A Polycrystalline Approach to the Cyclic Behaviour of f.c.c. Alloys – Intra‐Granular Heterogeneity

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AbstractFor several decades, the plastic deformation mechanisms of f.c.c. metals under cyclic loading have received considerable attention. The extensive work on this subject has gradually lead to the identification of the physical processes to be included in a formal scheme of fatigue behavior. Accordingly, we propose a review of the physical mechanisms of plastic deformation in f.c.c. metals and alloys to define the state‐of‐the‐art and motivate future studies. The aim is to demonstrate the importance of a good knowledge of the heterogeneous nature of deformation at the intra‐granular scale in defining a physical model of cyclic behavior. A large characterization of the different stages associated with the evolution of heterogeneous dislocation structures during tensile and cyclic loadings is given for an austenitic stainless steel AISI 316L. A unified view of these various structures is proposed in the form of a modified Pedersen's map [εmax = f(εpcum), where εmax is the maximum plastic strain and εpcum the cumulative plastic strain] in the case of tensile loading and different kinds of cyclic loading: uni‐axial and multi‐axial tests under stress or strain amplitude control. The specificities of each domain defined in the map are discussed in terms of long‐range internal stresses in order to formalize, in a simple composite scheme, the intra‐granular stress–strain field. The importance of taking into account this scheme and the nature of the different dislocations populations in a polycrystalline model is illustrated.