Grain refinement down to 0.2–0.5m is feasible by repeated
pressing via either route A or route BC. Due to the
microstructural characteristics generated by the two different
routes, the grain size is equivalent to the spacing of
the lamellar boundaries and to the equiaxed dislocation
cells for the case of the route A and the route BC, respectively.
The significantly evident grain refinement during
the initial pass of pressing and the insignificant refinement
in the subsequently repeated pressing indicate that
the lamellar grain boundaries formed by the first pass were
GNBs.