  In this paper a 3-phase Stefan problem solution method for 1D semi-infinity
alloy is developed. The problem is first solved for full enthalpy of the system
and then the thermal diffusivity has been eliminated from the divergence
operator by Kirchoff transformation. Moreover, we introduce a similarity
independent variable $\eta=x^{2}/\tau$ and original problem transforms to
ordinary differential equations (ODE) for each phase separately. These ODEs
have Dirichlet's type boundary conditions.
