scholarly journals Atomic Level Characterization of the Morphology of Phases in Chromindur Magnetic Alloys

1991 ◽  
Vol 232 ◽  
Author(s):  
M. K Miller ◽  
P. P. Camus ◽  
M. G. Hetherington
Keyword(s):  
Atom Probe ◽  
Heat Treatments ◽  
Miscibility Gap ◽  
Probe Field ◽  
Magnet Alloy ◽  
Two Phases ◽  
Isothermal Heat Treatments ◽  
Field Ion Microscope ◽  
Permanent Magnet Alloy

ABSTRACTThe atom probe field ion microscope has been used to characterize the morphology and determine the compositions of the iron-rich a and chromium-enriched α′ phases produced during isothermal and step cooled heat treatments in a Chromindur II ductile permanent magnet alloy. The good magnetic properties of this material are due to a combination of the composition of the two phases and the isolated nature and size of the ferromagnetic a phase. The morphology of the a phase is produced as a result of the shape of the miscibility gap and the step-cooled heat treatment and is distinctly different from that formed during isothermal heat treatments.

scholarly journals Specimen preparation of irradiated materials for examination in the atom probe field ion microscope

1994 ◽  
Vol 52 ◽  
pp. 882-883
Author(s):  
K. F. Russell ◽  
M. K. Miller
Keyword(s):  
Neutron Irradiation ◽  
Atom Probe ◽  
Specimen Preparation ◽  
Fine Scale ◽  
Probe Field ◽  
Taper Angle ◽  
Ion Microscopy ◽  
Remote Operations ◽  
Field Ion Microscope

The atom probe field ion microscope (APFIM) is well suited to the characterization of the fine scale features and defects that are formed in materials due to exposure to neutron irradiation. However, in order for the technique to be effective, suitable specimens are required. Atom probe field ion microscopy specimens are in the form of ultrasharp needles that are usually produced by a series of mechanical and chemical or electrochemical methods. These needles have a typical end radius of approximately 10 to 50 nm and a taper angle of between 1 and 5. The small dimensions mean that the specimens are extremely fragile and difficult to handle and do not easily lend themselves to remote operations in a hot cell. The small size and mass of the APFIM specimen has the advantage that the amount of material required is minimal.A concept in working with irradiated materials is to keep exposure to the operator "as low as reasonably achievable" (ALARA).

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.

A combined AEM/APFIM characterization of alloy X-750

1992 ◽  
Vol 50 (1) ◽  
pp. 174-175
Author(s):  
M.G. Burke ◽  
M.K. Miller
Keyword(s):  
Mechanical Properties ◽  
Analytical Electron Microscopy ◽  
Atom Probe ◽  
Alloy Development ◽  
Probe Field ◽  
Surrounding Matrix ◽  
The Matrix ◽  
Size And Morphology ◽  
Field Ion Microscope

In the development of advanced alloys for power system applications, the primary emphasis is placed on attaining specific mechanical properties with resistance to environmental attack. An important part of alloy development is the detailed characterization of the microstructure, because it is the composition, size and morphology of the microstructural features that define the mechanical properties of the material. The good mechanical properties of Ni-base superalloys are a result of the formation of fine coherent precipitates. In addition, other coarser phases may form which can degrade the properties of the alloys. Analytical electron microscopy (AEM) provides important information concerning the type and distribution of the phases in the alloys, but quantitative microchemical analysis of the ultra-fine precipitates is not readily obtainable with conventional AEM techniques. The high spatial resolution of the atom probe field-ion microscope (APFIM) makes this technique ideally suited to the analysis of the ultra-fine precipitates and surrounding matrix. The analysis of the matrix is particularly important in predicting the subsequent ageing response of the alloy, as previously shown in a detailed AEM/APFIM examination of Alloy 718. In this paper, a combined AEM/APFIM study of precipitation in Alloy X-750 is presented.

