Influence of reinforcement contiguity on the thermal expansion of alumina particle reinforced aluminium composites

Pore-free composites combining alumina particles within a matrix of pure aluminium are produced by pressure infiltration, varying systematically the degree of the contiguity, beta, of the ceramic phase by sintering prior to infiltration. The thermal expansion of these composites is characterized using repeated cycling in a dilatometer from 303 to 543 K. The initial composite thermal expansion measured immediately after changing the sign of the temperature-time function conforms with predictions from thermoelasticity. Upon further temperature excursion, upward deviations from thermoelastic predictions are found; these are attributed to the influence of matrix plasticity, the influence of which decreases as beta increases. The composite thermal expansion travels across 80% of the theoretical range of initial thermoelastic values as beta increases from 0 to 0.123, leading to the conclusion that even a small level of connectivity of the ceramic phase causes significant changes in the thermal expansion of isotropic metal/ceramic composites.