Forgeabilité des aciers inoxydables austéno-ferritiques

tel-00672279, version 1 - 21 Feb 2012
126 Chapter IV. STRAIN PARTITIONING
A relevant parameter which allows quantifying the strain partitioning is the ratio between the average
deformation in the ferrite divided by the average deformation in the austenite, see Table IV.6. The
results show that in both microstructures, the ferrite accommodates more deformation compared to the
austenite. However, the strain contrast between ferrite and austenite is significantly larger in the D2_W
microstructure compared to the D1_W microstructure. In the D1_W microstructure, the ferrite can be
deformed around 30% more than the austenite whereas in the D2_W the ferrite can be strained up to
60% more than the austenite on average.
D1_W
D2_W
� �
� � ��
eq � / ��
eq �
� overall
eq
Map 1 0.603 1.28
Map 2 0.809 1.20
Map 1 0.619 1.51
Map 2 0.572 1.60
Table IV.6. Calculation of the ratio between the average deformation in the ferrite over the average
deformation in the austenite, parameter that quantifies the strain partitioning between ferrite and
austenite in duplex stainless steels.
� Strain distribution functions
Another way to characterize the strain heterogeneity is to plot the strain distribution functions. In Fig-
ure IV.28, the strain distribution functions of the ferrite and the overall strain distribution functions are
superimposed for the large strain values whatever the considered microstructure. It means that the the
most strained regions are always located in the ferrite. Focusing on low strain values, the strain distri-
bution functions of the austenite and the overall strain distribution function are superimposed confirm-
ing that the less distorted regions are in the austenite.
The difference between D2_W and D1_W in terms of strain partitioning is also pointed out. The peak
strain relative to each phase are closer in the D1_W microstructure compared to in D2_W microstruc-
ture, the arrows in grey in Figure IV.28 emphasize this idea.