Mechanical properties and deformation mechanisms of the C14 Laves and \mu-phase in the ternary Ta-Fe(-Al) system

TL;DR

This study investigates the mechanical properties and deformation mechanisms of C14 Laves and mu-phases in the Ta-Fe(-Al) system, revealing how composition and crystal structure influence their behavior and slip mechanisms.

Contribution

It provides a systematic analysis of how composition and crystal structure affect the mechanical behavior of TCP phases in the Ta-Fe(-Al) system, including deformation mechanisms.

Findings

Composition affects indentation modulus in binary Ta-Fe.

Addition of Al does not significantly change mechanical properties.

Laves phase deforms mainly via non-basal slip; mu-phase favors basal slip.

Abstract

As structural and functional materials, topologically close-packed (TCP) phases of transition metal compounds offer a wide range of attractive properties. Due to their complex crystal structure and the resulting brittleness, the knowledge on their mechanical behaviour is still very limited, especially below the brittle-to-ductile transition temperature. In this study, we systematically analyse the influence of composition and crystal structure on the mechanical properties and deformation mechanisms in the binary Ta-Fe system as well as in the ternary Ta-Fe-Al system as both systems contain a hexagonal C14 Laves and a mu-phase. We use nanoindentation, slip trace analysis and transmission electron microscopy to study the influence of crystal structure, composition and crystal orientation. The composition strongly influences the indentation modulus in the binary Ta-Fe system, showing a decreasing trend with increasing Ta content. The addition of Al, however, does not lead to a significant change of the mechanical properties of the ternary TCP phases. The investigation of the deformation mechanisms revealed that the Laves phase primarily deforms via non-basal slip while the basal plane is the favoured slip plane in the mu-phase. By partly replacing Fe with Al, the plasticity is not affected strongly, but the proportion of non-basal slip slightly increases for both ternary TCP phases compared to the binary ones.