Rapid solidification by unstable combustion synthesis

1993 ◽  
Vol 8 (10) ◽  
pp. 2515-2523 ◽  
Author(s):  
H.P. Li ◽  
J.A. Sekhar
Keyword(s):  
Combustion Synthesis ◽  
Rapid Solidification ◽  
Synthesis Conditions ◽  
Unstable Combustion ◽  
Rapidly Solidified ◽  
First Time

During combustion/micropyretic synthesis, conditions that give rise to rapid solidification and rapidly solidified microstructures may be encountered. In this article, many such conditions are identified for the first time in a Ni–Al system. In addition, the banded structures and aligned dendrites that are encountered in this system are also examined. The various techniques of rapid solidification that may be initiated with combustion synthesis are examined and discussed.

Lorentz electron microscopy of magnetic domains in rapidly solidified and annealed Pt-Co-B alloys

1991 ◽  
Vol 49 ◽  
pp. 784-785
Author(s):  
N. Qiu ◽  
J. E. Wittig
Keyword(s):  
Rapid Solidification ◽  
Ion Beam ◽  
Magnetic Behavior ◽  
High Coercivity ◽  
Magnetic Domains ◽  
Beam Angle ◽  
Tem Analysis ◽  
Intrinsic Coercivity ◽  
Hard Magnets ◽  
Rapidly Solidified

PtCo hard magnets have specialized applications owing to their relatively high coercivity combined with corrosion resistance and ductility. Increased intrinsic coercivity has been recently obtained by rapid solidification processing of PtCo alloys containing boron. After rapid solidification by double anvil splat quenching and subsequent annealing for 30 minutes at 650°C, an alloy with composition Pt42Co45B13 (at.%) exhibited intrinsic coercivity up to 14kOe. This represents a significant improvement compared to the average coercivities in conventional binary PtCo alloys of 5 to 8 kOe.Rapidly solidified specimens of Pt42Co45B13 (at.%) were annealed at 650°C and 800°C for 30 minutes. The magnetic behavior was characterized by measuring the coercive force (Hc). Samples for TEM analysis were mechanically thinned to 100 μm, dimpled to about 30 nm, and ion milled to electron transparency in a Gatan Duomill at 5 kV and 1 mA gun current. The incident ion beam angle was set at 15° and the samples were liquid nitrogen cooled during milling. These samples were analyzed with a Philips CM20T TEM/STEM operated at 200 kV.

Transmission Electron Microscopic Observations of Al3Li and Al3Ti Precipitation in A Rapidly Solidified Al-3Li-0.2Ti ALLOY

1980 ◽  
Vol 38 ◽  
pp. 336-337
Author(s):  
J. E. O’Neal ◽  
K. K. Sankaran ◽  
S. M. L. Sastry
Keyword(s):  
Rapid Solidification ◽  
Metallic Substrate ◽  
Deformation Characteristics ◽  
Phase Decomposition ◽  
Electron Microscopic ◽  
Transmission Electron ◽  
Supersaturated Solid Solutions ◽  
Transmission Electron Microscopic ◽  
Rapidly Solidified ◽  
Microstructural Homogeneity

Rapid solidification of a molten, multicomponent alloy against a metallic substrate promotes greater microstructural homogeneity and greater solid solubility of alloying elements than can be achieved by slower-cooling casting methods. The supersaturated solid solutions produced by rapid solidification can be subsequently annealed to precipitate, by controlled phase decomposition, uniform 10-100 nm precipitates or dispersoids. TEM studies were made of the precipitation of metastable Al3Li(δ’) and equilibrium AL3H phases and the deformation characteristics of a rapidly solidified Al-3Li-0.2Ti alloy.

scholarly journals Combustion Synthesis of Aluminum Oxynitride in Loose Powder Beds

Materials ◽  
2021 ◽  
Vol 14 (15) ◽  
pp. 4182
Author(s):  
Alan Wilmański ◽  
Magdalena Zarzecka-Napierała ◽  
Zbigniew Pędzich
Keyword(s):  
Combustion Synthesis ◽  
Metal Powder ◽  
Weight Ratio ◽  
Nitrogen Pressure ◽  
Alumina Powder ◽  
Metal Powders ◽  
Aluminum Oxynitride ◽  
Synthesis Conditions ◽  
Aluminum Metal ◽  
Loose Powder

This paper describes combusting loose powder beds of mixtures of aluminum metal powders and aluminum oxide powders with various grain sizes under various nitrogen pressure. The synthesis conditions required at least 20/80 weight ratio of aluminum metal powder to alumina powder in the mix to reach approximately 80 wt% of γ-AlON in the products. Finely ground fused white alumina with a mean grain size of 5 μm was sufficient to achieve results similar to very fine alumina with 0.3 μm grains. A lower nitrogen pressure of 1 MPa provided good results, allowing a less robust apparatus to be used. The salt-assisted combustion synthesis upon addition of 10 wt% of ammonium nitrite resulted in a slight increase in product yield and allowed lower aluminum metal powder content in mixes to be ignited. Increasing the charge mass five times resulted in a very similar γ-AlON yield, providing a promising technology for scaling up. Synthesis in loose powder beds could be utilized for effective production of relatively cheap and uniform AlON powder, which could be easily prepared for forming and sintering without intensive grounding and milling, which usually introduce serious contamination.

