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.

Spinodal Decomposition in Fe-Cr-Co Alloys

1982 ◽  
Vol 21 ◽  
Author(s):  
S. S. Brenner ◽  
P. P. Camus ◽  
M. K. Miller ◽  
W. A. Soffa
Keyword(s):  
Phase Separation ◽  
Spinodal Decomposition ◽  
Atom Probe ◽  
Continuous Phase ◽  
Miscibility Gap ◽  
Two Phase ◽  
Probe Field ◽  
Long Wavelength ◽  
Composition Fluctuations ◽  
Kinetics Of

Continuous phase separation or spinodal decomposition occurs within a miscibility gap through the selective amplification of long wavelength concentration waves to produce a two-phase modulated microstructure. To comprehensively study the formation of these modulated microstructures and the kinetics of continuous phase separation the behavior of the composition fluctuations in the decomposing material should be monitored directly. The atom probe field-ion microscope is an ideal instrument for this type of investigation of fine-scale microstructures because of its ultra-high spatial resolution and microchemical analysis capability.

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.

Microstructural Characterization of Rapidly Solidified Ultrahigh Strength Aluminum Alloys

1998 ◽  
Vol 4 (S2) ◽  
pp. 98-99
Author(s):  
D. H. Ping ◽  
K. Hono ◽  
A. Inoue
Keyword(s):  
Rapid Solidification ◽  
Microstructural Characterization ◽  
Atom Probe ◽  
Probe Field ◽  
Amorphous Phases ◽  
Ultrahigh Strength ◽  
Icosahedral Phases ◽  
Transmission Electron ◽  
Solidification Processes ◽  
Rapidly Solidified

Recently, Inoue et al. succeeded in fabricating ultrahigh-strength Al-based alloys consisting of a nanoscale mixture of α-Al and amorphous phases or a mixture of a-Al, amorphous and icosahedral phases in Al-TM-Ce, Al-TM-Ln (TM: transition metals) and Al-Cr-Co-Ce systems by rapid solidification [1-3]. In order to understand the mechanism of the nanoscale microstructural evolution during the rapid solidification processes in these nanocomposite alloys, we have characterized the microstructures of rapidly solidified Al94.5Cr3Co1.5Ce1 and Al96V4Fe2 alloys by atom probe field ion microscopy (APFIM) and high resolution transmission electron microscopy (HREM).TEM investigations have revealed that the as-quenched Al94.5Cr3Co1.5Ce1 alloy is composed of a nanoscale mixture of amorphous and α-Al. A typical TEM bright field micrograph is shown in Fig. 1. The microdiffraction patterns taken at various locations in the darkly contrasted region have shown that the region consists of a few interconnected α-Al grains and many localized amorphous regions which are trapped within the Al grains.

Detection of Hyperfine Precipitates in Nickel-Base Alloys

1968 ◽  
Vol 26 ◽  
pp. 438-439
Author(s):  
P. Beardmore
Keyword(s):  
Fine Particles ◽  
Dark Field ◽  
Deformation Mechanisms ◽  
Second Phase ◽  
Two Phase ◽  
Realistic Interpretation ◽  
Metal Foils ◽  
Fluorescent Screen ◽  
Dark Field Microscopy ◽  
Nickel Base

One of the primary objectives of the use of the electron microscope in the examination of metal foils is to ascertain the exact details of the microstructure in order that a realistic interpretation of the deformation mechanisms can be made. However, problems can arise in two phase structures in which the second phase is present as particles of widely differing size. In such cases it is possible to overlook the extremely fine particles because of the predominance of the larger particles on the fluorescent screen. Thus, fine details of the microstructure can remain undetected. This is particularly true in alloys in which both the precipitate and matrix have a common crystal structure and differ only in state of order. In such a structure, the detection and clarity of the precipitates is enhanced by dark field microscopy.

The Earliest Stage of the Solid State Amorphization Reaction in the Zr-Co System

1994 ◽  
Vol 343 ◽  
Author(s):  
Ralf Busch ◽  
Frank Gaertner ◽  
Susanne Schneider ◽  
Rüdiger Bormann ◽  
Peter Haasen
Keyword(s):  
Solid State ◽  
Chemical Potential ◽  
Amorphous State ◽  
Atom Probe ◽  
Metastable Equilibrium ◽  
Two Phase ◽  
Probe Field ◽  
Emf Measurements ◽  
Amorphous Phases ◽  
State Amorphization

ABSTRACTBased on atom probe field ion microscopy (AP/FIM) studies, electromotive force (EMF) measurements and CALPHAD calculations we discuss the earliest stage of the solid state amorphization reaction (SSAR) in Zr/Co-layers. The AP measurements show that two amorphous phases are formed at the Zr/Co interface from the early stages of the reaction. The metastable two phase field between these amorphous phases is shown by direct measurement of the chemical potential of Zr in amorphous co-sputtered ZrCo alloys by the EMF method. The comparison between the atom probe data and the CALPHAD calculation shows that the interfaces between the different layers are far away from metastable equilibrium in the beginning of the reaction. The amorphous phase formation at the Zr/Co interface and in the hcp-Zr grain boundary is preceded by a supersaturation of the hep ZrCo solid solution that transforms polymorphically into the amorphous state.

