材料期刊网

An investigation has been made of the fatigue and fracture behavior of an Al-Li-Cu-Mg-Zr 8090-T6 alloy at room (300 K) and liquid nitrogen (77 K) temperatures. The fatigue and fracture strengths, as well as ductility of the alloy, have been found to increase with decreasing temperature. The observations by scanning electron microscopy (SEM) and transmission electron microscopy (TEM) reveal that the changes in fatigue and fracture behavior with temperature are considered to be associated with the change in the deformation and fracture modes. It has been found that the occurrence of the localized shear deformation bands in which the hard precipitates are sheared by moving dislocations is responsible for the reduction of fatigue and fracture strengths as well as ductility of the alloy at room temperature. However, the improvement of both strength and ductility of the alloy at liquid nitrogen temperature might be attributed to the deeper and larger delamination that occurred on the fracture surface.