Fig. 2 shows the color-coded hardness maps for pure Al
where the number of passes is indicated above each display
and the meanings of the colors are given at the lower right. The
map at upper left in Fig. 2 shows the as-received condition
immediately prior to ECAP and it is apparent that the values
of Hv, having an average value of Hv≈19, are essentially
independent of the location on the section thereby confirming
the presence of a reasonably homogeneous microstructure
throughout the billet.