We study Hamiltonian dynamics of a Fermi–Pasta–Ulam (FPU) chain with bi-stable elements. We show, that a quasi-static driving of a ‘cold’ chain beyond the spinodal threshold leads to complex dynamical behavior involving equipartition which suggests thermalization. The subsequent quasi-static cycling between the two energy wells produces reversible temperature oscillations which we link to the release (or absorbtion) of the latent heat. By adopting canonical distribution we obtain a thermodynamical description of the chain which agrees well with numerically computed time-averaged behavior of the corresponding dynamical system.