Effect of Temperature and Strain Rate on the Compressive Flow of Aluminum Composites Containing Submicron Alumina Particles

Uniaxial compression tests were conducted on aluminum composites containing 34 and 37 vol pet submicron alumina particles, to study the effect of temperature and strain rate on their flow stress. For temperatures between 25°C and 600°C and strain rates between 10^-3 and 1 s ^-1, the flow stress of the composites is significantly higher than that of unreinforced aluminum tested under similar conditions. This can be attributed to direct strengthening of the composites due to load sharing between the particles and the matrix, and an enhanced in-situ matrix flow stress resulting from a particle-induced increase in dislocation density. The composites, however, exhibit the same stress dependence on temperature and strain rate as unreinforced aluminum, indicating a common hardening mechanism, i.e., forest dislocation interactions. The forest hardening present under the explored testing conditions masks the effects of direct dispersion strengthening operative at lower deformation rates in these materials.