Abstract:Updated version of local non-equilibrium diffusion model (LNDM) for rapid solidification of binary alloys was considered. The LNDM takes into account deviation from local equilibrium of solute concentration and solute flux fields in bulk liquid. The exact solutions for solute concentration and flux in bulk liquid were obtained using hyperbolic diffusion equations. The results show the transition from diffusion-limited to purely thermally controlled solidification with effective diffusion coefficient →0 and complete solute trapping K^LNDM(v)→1 at v→v_Db for any kind of solid-liquid interface kinetics. Critical parameter for diffusionless solidification and complete solute trapping is the diffusion speed in bulk liquid v_Db. Different models for solute trapping at the interface with different interface kinetic approaches were considered.

Key words: binary alloys; solute trapping; rapid solidification; local-nonequilibrium diffusion; hyperbolic diffusion equation; solute concentration; solute flux fields