Abstract: Fe₆₀Ni₄₀ powders were prepared by mechanical alloying (MA) in a planetary ball milling in argon atmorsphere. XRD analysis pointed out that the Fe-Ni MA powders consist of α (bcc) and γ (fcc) noncrystalline supersaturated solid solutions. And the two phases transformed each other during milling. In initial stage, the a phase was dominant, then it decomposed and transformed into γ phase gradually during milling. Some structure parameters of the MA powders, such as lattice parameter, grain size and lattice strain and so on, were determined by analysing the XRD patterns. A thermodynamic model of MA of Fe-Ni system was developed based on Miedema semi-experimental theory to explain the phases transformation of Fe-Ni system during milling. The thermodynamic analysis showed that there is no chemical driving force to form amorphous alloy. And what type solution or solutions presented in the MA powders during milling was controlled by structural contribution of the forming enthalpy of the alloy. All of the results are agreed with the experiments.

Key words: thermodynamics, mechanical alloying, Fe-Ni alloy