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Influence de films fonctionnels sur les propriétés élastiques des substrats associés : application au système Ni/NiO

Abstract : This work aims to study the effect of native coatings (oxides) on the elastic properties of the associated substrate. It was performed on pure polycrystalline nickel, a model material for oxidation. Oxide scales were obtained at various temperatures and for different dwell times. All the scales exhibit a duplex microstructure, characterized by a layer of equiaxed grains topped by a layer of columnar grains. The elastic properties of the scales were characterized at room temperature using instrumented indentation tests. While an effect of the local microstructure of the scale was observed on the elastic behavior, it remains subtle. The macroscopic elastic properties of Ni/NiO systems were investigated in temperature using the dynamical resonant method. The temperature dependence of nickel moduli of elasticity exhibits a very atypical behavior. The presence of oxide scales, while representing a low volume fraction, impacts significantly the elastic response. Actually, this latter effect depends on the oxidation conditions and the structural configuration of coatings. The atypical elastic behavior in temperature is associated with a multi-physics coupling, due to the Ni ferromagnetic character. In this framework, we have suggested that the internal stresses generated in the nickel substrate, resulting from the oxidation, reduce the magneto-elastic effect and tend to result in a classic behavior purely elastic.
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Submitted on : Tuesday, February 5, 2013 - 5:19:34 PM
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Matthieu Tatat. Influence de films fonctionnels sur les propriétés élastiques des substrats associés : application au système Ni/NiO. Matériaux. ISAE-ENSMA Ecole Nationale Supérieure de Mécanique et d'Aérotechique - Poitiers, 2012. Français. ⟨NNT : 2012ESMA0024⟩. ⟨tel-00785259⟩

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