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.

Novel Baddeleyite-Based Zirconia Ceramics for Biomedical Applications

2017 ◽  
Vol 13 ◽  
pp. 9-14
Author(s):  
Alexander I. Tyurin ◽  
Andrey O. Zhigachev ◽  
Alexey V. Umrikhin ◽  
Vyacheslav V. Rodaev ◽  
Tatyana S. Pirozhkova
Keyword(s):  
Mechanical Properties ◽  
Fracture Toughness ◽  
Tetragonal Phase ◽  
Biomedical Applications ◽  
Zirconia Ceramics ◽  
Engineering Ceramics ◽  
Synthesis Conditions ◽  
Microstructure And Mechanical Properties ◽  
First Time

For the first time nanostructured engineering ceramics were prepared from natural zirconia mineral (baddeleyite) with CaO as a tetragonal phase stabilizer. The effect of synthesis conditions on microstructure and mechanical properties of the baddeleyite-based ceramics is reported, furthermore, the effect of calcia content on hardness and fracture toughness is studied. Optimal calcia concentration and synthesis conditions are found, corresponding hardness and fracture toughness values are 10,8 GPa and 13,3 MPa×m1/2. The reported mechanical properties are comparable to those typically reported for yttria-stabilized engineering zirconia ceramics, prepared from chemically synthesized zirconia.

Microstructural Characterization of Rapidly Solidified Ultrahigh Strength Aluminum Alloys

1998 ◽  
Vol 4 (S2) ◽  
pp. 98-99
Author(s):  
D. H. Ping ◽  
K. Hono ◽  
A. Inoue
Keyword(s):  
Rapid Solidification ◽  
Microstructural Characterization ◽  
Atom Probe ◽  
Probe Field ◽  
Amorphous Phases ◽  
Ultrahigh Strength ◽  
Icosahedral Phases ◽  
Transmission Electron ◽  
Solidification Processes ◽  
Rapidly Solidified

Recently, Inoue et al. succeeded in fabricating ultrahigh-strength Al-based alloys consisting of a nanoscale mixture of α-Al and amorphous phases or a mixture of a-Al, amorphous and icosahedral phases in Al-TM-Ce, Al-TM-Ln (TM: transition metals) and Al-Cr-Co-Ce systems by rapid solidification [1-3]. In order to understand the mechanism of the nanoscale microstructural evolution during the rapid solidification processes in these nanocomposite alloys, we have characterized the microstructures of rapidly solidified Al94.5Cr3Co1.5Ce1 and Al96V4Fe2 alloys by atom probe field ion microscopy (APFIM) and high resolution transmission electron microscopy (HREM).TEM investigations have revealed that the as-quenched Al94.5Cr3Co1.5Ce1 alloy is composed of a nanoscale mixture of amorphous and α-Al. A typical TEM bright field micrograph is shown in Fig. 1. The microdiffraction patterns taken at various locations in the darkly contrasted region have shown that the region consists of a few interconnected α-Al grains and many localized amorphous regions which are trapped within the Al grains.

Investigation of propagation modes and temperature/velocity variation on unstable combustion synthesis

2002 ◽  
Vol 17 (12) ◽  
pp. 3213-3221 ◽  
Author(s):  
H. P. Li
Keyword(s):  
Activation Energy ◽  
Combustion Synthesis ◽  
Combustion Front ◽  
Propagation Velocity ◽  
Combustion Temperature ◽  
Front Propagation ◽  
Combustion Reaction ◽  
Velocity Variation ◽  
Material Synthesis ◽  
Unstable Combustion

Combustion synthesis/micropyretic synthesis is a technique in which material synthesis is accomplished by the propagation of a combustion front across the sample. In some cases, the combustion front may propagate in an unstable mode where the propagation velocity and combustion temperature of the combustion front are altered periodically. In this study, the processing conditions leading to unstable combustion reaction were first studied theoretically. The boundary temperatures separating stable and unstable reactions were then determined. The numerical analysis showed that the combustion temperature and the propagation velocity changed periodically during unstable combustion. As the combustion reaction became unstable, the average propagation velocity and the oscillatory frequency of front propagation decreased. The products of unstable combustion synthesis possessed the banded structures, implying the occurrence of the unstable oscillatory propagation, as demonstrated experimentally. In this study, high activation energy combustion (Ti + 2B reaction) and low activation energy combustion (Ni + Al reaction) were both chosen to illustrate the effect of unstable combustion. It is the first time the experimental and numerical results were combined to investigate the temperature and propagation velocity variations during unstable combustion.

