Precipitation behavior in the early stage of aging in an Al–Li°Cu–Mg–Zr–Ag (Weldalite 049) alloy

1999 ◽  
Vol 14 (2) ◽  
pp. 384-389 ◽  
Author(s):  
Kap Ho Lee ◽  
Yeung Jo Lee ◽  
Kenji Hiraga
Keyword(s):  
Aging Process ◽  
Early Stage ◽  
High Resolution Electron Microscopy ◽  
S Phase ◽  
Precipitation Behavior ◽  
Ordered Structures ◽  
Resolution Electron ◽  
The Matrix ◽  
Habit Planes

The precipitation behavior of various phases during the aging process of an Ag–Li°Cu–Mg–Zr–Ag (Weldalite 049) alloy was investigated by high-resolution electron microscopy and in situ hot-stage microscopy. Two kinds of domains with L12-type ordered structures, which are considered to be δ′ and β′ phases, are observed with different domain sizes in the alloy quenched from 530 °C. In the early stage of aging at 190 °C, the δ′ phase is precipitated as surrounding the β' phase, and the δ′ domains appear with in-phase and antiphase relationships to the β′ lattices. In situ observations at 190 °C clearly show that the T1 phase precipitates predominantly on dislocations at subgrain boundaries and then is homogeneously formed in the matrix with increasing aging time. The nucleation of the S′ phase is associated with clustering of Cu and Mg in the matrix, and the S0 domains are grown with {210} habit planes.

scholarly journals In situ HREM observation of interphase boundary motion in 95Pb-5Sn solder

1986 ◽  
Vol 44 ◽  
pp. 410-411
Author(s):  
J.B. Posthill ◽  
Darrel Frear ◽  
J.W. Morris
Keyword(s):  
High Resolution Electron Microscopy ◽  
Atomic Level ◽  
Subsequent Aging ◽  
Microstructural Study ◽  
Precipitate Dissolution ◽  
Electrical Interconnection ◽  
Resolution Electron ◽  
Mechanical Attachment ◽  
Habit Planes

The use of solder to provide mechanical attachment and electrical interconnection for electronic packaging is widespread throughout the industry. One application for a lead-rich solder is in the IC chip/ceramic carrier connection. It is well-established that this joint is susceptible to thermal-fatigue failure and, hence, a thorough microstructural study is warranted. Previous work has shown that 95Pb-5Sn contains β-Sn precipitates that have formed upon solidification and subsequent aging at ambient temperature. Diffraction contrast TEM demonstrated that the precipitates lie on {111}pb habit planes. High-resolution electron microscopy was undertaken to establish whether or not the habit plane was faceted on the atomic level. This contribution reports on an observation of beam-induced precipitate dissolution.

Formation and structure of polymeric carbons

1972 ◽  
Vol 327 (1571) ◽  
pp. 501-517 ◽  
Keyword(s):  
Glassy Carbon ◽  
Molecular Orientation ◽  
Early Stage ◽  
Structural Difference ◽  
Direct Consequence ◽  
High Resolution Electron Microscopy ◽  
Polymer Chains ◽  
Resolution Electron ◽  
Ribbon Structure ◽  
Phenolic Polymer

Glassy carbon has been prepared in the shape of disk and fibre by direct pyrolysis of a phenolic resin. Carbonization studies indicate that the unique structure of the final glassy carbon is a direct consequence of the production of very stable aromatic ribbon molecules by the coalescence of phenolic polymer chains at an early stage of pyrolysis. It is shown that molecular orientation induced in the initial polymer before pyrolysis is 'memorized’ to some extent after carbonization. Molecular orientation imposed in this type of carbon is not an intrinsic structural feature, but a physical characteristic which can be varied by the formation process or by extension at high temperatures; there is no essential structural difference apart from preferred orientation between polymeric units or microfibrils in well-oriented carbon fibres and isotropic glassy carbon. High resolution electron microscopy confirms this directly. We thus identify a new class of ‘polymeric carbons’, that consist of intertwined microfibrils comprising stacks of narrow graphitic ribbons. The fibrils are held together with covalent interfibrillar links of strength lower than that in the ribbons themselves. A ribbon structure has been proposed previously by Ruland (1971) for the specific case of high modulus carbon fibre. The structure is elaborated and extended here to cover all polymeric carbons and the steps in its development during carbonization are decisively detailed.

