Metastable solid solution extension of mullite by rapid solidification

1988 ◽  
Vol 3 (2) ◽  
pp. 375-379 ◽  
Author(s):  
John P. Pollinger ◽  
Gary L. Messing
Keyword(s):  
Solid Solution ◽  
Rapid Solidification ◽  
Lattice Parameters ◽  
Tetragonal Symmetry ◽  
Metastable Solid Solution ◽  
Cooling Rates ◽  
Compositional Range ◽  
Melt Cooling ◽  
Rapidly Solidified

The melt self-quenching technique has been used to examine the metastable solid solution extension of mullite formed from rapidly solidified Al2O3.SiO2 melts. Increasing melt cooling rates were seen to increase the Al2O3 content of mullite, decrease the amount of mullite precipitating, and decrease the melt compositional range over which mullite forms. The maximum mullite Al2O3 content achieved was 77.3 mol % for cooling rates between 103 and 105 K/s. The highest Al2O3 content mullite also exhibited very similar ao and bo lattice parameters indicating a structure close to tetragonal symmetry (equilibrium mullite is orthorhombic).

A STEM Microstructural Analysis of Rapidly Solidified High-Sulfur Austenitic Steel

1980 ◽  
Vol 38 ◽  
pp. 394-395
Author(s):  
Thomas F. Kelly
Keyword(s):  
Rapid Solidification ◽  
Average Particle Size ◽  
Microstructural Analysis ◽  
Scanning Transmission Electron Microscope ◽  
Average Particle ◽  
Cooling Rates ◽  
Scanning Transmission ◽  
High Cooling Rates ◽  
Carpenter Technology Corporation ◽  
Rapidly Solidified

Rapid solidification processing (RSP) has been viewed as a means of obtaining better properties from (crystalline) metal alloys where the improvements are a result of the various effects of high cooling rates (> 105°K/sec) on the “as solidified” structure. Described herein are the results of an investigation into the microstructural and microchemical nature of a rapid solidification processed high sulfur, 303 stainless steel using a dedicated scanning transmission electron microscope (STEM). The RSP material of this study was prepared by forced convective cooling, in helium, of centrifugally atomized metal droplets to achieve cooling rates on the order of 105°K/sec. The resultant powder, of n 50 ym average particle size, was consolidated to a fully dense state. Equivalent conventionally processed 303 SS material was obtained from Carpenter Technology Corporation. The 303 SS material of this investigation was therefore studied in three processed states:the rapidly solidified powder, the rapidly solidified and consolidated bar stock, and the conventionally processed material.

scholarly journals Nucleation behaviour and microstructure of single Al-Si12 powder particles rapidly solidified in a fast scanning calorimeter

2021 ◽  
Author(s):  
Bin Yang ◽  
Qin Peng ◽  
Benjamin Milkereit ◽  
Armin Springer ◽  
Dongmei Liu ◽  
...  
Keyword(s):  
Cooling Rate ◽  
Rapid Solidification ◽  
Heterogeneous Nucleation ◽  
Cooling Rates ◽  
Solidification Behaviour ◽  
Nucleation Undercooling ◽  
In Situ Investigation ◽  
Solidification Processes ◽  
Powder Particles ◽  
Rapidly Solidified

AbstractThe understanding of rapid solidification behaviour, e.g. the undercooling versus growth velocity relationship, is crucial for tailoring microstructures and properties in metal alloys. In most rapid solidification processes, such as additive manufacturing (AM), in situ investigation of rapid solidification behaviour is missing because of the lack of accurate measurement of the cooling rate and nucleation undercooling. In the present study, rapid solidification of single micro-sized Al-Si12 (mass%) particles of various diameters has been investigated via differential fast scanning calorimetry employing controllable cooling rates from 100 to 90,000 K s−1 relevant for AM. Based on nucleation undercooling and on microstructure analysis of rapidly solidified single powder particles under controlled cooling rates, two different heterogeneous nucleation mechanisms of the primary α-Al phase are proposed. Surface heterogeneous nucleation dominates for particles with diameter smaller than 23 μm. For particles with diameter larger than 23 μm, the nucleation of the primary α-Al phase changes from surface to bulk heterogeneous nucleation with increasing cooling rate. The results indicate that at large undercoolings (> 95 K) and high cooling rates (> 10,000 K s−1), rapid solidification of single particle can yield a microstructure similar to that formed in AM. The present work not only proposes new insight into rapid solidification processes, but also provides a theoretical foundation for further understanding of microstructures and properties in additively manufactured materials.

