Properties of multilayered mullite/Mo functionally graded materials fabricated by powder metallurgy processing

Mullite/Mo functionally graded material (FGM) was developed with a powder metallurgy process. Microscopic observations revealed that the microstructure of the mullite/Mo FGM had a gradual stepwise variation. The thermomechanical properties of the mullite/Mo system had graded distributions that depend on the composition variation across the thickness. Thermal shock tests were done on the FGMs and on monolithic mullite. The FGM specimens had better thermal shock resistance than did monolithic mullite. The thermal shock resistance of FGMs was influenced by the sintering-induced residual thermal stress. Cracks caused by thermal shock were observed, and the mechanism of crack formation was discussed.