FORMATION AND STABILITY OF AL-ND AND AL-ND-FE METALLIC GLASSES

Partially amorphous Al91Nd9 and Al86Nd9Fe5 ribbons were prepared by me lt spinning. Metastable crystalline phases were found in both alloys. Complete amorphization of Al86Nd9Fe5 was also achieved. Crystallizatio n was monitored by differential scanning calorimetry (DSC). It occurs in two stages at 440 and 510 K for Al91Nd9. Al86Nd9Fe5 presented a eut ectic crystallization at 550 K. Microscopy observations, combined with Johnson-Mehl-Avrami (JMA) analyses performed in isothermal DSC traces , showed that Al91Nd, transforms via growth on pre-existing crystals. Al86Nd9Fe5 transformed via heterogeneous nucleation on sites unevenly distributed through the ribbon. The fitting of isothermal peaks by mea ns of the JMA equation was less satisfactory. The limits of this appro ach are discussed.