Coarsening and Microsegregation during Solidification of Ni-AI-Cr Dendritic Monocrystals

Montoya-Cruz, J. J.; Kadalbal, R.; Kattamis, T. Z.; Giamei, A. F.

doi:10.1007/bf02645496

Cited by 13 publications

(1 citation statement)

References 4 publications

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“…[13,18] An increased solidification cooling rate has two contradictory effects on microsegregation. On the one hand, it decreases the diffusion time at high temperatures of the solid solution in the mushy zone, resulting in an increase in microsegregation.…”

Section: High-temperature Stress-rupture Lifementioning

confidence: 99%

Influence of solid/liquid interfaces on the microstructure and stress-rupture life of the single-crystal nickel-base superalloy NASAIR 100

Guo

Sun

1997

Metall Mater Trans A

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The [001] oriented single crystals of nickel-base superalloy NASAIR 100 with the planar, cellular, coarse-dendritic, and fine-dendritic solid/liquid (S/L) interfaces were prepared, respectively, and their microstructure and stress-rupture behavior at 1050 ЊC were investigated in both as-cast and solution heat-treated conditions. It was found that in as-cast single crystals of NASAIR 100, microsegregation and ␥/␥' eutectic produced in the solidification process increased, ␥' size decreased, and ␥' shape tended progressively to be cuboidal, with the successive transition of the S/L interface from planar to cellular, then to coarse-dendritic, and finally to fine-dendritic morphology. Furthermore, the solution temperature required to dissolve all as-cast ␥ ' and most of the ␥/␥' eutectic increased with the aforementioned successive transition of S/L interfaces. The reprecipitated ␥', after solution heat treatment (SHT), was usually fine and cuboidal. However, some W-rich phase was present in the heat-treated dendritic single crystals. Both the planar and the cellular single crystals of NASAIR 100 exhibited no superiority in stress-rupture life, irrespective of the heat-treatment conditions. Instead, the single crystals with dendritic morphology possessed excellent stress-rupture lives, after heat treatment at 1320 ЊC for 4 hours, followed by air cooling (AC). Perfect ␥ ' rafts with high-average aspect ratios formed during the stress-rupture tests of dendritic single crystals; in contrast, irregularly coarsening structures appeared in both the planar and cellular single crystals. The microstructure and solution behavior were illustrated in detail. Furthermore, the microstructural factors to affect the high-temperature stress-rupture life of the single crystals of NASAIR 100 were also analyzed.

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Section: High-temperature Stress-rupture Lifementioning

confidence: 99%