Decomposition in Pd40Ni40P20 Bulk Metallic Glass

1998 ◽  
Vol 554 ◽  
Author(s):  
M. K. Miller ◽  
R. B. Schwarz ◽  
Yi He
Keyword(s):  
Phase Separation ◽  
Metallic Glass ◽  
Cast Alloy ◽  
Atom Probe ◽  
Probe Field ◽  
3 Dimensional ◽  
Short Range Ordering ◽  
Field Ion Microscope ◽  
Temperature Crystallization

AbstractAn atom probe field ion microscope and 3-dimensional atom probe characterization of the solute distribution in a bulk Pd40Ni40P20 metallic glass in the as-cast state and after annealing has been performed. Statistical analysis of the atom probe atom-by-atom data detected the presence of short range ordering in the as-cast alloy. Phase separation at the nanometer level is observed in glassy samples after annealing above the glass-transition temperature. Crystallization proceeds by phase separation into three distinct crystalline phases. Atom probe analysis of the alloy annealed for 1 h at 410°C revealed that the primary nickel phosphide phase contained significant levels of palladium, the palladium-rich Pd3P phosphide phase contained low levels of nickel and there was a small amount of a palladium-nickel solid solution.

A Comparison of Tem and Apfim to the Interpretation of Modulated Microstructures

1985 ◽  
Vol 43 ◽  
pp. 70-71
Author(s):  
M.G. Burke ◽  
M.K. Miller
Keyword(s):  
Low Temperature ◽  
Microstructural Characterization ◽  
Superlattice Reflection ◽  
High Volume ◽  
Atom Probe ◽  
Dark Field ◽  
Miscibility Gap ◽  
Second Phase ◽  
Two Phase ◽  
Probe Field

Interpretation of fine-scale microstructures containing high volume fractions of second phase is complex. In particular, microstructures developed through decomposition within low temperature miscibility gaps may be extremely fine. This paper compares the morphological interpretations of such complex microstructures by the high-resolution techniques of TEM and atom probe field-ion microscopy (APFIM).The Fe-25 at% Be alloy selected for this study was aged within the low temperature miscibility gap to form a <100> aligned two-phase microstructure. This triaxially modulated microstructure is composed of an Fe-rich ferrite phase and a B2-ordered Be-enriched phase. The microstructural characterization through conventional bright-field TEM is inadequate because of the many contributions to image contrast. The ordering reaction which accompanies spinodal decomposition in this alloy permits simplification of the image by the use of the centered dark field technique to image just one phase. A CDF image formed with a B2 superlattice reflection is shown in fig. 1. In this CDF micrograph, the the B2-ordered Be-enriched phase appears as bright regions in the darkly-imaging ferrite. By examining the specimen in a [001] orientation, the <100> nature of the modulations is evident.

Fabrication and characterization - by High Resolution Electron Microscopy and atom probe microanalysis - of Co-based metallic multilayer films

1990 ◽  
Vol 48 (4) ◽  
pp. 772-773
Author(s):  
Amanda K. Petford-Long ◽  
A. Cerezo ◽  
M.G. Hetherington
Keyword(s):  
Electron Microscopy ◽  
High Resolution ◽  
High Resolution Electron Microscopy ◽  
Atom Probe ◽  
Multilayer Films ◽  
Interface Roughness ◽  
Probe Field ◽  
Resolution Electron ◽  
Potential Applications ◽  
Field Ion Microscope

The fabrication of multilayer films (MLF) with layer thicknesses down to one monolayer has led to the development of materials with unique properties not found in bulk materials. The properties of interest depend critically on the structure and composition of the films, with the interfacial regions between the layers being of particular importance. There are a number of magnetic MLF systems based on Co, several of which have potential applications as perpendicular magnetic (e.g Co/Cr) or magneto-optic (e.g. Co/Pt) recording media. Of particular concern are the effects of parameters such as crystallographic texture and interface roughness, which are determined by the fabrication conditions, on magnetic properties and structure.In this study we have fabricated Co-based MLF by UHV thermal evaporation in the prechamber of an atom probe field-ion microscope (AP). The multilayers were deposited simultaneously onto cobalt field-ion specimens (for AP and position-sensitive atom probe (POSAP) microanalysis without exposure to atmosphere) and onto the flat (001) surface of oxidised silicon wafers (for subsequent study in cross-section using high-resolution electron microscopy (HREM) in a JEOL 4000EX. Deposi-tion was from W filaments loaded with material in the form of wire (Co, Fe, Ni, Pt and Au) or flakes (Cr). The base pressure in the chamber was around 8×10−8 torr during deposition with a typical deposition rate of 0.05 - 0.2nm/s.

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