Prediction of the solidification path of Al-4.37Cu-27.02Mg ternary eutectic alloy with a unified microsegregation model coupled with Thermo-Calc

Abstract

Abstract An extended unified microsegregation model with solid back diffusion effects and five different dendrite morphologies was used to investigate the solidification path of Al-4.37Cu-27.02Mg (wt.%) ternary eutectic alloy at different cooling rates and solid back diffusion coefficients, coupled with Thermo-Calc. It was indicated that the cooling rates (Rf ) had no obvious effect on the solidification path which was (L + α) → (L + α + T) → (L + α + β + T); but the solid back diffusion coefficient (Φ) had a great effect on the solidification path, which evolved gradually from (L + α) → (L + α + T) → (L + α + β + T) into (L + α) → (L + α + T) when Φ increased from 0 to 1. The volume fractions of primary α phase (V α), binary eutectic (V 2E) and ternary eutectic (V 3E) at each solidification path were calculated. It was shown that V 2E decreased with the increase of Rf whereas V 3E increased and V α was almost invariant. The dependence of V 2E, V 3E and Rf were determined by linear regression analysis given as: V 2E = −2.5lgRf + 47.5; V 3E = 6.4lgRf + 47. Increase in Φ lead to increases in V α and V 2E and decrease in V 3E. The predicted soldification paths and volume fractions of Al-4.37Cu-27.02Mg ternary eutectic alloy at different cooling rates were in good agreement with experimental results.