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Le Touquet – Paris-Plage, France

Bareggi A.,CNRS Contacts and Structural Mechanics Laboratory | Maire E.,INSA Lyon | Bouaziz O.,ARCELOR Research | Di Michiel M.,European Synchrotron Radiation Facility
International Journal of Fracture

Damage in a dual phase steel was measured using in situ high-resolution X-ray absorption tomography. A comparison with the behavior of its two constituents ferrite and martensite, taken separately, was also achieved in the present work. The method was particularly useful for analyzing the respective contribution of nucleation and growth of voids in the studied materials. Quantitative analysis of the damage events was carried out on a same 3D region inside the reconstructed volumes at different deformation steps for different samples cut from the three kinds of materials. Void number prediction and growth model, based on local stress triaxiality, show a good agreement with the experimental data. © 2012 Springer Science+Business Media B.V. Source

Bayraktar E.,Paris School of Engineering | Bayraktar E.,French National Conservatory of Arts and Crafts | Ayari F.,Paris School of Engineering | Katundi D.,Paris School of Engineering | And 2 more authors.
Advanced Materials Research

This paper reports the production and weldability and toughness evaluation of TiB 2 (ceramic particles) reinforced steel matrix composites. These ceramic particles are optimal reinforcements for steel matrix composites because of their high thermal stability at higher temperatures, high modulus of elasticity, good weldability, low density and relative stability within a steel matrix. This new composite family has received much attention as potential structural materials due to their high specific strength and stiffness. Thus, there is significant interest in developing iron and steel matrix composites and evaluating their dynamic behaviors due to their potential for use in the automotive industry. The goal of the research described in this paper is to study the usage of this new steel family in the manufacture of light structures. Therefore, titanium diboride TiB 2 reinforced steel matrix composites were characterized by optical and scanning electron microscopy. The dynamic behaviours of the base metal and welded specimens were tested under impact crash test conditions. © (2011) Trans Tech Publications, Switzerland. Source

Keller C.,University of Liege | Schwartz R.,University of Liege | Bobadilla M.,ARCELOR Research | Tchoufang Tchuindjang J.,University of Liege | And 2 more authors.
AIP Conference Proceedings

In the Continuous Casting (CC) process, products are sometimes rejected or called defective due to the presence of transversal cracks. This type of macroscopic damage is expected to be due to a ductility loss during cooling in the bending and unbending areas of the CC line. In order to study this damage, a 2D model has been developed to predict at the mesoscopic level the intergranular crack event taking into account the creep and diffusion of voids. Already validated for a microalloyed steel, the model is identified and used in this study to predict the crack formation for three different grades of peritectic steels. Results show encouraging predictions of the damage. These latter, which depend on the chemical composition, are discussed in terms of microstructure and experimental device. © 2011 American Institute of Physics. Source

Roumina R.,University of Tehran | Embury J.D.,McMaster University | Bouaziz O.,ARCELOR Research | Zurob H.S.,McMaster University
Materials Science and Engineering A

In this work, a new approach for processing high strength functionally graded martensitic microstructures with improved fracture properties is presented. The functionally graded martensitic steels are composed of a hard phase at the core and a soft phase at the surface of the structure. The tensile response of the graded steels was analyzed in terms of the extended elasto-plastic transition and a high initial work hardening rate. The behavior of the graded material was modeled using a composite model in which the continuous carbon gradient is replaced with four layers of uniform carbon content. © 2013 Elsevier B.V. Source

Chehab B.,McMaster University | Wang X.,McMaster University | Masse J.-P.,McMaster University | Bouaziz O.,ARCELOR Research | And 2 more authors.
Journal of Physics: Conference Series

Although a number of nanoscale metallic materials exhibit interesting mechanical properties the fabrication paths are often complex and difficult to apply to bulk structural materials. However a number of steels which exhibit combinations of plasticity and phase transitions can be deformed to produce ultra high strength levels in the range 1 to 3 GPa. The resultant high stored energy and complex microstructures allow new nanoscale structures to be produced by combinations of recovery and recrystallisation. The resultant structures exhibit totally new combinations of strength and ductility to be achieved. In specific cases this also enables both the nature of the grain boundary structure and the spatial variation in structure to be controlled. In this presentation both the detailed microstructural features and their relation to the strength, work-hardening capacity and ductility will be discussed for a number of martensitic and austenitic steels. © 2010 IOP Publishing Ltd. Source

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