Yielding Phenomenon of an Al-3% Li Alloy

where the specimens are recovered but not recrystallized. This second type of yielding is characterized by a sharp yield drop and long yield elongation. A mechanism of the second type of yielding has not been investigated, but it is clear that the yielding phenomenon is not due to a simple effect of strain aging, because the specimens has recovered so that dislocation arrangements should have changed on annealing. In the present study, the second type of yielding was investigated, by using mainly an AI-317o Li alloy which had been over-aged and then cold-rolled(1). By combining information obtained from the stress-strain curves, transmission electron microscopy, lattice constant measurement and electrical resistivity measurement, the necessary conditions for the appearance of the yielding were discussed in terms of heat-treatments, i.e. overaging, annealing and testing temperature. Further, the general requirements for the yielding were considered. II. Experimental Procedure