Comparative study of the effect of cold rolling on the structure of Al-RE-Ni-Co (RE = rare-earth metals) amorphous and glassy alloys

The present paper aims to compare the deformation-induced crystallization behavior of the rapidly solidified ribbon samples of Al₈₅Y₈Ni₅Co₂, Al₈₅Nd₈Ni₅Co₂, Al₈₅Gd₈Ni₅Co₂ and Al₈₅Mm₈Ni₅Co₂ non-crystalline alloys subjected to cold rolling with 33% reduction. It is found that amorphous Al₈₅Y₈Ni₅Co₂ alloys exhibiting glass-transition and Al₈₅Nd₈Ni₅Co₂ alloys exhibiting no glass-transition have somewhat different stabilities against crystallization under deformation at room temperature though their crystallization temperatures under heating without load or deformation are almost equal. Al₈₅Gd₈Ni₅Co₂ and Al₈₅Mm₈Ni₅Co₂ alloys (Mm = Mischmetal) did not exhibit deformation-induced crystallization at the reduction ratio used. Although, the formation of the primary nanoscale α-Al particles was observed in both Al₈₅Y₈Ni₅Co₂ and Al₈₅Nd₈Ni₅Co₂ alloys after the cold rolling, the size and volume fraction of the particles are larger in the Nd-bearing amorphous alloy as compared to the Y-bearing alloy. It is found that contrary to crystallization on heating no intermetallic compounds but only α-Al nano particles were formed during the deformation-induced crystallization of Al₈₅RE₈Ni₅Co₂ amorphous alloys. The local heating on deformation is hypothesized to affect the crystallization.