BIANNUAL REPORT 2018/19

Research Theme 5:
FLOW-SOLIDIFICATION
INTERACTION IN
MUSHY ZONES
M. Wu, H. Zhang, C. Rodrigues, A. Ludwig, A. Kharicha
Basic Research
Aims and key objectives
• To develop/refine numerical models for
solidification by considering flow interaction
with the advancing much zone.
• To investigate the solidification process under
the pure diffusive condition (micro-gravity)
and forced convection condition by applying
rotating magnetic field (RMF).
• To evaluate different permeability laws (or the dependency
of the permeability on the morphological
parameters of dendritic crystals in the mushy zone) by
comparison of the modelled solidification results with
the experiments where flow is well controlled by RMF.
• To investigate the flow influence on the microstructure
formation, in cooperation with some laboratory
experiments (micro-gravity and forced convection).
• To model the columnar-to-equiaxed transition
(CET) under the forced convection condition
by considering crystal fragmentation as the
origin of equiaxed crystals.
• To investigate the macrosegregation
mechanism under the RMF.
a
b
c
Figure 5.1:
Comparison of the experimentally-measured
(left)
and the numerically-calculated
(right) macrosegregation
in the unidirectionallysolidified
sample under the
rotating magnetic field.
Figure 5.2:
A two-phase columnar solidification model is used to calculate the unidirectional solidification
of AlSi7 alloy under the rotating magnetic field (RMF). (a) Geometry configuration and
boundary conditions; (b) modeling results to indicate the Tayler-Görtler vortices of the bulk
melt in front of the mushy zone, typically caused by RMF; (c) flow in the mushy zone, where
the volume fraction of liquid (upper) and the velocity direction and magnitude (lower) are
shown in color scale. The macrosegregation pattern in the as-solidified sample is shown in
Figure 5-1.
14 Research Theme 5: Flow-solidification Interaction in Mushy Zones