Description

Creep is the tendency of solid materials to undergo permanent gradual deformation under the influence of stresses. It occurs as a result of long term exposure of material to stress levels that are below its yield strength. Creep is more severe in materials that are exposed to elevated temperature (i.e. near melting point) for long time. Functionally graded materials (FGMs) are a new generation of engineering materials, in which the constituents or their contents vary with respect to position coordinates, which enable them to offer unique performance. The concept of FGM has been proposed with a view to obtain a new class of composite materials, consisting of heat resistant ceramic on the high temperature side and tough metals with high thermal conductivity on the low-temperature side, with a gradual variation in composition from the ceramic to metal phase. The application of concept of FGMs to MMCs has led to the development of materials/components, designed with the purpose of using selective reinforcement in regions where enhanced properties like increased modulus, strength and wear resistance are required.