Fatigue in precipitation hardened materials, a three dimension discrete dislocation dynamics modelling of the early cycles

Chan Sun Shin (1) , Christian Robertson (2) , Marc C. Fivel (3)

1 KAERI
2 DMN - Département des Matériaux pour le Nucléaire
3 SIMaP - Science et Ingénierie des Matériaux et Procédés

Three-dimensional dislocation dynamics (DD) fatigue simulations in precipitation hardened metals is a major challenge in terms of numerical development. Several precipitate configurations have been investigated with an original treatment of precipitate-dislocation interactions and a parallelized DD code. In grains containing single-sized shearable particles (rp = 160 nm), strain is localized in clear bands where the precipitates are totally sheared-off. The fatigue behaviour involves an initial hardening followed by severe cyclic softening and significant surface slip irreversibility. In the presence of large single-sized particles (rp = 400 nm), the PSB structures is accompanied by highly reversible surface displacements. Slip dispersion originates from Orowan loops that have little effect on the mechanical response. The mechanical behaviour of a bimodal distribution is intermediate between the two above cases with the above micro-structural features coexisting within the same grain. Unlike in the mono-modal large particle case where all the particles retain their initial strength, some of the large particles of the bimodal distribution undergo a significant strength reduction.

Mots clés: Physical Sciences

Domaines: Matériaux; Génie des procédés

Chan Sun Shin, Christian Robertson, Marc C. Fivel. Fatigue in precipitation hardened materials, a three dimension discrete dislocation dynamics modelling of the early cycles. Philosophical Magazine, 2007, 87 (24), pp.3657-3669. ⟨10.1080/14786430701393159⟩. ⟨hal-00513839⟩