Positron-annihilation studies of quasicrystalline-phase Al-Mn-Si-Ru and α-phase alloys

1994 ◽  
Vol 49 (5) ◽  
pp. 3573-3575 ◽  
Author(s):  
I. Kanazawa ◽  
Chi. Nakayama ◽  
J. Takahashi ◽  
T. Ohata ◽  
T. Iwashita ◽  
...  
Keyword(s):  
Positron Annihilation ◽  
Quasicrystalline Phase ◽  
Α Phase

A study of Fermi surfaces of the α-phase Cu-Ge and Cu-Si alloys by positron annihilation

1974 ◽  
Vol 5 (3) ◽  
pp. 269-274 ◽  
Author(s):  
Toshiharu Suzuki ◽  
Masayuki Hasegawa ◽  
Makoto Hirabayashi
Keyword(s):  
Positron Annihilation ◽  
Fermi Surfaces ◽  
Α Phase

The composition dependence of the effective vacancy formation enthalpy in copper-rich brass as deduced from the threshold temperature for positron trapping in vacancies

1978 ◽  
Vol 56 (8) ◽  
pp. 1077-1083 ◽  
Author(s):  
P. J. Schultz ◽  
T. E. Jackman ◽  
J. Fabian ◽  
E. A. Williams ◽  
J. R. MacDonald ◽  
...  
Keyword(s):  
Temperature Dependence ◽  
Positron Annihilation ◽  
Composition Dependence ◽  
Formation Enthalpy ◽  
Vacancy Formation ◽  
Threshold Temperature ◽  
Α Phase ◽  
Linear Decrease ◽  
Zn Concentration ◽  
Bcc Structure

The temperature dependence of the Doppler-broadened positron annihilation lineshape has been measured for 13 brass specimens with compositions varying from 0 to 48% by weight of Zn. The vacancy formation enthalpy deduced from these measurements shows a linear decrease of 22% with increasing Zn concentration through the α phase and a further 31% decrease on changing from fcc to bcc structure.

A Positron-Annihilation Study of α-Phase Copper-Aluminum Alloys

1974 ◽  
Vol 36 (1) ◽  
pp. 135-141 ◽  
Author(s):  
Takashi Akahane ◽  
Osamu Sueoka ◽  
Hiroshi Morinaga ◽  
Kunio Fujiwara
Keyword(s):  
Aluminum Alloys ◽  
Positron Annihilation ◽  
Α Phase ◽  
Positron Annihilation Study ◽  
Copper Aluminum

Microtomy of spherical Al2O3 powders

1983 ◽  
Vol 41 ◽  
pp. 74-75
Author(s):  
E.J. Jenkins ◽  
D.S. Tucker ◽  
J.J. Hren
Keyword(s):  
Thin Film ◽  
Size Range ◽  
Particle Aggregation ◽  
Ion Milling ◽  
Thin Sections ◽  
Α Phase ◽  
Convenient Means ◽  
Van Der Waals Attraction ◽  
Negative Feature ◽  
Film Substrate

The size range of mineral and ceramic particles of one to a few microns is awkward to prepare for examination by TEM. Electrons can be transmitted through smaller particles directly and larger particles can be thinned by crushing and dispersion onto a substrate or by embedding in a film followed by ion milling. Attempts at dispersion onto a thin film substrate often result in particle aggregation by van der Waals attraction. In the present work we studied 1-10 μm diameter Al2O3 spheres which were transformed from the amprphous state to the stable α phase.After the appropriate heat treatment, the spherical powders were embedded in as high a density as practicable in a hard EPON, and then microtomed into thin sections. There are several advantages to this method. Obviously, this is a rapid and convenient means to study the microstructure of serial slices. EDS, ELS, and diffraction studies are also considerably more informative. Furthermore, confidence in sampling reliability is considerably enhanced. The major negative feature is some distortion of the microstructure inherent to the microtoming operation; however, this appears to have been surprisingly small. The details of the method and some typical results follow.

High-resolution EM investigation about effect of stress on formation of ω-phase crystals in β-tttanium alloys

1996 ◽  
Vol 54 ◽  
pp. 1006-1007
Author(s):  
E. Sukedai ◽  
M. Shimoda ◽  
A. Fujita ◽  
H. Nishizawa ◽  
H. Hashimoto
Keyword(s):  
High Resolution ◽  
Titanium Alloys ◽  
High Resolution Electron Microscopy ◽  
Dark Field ◽  
Zone Refining ◽  
Ω Phase ◽  
Α Phase ◽  
Nucleation Sites ◽  
Resolution Electron ◽  
Bcc Structure

ω-phase particles formed in β-titanium alloys (bcc structure) act important roles to their mechanical properties such as ductility and hardness. About the ductility, fine ω-phase particles in β–titanium alloys improve the ductility, because ω-phase crystals becomes nucleation sites of α-phase and it is well known that (β+α) duplex alloys have higher ductility. In the present study, the formation sites and the formation mechanism of ω-phase crystals due to external stress and aging are investigated using the conventional and high resolution electron microscopy.A β-titanium alloy (Til5Mo5Zr) was supplied by Kobe Steel Co., and a single crystal was prepared by a zone refining method. Plates with {110} surface were cut from the crystal and were pressured hydrostatically, and stressed by rolling and tensile testing. Specimens for aging with tensile stress were also prepared from Ti20Mo polycrystals. TEM specimens from these specimens were prepared by a twin-jet electron-polishing machine. A JEM 4000EX electron microscope operated at 400k V was used for taking dark field and HREM images.

High-resolution observations of metastable γ’ precipitation in Al-15at.%Ag

1996 ◽  
Vol 54 ◽  
pp. 1004-1005
Author(s):  
N. V. Larcher ◽  
I. G. Solorzano
Keyword(s):  
Discontinuous Precipitation ◽  
Equilibrium Phase ◽  
Quantitative Description ◽  
Present Contribution ◽  
Α Phase ◽  
The Matrix ◽  
Aging Sequence ◽  
Matrix Precipitation ◽  
Considerable Detail ◽  
Kinetics Of

It is currently well established that, for an Al-Ag alloy quenched from the α phase and aged within the metastable solvus, the aging sequence is: supersaturated α → GP zones → γ’ → γ (Ag2Al). While GP zones and plate-shaped γ’ are metastable phases, continuously distributed in the matrix, formation of the equilibrium phase γ takes place at grain boundaries by discontinuous precipitation (DP). The crystal structure of both γ’ and γ is hep with the following orientation relationship with respect to the fee α matrix: {0001}γ′,γ // {111}α, <1120>γ′,γ, // <110>α.The mechanisms and kinetics of continuous matrix precipitation (CMP) in dilute Al-Ag alloys have been studied in considerable detail. The quantitative description of DP kinetics, however, has received less attention. The present contribution reports the microstructural evolution resulting from aging an Al-Ag alloy with Ag content higher than those previously reported in the literature, focusing the observations of γ' plate-shaped metastable precipitates.

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