The microstructure, hot cracking susceptibility, and mechanical properties of a novel Al–Cu–Y alloy were investigated. The Al–4.7Cu–1.6Y alloy demonstrated very good casting properties, hot cracking susceptibility that is similar to Al–Si–Mg alloys. Analysis of the solidification process showed that the primary Al solidification is followed by the eutectic reaction Liquid→ τ₁(Al₈Cu₄Y)+Al and the peritectic reactions Liquid+ τ₆(Al,Cu)₁₁Y₃)→Al+ τ₁(Al₈Cu₄Y) (612°C) and Liquid+ η(AlCu)→ τ₁(Al₈Cu₄Y)+ θ(Al₂Cu) (595°C). The τ₁(Al₈Cu₄Y) eutectic phase demonstrated high thermal stability during homogenisation treatment. The recrystallisation temperature was in the range 250–350°C after rolling with previous quenching at 540 and 590°C and without heat treatment. The recommended annealing mode for material in the as-rolled condition is 100°C for 1 h: YS = 273 MPa, UTS = 305 MPa and El. = 6.6%.

The microstructure and mechanical properties of the Al–4Cu–2.7Er–0.3Zr alloy were investigated. The precipitates of the L1 ₂ structured phase with sizes 37 ± 12 nm were formed in lines and homogenously distributed inside the aluminium matrix after annealing at 605°C for 1 h. The as-rolled Al–4Cu–2.7Er–0.3Zr alloy developed an increased hardness after 1 h annealing at 100–550°C and 0.5–6 h annealing at 150–250°C due to precipitation of the Al ₃ (Er,Zr) phase. Addition of Zirconium improved the tensile properties relative to those of the Zr-free alloy by approximately 20 MPa: yield strength = 273–296 MPa and ultimate tensile strength = 296–328 MPa in the alloys annealed at 100–150°C. GRAPHICAL ABSTRACT