Critical solid solubility of the Ni-Ti system determined by molecular dynamics simulation and ion mixing

From a realistic n-body potential of the Ni-Ti system, the critical concentrations of the Ni- and Ti-rich solid solutions were determined by molecular dynamics (MD) simulation to be 38 at% Ti and 15 at% Ni, respectively, beyond which a disordered atomic configuration was more stable than the respective crystalline solid solutions. It follows that the central composition range bounded by the critical solubilities, i.e. within 38-85 at% of Ti, can be considered as the glass-forming range of the system, which was confirmed by room temperature 200 keV xenon ion mixing of alternately deposited Ni-Ti multilayered films. Moreover, MD simulation of a Ni-Ti bilayer revealed that during the solid-state amorphization reaction. the growth of the amorphous interlayer followed exactly a t(1/2) law and grew faster towards the Ti lattice than to the Ni side. The physical origin of such an asymmetric behaviour was found to be due to a difference in critical solid solubilty of the constituent metals.