Seminars and Events

Initial stage of creep in Ni superalloys: a 3D discrete dislocation dynamics investigation

Date/Time: 15.09.2014. 2:30 p.m.
Place: Ruhr-Universität Bochum, Bochum, Germany

Marc Fivel, Science et Ingénierie des Matériaux et Procédés, Université Grenoble Alpes, St Martin d'Heres, France

For low applied stresses, 2-phase γ-γ' Ni superalloys display an abnormal behavior often referred to as negative creep. This surprising stage in the plasticity behavior corresponds to a contraction of the specimen length under tensile loading conditions. It results as the sum of two opposite contributions: the plastic creep strain associated with the area swept by dislocations within the narrow Ni matrix channels normal to the applied stress and the elastic relaxation they provide to the large internal stresses induced by the γ-γ'lattice misfit in these channels. In this presentation, negative creep of Ni superalloys is investigated using 3D discrete dislocation dynamics (DDD) modeling. The simulated volume corresponds to a 3D periodic cell of an array of γ'-Ni3Al cuboids deally aligned in a γ matrix and loaded along the (001) direction. Misfit stresses induced by the γ-γ' lattice mismatch (d=-3.10-3) is taken into account through a coupling of the DDD code with finite elements.

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