The two closely related properties, the thermal diffusivity and conductivity, are of great interest for all questions concerning heat transfer and thermal effects (e.g. heat transport, conduction, dissipation, etc.). However, measurements of these properties still lead to widespread results depending on the respective measurement technique used. This experience was used as a starting point for a common research project with Böhler Edelstahl GmbH & Co KG supported by FFG, whose main target is to compare directly and indirectly obtained diffusivities of highly alloyed steels. For this purpose, thermal diffusivity is on the one hand directly measured by means of a quasistatic laser flash technique (LFA) and, on the other hand, indirectly calculated via the Wiedemann-Franz law (WFL) from electrical resistivities. The latter are measured by means of a fast dynamic ohmic pulse-heating system capable of measuring a wide range of thermophysical and optical properties of conducting materials up to temperatures beyond melting into the liquid state.

A multiphase approach is used to study macrosegregation phenomena that occur during solidification of steel ingot castings. The goal is to enhance the understanding of different mechanisms of macrosegregation formation. 4 different cases are presented consecutively with increasing complexity of the model assumptions and increasing dimensions: (1) feeding-induced macrosegregations in 1-dimentional unidirectional solidification situation, (2) macrose gregations caused by thermosolutal buoyancy driven flow in a 2-dimensional axially symmetric benchmark ingot, (3) macrosegregations caused by grain sedimentation in the same 2-dimensional ingot, and (4) macrosegregations which form during mixed equiaxed-columnar solidification in a full 3-dimensional benchmark ingot.