The effects of thermodynamic and dynamic factors on nucleation process have been integrated in a theoretical formula representing the dependence of
undercooling on parameters concerned. Moreover, a method to determine the kind and amount of the most effective
catalyst in an undercooled melt has been acquired. The results show that the undercooling increases with the decreasing surface area of the most effective catalyst and the increasing
cooling rate as the kind of the most effective catalyst is constant. It increases to a maximum value when the
ratio of the surface area of catalyst ( Sv V) to the cooling rate of melt (
rc) decreases to a critical value. The maximum undecooling not only
depends on the ratio of non-dimensional factor of activation energy for an atom to diffuse (φ) to non-dimensional factor of driving force for nucleus to form (ψ), but also depends on the contact angle of the most effective catalyst; the
smaller the ratio of φ to ψ, the higher the maximum undercooling, but it does not exceed the value of 2/3 melting point; the smaller the contact angle of the most effective catalyst, the lower the maximum undercooling, and the smaller the requisite value of Sv V/RC for the maximum undercooling also.