The discovery of Duralumin took place in a military context. The Prussian engineer Alfred Wilm had been mandated in Neubabelsberg near Berlin to develop such an improved alloy, the name of which is as much due to the fact that it is hard as to the fact it has first been industrially produced in Düren. International cooperations as well as harsh competitions have accompanied the first researches on this alloy in the beginning of the twentieth century.

This article synthesizes a number of studies involving both quantitative characterization of precipitate microstructures (size and volume fraction) and modelling of precipitation kinetics. The main experimental methods used are Small Angle X-ray and Neutron Scattering and Transmission Electron Microscopy. The modelling is based on semi-analytical models (coupled differential equations) and on numerical models (based on the discretization of the precipitate size distribution). A variety of systems are studied, both aluminium alloys and steels. After considering isothermal precipitation, the issues of dynamic and non-isothermal precipitation are discussed. Finally, precipitation phenomena occurring during welding are characterized.

A micromechanical model based on a new self-consistent formulation has been applied to describe the elastic-viscoplastic behaviour of steels at high strain rates. A good agreement between experimental and calculated data is found concerning the behaviour of a ferritic single-phase IF steel in uniaxial tests in a large range of strain rates. Because of the introduction of relevant physical parameters in the modelling, a good description of the difference observed between the Dual-phase steel and the single-phase steel is obtained.

The method of residual stress determination based on X-ray diffraction has been used for the study of different types of stainless steels: single phase or multiphase microstructures, different inclusion contents. A thermomechanical model associated with a finite element code is proposed for the determination of the stress field in relationship with the actual microstructure and texture of the materials. The numerical calculations are validated by comparing the obtained results to those experimentally determined and by scanning electron microscope observations on the initiation zones of microcracks.

In spite of an extensive bibliography available, the solubility limit of carbon in ferrite is still uncertain (between 50 and 100 ppm at 600°C for example), and this is not sufficient for the improvement of steel processing. Therefore we have tried to establish as accurately as possible the solubility of carbon between 500 and 750°C in a low carbon aluminium killed steel using a thermoelectric power protocol, which enables to calculate the amount of free interstitials in a ferritic matrix from the amount of interstitials that segregate on dislocations after strain. The solubility limit has been determined at ± 2 ppm between 550 and 730°C, and described by the relation: C(%wt) = 6.63 exp(-11.8 kcal/mol/RT). At a time when metallurgical phenomena are more and more simulated, we believe that a similar procedure should be used for other experimental studies providing basic data for modelling.

Samples of AISI 304 steel with layers nitrided at low temperature (< 450°C) have been heated isothermally under neutral atmosphere for times ranging from 4 to 3,000 h. The stability of the layers varies depending on holding temperature. At temperatures greater than 450°C, the initial FCC disordered metastable solid solution, supersaturated in nitrogen ($\gamma_{\rm N}$), decomposes in a relatively short time (4 h). At lower temperatures, however, no change in supersaturation and no decomposition occur, even for holding times exceeding 3,000 h. Nevertheless, an increase in layer thickness is noted and the hardness within the layers remains high (800 HV10).

During the reactive sintering of W-6%Co-C powder mixtures at 1,500°C under pressure, the reaction product between these elements depends on the relative contents of carbon and cobalt. With a carbon content of 7% by mass, the WC monocarbide forms alone and densification occurs in the presence of a cobalt-based liquid phase. With lower carbon contents, the hemicarbide W2C forms first and reacts with cobalt to form the mixed carbide Co3W9C4. The hardness is increased, but the amount of liquid phase is reduced and the sintering densification is limited. In the presence of the mixed carbide, the cobalt content should be sufficient to be able to produce the amount of liquid phase required for sintering densification. For carbon contents greater than 7%, one obtains the formation of the WC carbide, densified by the cobalt binder, and the precipitation of free graphite. The choice of the initial carbon content allows thus to influence the type of phases obtained and the conditions of liquid phase sintering densification.

The rate of air oxidation towards 1,000°C of the Si3N4-bonded silicon carbide refractory is low. It is found that the porous nitride-bonding phase oxidizes mainly and that the SiC oxidation is negligible. The decrease of specific surface area, due to the growing of a dense silica layer, induces much slower kinetics.