Interdiffusion in (fcc) Ni-Cr-X (X = Al, Si, Ge or Pd) Alloys at 700°C

2007 ◽  
Vol 266 ◽  
pp. 191-198 ◽  
Author(s):  
N. Garimella ◽  
M.P. Brady ◽  
Yong Ho Sohn
Keyword(s):  
Cross Sections ◽  
Electron Probe Microanalysis ◽  
Electron Probe ◽  
Concentration Profiles ◽  
Diffusion Couples ◽  
Alloying Additions ◽  
Cr2o3 Scale ◽  
Solid Diffusion ◽  
Ternary Alloying ◽  
Interdiffusion Coefficients

Interdiffusion at 700°C for Ni-22at.%Cr (fcc γ phase) alloys with small additions of Al, Si, Ge, or Pd was examined using solid-to-solid diffusion couples. Rods of Ni-22at.%Cr, Ni- 21at.%Cr-6.2at.%Al, Ni-22at.%Cr-4.0at.%Si, Ni-22at.%Cr-1.6at.%Ge and Ni-22at.%Cr-1.6at.%Pd alloys were cast using arc-melt and homogenized at 900°C for 168 hours. The diffusion couples were assembled with alloy disks in Invar steel jig, encapsulated in Argon after several hydrogen flushes, and annealed at 700°C for 720 hours. Experimental concentration profiles were determined from polished cross-sections by using electron probe microanalysis with pure standards of Ni, Cr, Al, Si, Ge and Pd. Interdiffusion fluxes of individual components were calculated directly from the experimental concentration profiles, and the moments of interdiffusion fluxes were examined to determine average ternary interdiffusion coefficients. Effects of ternary alloying additions on the interdiffusional behavior of Ni-Cr-X alloys at 700°C are presented in the light of the diffusional interactions and the formation of protective Cr2O3 scale.

Ternary and Quaternary Interdiffusion in γ (fcc) Fe-Ni-Cr-X (X = Si, Ge) Alloys at 900°C

2008 ◽  
Vol 595-598 ◽  
pp. 1145-1152 ◽  
Author(s):  
N. Garimella ◽  
M.P. Brady ◽  
Yong Ho Sohn
Keyword(s):  
Cross Sections ◽  
Electron Probe ◽  
Concentration Profiles ◽  
Diffusion Couples ◽  
Alloying Additions ◽  
Cr2o3 Scale ◽  
Interdiffusion Flux ◽  
Solid Diffusion ◽  
Interdiffusion Coefficients ◽  
And Diffusion

Interdiffusion in Fe-Ni-Cr (fcc γ phase) alloys with small additions of Si and Ge at 900°C was studied using solid-to-solid diffusion couples. Alloy rods of Fe-24 at.%Ni, Fe-24 at.%Ni- 22at.%Cr, Fe-24 at.%Ni-22at.%Cr-4at.%Si and Fe-24 at.%Ni-22at.%Cr-1.7at.%Ge were cast using arc-melt, and homogenized at 900°C for 168 hours. Sectioned alloy disks from the rods were polished, and diffusion couples were assembled with in Invar steel jig, encapsulated in Argon after several hydrogen flushes, and annealed atz 900°C for 168 hours. Polished cross-sections of the diffusion couples were characterized to determine experimental concentration profiles using electron probe microanalysis with pure elemental standards. Interdiffusion fluxes of individual components were calculated directly from the experimental concentration profiles, and the moments of interdiffusion flux profiles were examined to determine the average ternary and quaternary interdiffusion coefficients. Effects of alloying additions on the interdiffusional behavior of Fe-Ni- Cr-X alloys at 900°C are presented with due consideration for the formation of protective Cr2O3 scale.

Ternary Interdiffusion in L12-Ni3Al with Ir Alloying Addition

2008 ◽  
Vol 273-276 ◽  
pp. 637-642 ◽  
Author(s):  
Machiko Ode ◽  
N. Garimella ◽  
Muneaki Ikeda ◽  
Hideyuki Murakami ◽  
Yong Ho Sohn
Keyword(s):  
Vacuum Arc ◽  
Concentration Profiles ◽  
Diffusion Couples ◽  
Interdiffusion Flux ◽  
Solid Diffusion ◽  
Arc Melting ◽  
Vacuum Arc Melting ◽  
Dependent Component ◽  
Interdiffusion Coefficients ◽  
And Diffusion

