Structural investigation of the amorphization reaction by mechanical alloying of the Mo50Ni50 system

The Mo 50 Ni 50 system has been prepared by mechanical alloying, starting from a mixture of pure crystalline elements. Contrary to the case of meltquenching methods, an amorphous Mo x Ni 1− x phase has been observed after milling. A structural study by X-ray diffraction and EXAFS has shown that nickel atoms are already totally involved in the solid-state amorphization reaction after 10 h, whereas more milling time is needed to amorphize the residual crystalline b.c.c. molybdenum. Because of the relatively low ΔH for calculated according to thermodynamic models for this system, the requirement of a strong negative heat of formation as a necessary condition for amorphization does not seem to be very stringent.