Microstructure of Rapidly Solidified Cu-Fe Alloys

1983 ◽  
Vol 28 ◽  
Author(s):  
Uwe Köster ◽  
Christoph Caesar
Keyword(s):  
Cross Sections ◽  
Contact Surface ◽  
Iron Content ◽  
Melt Spinning ◽  
Volume Fraction ◽  
Thermal Contact ◽  
Lattice Parameter ◽  
Good Thermal Contact ◽  
Fe Alloys ◽  
Rapidly Solidified

ABSTRACTRapidly solidified ribbons of Cu-Fe alloys with iron contents up to 20 at.−% have been prepared by melt-spinning. Optical and electron microscopy as well as x-ray and electron diffraction techniques were used to characterize quantitatively the microstructure, i.e., grain size and shape, solubility of iron, lattice parameter, volume fraction and distribution of precipitated iron-particles, etc.Whereas the free surfaces of melt-spun Cu-Fe ribbons have been found to be very smooth, the contact surfaces usually consist of isolated areas of good thermal contact with small equiaxed grains separated by bands without contact during casting and therefore poor heat transfer. The cross sections of the ribbons generally exhibit a strong anisotropy in their microstructure: very fine crystals adjacent to the contact surface develop into narrow columnar grains, generally significantly elongated and extending across the whole section. The average columnar width of the grains has been found to decrease significantly with increasing iron content. Precipitation of iron not only depends on the iron content but also on the distance from the contact surface.

Phase transformations in rapidly solidified Nd33Fe77 alloy

1992 ◽  
Vol 50 (1) ◽  
pp. 56-57
Author(s):  
A. Zaluska ◽  
L.X. Liao ◽  
X. Chen ◽  
Z. Altounian ◽  
J.O. Ström-Olsen
Keyword(s):  
Phase Transformations ◽  
High Performance ◽  
Melt Spinning ◽  
Permanent Magnets ◽  
New Materials ◽  
Amorphous Precursor ◽  
Eutectic Melting ◽  
Subsequent Transformation ◽  
Fe Alloys ◽  
Rapidly Solidified

Nd-Fe alloys are important for high performance permanent magnets (usually in combination with B, C or N) and a knowledge of the metastable and stable phases of the system is necessary for the development of these new materials. An effective way to investigate such phases is by crystallizing an amorphous precursor.Amorphous ribbons of the binary alloy Nd33Fe77 were produced by melt-spinning. The phase transformations induced by heat treatment of the as-quenched ribbons is complex involving first the production of metastable phases followed by subsequent transformation into stable phases and finally eutectic melting.

Metastable Phases in Rapidly Solidified Aluminum-Rich Al-Fe Alloys

1982 ◽  
Vol 19 ◽  
Author(s):  
D. Shechtman ◽  
L.J. Swartzendruber
Keyword(s):  
Electron Microscopy ◽  
Heat Treatment ◽  
Melt Spinning ◽  
Gamma Ray ◽  
Resonance Spectrum ◽  
Metastable Phase ◽  
Metastable Phases ◽  
Transmission Electron ◽  
Fe Alloys ◽  
Rapidly Solidified

ABSTRACTAluminum-rich Al-Fe binary alloys up to and including Al3Fe were prepared by melt spinning in order to study the metastable phase structure and its transformation following heat treatment. Transmission electron microscopy and nuclear gamma-ray resonance were utilized in the study. The rapidly solidified structure was found to contain up to three metastable phases. One of the phases, with a composition and a gamma-ray resonance spectrum appropriate for Al6Fe, has either a globular or a cellular morphology upon quenching.

Sample preparation of sub-micron precipitates in rapidly solidified Mg-20Nd

1988 ◽  
Vol 46 ◽  
pp. 984-985
Author(s):  
Ralph E. Omlor ◽  
Lt Erica Robertson ◽  
Pamela F. Lloyd
Keyword(s):  
Melt Spinning ◽  
Volume Fraction ◽  
Carbon Film ◽  
Large Volume Fraction ◽  
The Matrix ◽  
Carbon Coated ◽  
Order Of Magnitude ◽  
Rapidly Solidified ◽  
Oxide Precipitate ◽  
A Current

The Mg-20Nd melt spun ribbonsare being examined in depth because of their potentiodynamic polarization response as compared to that of 7075-T73 aluminum. The Mg-20Nd ribbon exhibited pseudopassivation behavior at a current density approximately one order of magnitude less than the aluminum alloy. In previous work, this was found to be due to the presence of a tessellatal precipitated network which formed in the ribbons during melt spinning. EDS results on TEM foils gave similar compositional values on both matrix and precipitates. These results were not trusted due to the small size and large volume fraction of the precipitates.The Mg-20Nd ribbon was swabbed with a dilute solution of sulfuric acid to loosen the particles in the matrix. A heavy oxide film was also formed on the surface at this time. Plastic replication solution was then applied to this surface and stripped away when dry. The particle side of the plastic film was then carbon coated. This film was placed on 3mm grids and the plastic dissolved away leaving the carbon film and the oxide precipitate mixture.

