Microstructure of Rapidly Solidified Al-Si Exhibiting Enhanced Superconducting Properties

1985 ◽  
Vol 62 ◽  
Author(s):  
M. A. Noack ◽  
A. J. Drehman ◽  
A. R. Pelton
Keyword(s):  
Melt Spinning ◽  
Thick Layer ◽  
Bottom Surface ◽  
Superconducting Transition ◽  
Superconducting Properties ◽  
Fine Grained ◽  
Melt Spun ◽  
The Matrix ◽  
Rapidly Solidified ◽  
Insight Into

ABSTRACTTsuei and Johnson previously reported significantly enhanced superconducting transition temperatures for rapidly solidified Al-Si alloys. Here we report a microstructural study of melt spun Al80 Si20 ribbons to determine the mechanism responsible for this enhancement.Results of this investigation revealed three distinct microstructures from the top surface to the more rapidly cooled bottom surface (which was in contact with the melt-spinning wheel). Near the top, the microstructure is of hypoeutectic morphology even though this is a hypereutectic alloy. The predominant microstructure is cellular. A 1 to 3 Wm thick layer at the bottom of the ribbon was found to be responsible for the largest enhancement. This layer is composed of fine-grained supersaturated fcc Al containing densely distributed dc Si precipitates. Microdiffraction analysis revealed a cube/cube orientation relationship between the precipitates and the matrix. These results provide insight into the possible mechanism for the enhancement.

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.

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.

Investigation of Al–Pb nanocomposites synthesized by nonequilibrium processes

1998 ◽  
Vol 13 (2) ◽  
pp. 308-315 ◽  
Author(s):  
H. W. Sheng ◽  
F. Zhou ◽  
Z. Q .Hu ◽  
K. Lu
Keyword(s):  
Melt Spinning ◽  
Milling Time ◽  
Nanometer Scale ◽  
Maximum Hardness ◽  
Nonequilibrium Processes ◽  
Minimum Particle Size ◽  
Melt Spun ◽  
The Matrix ◽  
Orientational Relationship ◽  
Al Matrix

Two nonequilibrium processes (melt-spinning and ball-milling) were successfully employed to synthesize Al1−xPbx (x = 5, 10, 20, 30 wt. %) nanocomposites with distinct microstructures. In the melt-spun (MS) Al–Pb alloys, the nanometer-sized Pb particles are uniformly distributed in the micrometer-grained Al matrix and have an orientational relationship with the matrix, while in the ball-milled (BM) samples, both Pb and Al components are refined with prolonged milling time, forming nanocomposites with Pb particles homogeneously dispersed into the Al matrix. The minimum particle size of Pb in the milled samples linearly increases with the Pb content. The microhardness of the BM Al–Pb samples is much larger than that of the MS samples, which mainly results from strengthening effects of the nanometer scale Al grains following the Hall–Petch relationship. The microhardness for both BM and MS Al–Pb samples varies with the Pb content, and maximum hardness for both samples exists when Pb content is about 5 wt. %, indicating that small amounts of Pb, in the form of nanoparticles, may strengthen the Al matrix.

HRTEM Study of Nanostructures in Hydrogen-Absorbing Mg-Ni and Mg-Ni-La Alloys Prepared by Melt-Spinning

2007 ◽  
Vol 561-565 ◽  
pp. 1629-1632 ◽  
Author(s):  
K. Tanaka ◽  
T. Miwa ◽  
K. Morishita ◽  
Katsuhiro Sasaki ◽  
Kotaro Kuroda
Keyword(s):  
Nanostructured Materials ◽  
Melt Spinning ◽  
Hydrogen Transport ◽  
Melt Spun ◽  
The Matrix ◽  
Nano Grains

The structure of melt-spun and crystallized Mg-10%Ni and Mg-10%Ni-5%La alloys is studied using HRTEM, coupled with ED and EELS techniques, for specimens subjected to hydrogenation and dehydrogenation. The presence of nano-sized (5-10nm) Mg2Ni grains dispersed in the matrix of Mg nano-grains is observed before hydrogenation. This structure is almost preserved after hydrogenation and dehydrogenation at 300°C. In the hydrogenated specimen, nanoboundaries lying between MgH2 and Mg2NiH4 nano-grains are observed. They appear to provide main routes for the hydrogen transport in these nanostructured materials.

