The State of Grain Boundaries and Grain-Boundary Diffusion in Ultrafine-Grained Mo Obtained by Severe Plastic Deformation

2016 ◽  
Vol 367 ◽  
pp. 130-139 ◽  
Author(s):  
Vladimir V. Popov ◽  
A.V. Sergeev
Keyword(s):  
Plastic Deformation ◽  
High Pressure ◽  
Grain Boundary ◽  
Severe Plastic Deformation ◽  
Grain Boundaries ◽  
Boundary Diffusion ◽  
High Pressure Torsion ◽  
Grain Boundary Diffusion ◽  
Fast Diffusion ◽  
Non Equilibrium

The grain-boundary diffusion of Co in ultra-fine grained Mo processed by high-pressure torsion has been studied by emission Mössbauer spectroscopy and radio-tracer analysis. It is demonstrated that under the severe plastic deformation by high-pressure torsion the non-equilibrium grain boundaries are formed which are the ultra-fast diffusion paths. At annealing in the temperature range of 623-823 K the relaxation of the non-equilibrium boundaries proceeds and their properties approach to those of equilibrium boundaries of recrystallization origin.

Modern Models of Grain Boundary Diffusion

2011 ◽  
Vol 312-315 ◽  
pp. 1116-1125
Author(s):  
Vladimir V. Popov
Keyword(s):  
Plastic Deformation ◽  
Grain Boundary ◽  
Severe Plastic Deformation ◽  
Nanocrystalline Materials ◽  
Boundary Diffusion ◽  
Grain Boundary Diffusion ◽  
Coarse Grained ◽  
Gas Condensation ◽  
Non Equilibrium

Recent models of grain-boundary diffusion are briefly reviewed. Models of diffusion along equilibrium boundaries of recrystallization origin in coarse-grained materials and along non-equilibrium boundaries in nanocrystalline materials obtained by gas condensation and compacting or by severe plastic deformation are considered separately.

Structure and Properties of Grain Boundaries in Submicrocrystalline W Obtained by Severe Plastic Deformation

2009 ◽  
Vol 283-286 ◽  
pp. 629-638 ◽  
Author(s):  
Vladimir V. Popov ◽  
Ruslan Valiev ◽  
E.N. Popova ◽  
A.V. Sergeev ◽  
A.V. Stolbovsky ◽  
...  
Keyword(s):  
Thermal Stability ◽  
Plastic Deformation ◽  
High Pressure ◽  
Severe Plastic Deformation ◽  
Grain Boundaries ◽  
High Pressure Torsion ◽  
Submicrocrystalline Structure ◽  
Emission Mössbauer Spectroscopy ◽  
Structure And Properties ◽  
Initial State

Submicrocrystalline structure of W obtained by severe plastic deformation (SPD) by high pressure torsion (5 revolutions of anvils at 4000C) and its thermal stability have been examined by TEM. Grain boundaries of submicrocrystalline W have been studied by the method of the emission Mössbauer spectroscopy in the initial state and after annealing at 400-6000С.

Grain Boundary Diffusion of Hydrogen in Nano-Structured Pd/Ag Alloy Membranes

2008 ◽  
Author(s):  
Logan S. McLeod ◽  
Levent F. Degertekin ◽  
Andrei G. Fedorov
Keyword(s):  
Grain Boundary ◽  
Diffusion Process ◽  
Grain Boundaries ◽  
Boundary Diffusion ◽  
Grain Boundary Diffusion ◽  
Coarse Grained ◽  
Appreciable Amount ◽  
Bottom Surface ◽  
Fast Diffusion ◽  
Average Grain Size

Palladium and its alloys have long been used as hydrogen separation membranes due to their extremely high permeability and selectivity to hydrogen over all other gases [1]. The hydrogen permeation process begins with selective chemisorption of the gas onto the metal surface. As the adsorption process is the point in the permeation sequence where the majority of gases become excluded, it follows that a cleverly designed device could be created to take advantage of the so-called ‘fast’ diffusion paths of surface and grain-boundary diffusion to further enhance permeability without sacrificing selectivity. The contribution of grain-boundary diffusion to the overall permeation rate is dependent on the relative volume in the membrane occupied by grain-boundaries versus bulk material. Typically, grain boundaries only make up a miniscule fraction of the overall volume and therefore only contribute an appreciable amount to the overall diffusion process at temperatures low enough to make the bulk diffusion process nearly stagnant. However, in the case of a nanostructured membrane this paradigm is no longer valid. The fabrication methods associated with extremely thin membrane deposition typically lead to highly non-equilibrium microstructure with an average grain size on the order of tens of nanometers [2]. In order to exploit the potential advantages of grain boundary diffusion the nano-scale grains must persist throughout operation. To avoid the tendency for the grain structure to relax to a more equiaxed, coarse-grained morphology the self-diffusion of metal atoms in the film must be minimized by operating the membranes at a temperature much lower than the membrane melting temperature. Figure 1 shows the microstructural changes in a thin, sputtered, Pd/Ag alloy film before and after annealing. The initial fine-grained structure on the bottom surface of the membrane is due to a combination of low substrate temperature during deposition and the Ti adhesion layer onto which the Pd/Ag layer was deposited. After annealing at 400 C the grains have coarsened and the top and bottom structure are identical.