The Microstructure of Rapidly Solidified Al-Zn-Mg-Cu Alloys with Zr Addition

2010 ◽  
Vol 163 ◽  
pp. 42-45 ◽  
Author(s):  
Lidia Lityńska-Dobrzyńska ◽  
Patrick Ochin ◽  
Anna Góral ◽  
Marek Faryna ◽  
Jan Dutkiewicz
Keyword(s):  
Solid Solution ◽  
Melt Spinning ◽  
Volume Fraction ◽  
Cast Alloy ◽  
Dendritic Microstructure ◽  
X Ray ◽  
Cu Alloys ◽  
Transmission Electron ◽  
Cast Alloys ◽  
Rapidly Solidified

The effect of rapid solidification on the microstructure of Al-Zn-Mg-Cu alloys with 8 wt.% Zn-2 wt.% Mg-2.3 wt.% Cu and 0.2 or 0.5 wt.% of Zr additions were investigated using X-ray diffraction measurements (XRD), scanning (SEM) and transmission electron microscopy (TEM) combined with energy dispersive X-ray (EDX) microanalysis. Rapidly solidified ribbons with thickness of 70-100 m were performed by melt spinning technique. The mould cast alloys as well as the melt spun ribbons revealed dendritic microstructure of (Al) solid solution and η Mg(Zn,Cu)2 phase in interdendritic areas. The refinement of the microstructure and reduction of the volume fraction of the η phase up to 1.7%, as compared to 4% in the mould cast alloys was observed in the ribbons. Copper dissolution up to about 20 wt % in the η phase causes a decrease of the lattice parameters. The Al3Zr primary precipitates were observed in the mould cast alloy containing 0.5 wt % of Zr while in the ribbons all zirconium dissolved in the aluminium solid solution.

Nanoporous Behavior Induced by Excess Vacancy Clustering in Rapidly-Solidified B2 FeAl Ribbons

2002 ◽  
Vol 753 ◽  
Author(s):  
Tomohide Haraguchi ◽  
Kyosuke Yoshimi ◽  
Man H. Yoo ◽  
Hidemi Kato ◽  
Shuji Hanada ◽  
...  
Keyword(s):  
Heat Treatment ◽  
Concentration Dependence ◽  
Defect Structure ◽  
Melt Spinning ◽  
Volume Fraction ◽  
Excess Vacancy ◽  
Dsc Measurements ◽  
Large Numbers ◽  
Rapidly Solidified ◽  
Nanoporous Surfaces

ABSTRACTRapidly solidified ribbons of B2-ordered Fe-40, 45 and 50mol%Al were produced by a conventional single-roll melt-spinning method. The lattice parameters of as-spun ribbons are fully restored by annealing at 723 K for 24 h. This suggests that large numbers of supersaturated thermal vacancies are removed by the heat treatment. After the heat treatment, it is found that clustering of the supersaturated vacancies leads to a large number of pores that have a few hundreds nm or less in diameter near the surfaces, thus creating nanoporous surfaces. DSC measurements show irreversible exothermic peaks due to vacancy clustering. Vacancy complexes such as dislocations and pores are also observed inside the ribbons by TEM. The volume fraction of the overall vacancy complexes shows Al concentration dependence, demonstrating that defect structure formed by clustering of the excess vacancies is controllable by changing Al concentration in rapidly solidified FeAl ribbons.

EM of rapidly solidified permanent magnets

1992 ◽  
Vol 50 (1) ◽  
pp. 198-199
Author(s):  
Raja K. Mishra
Keyword(s):  
Melt Spinning ◽  
Permanent Magnets ◽  
Dark Field Image ◽  
Dark Field ◽  
Maximum Energy ◽  
Quench Rate ◽  
Maximum Energy Product ◽  
Energy Product ◽  
Annular Dark Field ◽  
Rapidly Solidified

The discovery of a new class of permanent magnets based on Nd2Fe14B phase in the last decade has led to intense research and development efforts aimed at commercial exploitation of the new alloy. The material can be prepared either by rapid solidification or by powder metallurgy techniques and the resulting microstructures are very different. This paper details the microstructure of Nd-Fe-B magnets produced by melt-spinning.In melt spinning, quench rate can be varied easily by changing the rate of rotation of the quench wheel. There is an optimum quench rate when the material shows maximum magnetic hardening. For faster or slower quench rates, both coercivity and maximum energy product of the material fall off. These results can be directly related to the changes in the microstructure of the melt-spun ribbon as a function of quench rate. Figure 1 shows the microstructure of (a) an overquenched and (b) an optimally quenched ribbon. In Fig. 1(a), the material is nearly amorphous, with small nuclei of Nd2Fe14B grains visible and in Fig. 1(b) the microstructure consists of equiaxed Nd2Fe14B grains surrounded by a thin noncrystalline Nd-rich phase. Fig. 1(c) shows an annular dark field image of the intergranular phase. Nd enrichment in this phase is shown in the EDX spectra in Fig. 2.

