Forgeabilité des aciers inoxydables austéno-ferritiques
Forgeabilité des aciers inoxydables austéno-ferritiques
Forgeabilité des aciers inoxydables austéno-ferritiques
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tel-00672279, version 1 - 21 Feb 2012<br />
144 Chapter IV. STRAIN PARTITIONING<br />
� Secondly, an additional deformation mechanism seems to be activated in the equiaxed mor-<br />
phology: sliding at the interphase boundaries, see Figure IV.42. The microgrid pattern turns<br />
out to be very useful to determine such a deformation mechanism. Sliding at the interphase<br />
boundaries is frequently observed in the microstructure showing an equiaxed morphology<br />
whereas it is very rare to see this mechanism when the austenite presents a Widmanstätten<br />
morphology. These observations are in agreement with literature data since they confirm the<br />
results published by Pinol-Juez et al. [12, 95]. The authors have shown that the activation of<br />
sliding at the interphase boundaries depends on the nature of the interface. In the equiaxed<br />
morphology, the interfaces are incoherent; consequently they are more able to slide. On the<br />
contrary, in the Widmanstätten morphology as the δ/γ interphase boundaries are related by a<br />
Kurdjumov-Sachs orientation relationship, the interfaces are semi-coherent and the ability of<br />
the interface to slide is suppressed.<br />
Sliding<br />
δ<br />
γ<br />
10 μm<br />
a) b)<br />
δ<br />
Sliding<br />
γ<br />
5 μm<br />
Figure IV.42. Illustration at different magnifications and different locations of the δ/γ sliding mechanism<br />
occurring along the incoherent interface boundaries in the equiaxed microstructure.<br />
All the results obtained for the strain partitioning index are summarized in Table IV.20. To highlight a<br />
possible influence of the phase morphology, the strain partitioning index relative to each morphology<br />
has to be compared for a given temperature. Whatever the morphology, the strain partitioning tends to<br />
increase when the austenite presents an equiaxed morphology in comparison with a Widmanstätten<br />
austenite. This difference is attributed to an additional deformation mechanism: the sliding at the δ/γ<br />
interfaces.<br />
T = 850°C<br />
T = 950°C<br />
� �<br />
� � ��<br />
eq � / ��<br />
eq �<br />
� overall<br />
eq<br />
D1_E 0.509 1.32<br />
D1_W 0.490 1.18<br />
D1_E 0.435 1.41<br />
D1_W 0.489 1.28<br />
Table IV.20. Summary of the results of the strain partitioning index for both morphologies at T =<br />
850°C and T = 950°C.
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