The different models of sintering are reviewed, with a special attention to the developments in the last fifteen years. The models are classified between microscopic models, which describe the evolution of the material with a cell containing one or a few particles, models at the scale of the particle packing, and macroscopic models, which describe the evolution at a scale which is large compared to the particle size. Perspectives for the future are briefly discussed.

Parts are produced from steel powder in a two step process : the powder is first compressed in a hard matrix and then sintered under a reducing atmosphere. During the second step, the part may be submitted to non-isotropic strains. Based on different experimental set-ups, the effect of the applied strain on the part deformation anisotropy has been assessed. This anisotropy increases with the density of the raw compressed material. The actual viscosity of the material has been derived from the measured strains with the help of a simple analytical model. The possible application of these results, to predict the shape alterations of industrial parts during sintering, is then discussed.

In this paper an extension of the sintering method at atmospheric pressure, already used for tool steels, is proposed for prealloyed duplex stainless steel powders. A wide temperature range is tested and the effectiveness of boron as activator of the process is investigated. In all the samples no evidence of liquid phase is observed ; the sintering process allows full density in case of no boron addition and it occurs by solid phase diffusion, enhanced by the presence of two phases, austenite and ferrite : this makes needless to add boron as activator. We obtain density and hardness values comparable with the “as-cast” ones, isotropic phases structure and γ/δ ratio of about 50/50 for the best sintering temperature (1150 °C).

Powders obtained by high energy crushing are often easier to compact than conventional polycrystalline powders. In the present work, phase transformations during thermal treatments in high speed steels, prepared by compaction of nanostructured powders obtained by mechanical synthesis, are studied. These transformations and the resulting microstructures are compared to those of conventional steels produced by melting and solidification.

This paper describes a method for producing model composites by the powder metallurgy route in order to control the spatial distribution of the reinforcement in a metallic matrix. The materials are fabricated by successive steps including mixing and extrusion. They are then characterized in 3D by X-ray tomography.

The components for electronics and electrotechnics are usually classified in two families with similar market shares: the “active” components and the “passive” components. The aim of this paper is to analyze and to describe a range of ceramics passive components. The materials properties and the resulting service properties of ceramics parts are presented. This presentation is then illustrated with some significant examples of ceramics components.

Nanocrystalline oxide ceramic powders are usually metastable and tend to transform into a stable phase during sintering. In this paper dealing with the sintering behaviour of nanosized alumina powders, we present the effects of several parameters on the macroscopic and microscopic behaviours during the pressureless sintering.

Discontinuous elaboration or transformation processes treat separate batches of raw materials. The properties of the raw materials may differ from one batch to the other, thus altering the kinetics of the transformation process. When these changes are significant and they are not taken into account by the transformation process, the final product may be unsatisfactory. It is shown that a feedback command is usually not able to restore the requested quality of the final product. A process model that can be re-identified during the operation makes it possible to define the adjustments to the process parameters that will yield a final product with satisfactory properties. In this paper, a feed-forward command based on a linear approximation of the process model is proposed in order to predict the necessary adjustments. This method is much simpler and requires less computing time than the usual non-linear optimization methods, in particular for multivariable processes. As an example, this technique is applied to control a multivariable elaboration process of materials : the hot isostatic sintering of alumina powder.

The crystallographic texture of a great number of polyethylene films manufactured by the film blowing process has been investigated by X-ray diffraction. Some films present a classical texture (c-axis in the machine direction), which can be interpreted using existing morphological models. Other exhibit an original texture (c-axis in the film thickness) and no satisfactory morphological model has been proposed until now.

The effect of methionine ethyl ester (MetOC2H5), a non-toxic compound on the corrosion of iron in citric-chloride solution at pH = 5, has been investigated by various corrosion monitoring techniques. Results obtained reveal that this compound is a very good inhibitor. Potentiodynamic polarization studies show that MetOC2H5 is a mixed-type inhibitor and that it acts on the cathodic reaction without changing the mechanism of hydrogen evolution. Variation in impedance parameters (Rt and Cdl) are indicative of adsorption of MetOC2H5 on the metal surface. The adsorption of this product on the iron surface obeys a Temkin adsorption isotherm. The effect of temperature indicates that inhibition efficiency of MetOC2H5 slightly changes with increasing temperature in the range of 30-60 °C.

The three-dimensional atom-probe is the only analytical microscope able to map out the 3D distribution of chemical species at the atomic scale. Combined with a Field Ion Microscope, 3D Atom Probe is particularly well adapted to the investigation of the fine-scale features of the microstructure of metallic alloys. 3D atom probe makes it possible to measure quantitatively the composition in a small region that can be selected arbitrarily in the reconstructed volume. This way, the composition of small precipitates or that of the surrounding solid solution or even that of a thin layer close to interfaces can be measured. The potential of this new generation of analytical microscope is illustrated through examples (segregation of boron to planar faults in FeAl and superalloys, precipitation and ordering...).