Effect of flow, heat transfer and magnetic energy on the grain refinement of 7A04 alloy under electromagnetic pulse

Abstract

Abstract In this paper, a transient numerical simulation method was used to analyze the direct chill casting process of 7A04 alloy under electromagnetic pulse treatment. The distribution and evolution of the electromagnetic force, fluid and thermal fields were studied to determine their effect on the solidification characteristics of alloy ingots. A modified nucleation theory for the refinement of grain size was presented considering the effect of electromagnetic energy on the critical Gibbs free energy Δ G * $\Delta {G^*}$ of the unity, which was verified by the corresponding experiments. The results showed that the swirl rings of the axial section in the melt were restrained and a lower temperature gradient was formed in the radial section when the magnetic flux intensity was increased. Under these conditions for nucleation, the grain refinement could be explained by the electromagnetic pulse energy that reduced the energy barrier and improved the nucleation rate, either heterogeneous nucleation or homogeneous nucleation.