On The Effect of Au Addition and the Role of B on Nanocrystallization of Fe-Zr-B Amorphous Alloy

1999 ◽  
Vol 580 ◽  
Author(s):  
Y. Zhang ◽  
N. Wanderka ◽  
U. Czubayko ◽  
F. Zhu ◽  
H. Wollenberger
Keyword(s):  
Amorphous Alloy ◽  
Early Stage ◽  
Primary Crystallization ◽  
Atom Probe ◽  
Chemical Compositions ◽  
Probe Field ◽  
Heterogeneous Distribution ◽  
Nucleation Barrier ◽  
Nucleation Sites

AbstractUsing atom probe field ion microscopy (APFIM) we examined the local chemical compositions of Fe-7Zr-5B-lAu and Fe-14B amorphous alloys in the course of primary crystallization. Au rich clusters are formed during primary crystallization of Fe-7Zr-5B-lAu alloy. However, these clusters do not act as nucleation sites for α-Fe particles. In the early stage of primary crystallization, heterogeneities of Fe and B evolve in the amorphous phase. Heterogeneous distribution of B was found in the as-melt-spun Fe-14B amorphous alloy. During primary crystallization, B is highly supersaturated not only in the nanometer sized α-Fe particles in Fe-7Zr-5B-lAu alloy, but also in those of large diameters in Fe-14B alloy. From the results it is concluded that presence of B lowers the nucleation barrier for primary crystallization.

Effect of Gold Addition on the Nanostructure of Amorphous Fe–Zr–B Alloy

2000 ◽  
Vol 15 (6) ◽  
pp. 1271-1279 ◽  
Author(s):  
Y. Zhang ◽  
U. Czubayko ◽  
N. Wanderka ◽  
F. Zhu ◽  
H. Wollenberger
Keyword(s):  
Amorphous Alloys ◽  
Crystallization Process ◽  
Amorphous Matrix ◽  
Early Stage ◽  
Primary Crystallization ◽  
Atom Probe ◽  
Probe Field ◽  
Au Clusters ◽  
Transmission Electron ◽  
Ion Microscopy

The behavior of Au in the course of the primary crystallization process of Fe87Zr7B5Au1 amorphous alloy was examined by use of atom probe field ion microscopy and transmission electron microscopy. In the early stage of crystallization, Au atoms were still distributed uniformly in the amorphous matrix. Au atoms form clusters at a later stage when more α–Fe particles are present. The Au clusters were observed to be separated from α–Fe particles, indicating that Au clusters do not stimulate nucleation of α–Fe particles. During the growth of α–Fe grains, cosegregation of Au and Zr occurred without any influence on the α–Fe grain growth. We conclude that Au addition has no effect on nanocrystallization of Fe–Zr–B amorphous alloys.

APFIM Studies of Nanocrystallizations of Amorphous Alloys

1995 ◽  
Vol 400 ◽  
Author(s):  
K. Hono ◽  
Y. Zhang ◽  
A. Inoue ◽  
T. Sakurai
Keyword(s):  
Amorphous Alloys ◽  
Amorphous Matrix ◽  
Primary Crystallization ◽  
Atom Probe ◽  
Nucleation And Growth ◽  
Cu Alloy ◽  
Nucleation Sites ◽  
Medium Range ◽  
Crystallization Reaction ◽  
Primary Crystals

AbstractThis paper reports recent atom probe analysis results of Fe-Zr-B(-Cu) and Al-Ni-Ce(-Cu) amorphous alloys, in which nanocrystalline microstructures develop by primary crystallization. In these alloy systems, enrichment of slow diffusing solute was found at the interfaces between primary crystals and amorphous matrix during the nucleation and growth stage. In the case of ternary Fe-Zr-B, no evidence for compositional heterogeneities were found prior to the onset of crystallization reaction. On the other hand, clustering of Cu atoms was observed in quaternary Fe-Zr-B-Cu alloy prior to the crystallization reaction. In the ternary Fe-Zr-B alloy, nucleation sites seem to be provided by the quenched-in nuclei which were observed as medium range ordered (MRO) domains by HREM. In the as-quenched Al-Ni-Ce(-Cu) alloy, compositional fluctuations were present from the as-quenched state. These observations suggest that nuclei for primary crystallization are provided in various forms such as MRO domains, solute clusters and compositional heterogeneities.

