Papers by Author: Christophe Poizat

Abstract: Due to the deformation mechanisms and the typical basal texture rolled magnesium sheets show a significant asymmetry of flow stress in tension and compression. In order to avoid this undesired behavior it is necessary to achieve non-basal texture during rolling, or at least, to reduce the intensity of the basal texture component. The reduction of the anisotropy caused by the basal texture is very important for subsequent forming processes. This project aims at optimizing the hot rolling process with special consideration of texture effects. The development of the model is carried out in close cooperation with the experimental work on magnesium alloy AZ31 .The experimental results are required for the determination of model parameters and for the verification of the model. Deformation-induced texture is described by the visco-plastic self-consistent (VPSC) model of Lebensohn and Tomé. The combination of deformation and recrystallization texture models is applied to hot compression tests on AZ31, and it is found, that the model describes the observed texture and hardening/softening behavior well. In some cases rotation recrystallization occurs in AZ31 which appears to be a possibility to reduce the undesired basal rolling texture.

Abstract: The aim of the research project described here is to increase the durability of components under cavitation erosion by electrodeposition of gradient layers. Parallel to the material development, a simulation tool is elaborated to determine the optimal gradient layers for improved load resistance. This helps in minimising the number of prototype layer systems to be manufactured within the project. The initial experiments were executed with the nickel-phosphorus system, which is well-known for its favourable properties regarding hardness, corrosion resistance and tribology. Single and gradient layers are characterised and evaluated in view of the following properties: hardness, internal stresses, ductility, coefficient of friction, wear resistance, elastic modulus and tensile strength.