Effect of Different Cooling Speed and Rare Earth La on the Microstructures and Phase Constitution of Al-Fe Alloy

2010 ◽  
Vol 44-47 ◽  
pp. 2126-2130 ◽  
Author(s):  
Guo Fa Mi ◽  
Cui Fen Dong ◽  
Da Wei Zhao
Keyword(s):  
Rare Earth ◽  
Melt Spinning ◽  
Metastable Phase ◽  
Melting Furnace ◽  
High Melting Point ◽  
The Matrix ◽  
Cooling Speed ◽  
Matrix Morphology ◽  
Rapidly Solidified ◽  
Rare Earth La

The casting, sub-rapid solidified and rapidly solidified A1-5Fe alloys, with or without rare earth La have been respectively prepared by vacuum melting furnace, suction casting and melt spinning furnace. And the alloys were investigated with OM, TEM and XRD. The results show that the microstructure was apparently refined by the increasing of cooling rate. Meanwhile, the acicular Al3Fe phase transferred to flower-like phase in casting A1-5Fe alloy and the matrix morphology of the alloy also was changed in sub-rapidly solidified Al-5Fe alloy, while 1.5wt% La was added. The metastable phase A16Fe and Al11La3 phase with high melting point were found in Al-5Fe alloy and A1-5Fe-1.5La alloy.

The Microstructure of Melt-Spun Iron Neodymium Permanent Magnet Materials

1985 ◽  
Vol 43 ◽  
pp. 210-211
Author(s):  
R. C. Dickenson
Keyword(s):  
Heat Treatment ◽  
Magnetic Properties ◽  
Melt Spinning ◽  
Ion Milling ◽  
X Ray ◽  
Fine Grained ◽  
Cold Stage ◽  
Melt Spun ◽  
Fine Grained Structure ◽  
Permanent Magnet Materials

Rapidly-quenched iron rare-earth boron alloys, with appropriate heat treatment, exhibit commercially promising permanent magnetic properties. This paper will report the results of an AEM characterization undertaken to explain the origin of the magnetic properties of an iron-neodymium-boron alloy in terms of its microstructure. Ribbons of Fe76 Nd16 B8 were prepared by melt-spinning, and were subsequently annealed at 700°C for 6 minutes to promote growth of a fine-grained structure. Samples were prepared for AEM by ion-milling the ribbons on a cold stage and examined using a Philips 400T TEM/STEM equipped with an energy dispersive x-ray unit.Three different microstructures are commonly observed in these alloys, and several others have been found in isolated cases.

Influence of W additions in rapidly solidified nial

1987 ◽  
Vol 45 ◽  
pp. 212-213
Author(s):  
I. E. Locci ◽  
M. V. Nathal
Keyword(s):  
Low Temperature ◽  
Melt Spinning ◽  
Matrix Composition ◽  
X Ray ◽  
Fine Grained ◽  
Free Jet ◽  
High Temperature Structural Material ◽  
Low Temperature Toughness ◽  
Pure Metals ◽  
Rapidly Solidified

The B2 aluminide NiAl has potential as a high temperature structural material, although its lack of low temperature toughness is a major obstacle. One strategy for improving low temperature toughness is by grain refinement. Fortunately, fine grained intermetallics appear to retain their strengths to much higher fractions of their melting point than do pure metals and alloys. The purpose of this study was to investigate the effects of melt spinning and small W additions on the grain size and stability of NiAl.Two alloys of the same matrix composition, equiatomic NiAl, were examined. One also contained 0.5 W at% (NiAl+W). The alloys were cast as ribbon ∼45 pm thick by ∼2.5 mm wide using a free jet melt spinning apparatus. To simulate consolidation conditions, sections of ribbon were annealed for 1 hour at either 1273 or 1573 °K in purified argon. Optical, X-ray and electron analyses of the as-spun and annealed ribbons were performed.