Evolution of Twin-Related Variants of α Phase in a Ti-V-Cu Alloy

2011 ◽  
Vol 172-174 ◽  
pp. 481-486 ◽  
Author(s):  
Hoi Pang Ng ◽  
Colleen J. Bettles ◽  
Barry C. Muddle
Keyword(s):  
Electron Microscopy ◽  
Early Stage ◽  
Twin Plane ◽  
System A ◽  
Cu Alloy ◽  
Α Phase ◽  
Transmission Electron ◽  
Nucleation Sites ◽  
Isothermal Ageing

The precipitation of a-phase has been investigated in a concentrated b-alloy of the Ti-V-Cu system. a-precipitates in geometrically coupled forms were developed in the alloy when subject to isothermal ageing at 500°C. High-resolution transmission electron microscopy (HRTEM) revealed that a-phase embryos tend to nucleate in a symmetrical manner directly from an early-stage solute-partitioned diffusional product. The a-precipitates so developed constitute twin-related variants characterized by a twin plane lying on one of the {0111}a planes. The results are discussed with respect to the role of Cu on the formation of heterogeneous nucleation sites for a-phase.

The role of atom-probe field ion microscopy in alloy development and phase transformation studies

1994 ◽  
Vol 52 ◽  
pp. 822-823
Author(s):  
M. K. Miller ◽  
R. Jayaram ◽  
K. F. Russell
Keyword(s):  
Grain Boundaries ◽  
Gas Turbines ◽  
Atom Probe ◽  
Solid Solution Hardening ◽  
Alloy Development ◽  
Probe Field ◽  
Hardening Mechanism ◽  
Boron Segregation ◽  
Large Effort

One of the important parameters in the design of new materials is the distribution of the alloyingelements in the microstructure and whether these elements are involved in the formation of precipitates or in segregation to internal interfaces such as grain boundaries. The atom probe field ion microscope is an extremely effective tool for these types of fine scale characterizations. Recently, therehas been a large effort to develop new, more efficient materials for high temperature applications such as gas turbines. A candidate material for this application is NiAl. However, the low temperature ductility of NiAl is extremely small and hinders fabrication. Therefore, attempts have been made to alleviate these problems with the use of microalloying additions such as boron. The atom probe has beenused to determine the location of boron in the microstructure and correlate its distribution with themechanical properties. Atom probe analyses have revealed that the solubility of boron in NiAl is extremely low and most of the excess boron is precipitated in the form of ultrafine MB2 precipitates as shown in Fig. 1. In addition, boron segregation to the grain boundaries has been observed, Fig. 2. Theobserved increase in the yield strength is therefore primarily due to a precipitation hardening mechanism with a contribution from solid solution hardening and this offsets the beneficial effect of the boron at the grain boundaries.

An Atom Probe Field Ion Microscope Investigation Of The Role Of Boron In Precipitates And At Grain Boundaries In NiAl

1991 ◽  
Vol 238 ◽  
Author(s):  
Raman Jayaram ◽  
M. K. Miller
Keyword(s):  
Grain Boundaries ◽  
Atom Probe ◽  
Probe Field ◽  
Analytical Technique ◽  
Boron Segregation ◽  
Boron Doped ◽  
Nial Alloy ◽  
The Matrix ◽  
Boride Phases

ABSTRACTThe high resolution analytical technique of Atom Probe Field Ion Microscopy (APFTM) haseen used to characterize grain boundaries and the matrix of a stoichiometric NiAl alloy doped with 0.04 (100 wppm) and 0.12 at. % (300 wppm) boron. Field ion images revealed boron segregation to the grain boundaries. Atom probe elemental analysis of the grain boundaries measured a boron coverage of up to 30% of a monolayer. Extensive atom probe analyses also revealed a fine dispersion of nanoscale boride precipitates in the matrix. The boron segregation to the grain boundaries was found to correlate with the observed suppression of intergranular fracture. However, the decrease in ductility of boron-doped NiAl is attributed in part to the precipitation hardening effect of the boride phases.

Apfim and HREM Studies of Nanocomposite Soft and Hard Magnetic Materials

1998 ◽  
Vol 4 (S2) ◽  
pp. 108-109
Author(s):  
K. Hono ◽  
D. H. Ping ◽  
M. Ohnuma
Keyword(s):  
High Resolution Electron Microscopy ◽  
Atom Probe ◽  
Hard Magnetic Materials ◽  
Probe Field ◽  
Field Ion Microscopy ◽  
Cu Alloy ◽  
Nucleation Sites ◽  
Resolution Electron ◽  
Ferromagnetic Exchange ◽  
Ion Microscopy

Atom probe field ion microscopy is the most suitable technique for determining local chemical composition changes during nanocrystallization processes of amorphous alloys. In this talk, we report atom probe field ion microscopy (APFIM) and high resolution electron microscopy (HREM) studies on nanocrystallization processes in Fe-Si-B-Nb-Cu soft magnet and Fe-Nd-B-Co-Ga exchange spring magnet.Fe or Co based alloys with nanocrystalline microstructure show excellent permeability because the net magnetocrystalline anisotropy is significantly reduced when the grain size becomes smaller than the ferromagnetic exchange length. Fe-Si-B-Nb-Cu alloy is the pioneering nanocrystalline soft magnetic material invented by Yoshizawa et al. in 1988 [1]. Our previous works [2,3] reported evidence for clustering of Cu prior to the onset of the crystallization reaction. However, in the previous studies, it was not confirmed that these Cu clusters work as heterogeneous nucleation sites for a-Fe primary crystals.

