Anisotropy of thermal expansion coefficient in hot pressed Mo/PSZ composites

The anisotropy of the thermal expansion coefficient in hot pressed particulate composites of molybdenum/partially stabilized zirconia was measured over a whole composition range by the laser speckle photography that had been specifically designed for the determination of regional thermal displacement in a sintered compact. On the presumption that the anisotropy is closely related to the microstructural orientation resulted from the uniaxial loading of hot pressing, the flattening and preferred orientation of the dispersed particles were quantified using the concept of equivalent ellipsoids and also with an anisotropic parameter, i.e. the deviation angle distribution. The definite anisotropy in the thermal expansion coefficients has been found; the thermal expansion coefficient parallel to the hot pressing direction is larger than that in the normal direction. It has been found that the difference in the thermal expansion coefficient is dependent on the composition with the largest difference at around 60 vol%PSZ. The anisotropy (difference in the thermal expansion coefficient between the two directions) is linearly related to the anisotropic parameter that represents the particle orientation. The dependence of thermal expansion coefficient on the oriented particle distribution has been discussed by the Eshelby's theory. The experimental trend has been well explained by the present prediction.