Spherulite Structures in a Melt Spun Fe-Ni Austenitic Steel

1985 ◽  
Vol 43 ◽  
pp. 52-53
Author(s):  
G. M. Michal ◽  
T. K. Glasgow ◽  
T. J. Moore
Keyword(s):  
Austenitic Steel ◽  
Room Temperature ◽  
Elevated Temperatures ◽  
Large Range ◽  
Amorphous Structure ◽  
Nucleation And Growth ◽  
Ni Alloys ◽  
Melt Spun ◽  
Crystal Fibers ◽  
Rapidly Solidified

Large additions of B to Fe-Ni alloys can lead to the formation of an amorphous structure, if the alloy is rapidly cooled from the liquid state to room temperature. Isothermal aging of such structures at elevated temperatures causes crystallization to occur. Commonly such crystallization pro ceeds by the nucleation and growth of spherulites which are spherical crystalline bodies of radiating crystal fibers. Spherulite features were found in the present study in a rapidly solidified alloy that was fully crysstalline as-cast. This alloy was part of a program to develop an austenitic steel for elevated temperature applications by strengthening it with TiB2. The alloy contained a relatively large percentage of B, not to induce an amorphous structure, but only as a consequence of trying to obtain a large volume fracture of TiB2 in the completely processed alloy. The observation of spherulitic features in this alloy is described herein. Utilization of the large range of useful magnifications obtainable in a modern TEM, when a suitably thinned foil is available, was a key element in this analysis.

New method for the production of bulk amorphous materials of Nd–Fe–B alloys

2005 ◽  
Vol 20 (3) ◽  
pp. 563-566 ◽  
Author(s):  
Tetsuji Saito ◽  
Hiroyuku Takeishi ◽  
Noboru Nakayama
Keyword(s):  
Electron Microscopy ◽  
Amorphous Materials ◽  
Room Temperature ◽  
Amorphous Structure ◽  
X Ray Diffraction ◽  
Bulk Materials ◽  
X Ray ◽  
Transmission Electron ◽  
Melt Spun ◽  
Melt Spun Ribbons

We report a new compression shearing method for the production of bulk amorphous materials. In this study, amorphous Nd–Fe–B melt-spun ribbons were successfully consolidated into bulk form at room temperature by the compression shearing method. X-ray diffraction and transmission electron microscopy studies revealed that the amorphous structure was well maintained in the bulk materials. The resultant bulk materials exhibited the same magnetic properties as the original amorphous Nd–Fe–B materials.

Structure and Properties of the Melt-Spun Fe41Ni39P10Si5B5 Alloy Heat Treated at Elevated Temperatures

2010 ◽  
Vol 163 ◽  
pp. 101-105
Author(s):  
Krzysztof Ziewiec ◽  
Krystian Prusik
Keyword(s):  
Glass Transition ◽  
Phase Transformations ◽  
Storage Modulus ◽  
Elevated Temperatures ◽  
Amorphous Structure ◽  
Transmission Electron ◽  
Melt Spun ◽  
Different Temperatures ◽  
Alloy Heat ◽  
Two Stages

The aim of the work was to provide information on structure development and change of properties at elevated temperatures in Fe41Ni39P10Si5B5 amorphous alloy. The alloy was characterized by X-ray diffraction. The changes of properties were characterized with use of dynamic mechanical thermal analysis (DMTA) and the resistivity measurements at elevated temperatures. The microstructure of the melt spun ribbon was investigated with use of transmission electron microscope (TEM) at different stages of phase transformations after heating to different temperatures. The initially amorphous structure undergoes phase transformations due to glass transition and crystallization of the alloy. The appearance of glass transition region results in decrease of storage modulus and in a reversible change of temperature coefficient of resistivity (TCR). The phases are characterized with use of TEM. The crystallization was found to have the two stages. Formation of bcc crystals and Ni12P5 is followed by transformation of the products into fcc crystals and Ni3P. Temporary changes of the storage modulus and elongation of the sample suggest formation of hard phases during crystallization.

A Comparative Study of The Crystallization of Ni-P Amorphous Alloys Produced By Ion-Implantation And Melt Spinning.

1985 ◽  
Vol 51 ◽  
Author(s):  
James Hamlyn-Harris ◽  
D. H. St. John ◽  
D. K. Sood
Keyword(s):  
Amorphous Alloys ◽  
Melt Spinning ◽  
Room Temperature ◽  
Nucleation And Growth ◽  
Nominal Composition ◽  
Similar Composition ◽  
Melt Spun ◽  
Dta Analysis ◽  
Amorphous Surface ◽  
Effect Of Surface

