Microstructural Aspects of Serrated Yielding Behavior in the Al-Li 8090 Alloy

摘要

The manifestations of serrated yielding behavior at room temperature accompanied with the microstructural transitions in the 8090 alloy were systematically studied. Differential scanning calorimetric analyses in combination with transmission electron microscopic observations were employed to identify the microstructures for specimens tempered under various conditions. Experiments revealed that two types of serration in the stress-strain curves of the 8090 alloy existed, which were clearly related to their microstructural changes and dislocation interactions. The type A serration was mainly due to the work softening of the shearing slip of δ'(Al_3Li) particles which was found in the specimens of as-quenched, natural-aged and under-aged conditions. Otherwise, the type B serration, which was observed in the stress-strain curves of all the specimens except for over-aged condition, was primarily attributed to the interaction of Cu and/or Mg atoms with dislocations in the solid solution, i. e., resulting from dynamic strain aging.