Unloading effects in aluminium and aluminium-zinc single crystals

Abstract

Interrupted tensile tests have been earned out on single crystals of super-purity aluminium and solid solutions of aluminium-zinc. Partial load removal during an interruption of the test is shown to have several effects on subsequent plastic flow. Unloading yield points are formed during tests on both alloy and aluminium specimens, while strain ageing yield points formed during tests on alloy specimens are shown to be either enhanced or diminished, depending on the sequence of prior ageing and unloading. Finally the relationship between unloading and room temperature recovery is examined and the results suggest that the trapping of glissile dislocations, as a result of unloading, leads to a partial suppression of recovery.