  Brittle topologically close-packed precipitates form in many advanced alloys.
Due to their complex structures little is known about their plasticity. Here,
we present a strategy to understand and tailor the deformability of these
complex phases by considering the Nb-Co {\mu}-phase as an archetypal material.
The plasticity of the Nb-Co {\mu}-phase is controlled by the Laves phase
building block that forms parts of its unit cell. We find that between the bulk
C15-NbCo$_2$ Laves and Nb-Co {\mu}-phase, the interplanar spacing and local
elastic modulus of the Laves phase building block change, leading to a strong
reduction in hardness and elastic modulus, as well as a transition from
synchroshear to crystallographic slip. Furthermore, as the composition changes
from Nb$_6$Co$_7$ to Nb$_7$Co$_6$, the Co atoms in the triple layer are
substituted such that the triple layer of the Laves phase building block
becomes a slab of pure Nb, resulting in inhomogeneous changes in elasticity and
a transition from crystallographic slip to a glide-and-shuffle mechanism. These
findings open opportunities to purposefully tailor the plasticity of these
topologically close-packed phases in bulk, but at the atomic scale of
interplanar spacing and local shear modulus of the fundamental crystal building
blocks in their large unit cells.
