Formation mechanism of band structure and phase selection during directional solidification of peritectic alloys - I. Formation mechanism of band structure

Solute compositional distributions at and ahead of the solid-liquid interfaces are analyzed during the plane-front growth for both the primary and peritectic phases as single phase and nucleation phase for peritectic alloys directionally solidified at low growth rates from initial transient to steady state. Taking the nucleation and compositional undercooling criterion and assuming that the maximum interface growth temperature of phase growth is more stability during the directional solidification, the nucleation transitions during the transient period are investigated and compositional range of band structure formation is determined. Considering the history-dependant growths of a phase, the band structure can be differentiated as cycling band and single band structure, which can explain the experimental phenomena appropriately. The calculated results for Ti-Al alloy are identical with the theoretical analyses.