Determination of the Coherency Strain of γ and γ′ Phases in Nickel-Base Superalloys at High Temperatures

AbstractA method for using syncrotoron-radiation parallel-beam X-ray diffractometry for precise lattice parameters and strains of γ-γ′ type Nickel base superalloys at elevated temperature is described. The superalloys have γ′ precipitates which are an ordered L12 structure based on Ni3Al, in y-matrices having a disordered FCC structure. Lattice misfit between γ and γ′ phases was very small and peaks reflected from γ and γ′ phases made unresolved clusters of peaks.Profile fitting with a pseudo-Voigt function is used to resolve overlapping peaks. Instrumental broadening of the peak profile was removed using a deconvolution method. The standard errors of the calculated peak angle were less than 0.002°. The elastic strain of the γ′ precipitates in the alloys were smaller than those of γ-matrices.

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Determination of Lattice Parameter and Strain of ϒ' Phases in Nickel-Base Superalloys by Synchrotron Radiation Parallel Beam Diffractometry

Advances in X-ray Analysis ◽

10.1154/s0376030800014816 ◽

1990 ◽

Vol 34 ◽

pp. 493-499

Author(s):

Katsumi Ohno ◽

Kazumasa Ohsumi ◽

Hiroshi Harada ◽

Toshihiro Yamagata ◽

Michio Tamazaki

Keyword(s):

Synchrotron Radiation ◽

Preparation Method ◽

Turbine Blades ◽

Lattice Misfit ◽

Lattice Parameter ◽

Parallel Beam ◽

Nickel Base Superalloys ◽

Nickel Base ◽

Fcc Structure

AbstractThe lattice parameters and strain of ϒ'-phase particles in Nickel-base superalloys, which are duplex type alloys designed for turbine blades and widely called “Ni-base single crystal superalloys”; they are accurately determined by Synchrotron Radiation parallel-beam diffractometry. The superalloys have ϒ' precipitates, an ordered FCC structure based on Ni3Al, in a γ-matrix having disordered FCC structure.In addition, the preparation method of stress-free ϒ'-phase particles, with no composition change in the preparation process, was newly developed to measure the coherency strain of ϒ'-particles due to lattice misfit. The prepared ϒ'-phase particles are similar in composition and form to ϒ'-phase particles in the γ-matrices. The method for determining of the lattice misfit between the γ and γ’ particles was previously reported.

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X-ray Diffractometric Determination of Lattice Misfit Between γ and γ' Phases in Ni-Base Superalloys

Advances in X-ray Analysis ◽

10.1154/s037603080002067x ◽

1988 ◽

Vol 32 ◽

pp. 365-375 ◽

Cited By ~ 1

Author(s):

Katsumi Ohno ◽

Hirosi Harada ◽

Toshihiro Yamagata ◽

Michio Yamazaki ◽

Kazumasa Ohsumi

Keyword(s):

Lattice Misfit ◽

Least Square Method ◽

Least Square ◽

X Rays ◽

Deconvolution Method ◽

X Ray ◽

Window Functions ◽

Profile Fitting ◽

Overlapping Peaks

AbstractThe lattice misfits between γ and γ' phases in Ni-base superalloys (single crystal) were accurately determined for filings of specimens by using both a conventional X-ray tube focusing diffractometer(CXRFD) and a synchrotron-radiation parallel beam X-ray diffractometer (SRPXRD). All reflection peaks measured with the CXRFD were in a cluster of overlapping peaks because of the very small differences in the lattice parameters of both phases and the instrumental broadening due to X-ray optics including the spectral distribution of Xray source such as CuKα doublet. The deconvolution method was applied to remove the instrumental broadening from the peaks measured with the CXRFD. The window functions for the deconvolution method were calculated from CuKα doublet reflection of Si standard by a nonlinear least-square method.The instrumental broadening of SRPXRD was much smaller than that of CXRFD since the monochromatic X-rays produced single peak profiles and constant profile shape over a wide 2θ range. A profile fitting with a pseudo-Voigt function was used to determine 2θ angles to 0.0005 deg. for the synchrotron powder data. The peak angle and shape reflected from γ' phases in γ-matrix and those fron electrochemically extracted γ'-phase were significantly different.