Average ternary interdiffusion coefficients in Ni3Al with Ir additions have been determined using solid-to-solid diffusion couples annealed at 1200°C for 5 hours. Disc shaped alloy specimens were prepared by the vacuum arc melting at compositions of Ni-24Al, Ni-25Al, Ni-26Al, Ni-23.5Al-1Ir, Ni-24.5Al-1Ir, Ni-23Al-2Ir, Ni-23Al-2Ir, Ni-24Al-2Ir, Ni-23Al-3Ir (at.%). Surfaces of alloys were polished down to 1200 grit and diffusion couples were assembled in Si3N4 jig for initial bonding heat treatment at 1200°C for 0.5 hours. Additional diffusion anneal was carried out at 1200°C for 4.5 hours outside of Si3N4 jig so that diffusion couples can be water quenched. Concentration profiles of individual components were measured by electron probe microanalysis using pure standard of Ni, Al and Ir. Interdiffusion flux of individual component was determined directly from the experimental concentration profiles, and the moments of interdiffusion flux were examined to calculate the average ternary interdiffusion coefficients, D˜ ij k either with Al or Ni as dependent component. Calculated interdiffusion coefficients suggest that Ir-alloyed Al2O3-forming oxidation resistant coatings would be beneficial to reduce the interdiffusion flux of Ni from superalloy substrates to the coating, and reduce the interdiffusion flux of Al from the coating to the superalloy substrate.

scholarly journals Calculated interdiffusivities resulting from different fitting functions applied to measured concentration profiles in Cu-rich fcc Cu-Ni-Sn alloys at 1073 K

2017 ◽  
Vol 53 (3) ◽  
pp. 255-262 ◽  
Author(s):  
Y. Liu ◽  
D. Liu ◽  
Y. Du ◽  
S. Liu ◽  
D. Kuang ◽  
...  
Keyword(s):  
Error Propagation ◽  
Scientific Method ◽  
Electron Probe ◽  
Bulk Diffusion ◽  
Ternary Systems ◽  
Concentration Profiles ◽  
Diffusion Couples ◽  
Green Method ◽  
Measured Concentration ◽  
Interdiffusion Coefficients

Employing six groups of bulk diffusion couples together with electron probe microanalysis technique, the compositiondependences of ternary interdiffusion coefficients in Cu-rich fcc Cu-Ni-Sn alloys at 1073 K were determined via the Whittle and Green method. Different fitting functions applied to the measured concentration profiles are utilized to extract the interdiffusion coefficients of fcc Cu-Ni-Sn alloys. The errors for the obtained interdiffusivities are evaluated by a scientific method considering the error propagation. The calculated diffusion coefficients using the Boltzmann and additive Boltzmann functions are found to be with reasonable errors and show a general agreement with those using other fitting functions. Based on the Boltzmann and additive Boltzmann functions, the interdiffusivities in Cu-rich fcc Cu-Ni-Sn alloys at 1073 K are obtained and validated by thermodynamic constraints. The Boltzmann and additive Boltzmann functions are recommended to be used for the fitting of measured concentration profiles in other ternary systems for the sake of extracting ternary diffusivities.

scholarly journals Interdiffusion behavior in sigma-phase using Ni3Al/Mo diffusion couples

2011 ◽  
Vol 47 (2) ◽  
pp. 171-177
Author(s):  
C. Zhou ◽  
W. Gong ◽  
S. Huang ◽  
H. Wei
Keyword(s):  
Activation Energy ◽  
Concentration Dependence ◽  
Phase Formation ◽  
Electron Probe Microanalysis ◽  
Electron Probe ◽  
Sigma Phase ◽  
Diffusion Couples ◽  
Diffusional Interaction ◽  
Parabolic Growth ◽  
Interdiffusion Coefficients

The sigmaNiMo( Al) phase was formed using Ni3Al/Mo diffusion couples at 1423, 1473 and 1523 K. The growth of formed phase and the concentration-distance profiles for each component in the diffusion couples were examined by electron probe microanalysis (EPMA). The activation energy for the parabolic growth of ? phase is found to be 525.3 kJ/mol. The concentration dependence and average ternary interdiffusion coefficients in single ?-NiMo(Al) phase were calculated, and the Arrhenius equations of the D for the ?-NiMo(Al) phase are calculated, the diffusional interaction between Ni, Mo and Al in ?-NiMo(Al) phase was studied by the crossinterdiffusion coefficients. Moreover, these results were utilized to explain the ? phase formation and growth in ?? phase.

Site Preference and Diffusion in Ni3Al Alloyed with Ir, Ta or Re at 1200°C

2010 ◽  
Vol 297-301 ◽  
pp. 1322-1327 ◽  
Author(s):  
N. Garimella ◽  
H.J. Choi ◽  
Yong Ho Sohn
Keyword(s):  
Diffusion Coefficients ◽  
Tracer Diffusion ◽  
Site Preference ◽  
Solid Diffusion ◽  
Ordered Intermetallic ◽  
Ternary Alloying ◽  
Tracer Diffusion Coefficients ◽  
Interdiffusion Coefficients ◽  
And Diffusion

Diffusion in L12-Ni3Al with ternary alloying additions of Ir, Ta and Re was investigated at 1200°C using solid-to-solid diffusion couples, and examined with respect to site preference in ordered intermetallic compound. In addition to determination of average ternary interdiffusion coefficients [1-3], average effective interdiffusion coefficients were determined directly from the experimental concentration profiles. Ni has the largest magnitude of average effective interdiffusion coefficient, followed by Al, Ir, Re and Ta. The average effective interdiffusion coefficients for Ir, Re and Ta are much smaller than those for Ni and Al. Tracer diffusion coefficients determined by extrapolation technique, and available literature also followed the same trend. The relative tendency of Ni, Al, Ir, Re and Ta to occupy the -Ni and -Al sites are correlated to these diffusion coefficients, with due consideration for diffusion mechanisms and coordination of atoms.

