LAUSR

A phase field model is used to study dendritic growth in a media with impurities. The model consists of a square lattice where a parameter ψ can take values between 0 and 1 at each site. A site is in the solid phase for ψ>1, in the liquid phase for ψ=0, and the solid-liquid interface is expressed by 0<ψ<1. A fraction of the sites are considered impurities that cannot be solidified, i.e. ψ is fixed and taken as zero. These impurities are distributed randomly. As the probability p of impure sites in the lattice increases, the growth loses its dendritic characteristic. It is shown that the perimeter of the growing solid goes from quadratic to a linear function with time. It was also found that as the probability of impurities reaches p=0.004, the solid undergoes a transition from anisotropic to isotropic growth.