  Hydrogen can penetrate reversibly a number of metals, occupy the interstitial
sites and cause large expansion of the crystal lattice. The question discussed
here is whether the kinetics of the structural response matches hydrogen
absorption. We show that thin Pd and CoPd films exposed to a relatively rich
hydrogen atmosphere (4% H2) inflate irreversibly, demonstrate the controllable
shape memory, and duration of the process can be orders of magnitude longer
than hydrogen absorption. The dynamics of the out-of-equilibrium plastic creep
is well described by the Avrami - type model of the nucleation and lateral
domain wall expansion of the swelled sites.
