Forgeabilité des aciers inoxydables austéno-ferritiques

tel-00672279, version 1 - 21 Feb 2012
120 Chapter IV. STRAIN PARTITIONING
IV.5.1.2 Micro-scale strain analysis
IV.5.1.2.1 Qualitative analysis
Relevant areas were selected from the large SEM pictures of the deformed microgrids, and the dis-
placements of the grid intersections (with reference to their undeformed configurations) were used to
calculate the distribution of the local strain components and of the equivalent strain using the proce-
dure described in section IV.4.3. The calculated data were used to plot colour maps for different levels
of strain. The corresponding microstructures, in their undeformed configuration, were edited to extract
the interphase boundaries. The boundaries were then superimposed to the colour map in order to
reveal clearly the link with the microstructure.
It has been chosen to plot the strain maps using the undeformed configuration because it was easier
to extract the interphase boundaries from the initial microstructure compared to the deformed micro-
structure. Indeed, in the deformed configuration it is very difficult to see the interphase boundaries due
to a slight oxidation, or in some areas large distortion of the microgrids.
The equivalent strain maps of the two microstructures D1_W and D2_W are respectively shown in
Figure IV.23 and Figure IV.24. In each plane strain compression specimen, two different regions are
analyzed, hence two strain maps are plotted (map1 and map2).
Some general qualitative considerations concerning the deformation features can be made by observ-
ing the strain maps and the deformed microgrids.