Microstructures of aluminum compressed at various rates and temperatures

Abstract

Specimens of 1100 aluminum were compressed uniformly to a logarithmic strain of 0.7 (50 pct reduction) at constant true strain rates in a Cam Plastometer. Tests were conducted at strain rates between 220 and 0.1 sec−1 and between 500°C and 20°C. Exmination of the microstructures by electron microscopy indicated that the deformed structure consisted of dislocation cells or subgrains. As the temperature of testing was raised or the strain rate lowered, the resulting subgrains were larger, and the dislocations in the subboundaries were arranged in more orderly arrays. The cell sizes are related quantitatively to the flow parameters. The dependence of dynamic recovery on temperature and strain rate is compared to the dependence observed in extrusion of a similar alloy. At high strain rates at 400° and 500°C, partial recrystallization occurred while the specimens were cooling to room temperature.