Publications: Articles

Resume: A multiphase model for Ti-6Al-4V is proposed. This material is widely used in industrial applications and so needs accurate behaviour modeling. Tests have been performed in the temperature range from 25 degrees C to 1020 degrees C and at strain rates between 10(-3) s(-1) and 1 s(-1). This allowed the identification of a multiphase mechanical model coupled with a metallurgical model. The behaviour of each phase is calibrated by solving an inverse problem including a phase transformation model and a mechanical model to simulate tests under thermomechanical loadings. A scale transition rule (beta-rule) is proposed in order to represent the redistribution of local stresses linked to the heterogeneity of plastic strain. Finally this model is applied to two laser assisted processes: direct laser fabrication and laser welding. (C) 2009 Elsevier B.V. All rights reserved.

Equipe: Département SI2M : Microstructures et Contraintes

Resume: WxZr1-x thin films were deposited at room temperature on glass substrates by co-sputtering tungsten and zirconium targets in argon. The composition was found in the range 0 <= x <= 0.81. The grain size deduced from X-ray diffraction analysis ranged from 1.3 nm to 16 nm depending on the composition. The events in the resistivity, optical reflectivity and thickness evolutions were correlated with the X-ray diffraction analysis. Depending on the composition, the local organization can be attributed to a nanocrystalline solid solution of W in Zr, to a nanocomposite structure involving ZrW2 nanograins embedded in an amorphous matrix. to ZrW2 Laves phase nanograins and to a nanocrystalline solid solution of Zr in W. For 0 < x <= 0.72, the equivalent grain size is very small (less than 2 nm) and the evolution of the resistivity can be fitted by the estimated volume of the material perturbed by the grain boundaries. (C) 2008 Elsevier Ltd. All rights reserved.

Equipe: Département SI2M : Microstructures et Contraintes