Modeling of Young׳s modulus variations with temperature of Ni and oxidized Ni using a magneto-mechanical approach

Thin films and coatings are usually used to give functional properties to the surface of the underlying substrate but are never seen as load bearing due to a very low film to substrate thickness ratio. However, this ratio can increase in some specific domains (such as transportation), where the weight reduction is a high stake. This study deals with the influence of the thermally grown oxide (TGO) NiO on the evolution of the elastic modulus of nickel with temperature. For pure nickel, Young׳s modulus evolves non-linearly with temperature, from room temperature up to 360 °C, corresponding to the Curie temperature of nickel. The amplitude of these variations can be drastically reduced with the presence of the NiO TGO. The purpose of this study is to propose a modeling of these phenomena using magneto-mechanical approach. A first analytical modeling takes the change of the saturation magnetization, of the initial anhysteretic susceptibility and of the maximal magnetostriction with a relaxation of magneto-crystalline anisotropy concomitant to increasing temperature, into account. The second modeling is a numerical modeling giving the average behavior of a representative volume element. It allows a continuous description of the change with temperature of Young׳s modulus and a clear interpretation of the effect of a coating. This gives an insight for future promising applications.