  We study the relaxation properties of the Kondo lattice model using the
nonequilibrium dynamical mean field formalism in combination with the
non-crossing approximation. The system is driven out of equilibrium either by a
magnetic field pulse which perturbs the local singlets, or by a sudden quench
of the Kondo coupling. For relaxation processes close to thermal equilibrium
(after a weak perturbation), the relaxation time increases substantially as one
crosses from the local moment regime into the heavy Fermi liquid. A strong
perturbation, which injects a large amount of energy, can rapidly transform the
heavy Fermi liquid into a local moment state. Upon cooling, the heavy Fermi
liquid reappears in a two-stage relaxation, where the first step opens the
Kondo gap and the second step corresponds to a slow approach of the equilibrium
state via a nonthermal pathway.
