Microstructural Evolution, Precipitation Behavior, and Mechanical Property Response of Cast Al–Li–Cu–Cd–Mn–Zr–Ti Alloy

Abstract

The microstructural evolution and mechanical properties of cast Al–Li–Cu–Cd–Mn–Zr–Ti alloy during heat treatment are investigated systematically. In these findings, it is shown that the as-cast alloy exhibits fine and equiaxed grains. During the solid solution treatment, Al₂₀Cu₂Mn₃ dispersoids effectively restrict grain growth, and reducing the solid solution time has a similar effect. Subsequently, the precipitation behavior and its effect on the mechanical properties during the aging process are revealed. Al₃(Ti, Zr) particles are uniformly distributed throughout the matrix, acting as nucleation sites for δ′, θ′, and T₁ precipitates. Overtime, δ′ precipitates gradually coarsen and decrease in number, and some δ′ precipitates attach to Al₃(Ti, Zr) particles, forming core–shell Al₃(Li, Ti, Zr) phases. At the same time, plate-shaped θ′ and T₁ precipitates emerge and coarsen. After aging at 160 °C for 24 h, the alloy exhibits an excellent combination of strength (yield strength =293.3 ± 4 MPa, ultimate tensile strength =468.0 ± 3 MPa) and ductility (elongation =9.6 ± 0.4%), surpassing those reported in other cast Al–3Li–2Cu–X alloys. Critically, the underlying mechanisms behind the microstructure and mechanical properties are discussed extensively, providing valuable insights for the advancement of cast Al–Li alloys.