The morphology of the tweed pattern during phase separation of CuNiFe
single crystals has been followed by two-dimensional small-angle scatt
ering (2D SAS), taking advantage of the x-ray constant enhancement by
anomalous scattering. The 2D [100] intensity maps have maxima with a
fourfold symmetry and can be quantitatively described by three familie
s of independent rows of (100) platelets alternatively enriched in Cu
and in NiFe. Three length scales are defined: the mean platelet thickn
ess lambda/2 along the pile-up, its thickness distribution deltalambda
, and its diameter D. Their kinetics are lambda is-proportional-to tau
-0.2, deltalambda is-proportional-to t-0.27, and D is-proportional-to
t-0.4 respectively. These three length scales are thus independent: in
this tweed-pattern coarsening, there is no global scaling due to the
increase of the anisotropy and to the increase of the regularity in th
e pile-up.