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.

Effect of Cu On Microstructural Evolution of Nanocrystalline Soft and Hard Magnetic Materials

1999 ◽  
Vol 577 ◽  
Author(s):  
K. Hono ◽  
D. H. Ping ◽  
S. Hirosawa
Keyword(s):  
Amorphous Alloys ◽  
Three Dimensional ◽  
Atom Probe ◽  
Hard Magnetic Materials ◽  
Atom Clusters ◽  
Transmission Electron ◽  
Nucleation Sites ◽  
Final Microstructure ◽  
Crystallization Reaction ◽  
Primary Crystals

ABSTRACTThe nanocrystallization processes in Fe-Si-B-Nb-Cu and Fe-Nd-B(-Cu-Nb) amorphous alloys have been studied by transmission electron microscopy (TEM) and a three dimensional atom probe (3DAP). Cu additions are effective in refining the nanocrystalline microstructures of both alloys, because Cu atom clusters formed prior to the crystallization reaction serve as heterogeneous nucleation sites for the primary crystals. However, the clustering behaviors of Cu atoms in these two alloy systems are different, i.e., Cu completely dissolves in the Nd2Fe1 4B phase in the final microstructure of the Nd4.5Fe75.8B18.5Cu0.2Nb1 alloy, whereas CL' clusters grow to fcc-Cu particles in the Fe73.5Si13.5B9Nb3Cu1 alloy. The nanocrystallization processes in these two alloys clarified by the 3DAP results are compared.

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.

AEM analysis of crystallization in Ti-based amorphous alloys

1983 ◽  
Vol 41 ◽  
pp. 270-271
Author(s):  
A.R. Pelton ◽  
A.F. Marshall ◽  
Y.S. Lee
Keyword(s):  
Magnetic Properties ◽  
Amorphous Alloys ◽  
Amorphous Materials ◽  
Isothermal Annealing ◽  
Amorphous Matrix ◽  
Nucleation And Growth ◽  
Current Interest ◽  
Amorphous Films ◽  
Electrical And Magnetic Properties

Amorphous materials are of current interest due to their desirable mechanical, electrical and magnetic properties. Furthermore, crystallizing amorphous alloys provides an avenue for discerning sequential and competitive phases thus allowing access to otherwise inaccessible crystalline structures. Previous studies have shown the benefits of using AEM to determine crystal structures and compositions of partially crystallized alloys. The present paper will discuss the AEM characterization of crystallized Cu-Ti and Ni-Ti amorphous films.Cu60Ti40: The amorphous alloy Cu60Ti40, when continuously heated, forms a simple intermediate, macrocrystalline phase which then transforms to the ordered, equilibrium Cu3Ti2 phase. However, contrary to what one would expect from kinetic considerations, isothermal annealing below the isochronal crystallization temperature results in direct nucleation and growth of Cu3Ti2 from the amorphous matrix.

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.

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.

Clustering and Segregation of Ag and Mg Atoms in the Nucleation and Growth Stage of Ω And T1 Precipitates In Al-Cu(-Li) Alloys

1998 ◽  
Vol 4 (S2) ◽  
pp. 116-117
Author(s):  
M. Murayama ◽  
L. Reich ◽  
K. Hono
Keyword(s):  
Growth Stage ◽  
Atom Probe ◽  
Nucleation And Growth ◽  
Phase 2 ◽  
Alloy Plate ◽  
Cu Alloy ◽  
Cu Alloys ◽  
Ω Phase ◽  
Uniform Dispersion ◽  
T Phase

Trace additions of Ag and Mg in Al-Cu and Al-Li-Cu alloys change the precipitation processes drastically. In Al-Cu-Mg-Ag alloy, plate-like Ω phase precipitates on the {111} matrix planes. Similarly, additions of Ag and Mg to Al-Li-Cu alloy cause uniform dispersion of the T1 precipitate on the {111} matrix planes. Ω and T1 phases are structurally and morphologically similar, and a similar mechanism is expected to work in both alloy systems to enhance uniform dispersion of the plate-like precipitates on the {111} planes. A previous atom probe work [1] reported that Ag and Mg are segregated at the αΩ. interfaces in an Al-Cu-Mg-Ag alloy. In an Al-Li-Cu-Mg-Ag alloy, Ag and Mg atoms were found to be incorporated with the T, phase [2]; however, because of the thinness of the T1, plate, the exact location of these atoms with respect to the T1, phase could not be determined sucessfully by a conventional atom probe.

