Contribution à l'étude des diagrammes d'équilibre de phases des systèmes polyconstitués. Application aux systèmes C-Cr-Fe-Ni, C-Cr-Nb-Ni et C-Cr-Nb-Ni-W.

Thèse présentée à l'Institut national Polytechnique de grenoble This study shows the interest of the thermodynamical approach by using the multicomponent phase diagram calculation, for the research of new materials, particularly in the aeronautics field. In this work, we have formulated in a first step the equilibrium relations between phases in a multicomponent system, and developed a software allowing for "a priori" calculating the equilibriumphases and their composition in a N multicomponent