Nanotexture Change Caused by Strain-Induced Anisotropic Diffusion During Creep of Ni-Base Superalloy

2014 ◽  
Author(s):  
Ken Suzuki ◽  
Motoyuki Ochi ◽  
Hideo Miura
Keyword(s):  
Melting Point ◽  
Lattice Constant ◽  
Anisotropic Diffusion ◽  
Structure Model ◽  
Diffusion Constants ◽  
Directional Coarsening ◽  
Axial Tensile ◽  
Simple Interface ◽  
Base Superalloy ◽  
Diffusion Properties

In order to make clear the mechanism of the directional coarsening (rafting) of γ′ phases in Ni-base superalloys under uni-axial tensile strain, molecular dynamics (MD) analysis was applied to investigate dominant factors of strain-induced anisotropic diffusion of Al atoms and nanotexture change of fine dispersed γ′ precipitates. In this study, a simple interface structure model corresponding to the γ/γ′ interface, which consisted of Ni as γ and Ni3Al as γ′ structure, was used to analyze the effect of alloying element on diffusion properties. The diffusion constants of Al atoms were changed drastically by the dopant elements and their contents. When the lattice constant of the γ phase was increased and its melting point was decreased by the addition of Cr or Al atoms, the strain-induced anisotropic diffusion of Al atoms in the γ′ phase was accelerated. On the other hand, the addition of Co decreased the diffusion significantly. Therefore, changes of lattice constant and melting point depending on the chemical composition of the γ/γ′ interface are the dominant factors controlling the strain-induced anisotropic diffusion of Al atoms in the Ni-base superalloy.

Effect of Alloying Elements on Creep and Fatigue Damage of Ni-Base Superalloy Caused by Strain-Induced Anisotropic Diffusion

2013 ◽  
Author(s):  
Ken Suzuki ◽  
Tomohiro Sano ◽  
Hideo Miura
Keyword(s):  
Anisotropic Diffusion ◽  
Tensile Strain ◽  
Creep Damage ◽  
Atomic Radius ◽  
Alloying Elements ◽  
Directional Coarsening ◽  
Axial Tensile ◽  
Diffusion Characteristics ◽  
Base Superalloy ◽  
Effect Of Alloying

In order to make clear the mechanism of the directional coarsening (rafting) of γ′ phases in Ni-base superalloys under uni-axial tensile strain, molecular dynamics (MD) analysis was applied to investigate effects of alloying elements on diffusion characteristics around the interface between the γ phase and the γ′ phase. In this study, a simple interface structure model corresponding to the γ/γ′ interface, which consisted of Ni as γ and Ni3Al as γ′ structure, was used to analyze the diffusion properties of Ni and Al atoms under tensile strain. The strain-induced anisotropic diffusion of Al atoms perpendicular to the interface between the Ni(001) layer and the Ni3Al(001) layer was observed in the MD simulation, suggesting that the strain-induced anisotropic diffusion of Al atoms in γ′ phase is one of the dominant factors of the kinetics of the rafting during creep damage. The effect of alloying elements in the Ni-base superalloy on the strain-induced anisotropic diffusion of Al atoms was also analyzed. Both the atomic radius and the binding energy with Al and Ni of the alloying element are the dominant factors that change the strain-induced diffusion of Al atoms in the Ni-base super-alloy.

High Temperature Damage of Ni-Base Superalloy Caused by the Change of Microtexture due to the Strain-Induced Anisotropic Diffusion of Component Elements

2011 ◽  
Author(s):  
Hideo Miura ◽  
Ken Suzuki ◽  
Yamato Sasaki ◽  
Tomohiro Sano ◽  
Naokazu Murata
Keyword(s):  
High Temperature ◽  
Anisotropic Diffusion ◽  
Axial Strain ◽  
Creep Damage ◽  
Face Centered Cubic ◽  
Directional Coarsening ◽  
Damage Process ◽  
Temperature Damage ◽  
Face Centered ◽  
Base Superalloy

In order to assure the reliability of advanced gas turbine systems, it is very important to evaluate the damage of high temperature materials such as Ni-base superalloys under creep and fatigue conditions quantitatively. Since the micro texture of the gamma-prime (γ′) phase was found to vary during the creep damage process, it is possible, therefore, to evaluate the creep damage of this material quantitatively by measuring the change of the micro texture. The mechanism of the directional coarsening of γ′ phasesof Ni-base superalloy under uni-axial strain at high temperatures, which is called rafting, was analyzed by using molecular dynamics (MD) analysis. The stress-induced anisotropic diffusion of Al atoms perpendicular to the finely dispersed γ/γ′ interface in the superalloy was observed clearly in a Ni(001)/Ni3Al(001) interface structure. The stress-induced anisotropic diffusion was validated by experiment using the stacked thin films structures which consisted of the (001) face-centered cubic (FCC) interface. The reduction of the diffusion of Al atoms perpendicular to the interface is thus, effective for improving the creep and fatigue resistance of the alloy. It was also found by MD analysis that the dopant elements in the superalloy also affected the strain-induced diffusion of Al atoms. Both palladium and tantalum were effective elements which restrain Al atoms from moving around the interface under the applied stress, while titanium and tungsten accelerated the strain-induced anisotropic diffusion, and thus, the rafting phenomenon.

