Anisotropy and size effect in tensile mechanical properties of Al-Cu-Li 2198 alloy

The anisotropy effect on tensile mechanical properties of an Al-Cu-Li (2198) alloy with regard to thickness of the specimens under different ageing conditions was investigated. Occurring size effects between macro and micro (0.5, 3.2 and 5.0 mm thickness and 10 and 50 mm gauge length) tensile specimens was discussed. The mechanical behavior of AA2198 was examined by taking into account the experimental results from micro-flat and standard tensile specimens. Higher thickness specimens showed higher elongation at fracture values and slightly lower yield stress properties. Anisotropy seems to be higher at T3 condition, while the lowest was noticed at the peak-ageing condition. The results showed that the micro-flat tensile specimens in T3 condition presented slightly lower yield stress (10 MPa difference) and essentially lower elongation at fracture values (more than 40 % decrease), when compared with the respective of higher thickness specimens. It was also shown that thicker (5.0 mm) specimens exhibit slightly higher tensile ductility properties (almost 17 %) and slightly lower tensile strength properties than the respective 3.2 mm thickness specimens. There is evidence of relative difference in mechanical properties due to the rolling process in the two sheet directions (L and T directions); such anisotropy difference seems to be marginal at the peak-ageing condition.