AMORPHIZATION AND METASTABLE POLYMORPHS OF ORDERED INTERMETALLICS ZR3AL AND NI3AL

Observations of various metastable crystalline and amorphous polymorph s of L1(2)-type intermetallics Zr3Al and Ni3Al are summarized. The dif ference in the tendency of these two alloys to become amorphous is obv ious. Regardless of the nonequilibrium routes employed for synthesis a nd processing, amorphous Zr3Al is obtained easily, while amorphization of Ni3Al is rare. An analysis of thermodynamic and kinetic factors re sponsible for the observed polymorph selection and amorphization behav ior is presented. The inadequacy of a simplified model proposed earlie r is also discussed.