  We compute the $\Lambda$ and $\overline{\Lambda}$ global polarizations in
semi-central heavy-ion collisions using the core-corona model where the source
of $\Lambda$'s and $\overline{\Lambda}$'s is taken as consisting of a
high-density core and a less dense corona. We show that the overall properties
of the polarization excitation functions can be linked to the relative
abundance of $\Lambda$s coming from the core versus those coming from the
corona. For low collision energies, the former are more abundant whereas for
higher energies the latter become more abundant. The main consequence of this
reversing of the relative abundance is that both polarizations peak at
collision energies $\sqrt{s_{NN}}\lesssim 10$ GeV. The exact positions and
heights of these peaks depend not only on this reversal of relative abundances,
but also on the centrality class, which is directly related to the QGP volume
and lifetime, as well as on the relative abundances of $\Lambda$s and
$\overline{\Lambda}$s in the core and corona regions.The intrinsic
polarizations are computed from a field theoretical approach that links the
alignment of the strange quark spin with the thermal vorticity and modeling the
QGP volume and lifetime using a Bjorken expansion scenario. We predict that the
$\Lambda$ and $\overline{\Lambda}$ global polarizations should peak at the
energy range accessible to NICA and HADES.
