| Abstract Scope |
Freckle defects, a common type of macrosegregation channel in deformed superalloys during vacuum arc remelting (VAR), are primarily caused by the convection of solute-rich liquid in the mushy zone, significantly impairing mechanical properties and service life. Current Rayleigh criteria mainly consider the solidification interface inclination effect, but existing studies inadequately account for factors such as the solidification front angle and dendrite growth direction, leading to substantial errors in freckle prediction for deformed superalloys during remelting.This study optimizes the freckle criterion by addressing these factors. The results indicate that at higher melting rates, the equiaxed grain zone expands, dendrite growth directions become random, and the solidification front angle stabilizes at approximately 55° regardless of the molten pool morphology. Due to solute flow obstruction by grain boundaries with varying orientations, channel segregation is more likely to occur at the interface between equiaxed and columnar grains, increasing freckle susceptibility. Conversely, at lower melting rates, dendrite growth direction is more influenced by the temperature gradient, and the solidification front angle correlates with the molten pool morphology. However, due to the lower Rayleigh number, the probability of freckle formation decreases.The optimized criterion model provides theoretical and practical guidance for VAR process optimization, contributing to reduced freckle defect occurrence and improved alloy quality and performance. |