Factors determining crystal orientation of dendritic growth during solidification

Lee, Dong Nyung; Kim, Kyung-Hyun; Lee, Yong-gi; Choi, Chang-Hee

doi:10.1016/s0254-0584(97)80044-2

Cited by 55 publications

(13 citation statements)

References 7 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Morphological bending [50,74], on the other hand, represents a phenomenon where the alloy chemistry of the liquid phase locally affects undercooling conditions. This alters the preferential growth direction such that it deviates from the ideal direction promoted by crystallography [75,76]. Morphological bending only has a weak effect on the crystal lattice orientation.…”

Section: Discussionmentioning

confidence: 99%

On Crystal Mosaicity in Single Crystal Ni-Based Superalloys

et al. 2019

View full text Add to dashboard Cite

In the present work, we investigate the evolution of mosaicity during seeded Bridgman processing of technical Ni-based single crystal superalloys (SXs). For this purpose, we combine solidification experiments performed at different withdrawal rates between 45 and 720 mm/h with advanced optical microscopy and quantitative image analysis. The results obtained in the present work suggest that crystal mosaicity represents an inherent feature of SXs, which is related to elementary stochastic processes which govern dendritic solidification. In SXs, mosaicity is related to two factors: inherited mosaicity of the seed crystal and dendrite deformation. Individual SXs have unique mosaicity fingerprints. Most crystals differ in this respect, even when they were produced using identical processing conditions. Small differences in the orientation spread of the seed crystals and small stochastic orientation deviations continuously accumulate during dendritic solidification. Direct evidence for dendrite bending in a seeded Bridgman growth process is provided. It was observed that continuous or sudden bending affects the growth directions of dendrites. We provide evidence which shows that some dendrites continuously bend by 1.7° over a solidification distance of 25 mm.

show abstract

Section: Discussionmentioning

confidence: 99%

On Crystal Mosaicity in Single Crystal Ni-Based Superalloys

et al. 2019

View full text Add to dashboard Cite

show abstract

“…Single crystal turbine blades are manufactured by a unidirectional solidification casting process, such that the resulting material presents a columnar dendritic structure with the dendrites oriented in the turbine blade axis direction. Since in cubic materials dendrites grow in the h100i directions, in order to minimize their surface 23 and strain 24,25 energies, the turbine blades present a h100i direction aligned with the turbine blade, and since repairs are usually done on the turbine blade tip, the repair surface is parallel to a (100) crystal plane. G€ aumann et al 17 showed that clad layers of CMSX-4 Ni-based superalloy deposited under appropriate processing conditions on a (100) single crystalline substrate of the same material by laser cladding were single crystalline, with a crystallographic orientation similar to the substrate.…”

Section: Microstructure Of Laser Deposited Single Crystal Superalmentioning

confidence: 99%

Repair and manufacturing of single crystal Ni-based superalloys components by laser powder deposition—A review

Vilar

Almeida

2014

Journal of Laser Applications

View full text Add to dashboard Cite

Laser powder deposition is one of the most promising methods for the repairing of the single crystal Ni-based superalloys components used in the hot-section of gas turbine engines in order to extend their lifetime and reduce their overall cost. The microstructure of Ni-based superalloys deposited on single crystal substrates of similar materials depends mainly on the materials involved, on the orientation of the deposited tracks in relation to the substrate and on the deposition parameters. In the present paper these relations are discussed and illustrated for the case of single and multiple layer depositions of NiCrAlY and Rene N4 on (100) single crystal substrates of SRR99 and CMSX-4 Ni-based superalloys. On the other hand, when the aging treatment is applied directly to the solidification microstructure resulting from laser deposition, abnormal γ/γ′ microstructures may result, due to the inhomogeneity created by alloying elements partition during solidification. Performing a homogenization annealing before aging circumvents this difficulty. The homogenizing annealing also eliminates undesirable brittle phases present in the solidification microstructure, such as carbides and topologically close-packed compounds.

show abstract

“…Mosaicity is caused by the deformation of dendrites during solidification [37][38][39][40][41][42][43]. As each dendrite is expected to grow along its crystallographically preferred direction [44], the preparation of a perfect single crystal requires that all dendrites grow exactly parallel. In a technical single crystal, however, this is not the case.…”

Section: Introductionmentioning

confidence: 99%

A 3D Analysis of Dendritic Solidification and Mosaicity in Ni-Based Single Crystal Superalloys

et al. 2021

View full text Add to dashboard Cite

Ni-based single crystal superalloys contain microstructural regions that are separated by low-angle grain boundaries. This gives rise to the phenomenon of mosaicity. In the literature, this type of defect has been associated with the deformation of dendrites during Bridgman solidification. The present study introduces a novel serial sectioning method that allows to rationalize mosaicity on the basis of spatial dendrite growth. Optical wide-field micrographs were taken from a series of cross sections and evaluated using quantitative image analysis. This allowed to explore the growth directions of close to 2500 dendrites in a large specimen volume of approximately 450 mm3. The application of tomography in combination with the rotation vector base-line electron back-scatter diffraction method allowed to analyze how small angular differences evolve in the early stages of solidification. It was found that the microstructure consists of dendrites with individual growth directions that deviate up to ≈4° from the average growth direction of all dendrites. Generally, individual dendrite growth directions coincide with crystallographic <001> directions. The quantitative evaluation of the rich data sets obtained with the present method aims at contributing to a better understanding of elementary processes that govern competitive dendrite growth and crystal mosaicity.

show abstract

Factors determining crystal orientation of dendritic growth during solidification

Cited by 55 publications

References 7 publications

On Crystal Mosaicity in Single Crystal Ni-Based Superalloys

On Crystal Mosaicity in Single Crystal Ni-Based Superalloys

Repair and manufacturing of single crystal Ni-based superalloys components by laser powder deposition—A review

A 3D Analysis of Dendritic Solidification and Mosaicity in Ni-Based Single Crystal Superalloys

Contact Info

Product

Resources

About