Study of transformation kinetics in the Fe40Ni38Mo4B18 metallic glass by positron annihilation methods

Abstract

We report on transformations induced in the metallic glass Fe 40 Ni 38 Mo 4 B 18 by thermal treatments from the amorphous to the crystallized state, following the variation of the positron lifetime and the Doppler broadening of the annihilation line. The behaviour of the annihilation lineshape shows reversible and non-reversible contributions. We suggest the reversible part to be related to the changes induced by thermal expansion. The non-reversible variation chiefly shows phase transitions. Crystallization of the sample appears as a three-stage process. The results support the idea that positrons are trapped in the as-received metallic glass Etude experimentale des transformations de l'etat amorphe a l'etat cristallin induites par des traitements thermiques. Le comportement de la forme de la raie d'annihilation de positons montre des contributions reversible et irreversible. La partie reversible semble due aux changements induits par dilatation thermique; la partie irreversible correspond a la transformation de phases