The topography of grain boundary thermal grooves in the Ni-rich NiAl is studied by the atomic force microscopy. It is demonstrated how the processes of grain boundary sliding and surface faceting modify the shape of the grooves. The quantitative theory of grain boundary grooving that takes into account the above complications is developed. The great potential of grooving studies for the analysis of microstructure evolution is emphasized.

Developments in electronic structure calculations and computer performances have made it possible to perform ab-initio calculations of structural properties of materials, like defect parameters in transition metals. The values of vacancy formation and migration enthalpies calculated in this context agree with experimental data within less than 10% . Reliable self-diffusion coefficients for the vacancy mechanism can be deduced. This approach sheds new light on the so-called self-diffusion anomaly in body centred cubic metals.

A three-dimensional cellular automaton-finite element model has been developed over the past five years for the prediction of macrostructures formed in casting. The present article briefly summarizes the growth algorithm of the model. Applications are then given for the prediction of the grain structure formed in a directionally solidified turbine blade produced by investment casting, a continuously cast cylinder and a near-net shape steel sheet obtained by twin-roll casting.

This paper addresses several experimental techniques, which have been developed and validated with the aim of assessing the mechanical conditions of service-exposed primary plant components, particularly from the point of view of fracture toughness. Such techniques are based on the use of specimens of small or even miniaturized size, as an alternative to the "conventional" methodologies described by commonly used test standards.

In order to find the origin of the surface marks in meniscus free continuous casting, an experimental work has been carried out with two different experimental devices using metallic alloys and transparent organic compounds respectively. In a first companion paper, we showed the results of the observation of the samples obtained with the two devices. Here, we present the results of the direct observation of the solidification phenomena. These results permit us to propose a microscopic model of the formation of the marks.

For a HIP operation, conventional control of the process variables (T, P) is the current mode used. The process variables follow a prespecified trajectory (schedule) assumed to lead to the final quality of product. A second mode is advanced control, where on-line measurements of a product state variable enable to monitor the evolution of the product variables and if necessary to compute corrections to the schedule in order to obtain the desired quality of the final product. HIP advanced process control requires continuous monitoring of the sample density during all stages of the process and the on-line identification a process model. To this end, a dilatometer has been built for in situ monitoring densification during a HIP operation, the Ashby process model has been validated and on-line identification has been demonstrated. It is shown that advanced process control of a HIP operation can be performed in two steps : on-line identification of the process model and subsequent process path replanning. The first step can only be performed during the process variables plateau of the preset temperature- pressure cycle, and process path replanning consists of a new temperature- pressure plateau.

The instrumentation of an industrial vacuum arc refining furnace (VAR process) has allowed for the first time to visualize the electric arc during the remelting of a zirconium alloy. This device, recording fast video observations in synchronization with the high frequency voltage changes of the arc, has been applied to the study of the behaviour of the arc and of the transfer mechanisms of the liquid metal to the ingot. Results are given for current densities of about 10 to 20 A/cm2 and arc lengths smaller than 6 cm.

PSA., leader in the fabrication of Diesel engines, aims at increasing its productivity for the manufacture of forged steel crankshafts and controlling perfectly their quality. All industrial partners of PSA are contributing to the achievement of this goal. Detailed metallurgical studies and numerical simulation have been used internally to describe the microstructural transformations involved. It has been shown that numerical simulation allows to identify trends for the effect of the modification of various parameters without the need for expensive and time-consuming prototype studies.

A very great number of arrowheads and arrows of catapult was excavated from "Le Puy d'Issolud" , probable site of the fight of Uxellodunum, given by Caesar, in 51 B.C. Till now, only a typological study was devoted to them. Here are gathered the first data about microstructure and local analysis (OM, SEM, EDXS, XR, microhardness HV) of weapons selected for their archaeological value. In the same time were made: examination of metal (Fe-C alloys, between pure enough iron and quasi-eutectoid steel), of corrosion layers and of the two types of residual slags, produced during direct reduction or forging. This contributes to reach a better approach of treatments and forging practice, during the Roman period.