An Explanation for the Environmental Sensitivity of Ni3Al

1998 ◽  
Vol 552 ◽  
Author(s):  
D. B. Lillig ◽  
D. Legzdina ◽  
I. M. Robertson ◽  
H. K. Birnbaum
Keyword(s):  
Mass Spectrometry ◽  
Grain Boundary ◽  
Grain Boundaries ◽  
Secondary Ion Mass Spectrometry ◽  
Environmental Sensitivity ◽  
Boron Segregation ◽  
Boron Doped ◽  
Distribution Of Elements ◽  
Free Material ◽  
Secondary Ion

ABSTRACTSecondary Ion Mass Spectrometry has been used to study the distribution of elements in and near grain boundaries in boron-free and boron-doped Ni76Al24 alloys with and without ∼220 wt. ppm of deuterium. In boron-free alloys, sulfur was distributed about the grain boundaries in both deuterium- free and deuterium-charged samples. The distribution of deuterium followed that of sulfur and was segregated to grain boundaries. In the boron-doped material, sulfur was not found at most grain boundaries in the uncharged material, but was in the charged material. No deuterium was found at the grain boundaries in the boron-doped material. It is proposed that in the boron-free material it is the synergistic effect of sulfur and hydrogen that is responsible for the environmental sensitivity of this alloy. In boron-doped material, boron segregation to the grain boundary prevents sulfur, and to some extent hydrogen, segregating to the grain boundary.

Investigation of the Dopant Distribution in thin Epitaxial Silicon Layers by Means of Spreading Resistance Probe and Secondary Ion Mass Spectrometry

1997 ◽  
Vol 500 ◽  
Author(s):  
Ilya Karpov ◽  
Catherine Hartford ◽  
Greg Moran ◽  
Subramania Krishnakumar ◽  
Ron Choma ◽  
...  
Keyword(s):  
Mass Spectrometry ◽  
Secondary Ion Mass Spectrometry ◽  
Chemical Vapor ◽  
Doping Profile ◽  
Epitaxial Silicon ◽  
Spreading Resistance ◽  
Boron Doped ◽  
Ion Mass Spectrometry ◽  
Chemical Profiles ◽  
Secondary Ion

ABSTRACTIn this paper, we examine the dopant distributions in 1.8 to 4 micron-thick boron- and phosphorus-doped epitaxial silicon layers. These layers were grown by chemical vapor deposition (CVD) on arsenic-, antimony-, or boron-doped (100)- and (111)-oriented substrates. We performed doping profile studies by means of local resistivity measurements using a spreading resistance probe (SRP). Chemical profiles of the dopants were also obtained using secondary ion mass spectrometry (SIMS).

Grain Boundary Diffusion in Cation-Doped Superplastic 3Y-TZP

2006 ◽  
Vol 45 ◽  
pp. 1626-1631
Author(s):  
Marek Boniecki ◽  
Rafał Jakieła ◽  
Zdzislaw Librant ◽  
Wladyslaw Wesolowski ◽  
Danuta Dabrowska ◽  
...  
Keyword(s):  
Mass Spectrometry ◽  
Thin Films ◽  
Grain Boundary ◽  
Diffusion Coefficients ◽  
Boundary Diffusion ◽  
Secondary Ion Mass Spectrometry ◽  
Tetragonal Zirconia ◽  
Grain Boundary Diffusion ◽  
Depth Profiles ◽  
Secondary Ion

The superplastic flow in tetragonal zirconia polycrystals stabilised 3mol% Y2O3 (3YTZP) is strongly affected by the dopant cations, which segregate at the grain boundary. It is proposed that this flow is controlled by grain boundary diffusion of Zr4+ ions and therefore the dopant cations should change the grain boundary diffusion. In order to prove this thesis the measurements of grain boundary diffusion coefficients were made using Hf4+ ions as tracer. Zirconia samples were doped with 1mol% of Al2O3, SiO2, MgO, MgAl2O4, GeO2 and TiO2. The tracer was deposited on the surface of the zirconia specimens by placing several drops of hafnium nitrate and then drying at 373 K. In this way, thin films of HfO 2 were obtained. The samples were heated in the range 1553 – 1773 K for 1 to 24 h. The concentration versus depth profiles were measured using secondary ion mass spectrometry (SIMS). Calculated hence grain boundary diffusion coefficients were several times bigger for doped samples than for pure 3Y-TZP samples.

