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

Publikation: KonferenzbeitragPaperBegutachtung


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.
PublikationsstatusVeröffentlicht - 2023
VeranstaltungMCWASP XVI IOP Conf. Series: Materials Science and Engineering -
Dauer: 18 Juni 202323 Juni 2023


KonferenzMCWASP XVI IOP Conf. Series: Materials Science and Engineering

Bibliographische Notiz

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

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