DEFORMATION AND FRACTURE-BEHAVIOR OF AN 8090-AL-LI ALLOY AT CRYOGENIC TEMPERATURE

The deformation and fracture behavior of 8090 Al-Li alloy at low temperature has been studied by the in situ SEM observation of L-T and S-T oriented specimens. It shows that the overall deformation mode of both L-T and S-L oriented specimens changes from the planar slip to the homogeneous deformation with decreasing temperature. Such change in the deformation mode with the test temperature results in the increase in elongation of L-T oriented specimen with decreasing temperature, but not that of S-L oriented specimen. It has been suggested that the different mechanism is operating in controlling the low temperature mechanical behavior of Al-Li alloys depending on the specimen orientation. It shows that the overall deformation mode, e.g., homogeneous deformation vs. planar slip, is critical when the fracture occurs mostly transgranularly such as in L-T orientation. On the other hand, when the fracture occurs intergranularly such as in S-L orientation, other factors such as grain boundary strength play a more critical role than the overall deformation mode. © 1995.