Low-cyclic fatigue behaviour of an Al-Cu-MgAg alloy under T6 and T840 conditions

The low-cyclic fatigue (LCF) behaviour of an AA2139 alloy belonging to the Al-Cu-Mg-Ag system was investigated under T6 and T840 conditions. The T840 treatment involves cold rolling with a 40% reduction prior to ageing, and this was effective in increasing the tensile strength of the alloy. Under cyclic loading at total strain amplitudes (epsilon(ac)) of +/- 0.4 to +/- 1.0%, the mechanical behaviour is defined as the prevalence of elastic over plastic deformation processes under both the T6/T840 conditions. The initial weak hardening during one to two cycles of loading at epsilon(ac) > 0.55% and an insignificant softening upon following the cyclic loading to fracture was observed for the T6/T840 conditions. The LCF behaviour of the alloy under the T6/T840 conditions is described by the Basquin-Manson-Coffin relationship.