Ambient and cryogenic tensile properties of AA2195T87 sheets with pre-aging cold work by a combination of cold rolling and stretching

Al-Cu-Li-Mg-Ag-Zr alloy AA2195, in the form of 4 mm thick sheets, was heat treated to T87 temper with the pre-aging cold work provided by a combination of 5% cold rolling followed by 2% stretching. The tensile properties of the material were evaluated at ambient and cryogenic temperatures (i.e. −196 °C and −253 °C). Transmission electron microscopy of the heat treated (i.e. T87 treated) material revealed that the major strengthening precipitate is indeed the T1 (Al2CuLi) phase nucleated on the {111}Al planes. In addition, θ′ [metastable Al2Cu (θ)] precipitates on {100}Al planes, and “plate like features” lying on {111}Al planes were further observed. The one atom layer thick “plate like features” have the same crystal structure as that of the matrix Al. The possibility of such “plate like features” being either the early stages of the Ω phase (i.e. a chemically modified coherent form of θ-Al2Cu phase) in the constituent Al-Cu-Mg-Ag system or the evolutionary stages of the T1 phase itself is discussed.