Alpha factor

The α-factor is used to predict the solid–liquid interface type of a material during solidification.

Method

According to John E. Gruzleski in his book Microstructure Development During Metalcasting (1996):

α = (L/k*T_E)*(η/v)

where L is latent heat of fusion k is Boltzmann’s constant T_E is equilibrium freezing temperature η is the number of nearest neighbours an atom has in the interface plane v is the number of nearest neighbours in the bulk solid

Since L/T_E = ΔS_f

where ΔS_f is the molar entropy of fusion of the material

α = ΔS_f/k(η/v)

According to Martin Glicksman in his book Principles of Solidification : An Introduction to Modern Casting and Crystal Growth Concepts(2011):

α = ΔS_f/R_g(η₁/Z)

where R_g is the universal gas constant, (η₁/Z) is similar to previous, always 1/4<(η₁/Z)<1