The Influence of Niobium on the Interdiffusion Coefficients in α2 and γ of TiAl Alloys

2013 ◽  
Vol 747-748 ◽  
pp. 85-92
Author(s):  
Dong Dong Han ◽  
Xiang Jun Xu ◽  
Lai Qi Zhang ◽  
Yong Feng Liang ◽  
Jun Pin Lin
Keyword(s):  
Electron Probe ◽  
Single Phase ◽  
Activation Enthalpy ◽  
Diffusion Couples ◽  
Arrhenius Law ◽  
Exponential Factor ◽  
Tial Alloys ◽  
Electron Probe Microanalyzer ◽  
Interdiffusion Coefficients ◽  
Significant Concentration

nterdiffusion coefficients in α2-Ti3Al and γ-TiAl of conventional TiAl and TiAl-8Nb alloy were measured at the temperature ranging from 1273K to 1523K. Single-phase diffusion couples were employed, and the concentration profiles of Al after annealing were measured by an electron probe microanalyzer (EPMA), and the interdiffusion coefficients were calculated according to the Boltzmann-Matano method. The results showed that there was no significant concentration dependence of interdiffusion coefficients for all the alloys with various phases, and the values of interdiffusion coefficients covered three orders of magnitude (E-17-E-14) with the increase of temperature according to Arrhenius law. In α2-Ti3Al and γ-TiAl phase of conventional TiAl alloys, the pre-exponential factor and activation enthalpy were D0=3.95×10-5m2s-1,Q=276KJmol-1 ;D0=7.26×10-5m2s-1,Q=275KJmol-1 respectively. The pre-exponential factor and activation enthalpy were D0=4.54×10-6m2s-1, Q=244KJmol-1 in γ-TiAl phase of TiAl-8Nb alloys. However, the temperature dependence of interdiffusion coefficients in α2-Ti3Al of TiAl-8Nb alloys did not follow Arrhenius laws very well. With the addition of Nb, the interdiffusion coefficients increased significantly in α2-Ti3Al, but changed slightly in γ-TiAl at high temperature.

Calculating of Diffusion Profiles in Ternary Systems Using Effective Interdiffusion Coefficients of Components

2013 ◽  
Vol 333 ◽  
pp. 73-82
Author(s):  
Ü. Ugaste ◽  
J. Priimets
Keyword(s):  
Good Accuracy ◽  
Ternary Systems ◽  
Concentration Profiles ◽  
Diffusion Couples ◽  
Ternary Diffusion ◽  
Variable Diffusion Coefficient ◽  
Ternary Diffusion Couple ◽  
Variable Diffusion ◽  
Interdiffusion Coefficients ◽  
Diffusion Profiles

A method has been developed for calculating diffusion profiles in ternary systems by using effective interdiffusion coefficients of components and Boltzmanns solution for diffusion equation with variable diffusion coefficient. Using this method the concentration profiles for several diffusion couples in the systems Fe-Co-Ni and Cu-Fe-Ni are calculated as examples and some peculiarities of these calculations are discussed, particularly, how to solve some possible difficulties, which may sometimes arise at calculation procedures. It is shown that having the data on effective interdiffusion coefficients and their concentration dependence for at least two components in a ternary diffusion couple, the concentration profiles for all three components can be calculated with good accuracy.

Ionization Cross Sections for Quantitative Electron Probe Microanalysis

2001 ◽  
Vol 7 (S2) ◽  
pp. 672-673
Author(s):  
C. Merlet ◽  
X. Llovet ◽  
S. Segui ◽  
J.M. Fernández-Varea ◽  
F. Salvat
Keyword(s):  
Cross Section ◽  
Cross Sections ◽  
Electron Probe Microanalysis ◽  
Electron Probe ◽  
Ionization Cross Section ◽  
Ionization Cross ◽  
Quantitative Electron Probe Microanalysis ◽  
Ionization Cross Sections ◽  
Semi Empirical ◽  
Quantitative Epma

Quantitative procedures in electron probe microanalysis (EPMA) require the knowledge of various atomic parameters, the most fundamental of which is the ionization cross section. A number of semi-empirical, approximate analytical formulas have been proposed to calculate the ionization cross section. The simplicity of these formulas makes them suitable for quantitative EPMA procedures. However, it is difficult to assess their reliability because of the lack of accurate experimental data. Indeed, inspection of currently available data reveals that they are still scarce for many elements and, when they are available, one usually finds significant discrepancies between data from different authors. Fortunately, the inaccuracies in the semi-empirical cross section formulas used in EPMA have only a small effect on the analytical results when standards are used. Nonetheless, in quantitative EPMA studies at low overvoltages or using standardless methods, the evaluated compositions largely depend on the adopted ionization cross sections and, therefore, knowledge of accurate ionization cross sections is a requisite for the development of improved quantification methods.

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