Computational tools for simulation of phase transformations

University dissertation from Stockholm : Materialvetenskap

Author: Mikael Schalin; Kth.; [1999]

Keywords: ;

Abstract: A new software package, Thermite, for thermodynamiccalculations and process simulation is developed around theThermo-Calc databank. Thermite is a computational toolbox forequilibrium calculations and simulation of phasetransformations. It provides graphic visualisation and allowsmanipulation of the presented data.Two types of phase transformations have been implemented inthe software. First, it was used to simulate solidification ofalloys using the Gulliver-Scheil model. Simulations were madewith both Gulliver-Scheil model and with the DICTRA softwareand the predictions were compared with experimentalinformation. The interpretation of experimental cooling curveswas examined in detail and the role of back diffusion in thesolidified material has been considered. It was shown thatcooling curves with respect to time could be calculated fromenthalpy by integrating over the solidified layers.Secondly, it was used to study the role of phase interfacesfor solid-solid transformations. The Hillert-Sundman treatmentof solute drag has been extended to multi-component systems.Using this extended treatment, the influences of the differentmodel parameters for partitionless transformation wereinvestigated and a comparison was made with earlier work. Theeffect of solute drag on the movement of grain boundaries wasstudied.A technique was also developed to interface Thermo-Calc withother programs. This technique was used to link the DICTRAsoftware to the Thermite software package. The whole Thermitepackage is strictly organised in independent libraries toenable the substitution of each library. In particular, alibrary called Thermo-Calc C library has been designed tosupply thermodynamic calculations to many differentapplications.Keywords:thermodynamic calculations, simulation, phasetransformations, equilibrium, solidification, solute drag,massive transformations