Heterogeneous and architectured materials: a possible strategy for design of structural materials

Facing increasing demands for multifunctional solutions, the classical strategy of the metallurgist to improve properties, using microstructural refinement, reaches its limits: very often the function is not provided by the property only, but by the interplay between the shape, the properties, and possible association of materials. The purpose of the present paper is to outline new strategies for structural materials development offered by new degrees of freedom and by their combination; not only playing with the microstructure or with the macroscopic shape, but allowing a new scale for materials organization, the "architecture", and controlling a new degree of freedom, the "spatial heterogeneity". For these ideas to be effective, the question of processing such "heterogeneous architectured materials" in an affordable manner has to be kept in mind. Very often the development of architectured materials will require new processing methods.