Preferential Sputtering of Ni3Al Single Crystals Studied Using Atom-Probe Field-Ion Microscopy and XPS

1981 ◽  
Vol 39 ◽  
pp. 16-17
Author(s):  
M.P. Thomas ◽  
A.R. Waugh ◽  
M.J. Southon ◽  
Brian Ralph
Keyword(s):  
Single Crystals ◽  
Photoelectron Spectroscopy ◽  
Surface Composition ◽  
Depth Profiling ◽  
Analytical Techniques ◽  
Atom Probe ◽  
Probe Field ◽  
Preferential Sputtering ◽  
Argon Ion Bombardment ◽  
Argon Ion

It is well known that ion-induced sputtering from numerous multicomponent targets results in marked changes in surface composition (1). Preferential removal of one component results in surface enrichment in the less easily removed species. In this investigation, a time-of-flight atom-probe field-ion microscope A.P. together with X-ray photoelectron spectroscopy XPS have been used to monitor alterations in surface composition of Ni3Al single crystals under argon ion bombardment. The A.P. has been chosen for this investigation because of its ability using field evaporation to depth profile through a sputtered surface without the need for further ion sputtering. Incident ion energy and ion dose have been selected to reflect conditions widely used in surface analytical techniques for cleaning and depth-profiling of samples, typically 3keV and 1018 - 1020 ion m-2.

High-resolution x-ray imaging of small copper-rich precipitates in steels

1988 ◽  
Vol 46 ◽  
pp. 528-529
Author(s):  
J. R. Michael ◽  
K. A. Taylor
Keyword(s):  
Electron Microscopy ◽  
Thermomechanical Processing ◽  
Atom Probe ◽  
Ferrite Matrix ◽  
Scanning Transmission Electron Microscope ◽  
Probe Field ◽  
X Ray ◽  
Subsequent Transformation ◽  
Transmission Electron ◽  
Scanning Transmission

Although copper is considered an incidental or trace element in many commercial steels, some grades contain up to 1-2 wt.% Cu for precipitation strengthening. Previous electron microscopy and atom-probe/field-ion microscopy (AP/FIM) studies indicate that the precipitation of copper from ferrite proceeds with the formation of Cu-rich bcc zones and the subsequent transformation of these zones to fcc copper particles. However, the similarity between the atomic scattering amplitudes for iron and copper and the small misfit between between Cu-rich particles and the ferrite matrix preclude the detection of small (<5 nm) Cu-rich particles by conventional transmission electron microscopy; such particles have been imaged directly only by FIM. Here results are presented whereby the Cu Kα x-ray signal was used in a dedicated scanning transmission electron microscope (STEM) to image small Cu-rich particles in a steel. The capability to detect these small particles is expected to be helpful in understanding the behavior of copper in steels during thermomechanical processing and heat treatment.

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.

An Improved Method for the Preparation and TEM Examination of Sharp Pointed Tips used in APFIM and STM

1990 ◽  
Vol 48 (2) ◽  
pp. 102-103
Author(s):  
E.A. Fischione ◽  
P.E. Fischione ◽  
J.J. Haugh ◽  
M.G. Burke
Keyword(s):  
Atom Probe ◽  
Preparation Process ◽  
Improved Method ◽  
Ion Milling ◽  
Polishing Process ◽  
Probe Field ◽  
Scanning Tunnelling ◽  
Stm Tips ◽  
Tunnelling Microscopy ◽  
Ion Microscopy

A common requirement for both Atom Probe Field-Ion Microscopy (APFIM) and Scanning Tunnelling Microscopy (STM) is a sharp pointed tip for use as either the specimen (APFIM) or the probe (STM). Traditionally, tips have been prepared by either chemical or electropolishing techniques. Recently, ion-milling has been successfully employed in the production of APFIM tips [1]. Conventional electropolishing techniques are applicable to a wide variety of metals, but generally require careful manual adjustments during the polishing process and may also be time-consuming. In order to reduce the time and effort involved in the preparation process, a compact, self-contained polishing unit has been developed. This system is based upon the conventional two-stage electropolishing technique in which the specimen/tip blank is first locally thinned or “necked”, and subsequently electropolished until separation occurs.[2,3] The result of this process is the production of two APFIM or STM tips. A mechanized polishing unit that provides these functions while automatically maintaining alignment has been designed and developed.

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