Effect of Dopant Element on the Strength and Reliability of Ni-Base Superalloy at High Temperatures

2012 ◽  
Author(s):  
Tomohiro Sano ◽  
Ken Suzuki ◽  
Hideo Miura
Keyword(s):  
Thin Film ◽  
High Temperatures ◽  
Anisotropic Diffusion ◽  
Axial Strain ◽  
Face Centered Cubic ◽  
High Temperature Materials ◽  
Directional Coarsening ◽  
Face Centered ◽  
Dopant Element ◽  
Base Superalloy

In order to assure the reliability of advanced gas turbine systems, it is very important to evaluate the damage of high temperature materials such as Ni-base superalloys under creep and fatigue conditions quantitatively. The mechanism of the directional coarsening (rafting) of the γ′ phase (Ni3Al) of Ni-base superalloys under uni-axial strain at high temperatures was analyzed by molecular dynamics (MD) analysis. The strain-induced anisotropic diffusion of Al atoms perpendicular to the interface between the γ′ phase and the γ phase (Ni-matrix) was observed clearly at a Ni(001)/Ni3Al(001) interface. The strain-induced anisotropic diffusion was validated by the experiment using the stacked thin film structures with the (001) face-centered cubic (FCC) interface. The reduction of the diffusion of Al atoms perpendicular to the interface is thus, effective for improving the creep and fatigue resistance of the alloy. It was found by MD analysis that palladium was one of the most effective elements that restrain Al atoms from moving around the interface under the applied stress. The presence of the interaction between the different dopant elements was also clarified.

scholarly journals Creep and Fatigue Damages of Ni-Base-Superalloy Caused by Strain-Induced Anisotropic Diffusion of Component Elements

2009 ◽  
Vol 417-418 ◽  
pp. 261-264
Author(s):  
Hideo Miura ◽  
Ken Suzuki ◽  
Hiroyuki Ito ◽  
Tatsuya Inoue
Keyword(s):  
Molecular Dynamics ◽  
Fatigue Resistance ◽  
Anisotropic Diffusion ◽  
Axial Strain ◽  
Interface Structure ◽  
Directional Coarsening ◽  
Base Superalloy

The mechanism of the directional coarsening of ' phases (rafting) of Ni-base superalloy under an uni-axial strain was analyzed by molecular dynamics (MD) analysis. The stress-induced anisotropic diffusion of Al atoms perpendicular to the interface was observed clearly in a Ni(001)/Ni3Al(001) interface structure, The reduction of the diffusion of Al atoms perpendicular to the interface is thus, effective for improving the creep and fatigue resistance of the alloy. It was also found that the dopant elements in the superalloy also affected the strain-induced diffusion of Al atoms. Pd was one of the most effective elements which restrain Al atoms from moving around the interface.

High Temperature Damages of Ni-Base-Superalloy Caused by the Change of Nanotexture Due to Strain-Induced Anisotropic Diffusion

2010 ◽  
Author(s):  
Yamato Sasaki ◽  
Hiroyuki Itoh ◽  
Naokazu Murata ◽  
Ken Suzuki ◽  
Hideo Miura
Keyword(s):  
High Temperature ◽  
Anisotropic Diffusion ◽  
Axial Strain ◽  
Creep Damage ◽  
Face Centered Cubic ◽  
Gamma Prime ◽  
Directional Coarsening ◽  
Damage Process ◽  
Face Centered ◽  
Base Superalloy

In order to assure the reliability of advanced gas turbine systems, it is very important to evaluate the damage of high temperature materials such as Ni-base superalloys under creep and fatigue conditions quantitatively. Since the micro texture of the gamma-prime (γ′) phase was found to vary during the creep damage process, it is possible, therefore, to evaluate the creep damage of this material quantitatively by measuring the change of the micro texture. The mechanism of the directional coarsening of γ′ phases (rafting) of Ni-base superalloy under an uni-axial strain at high temperatures was analyzed by molecular dynamics (MD) analysis. The stress-induced anisotropic diffusion of Al atoms perpendicular to the initially finely dispersed γ/γ′ interface in the superalloy crystal was observed clearly in a Ni(001)/Ni3Al(001) interface structure. The stress-induced anisotropic diffusion was validated by experiment using the stacked thin films structures which consisted of the (001) face-centered cubic (FCC) interface. The reduction of the diffusion of Al atoms perpendicular to the interface is thus, effective for improving the creep and fatigue resistance of the alloy. It was also found by MD analysis that the dopant elements in the superalloy also affected the strain-induced diffusion of Al atoms. Palladium was one of the most effective elements which restrain Al atoms from moving around the interface under the applied stress.

