Microstructural investigation of temper embrittlement in 2.25% Cr-1%Mo steels with and without La additions

1986 ◽  
Vol 44 ◽  
pp. 576-577
Author(s):  
M.G. Burke ◽  
C. I. Garcia ◽  
A. J. DeArdo
Keyword(s):  
Analytical Electron Microscopy ◽  
Temper Embrittlement ◽  
Earth Metal ◽  
Thin Foil ◽  
Atom Probe ◽  
Extraction Replica ◽  
Probe Field ◽  
Microstructural Investigation ◽  
Carbon Extraction Replica ◽  
Heat Treated

Lanthanide (rare earth) metal additions to 2.25% Cr-1% Mo steels have been found to alleviate the material's susceptibility to temper embrittlement. To elucidate the manner by which such additions impart immunity to temper embrittlement, analytical electron microscopy (AEM) and atom probe field-ion microscopy (APFIM) have been employed to study the microstructures of tempered 2.25% Cr-1% Mo steels containing tramp elements with and without lanthanum additions.Thin-foil and carbon extraction replica specimens were prepared from the heat-treated 2.25% Cr-1% Mo steels. These samples were examined in a JEOL 200CX Temscan at 200 kV. Alloy carbides were identified by electron diffraction and STEM qualitative energy dispersive x-ray analysis.

A combined TEM/APFIM approach to the study of phase transformations: Phase identification in the Fe-Be system

1988 ◽  
Vol 46 ◽  
pp. 780-781
Author(s):  
M.G. Burke ◽  
M.K. Miller
Keyword(s):  
Phase Transformations ◽  
Microstructural Analysis ◽  
Analytical Electron Microscopy ◽  
Thin Foil ◽  
Atom Probe ◽  
Microstructural Development ◽  
Phase Identification ◽  
Probe Field ◽  
Isothermal Ageing ◽  
Microscopy Techniques

Phase transformation investigations rely on the identification and characterization of the microstructure in order to understand the formation, development, and relative stability of the constituent phases. Although transmission and associated analytical electron microscopy techniques have made substantial contributions by providing structural and chemical data necessary for the detailed microstructural analysis, the direct atomic structure and chemistry are not readily discernable. By combining TEM techniques with atom probe field-ion microscopy (APFIM), it is possible to obtain a complete structural and chemical analysis of the constituent phases. In this paper, the microstructural development which occurs during ageing in an Fe-25 at. % Be alloy is presented to illustrate the complementary nature of the techniques and demonstrate the applicability of the combined TEM/APFIM approach in the study of phase transformations.An Fe-25 at. % Be alloy was solution annealed at 1100°C for 0.5 h and water-quenched prior to isothermal ageing at 650°C for 4 h. Thin foil specimens were examined in a Philips EM430T operated at 300 kV and in a JEOL 200CX operated at 200 kV. FIM needle specimens were electropolished and analyzed in the ORNL energy-compensated APFIM.

scholarly journals Combined Atom-Probe and Electron Microscopy Characterization of Fine Scale Structures in Aged Primary Coolant Pipe Stainless Steel

1986 ◽  
Vol 82 ◽  
Author(s):  
J. Bentley ◽  
M. K. Miller
Keyword(s):  
Electron Microscopy ◽  
Analytical Electron Microscopy ◽  
Atom Probe ◽  
Primary Coolant ◽  
Probe Field ◽  
Α Phase ◽  
Complementary Nature ◽  
Microscopy Characterization

ABSTRACTThe capabilities and complementary nature of atom probe field-ion microscopy (APFIM) and analytical electron microscopy (AEM) for the characterization of finescale microstructures are illustrated by examination of the changes that occur after long term thermal aging of cast CF 8 and CF 8M duplex stainless steels. In material aged at 300 or 400°C for up to 70,000 h, the ferrite had spinodally decomposed into a modulated fine-scaled interconnected network consisting of an iron-rich α′ phase and a chromium-enriched α phase with periodicities of between 2 and 9 nm. G-phase precipitates 2 to 10 nm in diameter were also observed in the ferrite at concentrations of more than 1021 m−3. The reported degradation in mechanical properties is most likely a consequence of the spinodal decomposition in the ferrite.

