Structural phase transition in the Fe-Ta system studied by ion beam mixing

For the Fe-Ta system characterized by a negative heat of formation (-22 kJ/mol), 200 keV xenon ion beam mixing with nano-sized Fe-Ta multilayered films was conducted to study the non-equilibrium alloy phase formation. The results show that uniform amorphous alloys can be obtained within a composition range of 25-80 at.%Ta. which falls in the maximum possible amorphization range (MPAR) (3-93 at.% Ta) predicted by the empirical model. Besides, two metastable crystalline phases both of fcc structures, yet with different lattice constants were obtained. The possible mechanisms for the formation of both amorphous alloys and metastable crystalline phases are also discussed in terms of the atomic collision theory. (C) 2008 Elsevier B.V. All rights reserved.