Strip rolling processes depend critically on friction and lubrication for process control as well as for strip quality. Pechiney and Usinor companies have therefore joined with CNRS (National Scientific Research Centre of France) to build an ambitious project gathering seven French public laboratories and their own research centres, Irsid and Centre de Recherches de Voreppe. The two major fields of lubrication were addressed: the formation of fluid lubricant films between rough deformable surfaces, and the formation of boundary films (tribochemistry). The final purpose was to derive a model of rolling processes including a predictive, local friction model. This issue and a future issue of Science et Génie des Matériaux present the efforts and the results of this Research Programme Contract "Materials forming: metal - tools - lubricant contact".

In order to improve a cold rolling lubrication model, the effects of this process on the formation and evolution of superficial layers in two alloys were studied by coupled surface and microscopy analysis. On the Al-Mg alloy, the friction on the metal asperities and their crushing provoke, by localized hardening and heating, the burying of debris in the substrate, the recrystallization of the metal within a layer of 250 nm and its recovery down to 20 μm. On the steel, the oxide layer mainly becomes amorphous and plastic, because of a high incorporation of the lubricant, and heterogeneous at the nanoscopic scale.

During the cold rolling of metal alloy sheets, the control of lubrication constitutes one of the major industrial problems. The aim of the study reported in this article concerns the rheological characterization of two industrial lubricants, under conditions close to those met in rolling. The application of EHD models then allows to calculate the lubricant film thickness, which is compared to the values measured by interferometry in a ball/disk contact.

The demand for improvements in surface quality and increased productivity in industrial cold metal rolling requires a good understanding of lubrication mechanisms. The limitations are due to boundary friction, controlled by the physico-chemistry of lubricant additives. The phenomena are complex and require a simplified approach. Consequently, a new method was developed by using an UHV tribometer associated with surface analytical tools to simulate the molecule chemical reactivity toward surfaces.

The chemisorption of cold rolling oil additives on steel and aluminium surfaces is studied with a mass spectrometry technique, ToF-SIMS. Preliminary experiments underline adsorption competition, and thermal threshold for desorption or decomposition. This results fit well with experimental cold rolling results.

The limit condition for the flow rate at the wall for a Newtonian fluid with various solid/liquid interfaces was studied experimentally using an original high resolution technique. A notable interfacial slipping was shown for the hexadecane flowing on a surface with low roughness and covered with methyl groups (non wetting surface for the hexadecane). The systematic study of various modified surfaces made it possible to identify two key parameters fixing the amplitude of slipping at the wall and acting in an antagonistic way on the roughness of the surface (geometric and chemical) and the fluid/surface interactions.

The understanding of the molecular aspects of adhesion needs the determination of the molecular order of macromolecular chains at the polymer/metal interface. Thin supported polymer films are studied by FTIR reflectance analysis (IRRAS). It is shown that the development of specific acid-base interactions at the interface is able to strongly organize and order macromolecular chains at the vicinity of the interface. Microstructural parameters of the polymer are shown to influence both interfacial organization and adhesion.

The objective of the study is to determine the influence of forming on the adherence properties of sheet steel laminates. Drawing is then decomposed in different deformation modes: stretching (or biaxial tension), plane strain tension, uniaxial tension and shear deformation. Two adherence tests are used - the torsion shear test (napkin-ring) and the wedge test - in order to evaluate the metal/polymer adhesion before and after deformation.

The oxidation behaviour of a β-NiAl material (produced by powder metallurgy) was investigated in the temperature range 1200°C < T < 1400°C. In isothermal runs at 1200 and 1400°C, an alumina scale grew according to a parabolic growth law. At 1300°C, catastrophic oxidation was observed, but a short anneal at low oxygen partial pressure at 1200°C, prior to the oxidation at 1300°C, initiated a parabolic scale growth. Further, cyclic oxidation tests were carried out and the growth mechanism of the scale was identified by two-stage oxidation (16O2/18O2) in combination with SNMS isotope profile analysis.

In this article, we briefly recall the physical mechanisms at the origin of the Barkhausen effect in ferromagnetic mediums and the thermoelectric power in conductor metals. We then present, for each of these phenomena, the measurement principles and their sensitivity to the microstructural state, notably in the case of precipitation phenomena and in the ones linked to plastic deformation. Finally, in the case of the formation of precipitates in an iron-based alloy, we show the complementarity of both techniques.

1 GHz very high frequency acoustical imaging displays a micronic resolution. Owing to its nature of sub-surface imaging, it is well adapted to the characterization of porosity. Used as a means for quantitative measurements through acoustic signature processing, it provides sufficiently localized information to characterize the elastic properties proper to each component of a SiC/SiC minicomposite, the fiber and the matrix.