Apfim Investigation of Segregation in a Nickel Base Alloy

1998 ◽  
Vol 4 (S2) ◽  
pp. 118-119
Author(s):  
M. Thuvander ◽  
K. Stiller
Keyword(s):  
Grain Size ◽  
Base Alloy ◽  
Atom Probe ◽  
Model Alloy ◽  
Probe Field ◽  
Inconel 600 ◽  
Carbon And Nitrogen ◽  
Heat Treated ◽  
Nickel Base ◽  
Boron Carbon

Segregation of boron, carbon and nitrogen to grain boundaries in a nickel based model alloy has been investigated using atom probe field ion microscopy (APFIM). The material corresponds to a commercial alloy (Inconel 600), but contains lower levels of alloy additives and impurities. The major composition was Ni-16Cr-10Fe (wt.%). The alloy was solution annealed at 950°C for 10 min, which resulted in a grain size of 20 μ. Subsequently heat treatments for 1 h at temperatures of 550°C, 600°C and 700°C were applied. TEM investigation showed that the heat treatment at 700°C resulted in precipitation of intergranular chromium-rich carbides. The other temperatures were obviously too low and the aging times too short to cause precipitation, since carbides were not observed in the materials heat treated at 550°C and 600°C.As the grain size was about 100 times larger than the accessible depth of APFIM analysis (≃200 nm), much care had to be taken in preparing samples containing a grain boundary close to the tip apex.

SHaRE: Collaborative materials science research

1988 ◽  
Vol 46 ◽  
pp. 804-805
Author(s):  
Edward A. Kenik ◽  
Karren L. More
Keyword(s):  
Electron Microscope ◽  
Materials Science ◽  
Analytical Electron Microscopy ◽  
Science Research ◽  
Atom Probe ◽  
Probe Field ◽  
Transmission Electron ◽  
Wide Range ◽  
Analytical Electron ◽  
Electron Microscopes

The Shared Research Equipment (SHaRE) Program provides access to the wide range of advanced equipment and techniques available in the Metals and Ceramics Division of ORNL to researchers from universities, industry, and other national laboratories. All SHaRE projects are collaborative in nature and address materials science problems in areas of mutual interest to the internal and external collaborators. While all facilities in the Metals and Ceramics Division are available under SHaRE, there is a strong emphasis on analytical electron microscopy (AEM), based on state-of-the-art facilities, techniques, and recognized expertise in the Division. The microscopy facilities include four analytical electron microscopes (one 300 kV, one 200 kV, and two 120 kV instruments), a conventional transmission electron microscope with a low field polepiece for examination of ferromagnetic materials, a high voltage (1 MV) electron microscope with a number of in situ capabilities, and a variety of EM support facilities. An atom probe field-ion microscope provides microstructural and elemental characterization at atomic resolution.

Applications of atom-probe field-ion microscopy to the study of interfaces

1993 ◽  
Vol 51 ◽  
pp. 862-863
Author(s):  
M.G. Burke ◽  
M.K. Miller
Keyword(s):  
Analytical Electron Microscopy ◽  
Atom Probe ◽  
Pressure Vessels ◽  
Low Alloy Steels ◽  
Probe Field ◽  
Microchemical Analysis ◽  
Elemental Sensitivity ◽  
Alloy Steels ◽  
Field Ion Microscope ◽  
Microstructural Studies

The near-atomic resolution and elemental sensitivity of the atom probe field-ion microscope (APFIM) permit the detailed microstructural and microchemical analysis of phases and interfaces in a variety of materials. To overcome the limitation of this technique in terms of volume of material sampled, it is frequently necessary to perform complementary microstructural studies by other techniques such as analytical electron microscopy (AEM) or auger electron spectroscopy (AES). With such complementary data, the microstructural significance of the APFIM data can be exploited. In addition to specifically evaluating segregation at interfaces, the high spatial resolution of the APFIM technique can be used to determine microcompositional fluctuations in the vicinity of interfaces. In this overview, some selected examples illustrating the application of the APFIM technique to the evaluation of segregation to interfaces are presented.Considerable research has been performed on low alloy steels, particularly those such as A533B which are used in the pressure vessels of nuclear reactors.

