Papers by Author: Rim Dakhlaoui

Abstract: In this work, the influence of temperature on the mechanical properties of duplex steel is studied by performing monotonic “in situ” tension and compression at 200oC. The lattice strains in both phases were measured using the time-of-flight neutron diffraction method (at the ISIS spallation neutron source, STFC Rutherford Appleton Laboratory, UK). A thermal-elastic selfconsistent model was used to predict the expansion of the interplanar spacings during heating to 200°C. Subsequently, the variation of phase stresses during tensile and compressive loading at room temperature (20°C) and at 200°C were theoretically calculated by the elastoplastic self-consistent model. Comparing the model data with experimental results the critical resolved shear stresses and work hardening parameters were determined individually in each phase of the DSS. Finally, the yield stresses in each phase of the studied steel have been estimated. It was found that both yield points (of austenite and ferrite) are lower at 200°C than those at room temperature.

Abstract: A new method for determining the parameters characterising elastoplastic deformation of two-phase material is proposed. The method is based on the results of neutron diffraction, which are analysed using the self-consistent rate-independent model of elastoplastic deformation. The neutron diffraction method (time-of-flight technique) was applied and the self-consistent model was used to predict the second order stresses in austeno-ferritic duplex steel. Calculations based on the model were successfully compared with experimental results for both phases of the duplex steel.

Abstract: The aim of this work is to study the influence of residual stresses on the properties of textured duplex stainless steel (DSS). The properties of both phases in DSS were studied using Xray diffraction whilst external load was applied “in situ” to the sample. The interpretation of experimental data is based on the diffraction elastic constants calculated by the self-consistent model taking into account the anisotropy of the studied material. Carrying out measurements in both compression and tension by using neutron diffraction, important differences in the evolution of lattice strains were noticed. An elastoplastic model is used to predict the evolution of the internal stresses during loading and to identify critical resolved shear stresses and strain hardening parameters of the material. The influence of the initial residual stresses on the yield stresses of the phases is considered. The difference between tensile and compressive behaviour of the steel is explained when the initial stresses (measured in the as received non-loaded sample by diffraction methods) are taken into account in model calculations. The yield stresses in each phase of the studied steel have been experimentally determined and successfully compared with the results of the elastoplastic self-consistent model.