  We propose an explanation of anomalies observed in the behavior of
deformation hardening of Invars. An extremely strong volume magnetostriction,
typical of Invars, results in an enhancement of the exchange contribution to
the energy of the dislocation system by about three orders of magnitude with
respect to its value in conventional ferromagnetics. Both the self energy of
individual dislocations and the interaction between them, determined usually
only by the elastic deformation, in Invars is strongly diminished by the
contribution of the exchange energy. This fact explains a strong suppression of
the deformation hardening rate in the second stage as well as its strong
temperature and content dependence in Invars.
