KINETIC PROCESS OF MECHANICAL ALLOYING IN FE50CU50

It is shown that mechanical alloying in the immiscible Fe-Cu system is governed by the atomic shear event and shear-induced diffusion proces s. We found that an alpha-to-gamma phase transformation, as evidenced by the Nishiyama-Wasserman orientation relationship, occurs by simulta neous shearing process when the grain size reduces to about 20 nm and Cu content reaches 20 at. % in bcc-FerichCu grains in the intermediate stage of milling of Fe50Cu50. Further milling promotes the interdiffu sion between fcc-FerichCu and fcc-FeCurich, which is favored because o f the similarity of the lattice structures, until a complete fee Fe-Cu solid solution is formed. The results provide significant insight int o the understanding of recent experiments showing that chemical mixing of immiscible elements can bd induced by mechanical alloying. [S0163- 1829(98)51342-2].