Numerical study on the formation of spurious grains and freckles during the directional solidification of superalloys

Zhao Zhang, Menghuai Wu, Xiaoshan Liu, Min Song, Andreas Ludwig, Abdellah Kharicha

Research output: Contribution to conferencePaperpeer-review


Freckles, a significant issue encountered during the directional solidification of superal-
loys, are recognised by a trail of equiaxed grains parallel to the direction of gravity accompanied by
local eutectic enrichment. In the current study, a mixed-columnar-equiaxed multiphase volume-av-
erage solidification model was employed to study the formation of freckles in superalloy casting.
Fragments produced via flow-driven and capillary-driven fragmentation mechanisms are considered
as the source of spurious grains. The transport and the growth/remelting of the fragments are consid-
ered. According to the simulation results, some segregation channels develop at the corners of the
casting. Flow-driven fragments are produced in/around the segregation channels, whereas capillary-
driven fragments are produced at a certain depth of the mushy zone across the entire section of the
casting. The fragmentation rate caused by the flow-driven mechanism is several orders of magnitude
larger than that caused by the capillary-driven mechanism, i.e. the flow-driven fragmentation mech-
anism is dominant for the currently investigated sample. After the solidification process, four freckles
formed at the casting corners on the shadowed side, whereas it was freckle-free on the bright side.
Original languageEnglish
Number of pages11
Publication statusPublished - 2023
EventMCWASP XVI IOP Conf. Series: Materials Science and Engineering -
Duration: 18 Jun 202323 Jun 2023


ConferenceMCWASP XVI IOP Conf. Series: Materials Science and Engineering

Bibliographical note

This work was financially supported by the Austrian Science Fund in the framework of the FWF-NKFIN
joint project (FWF, I4278-N36).


  • formation of spurious grains
  • formation of spurious grains and freck- les
  • spurious grains and freck- les
  • directional solidification
  • superalloys

Cite this