Abstract
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.
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 language | English |
|---|---|
| Number of pages | 11 |
| DOIs | |
| Publication status | Published - 2023 |
| Event | MCWASP XVI IOP Conf. Series: Materials Science and Engineering - Duration: 18 Jun 2023 → 23 Jun 2023 |
Conference
| Conference | MCWASP XVI IOP Conf. Series: Materials Science and Engineering |
|---|---|
| Period | 18/06/23 → 23/06/23 |
Bibliographical note
This work was financially supported by the Austrian Science Fund in the framework of the FWF-NKFINjoint project (FWF, I4278-N36).
Keywords
- formation of spurious grains
- formation of spurious grains and freck- les
- spurious grains and freck- les
- directional solidification
- superalloys