (TEM). The results indicate that a supersaturated Al(Ti) solid solution with nanocrystalline size has been formed after mechanical alloyin g for 360 ks in consuming the elemental powders of Al and Ti and no further phase transformation can be detected upon longer milling. The MA powders a re unstable being irradiated by electron beams under the TEM observation, e xothermically forming various intermetallic compounds. The combustion phase transformation processes and products are depending on the time of mechani cal alloying. The structural changes and phase transformations during both mechanical alloying process and annealing process were also characterized b y using X-ray diffraction measuring. (C) 2000 Kluwer Academic Publishers.