Résumé:
The aim of the work that we have carried out in this thesis is the study of the
kinetics and the mechanism of the formation and the transformation of the intermediate
semi coherent phase p’ in the alloys of the Al-Mg system.
For this we have used many alloys of the Al-Mg system (8, 9, 10 and 12 wt %t
Mg) and several experimental methods simple but rigorous and adapted for this type of
scientific works, in order to follow the different structural evolutions : essentially
dilatometry and differential scanning calorimetry, completed by optical microscopy, X
ray diffraction and micro hardness measurements.
The synthesis and the analysis of the numerous and interesting results obtained
by those several methods have allowed us to assert that the intermediate p' phase
firstly precipitates under the form of globules which cluster then transform to needles
leading to a structure identical to a Widmanstatten one, before to come back to the
globular form characteristic of the equilibrium p phase.
In addition the dilatometry and the differential calorimetrical analysis by a lower
degree are sensitive to the structural transformations which occur during the
anisothermal heating in all alloys aged at 150°C to precipitate the semi coherent
intermediate p’ phase.