  A FePd alloy was nanostructured by severe plastic deformation following two
different routes: ordered and disordered states were processed by high pressure
torsion (HPT). A grain size in a range of 50 to 150 nm is obtained in both
cases. Severe plastic deformation induces some significant disordering of the
long range ordered L10 phase. However, Transmission Electron Microscopy (TEM)
data clearly show that few ordered nanocrystals remain in the deformed state.
The deformed materials were annealed to achieve nanostructured long range
ordered alloys. The transformation proceeds via a first order transition
characterized by the nucleation of numerous ordered domains along grain
boundaries. The influence of the annealing conditions (temperature and time) on
the coercivity was studied for both routes. It is demonstrated that starting
with the disorder state prior to HPT and annealing at low temperature
(400\degree C) leads to the highest coercivity (about 1.8 kOe).
