Influence of chemical composition on the room temperature plas-ticity of C15 Ca-Al-Mg Laves phases

TL;DR

This study investigates how variations in chemical composition affect the room temperature mechanical properties of C15 Ca-Al-Mg Laves phases, combining nanoindentation experiments, microscopic analysis, and atomistic simulations.

Contribution

It provides new insights into the relationship between chemical composition and deformation mechanisms in Ca-Al-Mg Laves phases at room temperature.

Findings

Hardness varies with composition, from 4.1 GPa to 4.9 GPa.

Multiple slip systems are activated during deformation.

Atomistic simulations reveal energy barriers for slip activation.

Abstract

The influence of chemical composition changes on the room temperature mechanical proper-ties in the C15 CaAl2 Laves phase were investigated in two off-stoichiometric compositions with 5.7 at.-% Mg addition (Ca33Al61Mg6) and 10.8 at.-% Mg and 3.0 at.-% Ca addition (Ca36Al53Mg11) and compared to the stoichiometric (Ca33Al67) composition. Cubic Ca-Al-Mg Laves phases with multiple crystallographic orientations were characterised and deformed using nanoindentation. The hardness and indentation modulus were measured to be 4.1 +- 0.3 GPa and 71.3 +- 1.5 GPa for Ca36Al53Mg11, 4.6 +- 0.2 GPa and 80.4 +- 3.8 GPa for Ca33Al61Mg6 and 4.9 +- 0.3 GPa and 85.5 +- 4.0 GPa for Ca33Al67, respectively. The resulting surface traces as well as slip and crack planes, were distinguished on the indentation surfac-es, revealing the activation of several different {11n} slip systems, as further confirmed by conventional transmission electron microscopic observations. Additionally, the deformation mechanisms and corresponding energy barriers of activated slip systems were evaluated by atomistic simulations.