Rapid Solidification of Metastable Materials

1981 ◽  
Vol 8 ◽  
Author(s):  
Howard Liebermann ◽  
John Walter
Keyword(s):  
Amorphous Alloy ◽  
Process Control ◽  
Melt Spinning ◽  
Rate Process ◽  
Quench Rate ◽  
Processing Methods ◽  
Splat Quenching ◽  
Deposition By Sputtering ◽  
Metastable Alloys ◽  
Rapidly Solidified

ABSTRACTThere are numerous processing methods available for the fabrication of rapidly-solidified metastable alloys. Examples include splat quenching, melt-spinning, surface melting and quenching, melt atomization and solidification, and deposition by sputtering and evaporation. Experimental aspects of each of these fabrication methods will be discussed. These include solidification and quench rate, process control, and final product morphology and microstructure. Some properties of an amorphous alloy prepared by several of these processing methods will be discussed.

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.

Devitrification behaviour of rapidly solidified Al87Ni7Cu3Nd3 amorphous alloy prepared by melt spinning method

2007 ◽  
Vol 14 (3) ◽  
pp. 285-290 ◽  
Author(s):  
Yu-de Xiao ◽  
Min Li ◽  
Jue Zhong ◽  
Wen-xian Li ◽  
Zheng-qing Ma
Keyword(s):  
Amorphous Alloy ◽  
Melt Spinning ◽  
Rapidly Solidified

On the Origin of the Microscystalline Structure in Rapidly Solidified IN-100 Powder

1977 ◽  
Vol 35 ◽  
pp. 260-261
Author(s):  
J. M. Walsh ◽  
K. P. Gumz ◽  
J. C. Whittles ◽  
B. H. Kear
Keyword(s):  
The Other ◽  
Coarse Grained ◽  
Microcrystalline Structure ◽  
Routine Examination ◽  
Atomization Process ◽  
Centrifugal Atomization ◽  
Splat Quenching ◽  
Powder Particles ◽  
Dendritic Microstructures ◽  
Rapidly Solidified

During a routine examination of the microstructure of rapidly solidified IN-100 powder, produced by a newly-developed centrifugal atomization process1, essentially two distinct types of microstructure were identified. When a high melt superheat is maintained during atomization, the powder particles are predominantly coarse-grained, equiaxed or columnar, with distinctly dendritic microstructures, Figs, la and 4a. On the other hand, when the melt superheat is reduced by increasing the heat flow to the disc of the rotary atomizer, the powder particles are predominantly microcrystalline in character, with typically one dendrite per grain, Figs, lb and 4b. In what follows, evidence is presented that strongly supports the view that the unusual microcrystalline structure has its origin in dendrite erosion occurring in a 'mushy zone' of dynamic solidification on the disc of the rotary atomizer.The critical observations were made on atomized material that had undergone 'splat-quenching' on previously solidified, chilled substrate particles.

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. 

New Fe-Ni Based Metal-Metalloid Glassy Alloys Prepared by Mechanical Alloying and Rapid Solidification

1996 ◽  
Vol 455 ◽  
Author(s):  
J. J. Suñol ◽  
M. T. Clavaguera-Mora ◽  
N. Clavaguera ◽  
T. Pradell
Keyword(s):  
Mechanical Alloying ◽  
Rapid Solidification ◽  
Melt Spinning ◽  
Magnetic Interaction ◽  
Processing Route ◽  
Mechanically Alloyed ◽  
Scanning Calorimetry ◽  
Glassy Alloys ◽  
Rapidly Solidified ◽  
Thermal Stability Of

ABSTRACTMechanical alloying and rapid solidification are two important routes to obtain glassy alloys. New Fe-Ni based metal-metalloid (P-Si) alloys prepared by these two different processing routes were studied by differential scanning calorimetry and transmission Mössbauer spectroscopy. Mechanical alloyed samples were prepared with elemental precursors, and different nominal compositions. Rapidly solidified alloys were obtained by melt-spinning. The structural analyses show that, independent of the composition, the materials obtained by mechanical alloying are not completely disordered whereas fully amorphous alloys were obtained by rapid solidification. Consequently, the thermal stability of mechanically alloyed samples is lower than that of the analogous material prepared by rapid solidification. The P/Si ratio controls the magnetic interaction of the glassy ribbons obtained by rapid solidification. The experimental results are discussed in terms of the degree of amorphization and crystallization versus processing route and P/Si ratio content.

