Forgeabilité des aciers inoxydables austéno-ferritiques

tel-00672279, version 1 - 21 Feb 2012
158 Chapter IV. STRAIN PARTITIONING
More quantitative prediction of strain partitioning is given in Figure IV.51. The comparison between
experimental and simulated average strain components is shown in Figure IV.51.a, while the compari-
son of dispersion in strain components is shown in Figure IV.51.b. It is clear from Figure IV.49 and
Figure IV.51 that the strain partitioning computed by FE model is in quite good agreement with that of
the experiment. The best Kocks-Mecking flow properties for the two phases are given in Table IV.24.
�
�
� 0 (MPa)
�
� 0 (MPa) β γ
�
� 0 (MPa)
�
� 0 (MPa) β δ
187.0 1789.2.0 20.16 136.2 1301.2 15.52
Table IV.24. Numerical values of the best Kocks-Mecking parameters for the two phases.
a) b)
Figure IV.51. Comparison of experimental (denoted as exp) and finite element predictions (denoted
as mod); a) average strain per phase; b) dispersion for strain components 11, 22 and 12. The
strains and dispersions are expressed relative to the respective totals in the map. aus stands for
austenite, and fer stands for ferrite.
The yield stress of austenite is found to be at least 1.3 times the yield stress of ferrite. Figure IV.52
compares the flow curves of the two phases with that of macroscopic material. The remarkable over-
lap of the experimental and simulated macroscopic flow curves comforts us in the belief that we have
found as the best possible solution. The degree of mismatch in the flow parameters of the two phases
clearly emphasizes the difference in rheological behaviour of the two phases. It can be inferred that
the strategy presented here is able to identify the phase properties quite well and indeed helps in un-
derstanding the strain partitioning in duplex stainless steels.
�`