On the origin of mosaicity in directionally solidified Ni-base superalloys

Strickland, Joel; Nenchev, Bogdan; Tassenberg, Karl; Perry, S. J.; Sheppard, Gareth; Dong, Haibo; Zhang, Ruiyao; Burca, Genoveva; D’Souza, N.

doi:10.1016/j.actamat.2021.117180

Cited by 19 publications

(5 citation statements)

References 52 publications

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“…During crystallization, various types of defects are formed, such as freckles [11,12], slivers [13][14][15], and subgrains separated by low-angle boundaries [16,17], which may negatively affect the strength parameters of the blades [18][19][20]. Misorientation of neighboring subgrains is caused by the deformation of dendrites during solidification, among other reasons [21][22][23].…”

Section: Introductionmentioning

confidence: 99%

Effect of Blade Geometry on γ′ Lattice Parameter and Primary Orientation of SX Cored Turbine Blades (I)

2022

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The γ′ lattice parameter aγ′ and the α angle defining the primary crystal orientation of the single-crystalline cored turbine blades made of CMSX-4 superalloy were measured in the areas located near the selector situated asymmetrically, considering the top view of the blade. The distributions of the aγ′ and the α angle were determined along the lines parallel to the vertical blade axis Z using X-ray diffraction methods. The relations between changes in the aγ′(Z) and α(Z) were analyzed on the Z levels where the shape of the blade’s cross-section changes. For the first time, the local increase in aγ′(Z) was found near the root–airfoil connection level and near certain other root levels, which is related to the change in blade section shapes on such levels. The local extremes in α(Z), representing the dendrite bend, were observed at these levels. The increase in the aγ′(Z) with the local bending of dendrites was discussed concerning the local redistribution of alloying elements and local residual stresses of the γ-dendrites. For the first time, a method of analyzing the local bending of the dendrites was proposed by studying the behavior of the α(Z). The presented results concern the first stage of the research covering areas relatively close to the selector, considering the top view of the blades. The second stage will include the analysis of the areas of the blade localized at a longer distance from the selector.

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Section: Introductionmentioning

confidence: 99%

Effect of Blade Geometry on γ′ Lattice Parameter and Primary Orientation of SX Cored Turbine Blades (I)

2022

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“…Mosaicity and kinematic diffraction.-It is known 44,45 that when a bulk material is transformed into a structure consisting of finely divided and smaller crystalline domains, the conditions of dynamic diffraction begin to diminish and that of the kinematic diffraction phenomena take over. In a perfect crystal, the condition for dynamic diffraction dominates where the multiple planes in the crystal are subjected to diffractions and the diffraction intensities are proportional to the magnitude of the structure factor.…”

Section: Resultsmentioning

confidence: 99%

In-Operando Neutron Diffraction Investigation of Structural Transitions during Lithiation of Si Electrode in Li-Ion Battery

Srinivasan¹,

Chandran²,

Chen³

et al. 2022

J. Electrochem. Soc.

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A major challenge for Si negative electrodes in Li-ion batteries is how to accommodate the large lithiation-induced volume expansion and prevent electrode fragmentation, such that impressive Li storage capacity of Si can be exploited in practice. Electrochemically etched Si mesoporous electrodes have significant potential in this context. This research is focused on an optimum mesoporous Si electrode structure that shows a very high energy storage density, electrochemically cycling well without cracking or fragmentation. To explore the factors causing the superior performance, this study performed in-operando neutron diffraction experiments on optimized electrode during lithiation-delithiation cycles in a simple in-situ electrochemical cell. It is shown that an unusual diffraction phenomenon arises from lithiation-induced expansion of Si leading to the development of mosaic structure in Si. This new phenomenon appears to arise from the increased contribution of kinematic diffraction from the lithiated Si, relative to the conventional dynamic diffraction. This is also supported by changes in diffraction intensities directly synchronizing with the volume changes in Si during lithiation-delithiation cycle. The in-operando experiments explain why the optimum mesoporous Si electrode possesses a high specific capacity without electrode fragmentation. The present findings can help to improve Si electrode designs for high energy density Li-ion batteries.

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“…Peter et al [22] simulated the deformation behavior of dendrites in three dimensions. However, recent research [23,24] has failed to clarify the cause of dendrite deformation in different castings. In addition, most previous studies have focused on solidification defects at the edge plate of the turbine blade.…”

Section: Introductionmentioning

confidence: 99%

Dendrite Deformation in the Rejoined Platforms of Ni‐Based Single‐Crystal Superalloys

2023

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Dendrite deformation often occurs during the preparation of single‐crystal superalloy blades by directional solidification and can cause solidification defects, such as low‐angle boundaries (LABs), slivers, and orientation deviations. Continuous dendritic deformation is uncommon and its mechanisms and influencing factors are poorly understood. However, this can lead to significant orientation deviation and performance degradation. Herein, a model with rejoined platforms is designed to study the dendrite growth and orientation evolution in a rejoined platform of Ni‐based single‐crystal superalloys. It is indicated in the results that, under certain conditions, the developed secondary dendrites deform continuously near the mold wall of the rejoined platforms and the resulting disorientation has a cumulative effect. Finally, LABs and dendritic fragments appear on the rejoined platforms. Thus, the integrity of the single crystal is destroyed. This can be the result of the local shrinkage stress on the long secondary dendrites within a sufficient growth space.

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On the origin of mosaicity in directionally solidified Ni-base superalloys

Cited by 19 publications

References 52 publications

Effect of Blade Geometry on γ′ Lattice Parameter and Primary Orientation of SX Cored Turbine Blades (I)

Effect of Blade Geometry on γ′ Lattice Parameter and Primary Orientation of SX Cored Turbine Blades (I)

In-Operando Neutron Diffraction Investigation of Structural Transitions during Lithiation of Si Electrode in Li-Ion Battery

Dendrite Deformation in the Rejoined Platforms of Ni‐Based Single‐Crystal Superalloys

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