Rare Earth Oxide Dispersoid Stability and Microstructural Effects in Rapidly Solidified Ti3Al and Ti3A1-Nb

1985 ◽  
Vol 58 ◽  
Author(s):  
J. A. Sutliff ◽  
R. G. Rowe
Keyword(s):  
Rare Earth ◽  
Titanium Aluminide ◽  
Melt Spinning ◽  
Analytical Electron Microscopy ◽  
Rare Earth Oxide ◽  
Microstructural Effects ◽  
Analytical Electron ◽  
The Matrix ◽  
Rapidly Solidified ◽  
Titanium Aluminide Alloys

ABSTRACTThe microstructures of titanium aluminide alloys containing a rare earth oxide dispersion have been characterized using analytical electron microscopy. The alloys, based on Ti3A1 (alpha-2), contained 0 to 10.7 atom% Nb and 0.5 atom% Er. Alloys were rapidly solidified by melt spinning and were subsequently consolidated by HIP and extrusion. The microstructure of each alloy was examined in the as-cast, as-HIP'ed, and as-extruded conditions. A fine dispersoid spaced less than 100 nm apart was observed in ribbon aged at 750°C. The effects of processing conditions on the dispersoid distribution as a function of matrix chemistry were studied. Hot deformation was also examined to investigate the nature of the interaction between the dispersoids and the matrix during deformation.

Processing and Microstructure of Melt Spun Niai Alloys

1988 ◽  
Vol 133 ◽  
Author(s):  
I. E. Locci ◽  
R. D. Noebe ◽  
J. A. Moser ◽  
D. S. Lee ◽  
M. Nathal
Keyword(s):  
Melt Spinning ◽  
Matrix Material ◽  
Fiber Reinforced Composites ◽  
Ribbon Thickness ◽  
Reinforced Composites ◽  
Continuous Fiber ◽  
Grain Sizes ◽  
Melt Spun ◽  
The Matrix ◽  
Microscopy Techniques

ABSTRACTThe influence of various melt spinning parameters and the effect of consolidation on the microstructure of melt spun NiAl and NiAl + W alloys have been examined by optical and electron microscopy techniques. It was found that the addition of 0.5 at.% W to NiAl results in a fine dispersion of W particles after melt spinning which effectively controls grain growth during annealing treatments or consolidation at temperatures between 1523 and 1723 K. Increased wheel speeds are effective at reducing both ribbon thickness and grain size, such that proper choice of both composition and casting parameters can produce structures with grain sizes as small as 2 μ m. Finally, fabrication of continuous fiber reinforced composites which used pulverized ribbon as the matrix material was demonstrated.

Effect of Annealing Temperature on the Structure of Al-Hf Films

1977 ◽  
Vol 35 ◽  
pp. 280-281
Author(s):  
P. J. Smith ◽  
J. K. Howard
Keyword(s):  
Thin Film ◽  
Annealing Temperature ◽  
Thick Layer ◽  
Atomic Ratio ◽  
Film Structure ◽  
Grain Structure ◽  
Bottom Surface ◽  
Fine Grained ◽  
Continuous Layer ◽  
Layer 2

The Al-Hf reaction is important because of the electromigration properties of Al-Hf thin-film conductors and because of the possible effect of the reaction on the barrier height of Hf Schottky barrier diodes (1). Previous studies of Al-Hf films had shown that the final structure was dependent on the grain structure of the A1 layer (2). When Hf was in contact with a largegrained A1 layer, Al3Hf formed as precipitates at A1 grain boundaries; when Hf was in contact with a fine-grained A1 layer, a continuous layer of Al3Hf formed at the Al-Hf interface. In the present work we show that, by varying the importance of A1 diffusion through Hf relative to Hf diffusion through Al, the annealing temperature influences both the overall film structure and the Al-Hf atomic ratio at the bottom surface. A 6000-Å-thick layer of Al was deposited on 1000 Å of Hf;

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