scholarly journals Diffusionless (chemically partitionless) crystallization and subsequent decomposition of supersaturated solid solutions in Sn–Bi eutectic alloy

2019 ◽  
Vol 377 (2143) ◽  
pp. 20180204 ◽  
Author(s):  
Olga V. Gusakova ◽  
Peter K. Galenko ◽  
Vasiliy G. Shepelevich ◽  
Dmitri V. Alexandrov ◽  
Markus Rettenmayr
Keyword(s):  
Solid Solution ◽  
Eutectic Alloy ◽  
Supersaturated Solid Solution ◽  
Eutectic Growth ◽  
Rapid Quenching ◽  
Cooling Rates ◽  
Internal Structures ◽  
Supersaturated Solid Solutions ◽  
Rapidly Solidified ◽  
Subsequent Decomposition

Results of a study on microstructural evolution of eutectic Sn-57 wt.% Bi processed with cooling rates of 10 −2 , 1 K s −1 and approximately 10 5  K s −1 are presented. In order to distinguish different mechanisms of microstructure formation, a comparison with microstructures of different hypoeutectic alloys with compositions down to below the maximum solubility of Bi in Sn–Bi is undertaken. It is found that at the cooling rates of 10 −2 and 1 K s −1 , coupled eutectic growth occurs, leading to lamellar structures with different length scales. At the rapid quenching rates of approximately 10 5  K s −1 , structure formation in the eutectic alloy is qualitatively different. Partitionless solidification resulting in a supersaturated solid solution with the initial composition is observed in both eutectic and hypoeutectic alloys. It is shown that the observed microstructure of the rapidly solidified alloys forms by the decomposition of the supersaturated solid solution. This article is part of the theme issue ‘Heterogeneous materials: metastable and non-ergodic internal structures’.

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 New Quaternary Chalcogenides Tl2MIIMIV3Se8 and Tl2MIIMIVX4

Proceedings ◽  
2020 ◽  
Vol 62 (1) ◽  
pp. 3
Author(s):  
Andrii Selezen ◽  
Yuri Kogut ◽  
Lyudmyla Piskach ◽  
Lubomir Gulay
Keyword(s):  
Crystal Structure ◽  
Ternary Systems ◽  
Lattice Parameters ◽  
Tetragonal Symmetry ◽  
Orthorhombic Symmetry ◽  
Component Ratio

New quaternary thallium-containing chalcogenides Tl2MIIMIV3X8 and Tl2MIIMIVX4 were synthesized, and their crystal structure was determined by XRD. Three Tl2MIIMIV3X8 chalcogenides crystallize in orthorhombic symmetry (S.G. P212121; Tl2CdGe3Se8 lattice parameters a = 0.76023(9), b = 1.2071(2), c = 1.7474(2) nm), eight isostructural Tl2BIIDIVX4 compounds crystallize in tetragonal symmetry, S.G. I-42m. These compounds form in the quasi-ternary systems Tl2X–MIIX–MIVX2 (X–S, Se, Te) at the component ratio 1:1:1 and 1:1:3 at the sections Tl2MIVX3–BIIX and Tl2MIIMIVX4–MIVX2, respectively. The composition of the Tl2CdGe3Se8 compound was additionally confirmed by SEM and EDS.

Decomposition of a metastable solid solution in uranium-molybdenum alloy

Atomic Energy ◽  
2000 ◽  
Vol 88 (1) ◽  
pp. 42-47 ◽  
Author(s):  
V. K. Orlov ◽  
V. M. Teplinskaya ◽  
N. T. Chebotarev
Keyword(s):  
Solid Solution ◽  
Molybdenum Alloy ◽  
Metastable Solid Solution

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.

Extension of Solid Solution in Rapidly Solidified Binary Alloys

1991 ◽  
Vol 38-39 ◽  
pp. 83-98
Author(s):  
Kamanio Chattopadhyay ◽  
K. Raviprasad
Keyword(s):  
Solid Solution ◽  
Binary Alloys ◽  
Rapidly Solidified
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