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 52 publications

(10 citation statements)

References 7 publications

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“…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

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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.

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Section: Discussionmentioning

confidence: 99%

On Crystal Mosaicity in Single Crystal Ni-Based Superalloys

et al. 2019

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“…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

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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.

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“…The local changes in crystal orientation are related to local changes in the direction of dendrite growth, while it is commonly assumed for alloys with an fcc structure that dendrites grow strictly along the [001]-type crystallographic direction [14], which is crystallographically determined. The interaction of dendrites with tilted mould walls may cause a deviation from the preferred crystal orientation during crystallization [15].…”

Section: Introductionmentioning

confidence: 99%

Primary Crystal Orientation of the Thin-Walled Area of Single-Crystalline Turbine Blade Airfoils

et al. 2019

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The thin-walled airfoil areas of as-cast single-crystalline turbine blades made of CMSX-4 superalloy were studied. The blades were produced by the industrial Bridgman technique at withdrawal rates of 2, 3 and 4 mm/min. The angle between the [001] crystallographic direction and blade axis, related to the primary orientation, was defined by the Ω-scan X-ray diffraction method at points on the camber line located near the tip of an airfoil and at points of a line located in parallel and near the trailing edge. Additionally, primary crystal orientation was determined by Laue diffraction at the selected points of an airfoil. The influence of mould wall inclination on the primary crystal orientation of the thin-walled areas is discussed. The effect of change in the [001] crystallographic direction, named as “force directing”, was considered with regard to the arrangement of primary dendrite arms in relation to the trailing edge and the camber line. It was stated that when the distance between the mould walls is less than the critical value of about 1.5 mm the “force directing” increases as the distance between the walls of the mould decreases. The effect may be controlled by selecting an appropriate secondary orientation using a seed crystal in the blade production process. The model of dendrite interaction with the mould walls, including bending and “deflection”, was proposed.

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Factors determining crystal orientation of dendritic growth during solidification

Cited by 52 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

Primary Crystal Orientation of the Thin-Walled Area of Single-Crystalline Turbine Blade Airfoils

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