Thermodynamics and interdiffusion at interfaces with potential jumps, part II

点击翻译按钮获取中文摘要

Interfaces in solid or liquid materials are characterized by high chemical and structural disorder. Interfaces are in general far from thermodynamic equilibrium, if two different materials come into contact with each other, or during rapid phase transformations. In the first part of the project, two different models for moving interfaces with a potential jump between the bulk phases were investigated. As a major result the so-called phase-field model with finite interface dissipation has been developed and calibrated using the partner model. It shall now be applied at the mesoscopic scale for the investigation of incomplete partitioning during rapid dendritic solidification. The key question is the inversion of the dependence of the dendrite tip radius on the initial undercooling during the transition towards partitionless solidification. This inversion leads to an increase of the radius with increasing undercooling, instead of the decrease during solute diffusion control. The solidification velocity, however, increases in this regime, according to experimental observations, only slightly, i.e. one would not expect increased trapping according to established theories. The project shall clarify this unexpected behavior.