Nanoclusters in stacking faults in Mg-Y-Zn alloys examined by small-angle X-ray scattering and extended X-ray absorption fine structure analysis

Abstract

A coarse-grained picture of segregation layers in MgYZn alloys as a two-dimensional cluster systems bound in stacking faults has been justified by a combined use of Extended X-ray absorption fine structure (EXAFS), small-angle X-ray scattering, and scanning tunneling microscopy. EXAFS analysis showed an identical relaxed atomic configuration around Y and Zn atoms as a finger print of molecular-like L12 clusters, characteristic of Long Period Stacking Ordered (LPSO) structures. The fingerprint was confirmed for wide range of compositions of cast ternary alloys containing bulk LPSO structures. The clusters in dilute MgYZn alloys, whose segregation layers were sparsely dispersed in the a-Mg matrix, showed the same fingerprint. The results suggested that the Y-Zn clusters in the segregation layers of Mg-Y-Zn alloys are identical, regardless of the cluster density in the layers or the number of segregation layers.