Microstructure and Properties of Rapidly Solidified Al-Zn-Mg-Cu Alloy

2020 ◽  
Vol 993 ◽  
pp. 203-207
Author(s):  
Wei Min Ren ◽  
Zi Yong Chen ◽  
Zhi Lei Xiang ◽  
Li Hua Chai
Keyword(s):  
Aluminum Alloy ◽  
Aluminum Alloys ◽  
Cooling Rate ◽  
Rapid Solidification ◽  
Second Phase ◽  
Alloy Strip ◽  
Roller Speed ◽  
Microstructure And Properties ◽  
Cu Alloy ◽  
Rapidly Solidified

Refining grain plays an important role in improving the mechanical properties of aluminum alloys. However, the conventional casting method with a slow cooling rate can be easy to cause coarseness of the microstructure and serious segregation. In this paper, the rapid solidification of Al-Zn-Mg-Cu alloy was prepared by the single-roller belt method. The alloy strip was studied by X-ray diffraction (XRD), scanning electron microscopy (SEM) and hardness test to study the microstructure and properties of the rapidly solidified aluminum alloy. The results show that the roller speed was an important parameters affecting the formability of the alloy. When the roller speed was 15 m/s, the aluminum alloy produced a thin bandwidth of 5 mm and a thickness of 150 um. As the rotation speed of the roller increased, the cooling rate of the melt increased, and the microstructure of the rapidly solidified Al-Zn-Mg-Cu aluminum alloy strip improved in grains refinement. Compared with the conventionally cast Al-Zn-Mg-Cu aluminum alloys, the Al-Zn-Mg-Cu aluminum alloys prepared by rapid solidification showed much finer crystal grains, and enhanced solid solubility of alloying elements with less precipitation of second phase and high hardness.

Microstructure and Mechanical Properties of Near Eutectic Β-Nial Plus α-Re Alloys Produced by Rapid Solidification and Extrusion

1990 ◽  
Vol 213 ◽  
Author(s):  
D.P. Mason ◽  
D.C. Van Aken
Keyword(s):  
Electron Microscopy ◽  
Rapid Solidification ◽  
Eutectic Composition ◽  
Extrusion Process ◽  
Solid Solution Strengthening ◽  
Size Refinement ◽  
Transmission Electron ◽  
Solution Strengthening ◽  
Rapidly Solidified ◽  
Strengthening Precipitate

ABSTRACTTwo β-NiAl plus α -Re alloys with near eutectic composition were produced by rapid solidification and then consolidated through a powder extrusion process. Microstructures of the rapidly solidified, as-consolidated, and deformed alloys were characterized by transmission electron microscopy. Both compression and tensile properties of these alloys were determined over the temperature range of 300–1300 K. The Re additions were found to greatly enhance low and intermediate temperature yield strengths when compared to other β-NiA1 alloys. This enhancement was attributed to a combination of solid solution strengthening, precipitate hardening, and grain size refinement. Above 1200K the strength of these Re-modified alloys was comparable to the binary β-NiAl compound.

Ti-Al-Nb Material for High-Temperature Applications: Combustion Synthesis from Oxide Raw Materials

2017 ◽  
Vol 746 ◽  
pp. 262-266
Author(s):  
D.E. Andreev ◽  
V.I. Yukhvid ◽  
Denis M. Ikornikov ◽  
Vladimir N. Sanin
Keyword(s):  
High Temperature ◽  
Combustion Synthesis ◽  
Raw Materials ◽  
High Gravity ◽  
Target Product ◽  
Oxide Materials ◽  
Centrifugal Shs ◽  
First Time ◽  
Metallic Impurities ◽  
Temperature Applications

This work is focused on preparation of Nb-doped Ti–Al material (Ti–29.3Al–17.6Nb wt %) by centrifugal SHS. Results of studying of combustion and synthesis regularities of intermetallic material on γ-TiAl base from oxide materials under high gravity are presented in the article. For the first time is used a reduction mixture on Al/Ca base which markedly increases the yield of Ti–Al–Nb and decreases the amount of non-metallic impurities (oxygen, nitrogen, carbon) in target product.

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