The effect of composition and cooling rate on the structure of rapidly solidified (Fe, Ni)3Al–C alloys

1989 ◽  
Vol 4 (1) ◽  
pp. 44-49 ◽  
Author(s):  
S. A. Myers ◽  
C. C. Koch
Keyword(s):  
Cooling Rate ◽  
Base Alloy ◽  
Weight Percent ◽  
Quench Rate ◽  
Transmission Electron ◽  
Metastable Structures ◽  
Metastable Structure ◽  
The Matrix ◽  
Rapidly Solidified ◽  
Kinetics Of

There is controversy in the literature regarding the existence of the metastable γ′ phase with an ordered Ll2 structure in rapidly solidified Fe–Ni–Al–C alloys. In this study, the quench rate–metastable structure dependence was examined in the Fe–20Ni–8Al–2C (weight percent) alloy. The effect of silicon on the kinetics of phase formation was studied by adding two weight percent silicon to a base alloy of Fe–20Ni–8Al–2C. Samples were rapidly solidified in an arc hammer apparatus and examined by transmission electron microscopy. In the Fe–20Ni–8Al–2C alloy, the nonequilibrium γ′ and γ phases were found in foils 65 to 100 μm thick. At higher quench rates, i.e., thinner samples, the matrix was observed to be disordered fcc γ with K-carbide precipitates. Samples containing silicon were found to have a matrix composed of γ′ and γ structures when the foils were thicker than 40 μm. At higher quench rates, the matrix was disordered fcc γ with K-carbide precipitates. The nonequilibrium γ′ and γ structures are present in samples with or without silicon, but are observed at higher cooling rates with the addition of silicon. This sensitivity to cooling rate and composition in resulting metastable structures may explain the differences reported in the literature for these rapidly solidified materials.

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.

Microstructure of Nb3 (AlSiB) superconducting tapes with extremely high critical current densities

1989 ◽  
Vol 4 (3) ◽  
pp. 526-529 ◽  
Author(s):  
Mireille Treuil Clapp ◽  
Zhang Jian ◽  
Tariq Manzur
Keyword(s):  
Critical Current ◽  
Melt Spinning ◽  
Quenching Rate ◽  
Fine Grained ◽  
Annealing Conditions ◽  
Second Phases ◽  
Current Densities ◽  
Rapidly Solidified ◽  
Equiaxed Grains ◽  
A15 Phase

Alloys of Nb73Al12Si14.5B0.5 were rapidly solidified into amorphous ribbons using the melt spinning technique. These were isothermally annealed at temperatures ranging from 660 to 780 °C. The A15 phase began to crystallize at 700 °C and small amounts of second phases appeared at the higher temperatures. Crystallization was dependent on quenching rate as well as annealing conditions. Below 750 °C nucleation was nonuniform and was enhanced by surfaces and quenched-in nuclei. Above 750 °C nucleation became more uniform and completely crystalline ribbons with equiaxed grains ∼30 nm in diameter were obtained. These ultra fine grained ribbons had extremely high superconducting critical current densities of 8 × 1010 A/m2 and 5 × 1010 A/m2 at magnetic fields of 0.5 and 15 tesla, respectively, at 4.2 K.

Nano-Refinement, Nano-Consolidation: Different Fabrication Routes of Nano-Crystalline Aluminium Alloys

2010 ◽  
Vol 667-669 ◽  
pp. 87-90
Author(s):  
Małgorzata Lewandowska ◽  
Henryk Dybiec ◽  
Mariusz Kulczyk ◽  
Jerzy Latuch ◽  
Krzysztof J. Kurzydlowski
Keyword(s):  
Mechanical Properties ◽  
Grain Refinement ◽  
Melt Spinning ◽  
Al Alloys ◽  
Grain Boundary Character ◽  
Nano Structures ◽  
Nano Crystalline ◽  
Grain Size And Shape ◽  
Rapidly Solidified ◽  
Warm Extrusion

The aim of the present work was to compare microstructures and mechanical properties of nano-Al alloys fabricated by two different methods: (i) SPD induced grain refinement, (ii) plastic consolidation of nano-powders or nano-crystalline ribbons. SPD grain refinement has been implemented by hydrostatic extrusion, HE. The ribbons were rapidly solidified using a melt spinning methods. Plastic consolidation of powder and ribbons was conducted by warm extrusion. The results of the studies show that by applying various fabrication routes for a given chemical composition, diverse nano-structures can be obtained, which differ in terms of grain size and shape, grain boundary character and dislocation density. As a result, the alloys also differ significantly in the mechanical properties. The findings are discussed in terms of the possibilities for optimizing properties of the bulk-nano-metals.

Sign in / Sign up

Export Citation Format

Share Document