Mechanical properties and microstructure evolution of an Al-Cu-Li alloy subjected to rolling and aging

The mechanical properties and microstructure of Al-Cu-Li alloy sheets subjected to cryorolling (−100 °C, −190 °C) or hot rolling (400 °C) and subsequent aging at 160 °C for different times were investigated. The dynamic precipitation and dislocation characterizations were examined via transmission electron microscopy and X-ray diffraction. The grain morphologies and the fracture-surface morphologies were studied via optical microscopy and scanning electron microscopy. Samples subjected to cryorolling followed by aging exhibited relatively high dislocation densities and a large number of precipitates compared with hot-rolled samples. The samples cryorolled at −190 °C and then aged for 15 h presented the highest ultimate tensile strength (586 MPa), while the alloy processed via hot rolling followed by 10 h aging exhibited the highest uniform elongation rate (11.5%). The size of precipitates increased with the aging time, which has significant effects on the interaction mechanism between dislocations and precipitates. Bowing is the main interaction method between the deformation-induced dislocations and coarsened precipitates during tensile tests, leading to the decline of the mechanical properties of the alloy during overaging. These interesting findings can provide significant insights into the development of materials possessing both excellent strength and high ductility.