Effect of thermal stresses on the thermal expansion and damping behavior of ZA-27/aluminite metal matrix composites

When the fabrication of a metal matrix composite (MMC) involves its cooling from a high temperature, plastic-elastic residual deformation fields can b e generated within and around the particle due to the differential thermal expansion between the particle and matrix metal. The present investigation is concerned with the effect of thermal residual stresses on the thermal ex pansion and damping behavior of aluminite particulate-reinforced ZA-27 allo y MMCs, Composites were prepared by the compocasting technique with 1, 2, 3 , and 4 wt.% of aluminite reinforcement. Thermal expansion and damping prop erties have been studied experimentally as a function of temperature over a temperature range 30 to 300 degreesC both in the heating and cooling cycle . The thermal expansion studies exhibited some residual strain, which incre ased with the increase in the weight percent of the reinforcement, The damp ing capacity of both the composites and matrix alloy is found to increase w ith the increase in temperature during the heating cycle, whereas in the co oling cycle, damping behavior exhibits a maximum, which becomes more pronou nced with the increase in the weight percentage of the reinforcement, The a ppearance of the maximum may be linked with dislocation generation and moti on as a result of plastic deformation of the matrix at the metal/reinforcem ent interface. This phenomenon is attributed to the thermal stresses genera ted as a result of coefficient of thermal expansion (CTE) mismatch between the composite constituent phases. The thermal stresses have been estimated in both the cases using simple models.