Study of Fe Diffusion in Cr2O3 by Secondary Ion Mass Spectrometry

2005 ◽  
Vol 237-240 ◽  
pp. 940-945
Author(s):  
Antônio Claret Soares Sabioni ◽  
Anne Marie Huntz ◽  
F. Silva ◽  
François Jomard
Keyword(s):  
Mass Spectrometry ◽  
Activation Energy ◽  
Grain Boundary ◽  
Boundary Diffusion ◽  
Secondary Ion Mass Spectrometry ◽  
Bulk Diffusion ◽  
Grain Boundary Diffusion ◽  
Iron Diffusion ◽  
Ion Mass Spectrometry ◽  
Secondary Ion

Chromia protective layers are used to prevent corrosion by oxidation of many alloys, such as the stainless steels, for instance. To check if chromia is a barrier to the outward diffusion of iron in these alloys, iron diffusion in chromia was studied in both polycrystals and oxide films formed by oxidation of Ni-30Cr alloy in the temperature range 700-1100°C at an oxygen pressure equal to 10-4 atm. An iron film of about 70 nm thick was deposited on the chromia surface, and after the diffusing treatment, the iron depth profiles were established by secondary ion mass spectrometry (SIMS). Using a solution of the Fick’s second law for diffusion from a thick film, effective or bulk diffusion coefficients were determined in a first penetration domain. Then, Le Claire’s and Hart’s models allowed both the bulk diffusion coefficient and the grain boundary diffusion parameter (aDgbd) to be obtained in a second penetration domain. Iron bulk and grain boundary diffusion does not vary significantly according to the nature-microstructure of chromia. The activation energy of grain boundary diffusion is at least equal or even greater than the activation energy of bulk diffusion, probably on account of segregation phenomena. Iron diffusion was compared to cationic self-diffusion and related to the protective character of chromia.

Local Electronic Structure and Cohesion of Grain Boundaries in Ni3Al

1994 ◽  
Vol 364 ◽  
Author(s):  
D. A. Muller ◽  
S. Subramanian ◽  
S. L. Sass ◽  
J. Silcox ◽  
P. E. Batson
Keyword(s):  
Grain Boundary ◽  
Grain Boundaries ◽  
Cohesive Energy ◽  
Bulk Material ◽  
Large Angle ◽  
Spatially Resolved ◽  
Boron Segregation ◽  
Environmental Embrittlement ◽  
Boron Doped ◽  
Local Electronic Structure

AbstractOne of the fundamental questions concerning Ni3Al is why doping with boron improves the room temperature ductility of the polycrystalline material. Boron is thought to prevent environmental embrittlement and increase the cohesive strength of grain boundaries since it changes the fracture mode from intergranular to transgranular. This change in cohesive energy must be reflected in the bonding changes at the grain boundary which can be probed using spatially resolved electron energy loss spectroscopy (EELS). We have examined grain boundaries in both undoped and boron doped Ni0.76Al0.24 using EELS, EDX and ADF imaging in a UHV STEM. Ni-enrichment is seen in a 0.5–1 nm wide region at large angle grain boundaries, both in the absence and presence of B. EELS shows that B segregation can vary along the interface. The Ni L2, 3 core edge fine structure which is sensitive to the filling of the Ni d-band, shows only the boron rich regions of the grain boundary to have a bonding similar to that of the bulk material. These results demonstrate that boron segregation increases the cohesive energy and hence improves the fracture resistance of the grain boundary, by making the bonding at boundaries similar to that in the bulk. The measured changes in d band filling may also affect the local solubility of hydrogen.

Boron and Hydrogen in NI3AL: Part II. Mechanical Testing of Bicrystals

1993 ◽  
Vol 319 ◽  
Author(s):  
Patricia E. Johnson ◽  
W. Gourdin ◽  
A. Gonis ◽  
N. Kioussis ◽  
M. Vaudin
Keyword(s):  
Water Vapor ◽  
Grain Boundary ◽  
Grain Boundaries ◽  
Tensile Tests ◽  
Stress And Strain ◽  
Boron Segregation ◽  
Environmental Embrittlement ◽  
Boron Doped ◽  
Low Symmetry ◽  
Strength And Ductility

AbstractTo provide a sensitive measurement of the effect of boron segregation on the strength and ductility of Ni3A1 grain boundaries, bicrystal tensile tests were performed on small specimens of boron doped Ni76A124 cut from extremely large-grained boules. Five specimens with the same “random” or low-symmetry grain boundary (disorientations measured by means of backscattered Kikuchi patterns) and two specimens with a second random grain boundary were tested in quenched and slow-cooled conditions. Duplicate tests performed in a low (7 ppm) water-vapor environment showed that the fracture mode and the stress and strain at fracture are altered by environmental embrittlement at individual, partially strengthened grain boundaries.

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