Rapidly Solidified Melt-spun Bi-Sn Ribbons: Surface Composition Issues

2016 ◽  
pp. 3287-3297
Author(s):  
Tarek El Ashram ◽  
Ana P. Carapeto ◽  
Ana M. Botelho do Rego
Keyword(s):  
Chemical Composition ◽  
Optical Microscopy ◽  
Melt Spinning ◽  
Surface Composition ◽  
Electrochemical Process ◽  
Melt Spun ◽  
Bismuth Alloy ◽  
The One ◽  
Rapidly Solidified ◽  
Melt Spinning Technique

Tin-bismuth alloy ribbons were produced using melt-spinning technique. The two main surfaces (in contact with the rotating wheel and exposed to the air) were characterized with Optical Microscopy and AFM, revealing that the surface exposed to the air is duller (due to a long-range heterogeneity) than the opposite surface. Also the XPS chemical composition revealed many differences between them both on the corrosion extension and on the total relative amounts of tin and bismuth. For instance, for the specific case of an alloy with a composition Bi-4 wt % Sn, the XPS atomic ratios Sn/Bi are 1.1 and 3.7 for the surface in contact with the rotating wheel and for the one exposed to air, respectively, showing, additionally, that a large segregation of tin at the surface exists (nominal ratio should be 0.073). This segregation was interpreted as the result of the electrochemical process yielding the corrosion products.

An analysis of the transport properties and mechanical stability of rapidly solidified Al-Sb alloy

2015 ◽  
Vol 10 (2) ◽  
pp. 2663-2681
Author(s):  
Rizk El- Sayed ◽  
Mustafa Kamal ◽  
Abu-Bakr El-Bediwi ◽  
Qutaiba Rasheed Solaiman
Keyword(s):  
Mechanical Properties ◽  
Thermal Conductivity ◽  
Melt Spinning ◽  
Elastic Moduli ◽  
Mechanical Stability ◽  
Microstructural Analysis ◽  
Alloy System ◽  
Antimony Content ◽  
The Stability ◽  
Rapidly Solidified

The structure of a series of AlSb alloys prepared by melt spinning have been studied in the as melt–spun ribbons  as a function of antimony content .The stability  of these structures has  been  related to that of the transport and mechanical properties of the alloy ribbons. Microstructural analysis was performed and it was found that only Al and AlSb phases formed for different composition.  The electrical, thermal and the stability of the mechanical properties are related indirectly through the influence of the antimony content. The results are interpreted in terms of the phase change occurring to alloy system. Electrical resistivity, thermal conductivity, elastic moduli and the values of microhardness are found to be more sensitive than the internal friction to the phase changes. 

High Temperature Mechanical Properties of Ni-Al-Cr Based Alloys with Refractory Alloying Elements

2006 ◽  
Vol 510-511 ◽  
pp. 358-361
Author(s):  
Won Yong Kim ◽  
Han Sol Kim ◽  
In Dong Yeo ◽  
Mok Soon Kim
Keyword(s):  
High Temperature ◽  
Volume Fraction ◽  
Lattice Parameter ◽  
Alloying Elements ◽  
Solid Solution Hardening ◽  
High Temperature Strength ◽  
High Temperature Mechanical Properties ◽  
Die Materials ◽  
The Matrix ◽  
Effective Role

We report on advanced Ni3Al based high temperature structural alloys with refractory alloying elements such as Zr and Mo to be apllied in the fields of die-casting and high temperature press forming as die materials. The duplex microstructure consisting of L12 structured Ni3Al phase and Ni5Zr intermetallic dispersoids was observed to display the microstructural feature for the present alloys investigated. Depending on alloying elements, the volume fraction of 2nd phase was measured to be different, indicating a difference in solid solubility of alloying elements in the matrix γ’ phase. Lattice parameter of matrix phase increased with increasing content of alloying elements. In the higher temperature region more than 973K, the present alloys appeared to show their higher strength compared to those obtained in conventional superalloys. On the basis of experimental results obtained, it is suggested that refractory alloying elements have an effective role to improve the high temperature strength in terms of enhanced thermal stability and solid solution hardening.

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