Crystallization of ternary Zr-based glasses—Kinetics and microstructure

1998 ◽  
Vol 13 (2) ◽  
pp. 504-517 ◽  
Author(s):  
G. K. Dey ◽  
R. T. Savalia ◽  
E. G. Baburaj ◽  
S. Banerjee
Keyword(s):  
Metallic Glasses ◽  
Composition Range ◽  
Amorphous Matrix ◽  
Primary Crystallization ◽  
Nucleation And Growth ◽  
Crystal Nucleation ◽  
Cubic Phase ◽  
Eutectic Crystallization ◽  
Kinetics Of

The effect of ternary addition on the thermal stability and the sequence and the kinetics of crystallization of metallic glasses Zr76Fe(24−x)Nix (x = 0, 4, 8, 12, 16, 20, 24) have been examined. It has been found that the surface crystallization occurs in the composition range 16 < x < 20, leading to the formation of an ordered Fe-rich (Fe, Ni)3Zr cubic phase, followed by the transformation of the bulk to a mixture of α−Zr and Zr2Ni. Crystallization of alloys containing 12 to 20% Fe occurs at lower temperatures by primary crystallization of Zr3(Fe, Ni), followed by decomposition of the remaining amorphous matrix by eutectic crystallization giving rise to α−Zr + Zr2Ni. At higher temperatures these alloys transform polymorphically to Zr3(Fe, Ni) in which Ni partially substitutes Fe in the Zr3Fe lattice. Copious nucleation of Zr3(Fe, Ni) phase in these alloys, leading to the formation of a nanophase structure, has been observed. This is consistent with the prediction of increasing nucleation rate for Fe-rich compositions. The crystal nucleation and growth kinetics have been examined for primary, eutectic, and polymorphic crystallization processes. The observed nucleation and growth behaviors have been rationalized by considering the role of the quenched in nuclei and the activation energies of nucleation and growth.

Oxygen Distribution in Zr-Based Metallic Glasses

1998 ◽  
Vol 554 ◽  
Author(s):  
D. H. Ping ◽  
K. Hono ◽  
A. Inoue
Keyword(s):  
Amorphous Phase ◽  
Metallic Glasses ◽  
Amorphous Alloys ◽  
Atom Probe ◽  
Oxygen Distribution ◽  
Crystalline Phases ◽  
Kinetics Of Crystallization ◽  
Crystallization Reaction ◽  
Impurity Oxygen ◽  
Kinetics Of

AbstractThis paper reports the atom probe analysis results of the oxygen dissolved in the as-cast amorphous and crystallized Zr65Cu15Al10Pd10 and Zr65Cul17.5Ni10Al17.5 alloys. Impurity oxygen ranging from 0.1 to 1 at.% is dissolved uniformly in the as-quenched Zr65Cu15A110Pd10 and Zr65Cu17.5Ni10Al7.5 amorphous alloys even though the oxygen is not added intentionally. When the Zr65Cu15Al10Pd10 alloy is crystallized, oxygen redistribution occurs; it is rejected from the primary Zr2 (Cu, Pd) crystals and partitioned in the subsequently crystallized phases. Oxygen atoms are enriched in some of the crystalline phases up to approximately 4 at.%, and virtually no oxygen is dissolved in the remaining amorphous phase. In the partially crystallized Zr65Cu17.5Ni10Al7.5 alloy, fine oxygen enriched particles containing ∼ 15 at.%O have been detected in direct contacted with crystalline grains. This work demonstrates that oxygen redistribution occurs during the crystallization reaction, thereby influencing the kinetics of crystallization.

Field ion microscope investigations of atomic processes at surfaces

1989 ◽  
Vol 47 ◽  
pp. 228-229
Author(s):  
G. L. Kellogg ◽  
P. R. Schwoebel
Keyword(s):  
Single Crystal ◽  
Crystal Surface ◽  
Linear Chain ◽  
Atom Probe ◽  
Nucleation And Growth ◽  
Single Atom ◽  
Initial Structure ◽  
Atomic Processes ◽  
Single Crystal Surfaces ◽  
Field Ion Microscope

Although no longer unique in its ability to resolve individual single atoms on surfaces, the field ion microscope remains a powerful tool for the quantitative characterization of atomic processes on single-crystal surfaces. Investigations of single-atom surface diffusion, adatom-adatom interactions, surface reconstructions, cluster nucleation and growth, and a variety of surface chemical reactions have provided new insights to the atomic nature of surfaces. Moreover, the ability to determine the chemical identity of selected atoms seen in the field ion microscope image by atom-probe mass spectroscopy has increased or even changed our understanding of solid-state-reaction processes such as ordering, clustering, precipitation and segregation in alloys. This presentation focuses on the operational principles of the field-ion microscope and atom-probe mass spectrometer and some very recent applications of the field ion microscope to the nucleation and growth of metal clusters on metal surfaces.The structure assumed by clusters of atoms on a single-crystal surface yields fundamental information on the adatom-adatom interactions important in crystal growth. It was discovered in previous investigations with the field ion microscope that, contrary to intuition, the initial structure of clusters of Pt, Pd, Ir and Ni atoms on W(110) is a linear chain oriented in the <111> direction of the substrate.

ATOM-PROBE ANALYSIS OF G.P. ZONES IN AN Al-1.7 at % Cu ALLOY

1987 ◽  
Vol 48 (C6) ◽  
pp. C6-349-C6-354
Author(s):  
K. Hono ◽  
T. Sakurai ◽  
H. W. Pickering
Keyword(s):  
Atom Probe ◽  
Cu Alloy ◽  
Probe Analysis ◽  
Atom Probe Analysis
Sign in / Sign up

Export Citation Format

Share Document