Forgeabilité des aciers inoxydables austéno-ferritiques

tel-00672279, version 1 - 21 Feb 2012
Chapter II. STATE OF THE ART 43
In hot rolled microstructures, sliding affects most interphase boundaries, but it is not necessarily asso-
ciated with damage nucleation at moderate strains under monotonic deformation conditions. In the as-
cast conditions, most of the interphase boundaries share a K-S orientation relationship. As a result,
strain accommodation is only possible through severe localized sliding at the incoherent interphases.
II.4 Conclusions
In this chapter, the main factors involved in the high temperature deformation of duplex stainless
steels have been reviewed. The main conclusions emerging from the analysis of the literature are the
followings.
� The presence of two ductile phases with different mechanical properties controls the complex
behaviour of these materials during hot working.
� Composition and temperature define phase ratio and strength, and become key parameters
for industrial processing, both for the constitutive behaviour, and for damage accumulation.
� Strain partitioning, rotation and interphase boundary sliding contribute to accommodate the
applied deformation between ferrite and austenite, but can be at the origin of localization and
crack nucleation.
� There is a significant effect of loading mode and microstructure evolution associated to it on
the macroscopic mechanical response.
� The literature is relatively rich about the hot deformation of duplex stainless steels. However,
the lack of quantitative data about strain partitioning as well as the lack of a method that prop-
erly characterizes the resistance to crack propagation at high temperature, remain the key is-
sues preventing the hot workability problem.