Effect of liquid film constitutional supercooling at the end of solidification on the hot cracking behavior of Al-4.0 wt.%Cu alloy

Abstract

• Molecular dynamics method was used to calculate the solute diffusion coefficient. • Effect of liquid film constitutional supercooling on hot cracking was studied. • The influence of dendrite growth on hot cracking behavior was excluded. In this study, the molecular dynamics (MD) calculation method was used to calculate the diffusion coefficient of solute atoms in the liquid film (LF) at the end of solidification, and the effect of constitutional supercooling in LF on the hot cracking tendency of Al-4.0 wt% Cu alloy was investigated combined with experiments. The MD calculation result indicated that the diffusion coefficient of Cu elements ( D L ) increased as the atomic percentage of that in the LF decreased at a specific temperature within the solidification range (620 °C was chosen in this study). Supercooling degree produced by constitutional supercooling ( ΔT c ) decreased while the constitutional supercooling zone width ( Δx ) increased with D L , which facilitated extending the LF complementary shrinkage zone during solidification, and cellular grains easily formed after solidification, thus reducing the hot cracking tendency of Al-4.0 wt.%Cu alloy. The experimental results concluded that the hot cracking tendency of Al-4.0 wt.%Cu alloy decreased as the atomic percentage of Cu elements in the LF decreased, which verified the accuracy of the MD calculation results.