In-Situ Studies of Epitaxial Thin-Film Growth

1964 ◽  
Vol 19 (7-8) ◽  
pp. 835-843 ◽  
Author(s):  
H. Poppa
Keyword(s):  
Film Growth ◽  
High Resolution Electron Microscopy ◽  
Thin Film Growth ◽  
Continuous Observation ◽  
Epitaxial Thin Film ◽  
Epitaxial Thin Film Growth ◽  
Resolution Electron ◽  
Substrate Surfaces ◽  
Kinetics Of

Early stages of oriented overgrowth of Ag, Au, and Pd on thin, single-crystal substrates of mica, molybdenite, Au and Pd were studied by high-resolution electron microscopy and diffraction. Cleaning of substrate surfaces and deposition of evaporated materials were conducted inside an electron microscope. High-magnification, continuous observation during growth permitted investigation of the kinetics of growth. A number of probably elementary epitaxial processes were studied in detail. Nucleation and growth behavior was examined for different supersaturations and free surface energies of substrate and overgrowth materials. The influence of alloying on growth and the spacing of parallel moiré structures was investigated.

In Situ HREm of Reactions at Interfaces

1997 ◽  
Vol 3 (S2) ◽  
pp. 621-622 ◽  
Author(s):  
R. Sinclair ◽  
T. Itoh ◽  
H. J. Lee ◽  
K. W. Kwon
Keyword(s):  
Chemical Interaction ◽  
High Resolution Electron Microscopy ◽  
Point Of View ◽  
Interface Chemistry ◽  
Amorphous Phases ◽  
Resolution Electron ◽  
Analogous Manner ◽  
The Stability ◽  
Basic Studies

Reactions at solid-solid interfaces are important both scientifically and technologically. Firstly, there is quite a wide variety of possibilities. Materials can react with one another, forming equilibrium, meta-stable or even amorphous phases. The interface can provide a means to promote phase reactions kinetically, in an analogous manner to catalysis. Even when the materials are mutually compatible chemically, the interface topography and atomic structure can evolve over the course of time. From the practical point-of-view, changes in the interface chemistry and structure can profoundly alter the physical properties. This is especially notable in thin film technology, whereby the interfaces constitute a signigicant proportion of the whole device. In this article, contributions to understanding this field are illustrated through application of in situ and high-resolution electron microscopy (HREM).Basic studies of metal-semicoductor interfacial reactions have been successfully carried out for a number of years. of increasing importance in microelectronics is the stability of layers which prevent chemical interaction, namely the diffusion barriers.

Structure Refinement of S-Phase Precipitates in Al-Cu-Mg Alloys by Quantitative HRTEM

1999 ◽  
Vol 589 ◽  
Author(s):  
R. Kilaas ◽  
V. Radmilovic ◽  
U. Dahmen
Keyword(s):  
Crystal Structure ◽  
Structural Parameters ◽  
Structure Refinement ◽  
High Resolution Electron Microscopy ◽  
S Phase ◽  
Quantitative Comparison ◽  
Phase Precipitate ◽  
Resolution Electron ◽  
Simulated Images ◽  
Al Matrix

AbstractThe crystal structure of the Al2CuMg S-phase precipitate in an Al matrix has been determined by quantitative high resolution electron microscopy. This work combines techniques of image processing and quantitative comparison between experimental and simulated images with automatic refinement of imaging and structural parameters.

The decagonal quasicrystal formed from an Al–Pd–Mn icosahedral quasicrystal

1995 ◽  
Vol 10 (5) ◽  
pp. 1146-1153 ◽  
Author(s):  
W. Sun ◽  
K. Hiraga
Keyword(s):  
Structural Characteristics ◽  
High Resolution Electron Microscopy ◽  
Icosahedral Quasicrystal ◽  
Two Phase ◽  
Growth Interface ◽  
Decagonal Quasicrystal ◽  
Resolution Electron ◽  
The Matrix ◽  
Solid State Phase Transformation ◽  
Phase Proceeds

We present a detailed investigation on the decagonal quasicrystal (D-phase) formed from an Al-Pd-Mn icosahedral quasicrystal (I-phase) through a solid-state phase transformation, including its formation, compositional and crystallographical relationships with the matrix I-phase, growth mode, and structural characteristics. The as-melt-spun Al70Pd20Mn10 alloy contains only I-phase. By annealing at 800 °C, the D-phase is found to grow cpitaxially from the I-phase to establish a D/I two-phase equilibrium with distinctly different composition between them. The D-phase exhibits a stepped growth interface, which consists of a facet plane, formed by sharing the tenfold plane with a fivefold plane of the matrix I-phase, and some ledges across it. The growth of the D-phase into the I-phase proceeds through lateral movement of the ledges along the tenfold plane. High-resolution electron microscopy reveals that the structure of the D-phase is constructed by an aperiodic arrangement of decagonal atom clusters with definite linkages and long-range quasiperiodic correlation.

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