  Understanding radial migration is a crucial point to build relevant chemical
and dynamical evolution models of the Milky Way disk. In this paper, we analyze
a high-resolution N-body simulation of a Milky Way-type galaxy to study the
role that the slowing down of a stellar bar has is generating migration from
the inner to the outer disk. Stellar particles are trapped by the main
resonances (corotation and Outer Lindblad resonance) which then propagate
outwards across the disk due to the bar slowing down. Once the bar strength
reaches its maximal amplitude, some of the stars, delivered to the outer disk,
escape the resonances and some of them settle on nearly circular orbits. The
number of the escaped stars gradually increases also due to the decrease of the
bar strength when the boxy/peanut bulge forms. We show that this mechanism is
not limited only to stars on nearly circular orbits: also stars initially on
more eccentric orbits can be transferred outwards (out to the OLR location) and
can end up on nearly circular orbits. Therefore, the propagation of the bar
resonances outwards can induce the circularization of the orbits of some of the
migrating stars. The mechanism investigated in this paper can explain the
presence of metal-rich stars at the solar vicinity and more generally in the
outer galactic disk. Our dynamical model predicts that up to 3% of stars in
between of corotation and the OLR can be formed in the innermost region of the
Milky Way. The epoch of the Milky Way bar formation can be potentially
constrained by analyzing the age distribution of the most metal-rich stars at
the solar vicinity.
