Evolution of Microstructure and Mechanical Properties of a New Al–Cu–Er Wrought Alloy

Abstract

The evolution of the microstructure and mechanical properties of deformed sheets made of a new Al–4Cu–2.7Er alloy has been studied in the course of homogenization and annealing. The structure of the cast alloy consists of a dispersed eutectic ((Al) + Al₈Cu₄Er), Al₃Er-phase inclusions located along the dendritic-cell boundaries, and a nonequilibrium AlCu phase. During annealing at 605°C before quenching, the intermetallic phases have high thermal stability: the particle size of Al₈Cu₄Er and Al₃Er phases does not exceed 1–4 µm. The annealing of deformed sheets at temperatures below 300°C leads to a slight decrease in the hardness; grains elongated along the rolling direction are observed in the structure. With an increase in the annealing temperature from 350 to 550°C, the recrystallized grain size increases from 8 ± 1 to 14.5 ± 1.5 μm. The uniaxial tensile tests showed that the annealed alloy possesses sufficiently high strength characteristics: yield stress of 260–280 MPa, ultimate tensile strength of 291–312 MPa, and relative elongation of 5.5–6.1%.