Diffusion in Ultrafine Grained Materials

2008 ◽  
Vol 584-586 ◽  
pp. 1012-1017 ◽  
Author(s):  
Sergiy V. Divinski ◽  
Gerhard Wilde
Keyword(s):  
Grain Boundaries ◽  
Short Circuit ◽  
High Mobility ◽  
Coarse Grained ◽  
Kinetic Properties ◽  
Fine Grained ◽  
Ultrafine Grained ◽  
Ultrafine Grained Materials ◽  
Diffusion Rates ◽  
Short Circuit Diffusion

The paper provides an overview of recent results of the radiotracer investigations of short-circuit diffusion in ultra fine grained (UFG) materials produced by severe plastic deformation (SPD). Different material classes (copper of different purity levels and Cu alloys) are considered. The study is focused on the existence of non-equilibrium grain boundaries after SPD. Although a dominant contribution of common high-angle grain boundaries with very similar diffusivities as those in the corresponding coarse-grained material is established, much faster diffusion rates are also observed experimentally. The nature and kinetic properties of these “high mobility” paths in different materials are investigated and critically discussed.

Mössbauer Spectroscopy of Grain Boundaries in Ultrafine-Grained Metal Materials

2014 ◽  
Vol 783-786 ◽  
pp. 2671-2676 ◽  
Author(s):  
Vladimir V. Popov
Keyword(s):  
Grain Boundaries ◽  
The State ◽  
Coarse Grained ◽  
Resonance Spectroscopy ◽  
Fine Grained ◽  
Nuclear Gamma Resonance ◽  
Ultrafine Grained ◽  
Emission Mode ◽  
Metal Materials

Capabilities of the Mössbauer (nuclear gamma-resonance) spectroscopy for investigation of the state of grain boundaries in ultra-fine grained materials are analyzed, and the main problems of such studies are discussed. The emission and absorption NGR spectroscopy are compared, and it is demonstrated that the emission mode of the Mössbauer spectroscopy is preferential for GB studies. These studies enable to reveal differences in the state of GBs in ultra-fine grained materials and coarse-grained polycrystals with GBs of recrystallization origin.

Application of Nuclear Gamma-Resonance Spectroscopy for Determination of Grain-Boundary Diffusion Characteristics and the State of Grain Boundaries

2019 ◽  
Vol 391 ◽  
pp. 201-214
Author(s):  
Vladimir V. Popov
Keyword(s):  
Grain Boundary ◽  
Grain Boundaries ◽  
Boundary Diffusion ◽  
Grain Boundary Diffusion ◽  
Coarse Grained ◽  
Resonance Spectroscopy ◽  
Diffusion Parameters ◽  
Ultrafine Grained ◽  
Ultrafine Grained Materials

Capabilities of application of Mössbauer spectroscopy for determination of grain-boundary diffusion parameters in coarse-grained and ultrafine-grained materials have been analyzed. Application of this method for revealing of non-equilibrium state of grain boundaries in ultrafine-grained materials obtained by severe plastic deformation is demonstrated.

Diffusion in Nanostructured Materials

2009 ◽  
Vol 289-292 ◽  
pp. 623-632 ◽  
Author(s):  
Sergiy V. Divinski
Keyword(s):  
Nanostructured Materials ◽  
Short Circuit ◽  
Coarse Grained ◽  
Kinetic Properties ◽  
Diffusion Kinetics ◽  
High Angle ◽  
Temperature Diffusion ◽  
Diffusion Paths ◽  
Short Circuit Diffusion ◽  
Proper Account

Recent results on diffusion in nanostructured materials are reviewed. The analysis highlights the importance of the proper account for a hierarchic microstructure which is often formed in nanostructured materials. The diffusion kinetics is such a material requires a special consideration in dependence on the temperature, diffusion time and the segregation level of the solute. Pressure-less sintering results in clustering of nanograins with significantly enhanced diffusivity of the inter-agglomerate boundaries. Severe plastic deformation produces a broad spectrum of high-angle grain boundaries (GBs) with different kinetic properties. The majority of the high-angle GBs reveals diffusivities very similar to those of general high-angle GBs in their well-annealed coarse-grained counterparts. Nevertheless, considerably faster short-circuit diffusion paths are detected, too. The origin, geometric arrangement, structural and kinetic properties of these high-diffusivity paths are comprehensively investigated and discussed.