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Determination of solute site occupancies within γ′ precipitates in nickel-base superalloys via orientation-specific atom probe tomography

Ultramicroscopy ◽

10.1016/j.ultramic.2015.04.015 ◽

2015 ◽

Vol 159 ◽

pp. 272-277 ◽

Cited By ~ 13

Author(s):

S. Meher ◽

T. Rojhirunsakool ◽

P. Nandwana ◽

J. Tiley ◽

R. Banerjee

Keyword(s):

Atom Probe Tomography ◽

Atom Probe ◽

Nickel Base Superalloys ◽

Nickel Base

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Evaluation of the Stability of Raft Structure in Nickel Base Superalloys Throughout their Lifetime

MRS Proceedings ◽

10.1557/proc-980-0980-ii08-08 ◽

2006 ◽

Vol 980 ◽

Author(s):

Katsushi Tanaka ◽

Toru Inoue ◽

Tetsu Ichitsubo ◽

Kyosuke Kishida ◽

Haruyuki Inui

Keyword(s):

Strain Energy ◽

Lattice Misfit ◽

Gamma Prime ◽

Lamellar Interface ◽

Nickel Base Superalloys ◽

Nickel Base ◽

The Stability ◽

Numerical Calculation Method ◽

Creep Deformations ◽

Lamellar Interfaces

AbstractStability of raft structure in nickel base superalloys has been examined by using elastic energy calculations based on a microelasticity theory. The numerical calculation method for a structurally heterogeneous system is applied. The results indicate that the raft structure is significantly stabilized by introductions of creep deformations till the critical creep deformation at which the lattice misfit between gamma and gamma-prime phases is completely compensated by creep dislocations. When the magnitude of creep deformations exceed the critical value, the (001) lamellar interfaces become elastically unstable and a tilted lamellar interface become the most stable one. This instability of the 001 raft structure leads a tilted or wavy lamellar interfaces for reducing the internal strain energy, that is a precursor to collapse the raft structure.

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Determination of the Coherency Strain of γ and γ’ Phases in Nickel-Base Superalloys at High Temperatures

Advances in X-Ray Analysis ◽

10.1007/978-1-4615-2972-9_58 ◽

1993 ◽

pp. 515-526

Author(s):

Katsumi Ohno ◽

Tadaharu Yokokawa ◽

Toshihiro Yamagata ◽

Hiroshi Harada ◽

Michio Yamazaki ◽

...

Keyword(s):

High Temperatures ◽

Coherency Strain ◽

Nickel Base Superalloys ◽

Nickel Base

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Lattice Parameter Determination Using Synchrotron Powder Data

Advances in X-ray Analysis ◽

10.1154/s0376030800021510 ◽

1986 ◽

Vol 30 ◽

pp. 373-382 ◽

Cited By ~ 1

Author(s):

W. Parrish ◽

M. Hart ◽

T. C Huang ◽

M. Bellotto

Keyword(s):

Lattice Parameter ◽

Parameter Determination ◽

Wavelength Selection ◽

Profile Fitting ◽

Angle Correction ◽

Average Accuracy ◽

The Mean ◽

The Individual ◽

Voigt Function

AbstractA method for using synchrotron-radiation parallel-beam X-ray diffractometry for precision measurement of scattering angles and lattice parameters is described. The important advantages of the method are the high P/B made possible by wavelength selection and high source intensity, the symmetrical profiles and the absence of most systematic errors making it unnecessary to use standards. Profile fitting with a pseudo-Voigt function is used to determine 2θ to 0.0001º. The zero-angle correction and lattice parameter were determined from least-squares refinement and the average accuracy of observed-calculated 2θs was 0.0020°. Average values of ∆d/d = ∆a/a directly calculated from the individual hkl measurements ranged from 2x 10-5 to 5.7 x 10-5. The precision estimated from the standard deviation of the mean is in the 10-6 range and 1 ppm precision was obtained for Si. The determination of the exact wavelength selected remains to be solved, but ratios of lattice spacings to standards such as NBS SRM 640a can be determined.

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