Papers by Author: D. Chaubet

Abstract: Nucleation and normal or abnormal grain growth of new grains have been observed in several metals and alloys during annealing after various levels of strain (from few percents for abnormal grain growth in steel and aluminium to 90 % strain for static recrystallization of highly deformed copper, zirconium and steel). For each of these cases, the links between the initial deformation state of the polycristalline samples and their final textures after annealing are analyzed in some details, by taking into acount the distribution of orientations and misorientations within the samples, as well as the repartition of stored energy . With the help of polycristalline models for the simulation of deformation and recrystallization processes, some general conclusions regarding the nucleation and growth processes are finally drawn.

Abstract: The evolution of crystallographic texture in a Zr-2Hf alloy has been investigated during deformation, primary recrystallisation and normal grain growth. The as-deformed states (50-90% deformation) are characterized by a major tilted {0001}<1010> texture component and this component is reinforced with increasing deformation. A decrease in the intensity of the tilted {0001}<10 10> component and a continuous increase in the intensity of the tilted {0001}<1120 > component take place during primary recrystallisation. Normal grain growth is associated with the coarsening of grains with the {0001}<1120 > orientation. This texture evolution is interpreted on the basis of the evaluation of the stored energy and the consideration of specific grain boundaries with low energy and/or high mobility.

Abstract: The recrystallization of a Zr-2Hf alloy sheet deformed by plane strain compression at room temperature and then heat treated in the temperature range 500-650°C is studied. The microstructure, local and global crystallographic textures are investigated by EBSD and X-ray techniques. The as-deformed condition exhibits a heterogeneous microstructure composed of highly and less deformed zones, the EBSD indexing of the latter ones being more reliable. The asdeformed condition displays a (0001) < 0 1 10 > crystallographic texture. The evolution of the microstructure during recrystallization very much depends on the amount of local deformation. Recrystallization begins in highly deformed zones, new grains having two variants of texture components, {0001} < 0 1 10 > and {0001} < 0 2 11 >. Some change of preferred orientations concomitant with grain growth at 600 and 650°C has been observed with a decrease in the {0001} < 0 1 10 > component and an increase in the {0001} < 0 2 11 > component.