MÖSSBAUER STUDY OF THE α-PHASE OF THE Ta-H SYSTEM

1974 ◽  
Vol 35 (C6) ◽  
pp. C6-515-C6-515 ◽  
Author(s):  
A. HEIDEMANN ◽  
G. KAINDL ◽  
D. SALOMON ◽  
G. WORTMANN
Keyword(s):  
1971 ◽  
Vol 42 (4) ◽  
pp. 1306-1308 ◽  
Author(s):  
L. Brossard ◽  
G. A. Fatseas ◽  
J. L. Dormann ◽  
P. Lecocq

Author(s):  
E.J. Jenkins ◽  
D.S. Tucker ◽  
J.J. Hren

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.


Author(s):  
E. Sukedai ◽  
M. Shimoda ◽  
A. Fujita ◽  
H. Nishizawa ◽  
H. Hashimoto

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.


Author(s):  
N. V. Larcher ◽  
I. G. Solorzano

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.


Author(s):  
H. Q. Ye ◽  
T.S. Xie ◽  
D. Li

The Ti3Al intermetallic compound has long been recognized as potentially useful structural materials. It offers attractive strength to weight and elastic modulus to weight ratios. Recent work has established that the addition of Nb to Ti3Al ductilized this compound. In this work the fundamental problem of this alloy, i.e. order-disorder and antiphase domain structures was investigated at the atomic scale.The Ti3Al+10at%Nb alloys used in this study were treated at 1060°C and then aged at 700°C for 2 hours. The specimens suitable for TEM were prepared by standard jet electrolytic-polishing technique. A JEM-200CX electron microscope with an interpretable resolution of about 0.25 nm was used for HREM.The [100] and [001] projections of the α2 phase were shown in Fig.l.The alloy obtained consist of at least two phases-α2(Ti3Al) and β0 structures. Moreover, a disorder α phase with small volume fraction was also observed. Fig.2 gives [100] and [001] diffraction patterns of the α2 phase. Since lattice parameters of the ordered α2 (a=0.579, c=0.466 nm) and disorder α phase (a0=0.294≈a/2, c0=0.468 nm) are almost the same, their diffraction patterns are difficult to be distinguished when they are overlapped with epitaxial orientation relationships.


1996 ◽  
Vol 40 (C2) ◽  
pp. C2-247-C2-249
Author(s):  
M. Tanaka
Keyword(s):  

1974 ◽  
Vol 35 (C1) ◽  
pp. C1-105-C1-106
Author(s):  
K. P. SCHMIDT ◽  
M. VAN ROSSUM ◽  
T. MEYKENS ◽  
G. LANGOUCHE ◽  
R. COUSSEMENT ◽  
...  
Keyword(s):  

1972 ◽  
Vol 33 (C6) ◽  
pp. C6-145-C6-149 ◽  
Author(s):  
Yu. V. BALDOKHIN ◽  
V. I. GOLDANSKII ◽  
E. F. MAKAROV ◽  
A. V. MITIN ◽  
V. A. POVITSKII

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