ABSTRACTImplantation of 4OkeV P+ ions into high purity Ni was employed at room temperature to a dose of 3×10E17 ions/cm2 to produce an 1100 A thick amorphous surface alloy of Ni-14 wt% P. Commercially available melt spun metallic glass ribbons of nominal composition, Ni-il wt% P were used for comparison of crystallization behaviour studied with TEM and RBS techniques. The DTA analysis was employed to construct a TTT curve for the melt spun glass, which was then used as a guide for selecting time and temperature of crystallization of the implanted amorphous alloy. The melt implanted glass is found to be less stable and crystallizes more readily than melt spun glass of similar composition. A detailed study on nucleation and growth of crystallites, mode of crystallization and effect of surface proximity will be presented.

scholarly journals HARC as an open-shell strategy to bypass oxidative addition in Ullmann–Goldberg couplings

2020 ◽  
Vol 117 (35) ◽  
pp. 21058-21064
Author(s):  
Marissa N. Lavagnino ◽  
Tao Liang ◽  
David W. C. MacMillan
Keyword(s):  
Room Temperature ◽  
Elevated Temperatures ◽  
Large Range ◽  
Aryl Halide ◽  
Oxidative Addition ◽  
Open Shell ◽  
Bond Forming ◽  
Aryl Bromides ◽  
Sterically Demanding ◽  
Rapid Diversification

The copper-catalyzed arylation of unsaturated nitrogen heterocycles, known as the Ullmann–Goldberg coupling, is a valuable transformation for medicinal chemists, providing a modular disconnection for the rapid diversification of heteroaromatic cores. The utility of the coupling, however, has established limitations arising from a high-barrier copper oxidative addition step, which often necessitates the use of electron-rich ligands, elevated temperatures, and/or activated aryl electrophiles. Herein, we present an alternative aryl halide activation strategy, in which the critical oxidative addition (OA) mechanism has been replaced by a halogen abstraction–radical capture (HARC) sequence that allows the generation of the same Cu(III)-aryl intermediate albeit via a photoredox pathway. This alternative mechanistic paradigm decouples the bond-breaking and bond-forming steps of the catalytic cycle to enable the use of many previously inert aryl bromides. Overall, this mechanism allows access to both traditional C–N adducts at room temperature as well as a large range of previously inaccessible Ullmann–Goldberg coupling products including sterically demandingortho-substituted heteroarenes.

Co-Deposition of Al–Ni Alloy in NiCl2-AlCl3-1-ethyl-3-methylimidazolium Bromide ([EMIM]Br) Ionic Liquid

2011 ◽  
Vol 121-126 ◽  
pp. 65-69
Author(s):  
Li Peng Zhang ◽  
Xian Jin Yu ◽  
Zhi Wei Ge ◽  
Yun Hui Dong ◽  
Dang Gang Li
Keyword(s):  
Electron Microscopy ◽  
Ionic Liquid ◽  
Room Temperature ◽  
Molar Ratio ◽  
X Ray Diffraction ◽  
X Ray ◽  
Ni Alloys ◽  
Ni Alloy ◽  
Rapidly Solidified ◽  
Scanning Electron

Al-Ni Alloys were obtained from NiCl2-AlCl3-1-ethyl-3-methylimidazolium bromide ([EMIM]Br) ionic liquid at room temperature. The analysis of Al-Ni alloys that co-deposited at different potentials for 2h were performed using Scanning Electron Microscopy (SEM) and X-ray diffraction analysis (XRD). It appears that Ni has been rapidly solidified in the alloys and homogeneous Al-Ni alloys can be obtained at room temperature. As increasing the overpotential, the amount of Ni in the alloys was decreased whereas the amount of Al was increased. The chloride pitting potentials of alloys with the molar ratio of NiCl2/AlCl3/[EMIM]Br 0.03:2:1 was approximately 0.3 V more than pure Al.

A Microstruciure Investigation on Rapidly Solidified Ni3Al Containing Boron

1983 ◽  
Vol 28 ◽  
Author(s):  
K.M. Ciiang ◽  
S.C. Huang ◽  
A.I. Taub
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Room Temperature ◽  
Martensitic Phase ◽  
Boron Addition ◽  
Transmission Electron ◽  
Melt Spun ◽  
Rapidly Solidified ◽  
Room Temperature Strength ◽  
Strength And Ductility

ABSTRACTA small amount of boron addition in rapidly solidified Ni3 Al has been found to yield remarkable improvements in bolh room-temperature strength and ductility. In this study, the microstructure of melt-spun Ni3Al ribbons with various boron modifications ranging from 0 to 6.0 at% was investigated in detail by using transmission electron microscopy. All alloy compositions studied reveal a completely ordered fcc L12 matrix phase, in which polygonized dislocation networks and subgrain boundaries are observed. The boron-free Ni3 Al contains a dispersion of an Al-rich martensitic phase consisting of alternate twins. The boron addition tends to suppress the formation of the martensitic phase, but excessive boron (≥ 2.0 at%) causes the precipitation of M23B6 type borides.

