BIANNUAL REPORT 2018/19

Research Theme 4:
DIRECT MEASUREMENTS
OF MELT CONVECTION
AND CRYSTAL MOTION
DURING SOLIDIFICATION
A. Kharicha, M. Stefan-Kharicha, M. Wu, A. Ludwig
Basic Research
Aims and key objectives
• To observe double-diffusive phenomena during
solidification of a transparent alloy with a
so-called Particle Image Velocity (PIV) system.
• To create a data base with well controlled boundary
conditions which can be used for validation of
world-wide existing solidification numerical models.
• To define an experimental benchmark for the
columnar to equiaxed transition (CET) and
the macroscopic shape of mushy zone.
• To measure the relative velocity of
equiaxed crystals and the melt and
therewith evaluate existing drag laws.
• To understand the interaction between solidification
and naturally driven melt flow convection.
• To develop a dendrite envelope
model on a semi-macroscopic scale.
a
b
c
Figure 4:
Ammonium chloride solidification in a die cast cell cooled from three sides: (a) Particle Image Velocimetry (PIV) measurements
and (b) simulation results (dendritic envelope model) and (c) crystals and liquid velocities map taken by the two-colour
PIV system. Note that the different motion of crystals and surrounding melt could be resolved.
12 Research Theme 4: Direct Measurements of Melt Convection and Crystal Motion During Solidification