The study of nonequilibrium Fe-Ti alloys prepared by high-energy mechanical deformation

We have studied the nature of the solid-state amorphization induced by mechanical deformation (ball milling) in the case of the Fe2Ti phase [mechanical milling (MM)] and that of the iron and titanium phases mixed in the atomic proportion Fe67Ti33 [mechanical alloying (MA)]. Neutron and x-ray diffraction, Combined with Mossbauer spectroscopy at room temperature, of samples mechanically treated for different times indicate that the MM of the Fe2Ti compound leads to a highly fragmented and disordered (micro)crystalline phase. No changes of the Fe2Ti (MgZn2-type) structure are observed in the mechanically and thermally treated Fe2Ti alloys. Conversely, the MA of the pure elements shows a partial amorphization reaction. The chemical short-range order observed in the neutron-diffraction data indicates that a true alloying of the elements occurs. In addition, the thermograms of the MA specimens are different from those of the equivalent MM products. In fact, the phases observed after annealing at 600 degrees C of the specimens MA 2 and 4 h are a mixture of alpha-iron and of disordered Fe-Ti intermetallic. A fully amorphous structure is obtained after annealing the samples MA treated for 8 and 16 h. (C) 1996 American Institute of Physics.