Pattern formation during diffusional transformations in the presence of triple junctions and lattice strain: Green's function methods

摘要

Obviously, the effect of elastic stresses in solid-solid transitions is of particular interest. Due to the structural differences of the phases, lattice strains appear, which lead to elastic stresses. The representation of the coupled elastic-thermal diffusional problem in closed form enables the investigation of the transitions essential physics. Speci?cally, the distinct elastic stresses induce selection of steady-state solutions where the relative orientation of growth direction and lattice strains proves to be of crucial importance. The obtained solutions show that elasticity-induced dendritic selection leads to higher transition velocities than classical dendritic growth. In eutectoid transitions, twinned isolated dendrites can appear when the initial seed includes both emerging solid phases. At low undercooling of the mother phase, the growth velocity of this pattern is higher than the velocities known from classical dendritic growth. In the case of monotectic transformations, we study the growth of an asymmetric solid dendrite along the liquid-liquid interface of the decomposed liquid phase. Apart from the dendritic selection of the transition velocity and the radii of curvature, the rotation of the triple junction and the asymptotic lateral shift of the liquid-liquid interface are calculated.