THE EFFECT OF COLD-ROLLING ON THE AGING BEHAVIOR OF ALUMINUM-LITHIUM ALLOYS

The effect of deformation by cold rolling in the range of 30 to 70% on the ageing behaviour of aluminium-lithium alloys containing 5.5 and 7 .6 at% lithium is investigated using hardness, TEM, and XSAS methods. If the deformation precedes the ageing treatment, a higher hardness is obtained. However, the hardness increment decreases with increasing d eformation when compared to quenched and aged samples. The phenomenon is due to a subsequent recrystallization after higher degrees of defor mation. Two types of precipitates of different sizes are found using t he XSAS method. The larger ones grow, while the smaller ones diminish during ageing. The superlattice reflections visible after quenching di sappear in the alloys deformed by more than 50%.