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Preferred growth orientation and microsegregation behaviors of eutectic in a nickel-based single-crystal superalloy

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ABSTRACT

A nickel-based single-crystal superalloy was employed to investigate the preferred growth orientation behavior of the (γ + γ′) eutectic and the effect of these orientations on the segregation behavior. A novel solidification model for the eutectic island was proposed. At the beginning of the eutectic island’s crystallization, the core directly formed from the liquid by the eutectic reaction, and then preferably grew along [100] direction. The crystallization of the eutectic along [110] always lagged behind that in [100] direction. The eutectic growth in [100] direction terminated on impinging the edge of the dendrites or another eutectic island. The end of the eutectic island’s solidification terminates due to the encroachment of the eutectic liquid/solid interface at the dendrites or another eutectic island in [110] direction. The distribution of the alloying elements depended on the crystalline axis. The degree of the alloying elements’ segregation was lower along [100] than [110] direction with increasing distance from the eutectic island’s center.

No MeSH data available.


(a) and (d) The morphologies of cruciform dendrites and (γ + γ′) eutectic island; (b) and (e) magnified photos of the eutectic island; (c) and (f) SEM micrographs of the eutectic island and the measuring paths of the EDX scans along [100] and [110] directions.
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Figure 1: (a) and (d) The morphologies of cruciform dendrites and (γ + γ′) eutectic island; (b) and (e) magnified photos of the eutectic island; (c) and (f) SEM micrographs of the eutectic island and the measuring paths of the EDX scans along [100] and [110] directions.

Mentions: Figures 1(a) and (d) show a typical dendritic microstructure and morphologies of the (γ + γ′) eutectic islands. Since [001] is the preferred direction for the crystal growth in cubic metals and the direction of the primary dendrite arm is [001], the transverse sections of the dendrite are cruciform with orthogonal secondary dendrite arms aligned in [100] and [010] directions. The details of the (γ + γ′) island shown in figures 1(b) (c) (e) and (f) demonstrate different microstructures depending on the crystallographic orientation.


Preferred growth orientation and microsegregation behaviors of eutectic in a nickel-based single-crystal superalloy
(a) and (d) The morphologies of cruciform dendrites and (γ + γ′) eutectic island; (b) and (e) magnified photos of the eutectic island; (c) and (f) SEM micrographs of the eutectic island and the measuring paths of the EDX scans along [100] and [110] directions.
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC5036469&req=5

Figure 1: (a) and (d) The morphologies of cruciform dendrites and (γ + γ′) eutectic island; (b) and (e) magnified photos of the eutectic island; (c) and (f) SEM micrographs of the eutectic island and the measuring paths of the EDX scans along [100] and [110] directions.
Mentions: Figures 1(a) and (d) show a typical dendritic microstructure and morphologies of the (γ + γ′) eutectic islands. Since [001] is the preferred direction for the crystal growth in cubic metals and the direction of the primary dendrite arm is [001], the transverse sections of the dendrite are cruciform with orthogonal secondary dendrite arms aligned in [100] and [010] directions. The details of the (γ + γ′) island shown in figures 1(b) (c) (e) and (f) demonstrate different microstructures depending on the crystallographic orientation.

View Article: PubMed Central - PubMed

ABSTRACT

A nickel-based single-crystal superalloy was employed to investigate the preferred growth orientation behavior of the (γ + γ′) eutectic and the effect of these orientations on the segregation behavior. A novel solidification model for the eutectic island was proposed. At the beginning of the eutectic island’s crystallization, the core directly formed from the liquid by the eutectic reaction, and then preferably grew along [100] direction. The crystallization of the eutectic along [110] always lagged behind that in [100] direction. The eutectic growth in [100] direction terminated on impinging the edge of the dendrites or another eutectic island. The end of the eutectic island’s solidification terminates due to the encroachment of the eutectic liquid/solid interface at the dendrites or another eutectic island in [110] direction. The distribution of the alloying elements depended on the crystalline axis. The degree of the alloying elements’ segregation was lower along [100] than [110] direction with increasing distance from the eutectic island’s center.

No MeSH data available.