Numerical simulation of macrosegregation phenomenon in Cu-6wt%Ag alloy ingots fabricated by electromagnetic stirring

Abstract

The development and research of high strength and conductivity materials are essential for the advancement of high-field magnets, including pulsed magnets. This study investigates the effect of electromagnetic fields on the solidification casting of binary Cu-6wt%Ag alloy ingots with diameters of 40 and 160 mm. A 3D numerical simulation is performed utilizing the continuum model with conservation of total momentum, mass, energy, and species. The results indicate that applying electromagnetic stirring (EMS) to small cross-section ingots can cause many randomly distributed small regions with higher segregation degrees inside the ingot, which is not conducive to improving the macrosegregation inside the ingot. For large cross-section ingots without EMS, compared to small cross-section ingots, there is more severe macrosegregation inside the ingot, especially the extreme center segregation with a maximum segregation degree of about 414%. EMS can effectively control macrosegregation within a specific range and eliminate center segregation. When the linear EMS's magnetic induction intensity is set to 0.06 T, the maximum segregation degree near the ingot center can be reduced to less than 260%. Simultaneously, the EMS induced forced convection is also instability, leading to numerous haphazard solute accumulations and depletions, which explains many small segregation regions in the ingot. In terms of improving macrosegregation in large cross-section ingots, Linear EMS has a definite advantage over rotary EMS. It is possible to keep the entire segregation degree in the ingot below 100% when the linear EMS's magnetic induction intensity is set to 0.036 T and the stirring frequency is 4 Hz. The ideal stirring parameters range for linear EMS is to maintain the magnetic induction intensity at around 0.036 T and the stirring frequency in the range of 4–8 Hz.