Abstract: The effect of the temperature of uniaxial tensile test on the plastification effect (PE) of ultrafine-grained (UFG) Al–1.5Cu (wt %) alloy is studied for the first time. The UFG structure in a material is formed by high-pressure torsion (HPT). A significant increase in the plasticity of an UFG alloy from ~3 to 22% while retaining a high ultimate tensile strength (450 MPa) is achieved due to additional thermomechanical treatment including short-term low-temperature annealing and subsequent small HPT deformation. The temperature range of the PE implementation is revealed. It is shown that a decrease in the deformation temperature results in a gradual decrease in the PE and its disappearance at –20°C. Copper doping results in significant narrowing of the PE implementation range from the low-temperature side in comparison with the UFG Al case. The possible causes of the effect of Cu doping on the temperature dependence of the PE is discussed.