  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.
