On the structure of defects in the Fe7Mo6 $\mu$-Phase

TL;DR

This study investigates the defect structure of the Fe7Mo6 μ-phase using nanoindentation and HR-TEM, revealing stacking faults likely caused by synchroshear in the Laves phase layers, advancing understanding of deformation in complex phases.

Contribution

It provides the first direct observation of mobile defects in the μ-phase and links them to specific deformation mechanisms like synchroshear.

Findings

Stacking faults observed via HR-TEM after nanoindentation.

Stacking faults are consistent with synchroshear mechanisms.

Deformation mechanisms in μ-phase involve complex defect structures.

Abstract

Topologically close packed phases, among them the $\mu$-phase studied here, are commonly considered as being hard and brittle due to their close packed and complex structure. Nanoindentation enables plastic deformation and therefore investigation of the structure of mobile defects in the $\mu$-phase, which, in contrast to grown-in defects, has not been examined yet. High resolution transmission electron microscopy (HR-TEM) performed on samples deformed by nanoindentation revealed stacking faults which are likely induced by plastic deformation. These defects were compared to theoretically possible stacking faults within the $\mu$-phase building blocks, and in particular Laves phase layers. The experimentally observed stacking faults were found resulting from synchroshear assumed to be associated with deformation in the Laves-phase building blocks.