Dealloying at High Homologous Temperature: Morphology Diagrams

2017 ◽  
Vol 164 (6) ◽  
pp. C330-C337 ◽  
Author(s):  
Ke Geng ◽  
Karl Sieradzki
Keyword(s):  
Homologous Temperature ◽  
High Homologous Temperature

scholarly journals Creep of Single Crystals of Nickel-Based Superalloys at Ultra-High Homologous Temperature

2018 ◽  
Vol 49 (9) ◽  
pp. 3973-3987 ◽  
Author(s):  
Alexander Epishin ◽  
Bernard Fedelich ◽  
Gert Nolze ◽  
Sina Schriever ◽  
Titus Feldmann ◽  
...  
Keyword(s):  
Single Crystals ◽  
Homologous Temperature ◽  
High Homologous Temperature

Enhancing the Operating Life and Performance of Lead-Acid Batteries via Grain-Boundary Engineering

MRS Bulletin ◽  
1999 ◽  
Vol 24 (11) ◽  
pp. 27-32 ◽  
Author(s):  
G. Palumbo ◽  
U. Erb
Keyword(s):  
Grain Boundary Engineering ◽  
Operating Life ◽  
Homologous Temperature ◽  
Dimensional Changes ◽  
Lead Acid Batteries ◽  
Battery Capacity ◽  
Significant Research ◽  
And Performance ◽  
High Homologous Temperature ◽  
Lead Acid

Although conventional lead-acid batteries are considered a rather mature technology, significant research and development efforts are currently under way to enhance their performance and operating life. These efforts are being driven by the demands of both the automotive and stationary (or standby) market sectors. Both major markets have need of lead-acid batteries with higher energy density or reduced size and weight; however, the automotive sector is also driven to mitigate the cycle-life reduction of its “starter, lighting, and ignition” (SLI) batteries that results from rising “under the hood” temperatures in modern automobiles.The operating and cycle lives of leadacid batteries are limited by the resistance of the positive Pb-alloy electrodes to intergranular-degradation processes (i.e., corrosion, cracking, and creep). Figure 1 shows an example of near-through-wall cracking and some inter-granular corrosion (grain-dropping at surface) observed in a Pb-lwt%Sb positive battery grid following approximately four years of service. In addition to the breaching of grid electrical continuity by corrosion and cracking processes (as indicated in Figure 1), the relatively high homologous temperature of operation for lead-acid batteries (i.e., >0.6 Tm, where Tm is the melting temperature) promotes intergranular-creep processes that result in dimensional changes in the electrodes over time (i.e., grid “growth”); this causes adjacent plates to short, leading to reduced battery capacity.

Modeling of High Homologous Temperature Deformation Behavior Using the Viscoplasticity Theory Based on Overstress (VBO): Part II—Characteristics of the VBO Model

1997 ◽  
Vol 119 (1) ◽  
pp. 1-6 ◽  
Author(s):  
Yukio Tachibana ◽  
Erhard Krempl
Keyword(s):  
Hold Time ◽  
Cyclic Strain ◽  
Tensile Tests ◽  
Temperature Deformation ◽  
Extreme Conditions ◽  
Alloy 800H ◽  
Homologous Temperature ◽  
High Homologous Temperature ◽  
Term Creep

Characteristics of the high homologous temperature VBO model under extreme conditions such as very fast and very slow tensile tests, long-term-creep and relaxation tests are investigated via numerical experiments and analysis. To this end, material constants of Alloy 800H determined from other tests in Part I were utilized for the prediction. Although no experiments are available for the extreme conditions, the predictions are plausible. For cyclic, strain controlled hold-time tests the predictions compare well with sparse experimental data. The results give confidence that VBO can be used to predict the long-term behavior at high homologous temperature once the constants have been determined from regular, short-term tests.

Interdiffusion Studies in the Co-Sb System

2020 ◽  
Vol 27 ◽  
pp. 35-39
Author(s):  
Amudha Armugam ◽  
Ravi Raju ◽  
Varun Baheti
Keyword(s):  
Crystal Structure ◽  
Electron Microscope ◽  
Electron Probe ◽  
Diffusion Mechanism ◽  
Bulk Diffusion ◽  
Diffusion Couples ◽  
Homologous Temperature ◽  
The Difference ◽  
High Homologous Temperature ◽  
Scanning Electron

CoSb based compounds have gained much importance in the fields of thermoelectric devices. In this work, we have conducted the solid–state conventional bulk diffusion couple experiments. To study the phase evolutions, Co/Sb diffusion couples are annealed at 450–550 °C. The interdiffusion zone is analysed using field emission gun equipped scanning electron microscope and the composition measurements are done in electron probe micro−analyser to confirm the growth of various product phases. The marker experiment indicates that the CoSb3 phase grows mainly by diffusion of Sb in the binary Co–Sb system. Growth of the CoSb3 phase is discussed based on assessment correlating the difference in mobilities of species with the high homologous temperature, crystal structure of the phase, and the concept of sublattice diffusion mechanism in line compounds.

Modeling of High Homologous Temperature Deformation Behavior Using the Viscoplasticity Theory Based on Overstress (VBO): Part I— Creep and Tensile Behavior

1995 ◽  
Vol 117 (4) ◽  
pp. 456-461 ◽  
Author(s):  
Yukio Tachibana ◽  
Erhard Krempl
Keyword(s):  
Cyclic Hardening ◽  
Back Stress ◽  
Tensile Tests ◽  
Tensile Behavior ◽  
Temperature Deformation ◽  
State Variables ◽  
Homologous Temperature ◽  
Variable Theory ◽  
Alloy 800 ◽  
High Homologous Temperature

The viscoplasticity theory based on overstress (VBO) is a state variable theory without a yield surface and without loading/unloading conditions. It contains two tensor valued state variables, the equilibrium (back) stress and the kinematic stress that is a repository for work hardening (softening). The scalar valued isotropic or time (rate)-independent stress models cyclic hardening (softening). For application to high homologous temperature, the effects of diffusion which counteracts the hardening of inelastic deformation has to be accounted for. Recovery of state terms are introduced in the growth laws for the state variables. A high homologous temperature VBO model is introduced and applied to the creep and tensile tests of Alloy 800 H between 750°C and 1050°C. Primary, secondary and tertiary creep as well as tensile behavior were well reproduced. It is shown that the transition to fluid state can be modeled with VBO.

On the Choice of the Power Law Flow Rule and its Consequences in Crystal Plasticity

2016 ◽  
Vol 725 ◽  
pp. 359-365 ◽  
Author(s):  
Helal Chowdhury ◽  
Holm Altenbach ◽  
Konstantin Naumenko
Keyword(s):  
Power Law ◽  
Crystal Plasticity ◽  
Lattice Rotation ◽  
Internal Variables ◽  
Flow Rule ◽  
Homologous Temperature ◽  
Rate Controlled ◽  
High Homologous Temperature ◽  
Very High ◽  
Classical Crystal

Three types of power law flow rules are commonly used in classical crystal plasticity. These laws are purely phenomenological. The foremost point is how to define operative or effective stress and drag or slip system resistance. Specific choice of the definition leads to a unique number of implications including lattice rotation and slip activities, and we will highlight a few of them. We examined these three flow rules within finite strain framework with a single crystalline Al-rich TiAl binary alloy at very high homologous temperature with three strain rate controlled experimental data . It is revealed that two internal variables based flow rules give better results with a wide variety of applicability in plasticity and related phenomena.

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