Fracture toughness of an Al-Li alloy at ambient and cryogenic temperatures

In this study, J-integral tests, both pure mode I and mixed mode I/III, have been carried out on the Al-Li alloy WELDALITE 049. The tests were performed at ambient temperature and at 77 K. The addition of the mode III loading component decreased the fracture toughness of the alloy at room temperature, while the opposite was found to be true at 77 K. Aging caused a decrease in the fracture toughness of the material. The results are consistent with mechanisms proposed for fracture in this class of alloy and with qualitative models for mixed mode fracture.