  We report on work aimed to describe the $\Lambda$ and $\bar{\Lambda}$ global
polarizations in a heavy-ion collision environment using the core-corona model,
where the source of these hyperons is 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 and
$\bar{\Lambda}$s coming from the core versus those coming from the corona. Both
global polarizations peak at collision energies $\sqrt{s_{NN}} \lesssim 10$
GeV. The exact positions and heights of these peaks depend not only on a
reversal of relative abundances with collision energy, but also on the
centrality class, both related to the QGP volume and lifetime.
