The Microchemistry of Grain Boundaries in Ni3Al

1988 ◽  
Vol 133 ◽  
Author(s):  
D. N. Sieloff ◽  
S. S. Brenner ◽  
Hua Ming-Jian
Keyword(s):  
Grain Boundary ◽  
Grain Boundaries ◽  
Atom Probe ◽  
High Concentration ◽  
Field Ion Microscopy ◽  
Boron Clusters ◽  
Ion Microscopy

ABSTRACTGrain boundary regions in B-doped as well as B-free Ni3AI were studied by field-ion microscopy and atom probe microanalysis. In the ductile, recrystallized, Ni-rich alloys the segregation of boron was often accompanied by an enrichment of nickel. Such an enrichment was not observed at boundaries in B-free alloys. Boron was also observed to segregate to the boundaries in a 25.2A1 - IB alloy which was reported to contain boron clusters. Such clusters were not observed, instead a high concentration of boron pairs were found.

Effect of Aluminum Level on Boron Clustering in Ni3Al

1988 ◽  
Vol 133 ◽  
Author(s):  
J. A. Horton ◽  
M. K. Miller ◽  
C. T. Liu ◽  
E. P. George ◽  
J. Bentley
Keyword(s):  
Grain Boundaries ◽  
Maximum Size ◽  
Atom Probe ◽  
Probe Field ◽  
Boron Clusters ◽  
Boron Segregation ◽  
Aluminum Level ◽  
Ion Microscopy ◽  
Rapidly Solidified ◽  
Nickel Enrichment

ABSTRACTIn alloys containing 0.24% boron, atom-probe field-ion microscopy (APFIM) revealed the presence of boron clusters in Ni-25 at. % Al and Ni-26 Al but not in Ni-24 Al. The observed boron clusters generally consisted of two to three boron atoms with a maximum size of 10 atoms. Quench rates that ranged from rapid solidification to furnace cooling had little effect on the clustering. The occurrence of the clustering coincides with a higher rate of boron strengthening as measured by an increase in the yield stress per atomic percent boron, and it also coincides with a reduced amount of boron segregation to grain boundaries. The levels of nickel and boron were highly variable on grain boundaries in rapidly solidified material and therefore no consistent indication of nickel enrichment at the grain boundaries associated with boron segregation was found. This result suggests that cosegregation of nickel with boron may not be necessary for the ductilization of Ni3Al by boron, since the rapidly solidified material is also ductilized by boron and exhibits segregation of only boron to the grain boundaries.

Characterization of Internal Interfaces by Atom Probe Field Ion Microscopy

1992 ◽  
Vol 295 ◽  
Author(s):  
M. K. Miller ◽  
Raman Jayaram
Keyword(s):  
Grain Boundaries ◽  
Compositional Analysis ◽  
Atom Probe ◽  
Probe Field ◽  
Field Ion Microscopy ◽  
Surrounding Matrix ◽  
Wide Range ◽  
Ion Microscopy ◽  
Field Ion Microscope

AbstractThe near atomic spatial resolution of the atom probe field ion microscope permits the elemental characterization of internal interfaces, grain boundaries and surfaces to be performed in a wide variety of materials. Information such as the orientation relationship between grains, topology of the interface, and the coherency of small precipitates with the surrounding matrix may be obtained from field ion microscopy. Details of the solute segregation may be obtained at the plane of the interface and as a function of distance from the interface for all elements simultaneously from atom probe compositional analysis. The capabilities and limitations of the atom probe technique in the characterization of internal interfaces is illustrated with examples of grain boundaries and interphase interfaces in a wide range of materials including intermetallics, model alloys, and commercial steels.

Fim/atom Probe Studies of B—doped and Alloyed Ni3Ai

1986 ◽  
Vol 81 ◽  
Author(s):  
D.D. Sieloff ◽  
S.S. Brenner ◽  
M.G. Burke
Keyword(s):  
Grain Boundaries ◽  
Boron Concentration ◽  
Atom Probe ◽  
Boundary Plane ◽  
Aluminum Concentration ◽  
Field Ion Microscopy ◽  
Ion Microscopy

AbstractField—ion microscopy and atom probe microanalysis have been used to determine thestructure and chemistry of grain boundaries in ductile, recrystallized Ni3Al containing 0.23 at % B (500 wt.ppm). The results indicate that the boron concentration fluctuates along the boundary plane and that the boron enriched zone is wider than expected from equilibrium—type adsorption. It was also found that boron lowers the aluminum concentration of some of the boundary regions.

FIELD-ION MICROSCOPY OBSERVATIONS AND ATOMISTIC SIMULATIONS OF RIGID-BODY SHIFTS AT TILT GRAIN BOUNDARIES IN TUNGSTEN

2008 ◽  
Vol 15 (05) ◽  
pp. 557-565 ◽  
Author(s):  
V. M. AZHAZHA ◽  
I. M. NEKLYUDOV ◽  
V. A. KSENOFONTOV ◽  
T. I. MAZILOVA ◽  
I. M. MIKHAILOVSKIJ ◽  
...  
Keyword(s):  
Grain Boundary ◽  
Rigid Body ◽  
Grain Boundaries ◽  
Mirror Symmetry ◽  
Dynamics Simulation ◽  
Field Ion Microscopy ◽  
Atomic Structures ◽  
Rigid Body Displacement ◽  
Ion Microscopy

Field-ion microscopy and molecular dynamics simulation were used for the characterization of the translation states at special grain boundaries in tungsten. It is revealed that rigid-body displacement had the component of displacement parallel to the [110] direction equal to 0 or 1 interplanar spacing. Full vectors of lateral shifts are described by broad statistical distribution. The mathematical simulation revealed two mirror-symmetry-breaking lateral translations along the [Formula: see text] direction of the Σ9 grain boundary corresponding to different atomic structures. It is shown that the partial disconnection with the [Formula: see text] Burgers vector can be considered as the elemental carriers of grain-boundary polymorphic transformation.

On the Shape of Field-Ion Emitters

1976 ◽  
Vol 34 ◽  
pp. 520-521
Author(s):  
H.C. Eaton ◽  
B.N. Ranganathan ◽  
T.W. Burwinkle ◽  
R. J. Bayuzick ◽  
J.J. Hren
Keyword(s):  
Grain Boundary ◽  
Spherical Shape ◽  
Theoretical Strength ◽  
Evaporation Process ◽  
Field Evaporation ◽  
Geometric Information ◽  
Field Ion Microscopy ◽  
Considerable Error ◽  
True Shape ◽  
Ion Microscopy

The shape of the emitter is of cardinal importance to field-ion microscopy. First, the field evaporation process itself is closely related to the initial tip shape. Secondly, the imaging stress, which is near the theoretical strength of the material and intrinsic to the imaging process, cannot be characterized without knowledge of the emitter shape. Finally, the problem of obtaining quantitative geometric information from the micrograph cannot be solved without knowing the shape. Previously published grain-boundary topographies were obtained employing an assumption of a spherical shape (1). The present investigation shows that the true shape deviates as much as 100 Å from sphericity and boundary reconstructions contain considerable error as a result.Our present procedures for obtaining tip shape may be summarized as follows. An empirical projection, D=f(θ), is obtained by digitizing the positions of poles on a field-ion micrograph.

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