Origin and Influence of Pre-Existing Segregation on Radiation-Induced Segregation In Austenitic Stainless Steels

1998 ◽  
Vol 540 ◽  
Author(s):  
E. A. Kenik ◽  
J. T. Busby ◽  
M. K. Miller ◽  
A. M. Thuvander ◽  
G. Was
Keyword(s):  
Electron Microscopy ◽  
Grain Boundaries ◽  
Stainless Steels ◽  
Analytical Electron Microscopy ◽  
Austenitic Stainless Steels ◽  
Atom Probe ◽  
Molecular Ions ◽  
Probe Field ◽  
Analytical Electron ◽  
Radiation Induced

AbstractThe pre-existing segregation at grain boundaries in two austenitic stainless steels has been investigated by atom probe field ion microscopy and analytical electron microscopy. In addition, the effect of radiation-induced segregation on the near-grain-boundary composition has been studied by analytical electron microscopy. Pre-existing enrichment of Cr, Mo, B, C and P and depletion of Fe and Ni near grain boundaries has been observed. Significant affinity between Mo and N in both alloys is indicated by the detection of MoN2+` molecular ions during field evaporation. The pre-existing segregation is modified by radiation-induced segregation resulting in Ni and Si enrichment near the boundary as well as depletion of chromium adjacent to the boundary resulting in a “W-shaped” Cr profile.

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.

Identification Of G-Phase In Aged Cast CF 8 Type Stainless Steel

1985 ◽  
Vol 43 ◽  
pp. 328-329 ◽  
Author(s):  
J. Bentley ◽  
M. K. Miller ◽  
S. S. Brenner ◽  
J. A. Spitznagel
Keyword(s):  
Stainless Steel ◽  
Nuclear Reactors ◽  
Analytical Electron Microscopy ◽  
Atom Probe ◽  
Duplex Structure ◽  
Primary Coolant ◽  
Probe Field ◽  
Aged Material ◽  
Type Stainless Steel ◽  
Analytical Electron

The microstructure of as-cast and aged CF 8 type stainless steel, used for the primary coolant pipes in pressurized light-water nuclear reactors, is being studied by analytical electron microscopy (AEM) and atom probe field-ion microscopy (APFIM). The phase transformations of the ferrite (∼19 vol % of the duplex structure) that occur after aging at 673 K for 7500 h are described by Miller et al. The present work deals with the identification of G-phase (prototype compound Ni16Ti6Si7) observed in the ferrite of aged material.In FIM images the precipitates had bright contrast, appeared roughly spherical, were ∼10 nm in diameter, and were present at a concentration of ∼1023 m-3. Atom probe selected area microchemical analyses of the central portion of five precipitates revealed that they were alloy silicides, Table 1.

Understanding complex phase chemistry in a Ni-base superalloy: A combined AEM/APFIM approach

1990 ◽  
Vol 48 (4) ◽  
pp. 208-209
Author(s):  
M.G. Burke ◽  
M.K. Miller
Keyword(s):  
Elevated Temperatures ◽  
Bulk Composition ◽  
Analytical Electron Microscopy ◽  
Atom Probe ◽  
Treatment Schedule ◽  
Alloy 718 ◽  
Microstructural Stability ◽  
Probe Field ◽  
Analytical Electron ◽  
Base Superalloy

Alloy 718 is a Nb-modified Ni-base superalloy widely-used for gas turbine and related applications which require microstructural stability and good mechanical properties at elevated temperatures (≈ 650°C). In order to achieve the desired properties, the alloy is given a multi-step thermal treatment during which a complex multiphase microstructure is developed. The primary strengthening phases in this alloy are DO22-ordered γ" and Ll2-ordered γ'. A variety of other phases such as Laves, MC-type carbides, and δ (Ni3Nb) have been observed in this material. In this study, the techniques of analytical electron microscopy (AEM) and atom probe field-ion microscopy (APFIM) have been successfully applied to characterize the microstructure of Alloy 718.The nominal bulk composition of the material examined in this investigation is listed in Table 1 together with the heat treatment schedule. Specimens for AEM characterization were examined in a Philips EM400T analytical electron microscope operated at 120kV and equipped with a Link LZ5/AN10-85S analyzer system.

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