Observations oh Nucleation and Growth of Voids in Nickel

1970 ◽  
Vol 28 ◽  
pp. 414-415
Author(s):  
J. L. Brimhall ◽  
H. E. Kissinger ◽  
B. Mastel
Keyword(s):  
High Purity ◽  
Growth Stage ◽  
Elevated Temperatures ◽  
Early Growth ◽  
Nucleation And Growth ◽  
Pure Nickel ◽  
Different Temperatures ◽  
Total Fluence ◽  
Neutron Exposure ◽  
Growth Of Voids

Some information on the size and density of voids that develop in several high purity metals and alloys during irradiation with neutrons at elevated temperatures has been reported as a function of irradiation parameters. An area of particular interest is the nucleation and early growth stage of voids. It is the purpose of this paper to describe the microstructure in high purity nickel after irradiation to a very low but constant neutron exposure at three different temperatures.Annealed specimens of 99-997% pure nickel in the form of foils 75μ thick were irradiated in a capsule to a total fluence of 2.2 × 1019 n/cm2 (E > 1.0 MeV). The capsule consisted of three temperature zones maintained by heaters and monitored by thermocouples at 350, 400, and 450°C, respectively. The temperature was automatically dropped to 60°C while the reactor was down.

Mechanical Properties and Dislocation Structure of Single Crystal Cdte Deformed in Compression at 300°C

1976 ◽  
Vol 34 ◽  
pp. 592-593
Author(s):  
Ernest L. Hall ◽  
J. B. Vander Sande
Keyword(s):  
Mechanical Properties ◽  
Single Crystal ◽  
Dislocation Structure ◽  
Room Temperature ◽  
Elevated Temperatures ◽  
Strain Curve ◽  
Optical Devices ◽  
Semiconductor Compound ◽  
Wide Range ◽  
Sample Orientation

The present paper describes research on the mechanical properties and related dislocation structure of CdTe, a II-VI semiconductor compound with a wide range of uses in electrical and optical devices. At room temperature CdTe exhibits little plasticity and at the same time relatively low strength and hardness. The mechanical behavior of CdTe was examined at elevated temperatures with the goal of understanding plastic flow in this material and eventually improving the room temperature properties. Several samples of single crystal CdTe of identical size and crystallographic orientation were deformed in compression at 300°C to various levels of total strain. A resolved shear stress vs. compressive glide strain curve (Figure la) was derived from the results of the tests and the knowledge of the sample orientation.

Microstructural Variations in Melt-Spun Rapidly Solidified Ribbons

1985 ◽  
Vol 43 ◽  
pp. 54-55
Author(s):  
L. A. Bendersky ◽  
W. J. Boettinger
Keyword(s):  
Solid State ◽  
Processing Parameters ◽  
Heat Extraction ◽  
Solid State Reactions ◽  
Careful Examination ◽  
Ion Milling ◽  
Melt Spun ◽  
Wheel Side ◽  
Rapidly Solidified ◽  
Heat Extraction Rate

Rapid solidification produces a wide variety of sub-micron scale microstructure. Generally, the microstructure depends on the imposed melt undercooling and heat extraction rate. The microstructure can vary strongly not only due to processing parameters changes but also during the process itself, as a result of recalescence. Hence, careful examination of different locations in rapidly solidified products should be performed. Additionally, post-solidification solid-state reactions can alter the microstructure.The objective of the present work is to demonstrate the strong microstructural changes in different regions of melt-spun ribbon for three different alloys. The locations of the analyzed structures were near the wheel side (W) and near the center (C) of the ribbons. The TEM specimens were prepared by selective electropolishing or ion milling.

Investigation of ultra-thin films of YBa2Cu3O7−δ grown on MgO

1990 ◽  
Vol 48 (4) ◽  
pp. 6-7
Author(s):  
S.K. Streiffer ◽  
C.B. Eom ◽  
J.C. Bravman ◽  
T.H. Geballet
Keyword(s):  
Thin Films ◽  
Room Temperature ◽  
Deposition Process ◽  
Nucleation And Growth ◽  
Multilayer Structures ◽  
Rf Power ◽  
Oxygen Loss ◽  
Transmission Electron ◽  
Single Target ◽  
Mtorr Argon

The study of very thin (<15 nm) YBa2Cu3O7−δ (YBCO) films is necessary both for investigating the nucleation and growth of films of this material and for achieving a better understanding of multilayer structures incorporating such thin YBCO regions. We have used transmission electron microscopy to examine ultra-thin films grown on MgO substrates by single-target, off-axis magnetron sputtering; details of the deposition process have been reported elsewhere. Briefly, polished MgO substrates were attached to a block placed at 90° to the sputtering target and heated to 650 °C. The sputtering was performed in 10 mtorr oxygen and 40 mtorr argon with an rf power of 125 watts. After deposition, the chamber was vented to 500 torr oxygen and allowed to cool to room temperature. Because of YBCO’s susceptibility to environmental degradation and oxygen loss, the technique of Xi, et al. was followed and a protective overlayer of amorphous YBCO was deposited on the just-grown films.

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