Hydrogen microporosity evolution and dendrite growth during long solidification of Al-Cu-Li alloys: Modeling and experiment

The hydrogen content of aluminum-lithium alloys in the molten is more than 10 times that of conventional aluminum-based alloys. Therefore, hydrogen microporosity is an extremely serious casting defect in aluminum-lithium alloy, which greatly affects the quality of castings. In this research, we used a 3D multi-component cellular automata (CA) model coupled with thermodynamic calculations to simulate and predict the evolution of primary phase microstructure, nucleation and growth, and kinetic growth of hydrogen microporosity during the solidification of ternary Al-Cu-Li alloys. The results of simulations under different cooling rates were verified by hydrogen microporosity quantitative characterization in a vacuum casting using X-ray computed tomography (XCT). The equivalent radius of the pore during solidification is closely related to the dendrite arm spacing, i.e. r (f_l, λ₁, λ₂) = max (f_l λ₁/2; λ₂/2). The maximum equivalent diameter of the porosity during solidification satisfies the Boltzmann function with temperature. In addition, the equivalent diameter of the porosity at different cooling rates satisfies y = 18.82x^−0.82 nonlinear relationship with sphericity. The validated hydrogen microporosity model provides a crucial link for the fabrication of Al-Cu-Li alloy products and the design of ICME.