Amorphization and metastable polymorphs of ordered intermetallics Zr₃Al and Ni₃Al

Observations of various metastable crystalline and amorphous polymorphs of Ll2-type intermetallics Zr3Al and Ni3Al are summarized. The difference in the tendency of these two alloys to become amorphous is obvious. Regardless of the nonequilibrium routes employed for synthesis and processing, amorphous Zr3Al is obtained easily, while amorphization of Ni3Al is rare. An analysis of thermodynamic and kinetic factors responsible for the observed polymorph selection and amorphization behavior is presented. The inadequacy of a simplified model proposed earlier is also discussed.