Prediction of critical formation condition of faceted columnar crystals in superconductive ReBCO Oxide

Abstract

To clarify the formation mechanism of the solidification macro/micro-structures of YBCO, the analytical and numerical studies are performed. The critical transition condition from columnar to equiaxed structure is studied for 123 macrostructures in unidirectionally solidified YBCO. By fitting the CCT-curve to the experimental data, calculated critical transition condition(R-G relation) from columnar to equiaxed-structure show good agreement with the experimental results. Further, the formation process of microstructure of YBCO is studied by two-dimensional numerical simulation with a new single-mesh model for the faceted growth. Main parameters in the model are the kinetic growth coefficient, the kinetic undercooling, the diffusion coefficient in the liquid, the interface energy of the solid phases against the liquid, and the initial distribution of primary particles. Solute distribution in the liquid ahead of the growing faceted interface is calculated by the explicit finite difference method using the direct discrete model. The growth process of faceted crystals are simulated and the calculated microstructures agree well with the experimental results.

Keywords:

• superconductor
• simulation
• YBCO
• peritectic
• facet