Gradient materials : An overview of a novel concept

This paper provides a definition and classification of functionally graded materials (FGM). FGM manufacturing processes based on the modification of existing techniques like powder metallurgy are compared to non-conventional methods such as sedimentation. The ability of FGM's to reduce thermal stresses is critically reviewed, and it is demonstrated that optimum performance can only be achieved if the thermomechanical property profile is adapted to the geometry and service conditions of the component. Determination of the thermomechanical property profile of FGM's will require new techniques with high spatial resolution. The potential of FGM's as high-temperature materials, hard materials, biomaterials and electronic materials is described and new applications in the field of functional materials are proposed.