Grain-boundary diffusion of nickel in submicrocrystalline molybdenum processed by severe plastic deformation

2008 ◽  
Vol 34 (2) ◽  
pp. 136-138 ◽  
Author(s):  
G. P. Grabovetskaya ◽  
I. P. Mishin ◽  
I. V. Ratochka ◽  
S. G. Psakhie ◽  
Yu. R. Kolobov
Keyword(s):  
Plastic Deformation ◽  
Grain Boundary ◽  
Severe Plastic Deformation ◽  
Boundary Diffusion ◽  
Grain Boundary Diffusion

Grain-Boundary Diffusion of 57Co in Ultrafine Nickel after Severe Plastic Deformation

2021 ◽  
Vol 122 (10) ◽  
pp. 976-980
Author(s):  
E. V. Osinnikov ◽  
S. A. Murzinova ◽  
A. Yu. Istomina ◽  
V. V. Popov ◽  
A. V. Stolbovskiy ◽  
...  
Keyword(s):  
Plastic Deformation ◽  
Grain Boundary ◽  
Severe Plastic Deformation ◽  
Boundary Diffusion ◽  
Grain Boundary Diffusion ◽  
Ultrafine Nickel

NGR Investigation of Grain-Boundary Diffusion in Poly- and Nanocrystalline Nb

2007 ◽  
Vol 263 ◽  
pp. 69-74 ◽  
Author(s):  
Vladimir V. Popov ◽  
V.N. Kaigorodov ◽  
E.N. Popova ◽  
A.V. Stolbovsky
Keyword(s):  
High Pressure ◽  
Grain Boundary ◽  
Emission Spectroscopy ◽  
Boundary Diffusion ◽  
High Pressure Torsion ◽  
Grain Boundary Diffusion ◽  
Recrystallization Annealing

The properties of grain boundary cores and adjacent areas in polycrystalline Nb manufactured by rolling with subsequent recrystallization annealing and nanocrystalline Nb obtained by high pressure torsion have been investigated by the Mössbauer emission spectroscopy on 119mSn nuclei.

Grain Boundary Diffusion-Controlled Processes and Properties of Bulk Nanostructured Alloys and Steels

2006 ◽  
Vol 503-504 ◽  
pp. 141-148 ◽  
Author(s):  
Yu.R. Kolobov ◽  
Konstantin Ivanov
Keyword(s):  
Plastic Deformation ◽  
Grain Boundary ◽  
Severe Plastic Deformation ◽  
Boundary Diffusion ◽  
Diffusion Processes ◽  
Grain Boundary Diffusion ◽  
Controlled Processes ◽  
Bioactive Coating ◽  
Diffusion Controlled ◽  
Theoretical Investigations

The experimental and theoretical investigations of grain boundary diffusion processes have been performed using metals and alloys in nanostructured state produced by severe plastic deformation and the respective polycrystalline counterparts. The main features of diffusioncontrolled mechanisms of plastic deformation observed by the creep of nanostructured metals are considered. The use of severe plastic deformation treatment and of the effect of activation of diffusion-controlled processes for enhancing the properties of nanostructured steels and alloys designed for engineering and medical applications (nanostructured titanium-bioactive coating composite included) is described and examples are offered.

scholarly journals The Effect of Predeformation on Creep Strength of 9% Cr Steel

Materials ◽  
2020 ◽  
Vol 13 (23) ◽  
pp. 5330
Author(s):  
Petr Král ◽  
Jiří Dvořák ◽  
Wolfgang Blum ◽  
Václav Sklenička ◽  
Zenji Horita ◽  
...  
Keyword(s):  
Plastic Deformation ◽  
High Pressure ◽  
Severe Plastic Deformation ◽  
Grain Boundaries ◽  
High Pressure Torsion ◽  
Tensile Creep ◽  
Initial Stresses ◽  
High Angle ◽  
Creep Tests ◽  
P92 Steel

Martensitic creep-resistant P92 steel was deformed by different methods of severe plastic deformation such as rotation swaging, high-pressure sliding, and high-pressure torsion at room temperature. These methods imposed significantly different equivalent plastic strains of about 1–30. It was found that rotation swaging led to formation of heterogeneous microstructures with elongated grains where low-angle grain boundaries predominated. Other methods led to formation of ultrafine-grained (UFG) microstructures with high frequency of high-angle grain boundaries. Constant load tensile creep tests at 873 K and initial stresses in the range of 50 to 300 MPa revealed that the specimens processed by rotation swaging exhibited one order of magnitude lower minimum creep rate compared to standard P92 steel. By contrast, UFG P92 steel is significantly softer than standard P92 steel, but differences in their strengths decrease with increasing stress. Microstructural results suggest that creep behavior of P92 steel processed by severe plastic deformation is influenced by the frequency of high-angle grain boundaries and grain coarsening during creep.

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