scholarly journals Crystal Viscoplasticity of a Ni-Base Superalloy in the Aged State

2018 ◽  
Vol 141 (1) ◽  
Author(s):  
M. M. Kirka ◽  
R. W. Neu
Keyword(s):  
Gas Turbines ◽  
Internal State ◽  
Kinetic Equations ◽  
State Variables ◽  
Aging Effects ◽  
Directional Coarsening ◽  
Industrial Gas Turbines ◽  
Effects Of Aging ◽  
Base Superalloy

Arising from long-term high temperature service, the microstructure of nickel-base (Ni-base) superalloy components undergoes thermally and deformation-induced aging characterized by isotropic coarsening and directional coarsening (rafting) of the γ′ precipitates. The net result of the morphological evolutions of the γ′ particles is a deviation of the mechanical behavior from that of the as-heat treated properties. To capture the influence of a rafted and isotropic aged microstructure states on the long-term constitutive behavior of a Ni-base superalloy undergoing thermomechanical fatigue (TMF), a temperature-dependent crystal viscoplasticity (CVP) constitutive model is extended to include the effects of aging. The influence of aging in the CVP framework is captured through the addition of internal state variables that measure the widening of the γ channels and in-turn update the material parameters of the CVP model. Through the coupling with analytical derived kinetic equations to the CVP model, the enhanced CVP model is shown to be in good agreement when compared to experimental behavior in describing the long-term aging effects on the cyclic response of a directionally solidified (DS) Ni-base superalloy used in hot section components of industrial gas turbines.

Lattice Constant and Crystallite Size of Condensed Gold Vapor

1966 ◽  
Vol 10 ◽  
pp. 250-264 ◽  
Author(s):  
Frank G. Karioris ◽  
Jerome J. Woyci ◽  
Richard R. Buckrey
Keyword(s):  
Particle Size ◽  
Melting Point ◽  
Crystallite Size ◽  
Lattice Constant ◽  
Isothermal Annealing ◽  
Barometric Pressure ◽  
Particulate Material ◽  
Ambient Atmosphere ◽  
Gold Wires ◽  
And Behavior

AbstractGold wires were vaporized by the exploding-wire phenomenon using a 20 μF capacitor bank charged to voltages up to 14 kV. The resulting condensate, an aerosol or metallic smoke, was collected on membrane filters and subjected to X-ray analysis to determine lattice constant, crystallite size, and behavior with isothermal annealing. Wire explosions were conducted in au ambient atmosphere of ait or nitrogen at barometric pressure. It is estimated that the quench rate for this material is of the order of 108 deg/sec from the melting point although no substrate is involved and it is expected that any effects of epitaxial origin on the structure would be minimized.Before annealing, diffractograms showed broad peaks apparently shifted to the high-angle side. Line breadth may be attributed primarily to particle size broadening, since ft correlates well with size determined by electron microscopy, (β cos θ) is linear with θ, and [(β cos θ)/λ] is approximately constant for three radiations used. Crystallite size is of the order of 400 Å and is observed to decrease roughly with increasing voltage used for vaporization. The observed lattice decrement, approximately 0.2%, generally increases with voltage used for vaporization, and apparently correlates rather well with the inverse of sise as has been reported in some work on thin gold films. However, studies of colloidal gold particles do not show significant lattice shifts, although the particle size is less than 100 Å so that the decrements observed may be due to factors other than size alone. For this black, particulate material, some lattice decrement apparently persists even after protracted isothermal annealing below the melting point. Crystallite size increases with annealing but remains below about 1000 Å. Results suggest that the lattice decrements observed in condensed gold vapor are due to surface tension effects and the presence of vacancy aggregates.

Abnormal anisotropic diffusion properties in pediatric myelomeningocele patients treated with fetal surgery: an initial DTI study

2019 ◽  
Vol 36 (4) ◽  
pp. 827-833 ◽  
Author(s):  
Francesco T. Mangano ◽  
Charles B. Stevenson ◽  
Usha Nagaraj ◽  
Adam Conley ◽  
Weihong Yuan
Keyword(s):  
Anisotropic Diffusion ◽  
Fetal Surgery ◽  
Diffusion Properties
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