scholarly journals Atom Probe Field Ion Microscopy of Poly Synthetically Twinned Titanium Aluminide

1998 ◽  
Vol 4 (S2) ◽  
pp. 102-103
Author(s):  
D. J. Larson ◽  
M. K. Miller ◽  
H. Inui ◽  
M. Yamaguchi
Keyword(s):  
Mechanical Properties ◽  
Titanium Aluminide ◽  
Lamellar Microstructure ◽  
Atom Probe ◽  
Ordered Structure ◽  
Two Phase ◽  
Probe Field ◽  
Tial Alloys ◽  
Structural Applications ◽  
Single Set

Two phase γ-based TiAl alloys are attractive for structural applications at high temperatures because they possess good elevated-temperature mechanical properties, low density, and good creep and oxidation resistance. The microstructures of these alloys consist of plates of the near equiatomic γ phase (L10-ordered structure) and the Ti3Al α2 phase (D019-ordered structure). It is of great interest to study the details of the lamellar α2+γ microstructure because the interface stability is the key to providing a usable high temperature material.Polysynthetically twinned (PST) TiAl crystals have been developed in order to systematically study the lamellar microstructure. These PST materials contain no high angle grain boundaries and have an single set of aligned lamellae of a α2 and γ phases, as shown in Fig. 1. Therefore, PST samples facilitate the study of the dependence of mechanical properties on lamellar structure by providing a known, consistent set of aligned lamellae.

Evolution of Nanoscale Ferromagnetic Particles in Co-Cr and Cr-Fe Alloys Observed by Atom Probe Field Ion Microscopy

1995 ◽  
Vol 384 ◽  
Author(s):  
K. Hono ◽  
R. Okano ◽  
K. Takanashi ◽  
H. Fujimori ◽  
Y. Maeda ◽  
...  
Keyword(s):  
Magnetic Properties ◽  
Elevated Temperatures ◽  
Three Dimensional ◽  
Microstructural Characterization ◽  
Atom Probe ◽  
Behavior Changes ◽  
Probe Field ◽  
Treatment Conditions ◽  
Sputter Deposited ◽  
Ferromagnetic Particles

ABSTRACTWith appropriate processing conditions, nanoscale ferromagnetic particles precipitate from nonmagnetic matrix phase in the Co-Cr and Cr-Fe systems. In these heterogeneous alloys, unique magnetic properties are observed. In order to correlate such magnetic properties with the microstructures, we have employed an atom probe field ion microscope (APFIM) and a three dimensional atom probe (3DAP). In the Co-22Cr thin film sputter-deposited at elevated temperatures (~500 K), both APFIM and 3DAP data convincingly showed that the film was composed of lamellae-like ferromagnetic and paramagnetic phases of approximately 8 nm in thickness. On the other hand, it was shown that the films sputter-deposited at ambient temperature was composed of s-Co single phase without significant compositional heterogeneity. Based on these observations, we conclude that phase separation progresses during the growth of the film on a heated substrate. In the Cr-Fe alloy, large negative MR was observed in the as-quenched alloy at liquid helium temperature. However, the MR behavior changes as the phase decomposition progresses by annealing. The change in the MR behavior observed in this alloy with various heat treatment conditions will be discussed based on the microstructural characterization results by APFIM and 3DAP.

scholarly journals FIB Lift-Out and Milling of Cylindrical Specimens for Electron Tomography (or Atom Probe Field Ion Microscopy)

2004 ◽  
Vol 12 (6) ◽  
pp. 34-35
Author(s):  
Lucille A. Giannuzzi
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Electron Beam ◽  
Amorphous Materials ◽  
Electron Tomography ◽  
Atom Probe ◽  
Dark Field ◽  
Specimen Thickness ◽  
Probe Field ◽  
Transmission Electron

Electron tomography using transmission electron microscopy (TEM) and related techniques (e.g., scanning transmission electron microscopy (STEM) or energy filtered TEM (EFTEM)) allow for 3-D microstructural and elemental mapping of specimens, and has been used successfully in the biological sciences where mass-thickness contrast dominates these mostly amorphous materials. Z-contrast STEM imaging via high angle annular dark field (HAADF) tomography has also been used successfully in the physical sciences. STEM, EFTEM, and holography tomography are more useful techniques for crystalline materials, since diffraction contrast in conventional TEM images can hinder image reconstruction. Typical tomography routines utilize conventional electron transparent foils, whereby the dimensions of the specimen perpendicular to the electron beam may be orders of magnitude greater than the specimen thickness parallel to the electron beam. Using this conventional specimen geometry, the effective specimen thickness increases as the specimen is tilted through the ± 70 degrees necessary for the tomographic acquisition process.

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