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

The influence of chemical composition changes on the room temperature mechanical properties in the binary Ca₃₃Al₆₇ C15 CaAl₂ Laves phase were investigated in two ternary alloys with off-stoichiometric compositions with 5.7 at.% Mg substitution (Ca₃₃Al₆₁Mg₆) and 10.8 at.% Mg and 3.0 at.% Ca substitution (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, taken from our previous study, respectively. The resulting surface traces as well as slip and crack planes, were distinguished on the indentation surfaces, 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.