Properties of Ultrafine-Grained Tungsten Prepared by Ball Milling and Spark Plasma Sintering

2016 ◽  
Vol 821 ◽  
pp. 399-404 ◽  
Author(s):  
Monika Vilémová ◽  
Barbara Nevrlá ◽  
Zdenek Pala ◽  
Lenka Kocmanová ◽  
Marek Janata ◽  
...  
Keyword(s):  
Ball Milling ◽  
Spark Plasma Sintering ◽  
Ball Mill ◽  
Planetary Ball Mill ◽  
Coarse Grained ◽  
First Wall ◽  
Fine Grained ◽  
Plasma Sintering ◽  
Ultrafine Grained ◽  
Spark Plasma

Tungsten is currently considered as the most suitable plasma facing material for the first wall of a nuclear fusion reactor. First wall will be subjected to harsh conditions that will gradually deteriorate properties of the wall material. Some studies point out that fine-grained tungsten could be more resistant to the structure and property changes than coarse-grained tungsten. However, tailoring of tungsten microstructure is very laborious. Due to its high melting point, tungsten is very often processed mechanically and subsequently sintered into a compact body. In this study, preparation of ultrafine-grained tungsten by mechanical processing in a planetary ball mill was examined. Three types of tungsten samples were compared. One was made from coarse grained tungsten powder consolidated by SPS (spark plasma sintering). Other two samples were prepared from the powder processed in a planetary ball mill with and without addition of Y2O3. After ball milling, the powders were consolidated by SPS, i.e. fast sintering process that allows preserving fine-grained structure of the powder material. Properties of the samples such as hardness and thermal conductivity were examined and correlated with the processing history and microstructure.

Fatigue Crack Growth in Ultrafine-Grained Copper Obtained by ECAP

2014 ◽  
Vol 891-892 ◽  
pp. 1099-1104 ◽  
Author(s):  
Mandana Arzaghi ◽  
Christine Sarrazin-Baudoux ◽  
Jean Petit
Keyword(s):  
Crack Growth ◽  
Growth Rates ◽  
Fatigue Cracks ◽  
Deformation Texture ◽  
Coarse Grained ◽  
Fine Grained ◽  
Angular Pressing ◽  
Ultrafine Grained ◽  
Crack Growth Rates ◽  
Threshold Regime

The propagation of long fatigue cracks in ultra fine-grained (UFG) copper obtained by equal channel angular pressing (ECAP) is investigated in the mid ΔK range and in the near threshold regime. The crack growth rates in UFG copper are substantially faster than in coarse-grained (CG) copper. A huge influence of environment is observed, with growth rates faster of more than two orders of magnitude in air compared to vacuum. The crack growth mechanisms are discussed on the basis of microfractographic observations and the deformation texture.

scholarly journals FINE GRAINED DUAL PHASE STEEL BY THERMO MECHANICAL PROCESSING

2013 ◽  
pp. 237-240
Author(s):  
NEERAJAGARWAL NEERAJAGARWAL ◽  
G.P. CHAUDHARI ◽  
S.K. NATH
Keyword(s):  
Dual Phase Steel ◽  
Intercritical Annealing ◽  
Hsla Steel ◽  
Coarse Grained ◽  
Dual Phase ◽  
Mechanical Processing ◽  
Dp Steel ◽  
Fine Grained ◽  
Ultrafine Grained ◽  
Open Die Forging

The effect of thermo mechanical processing (TMP) on the mechanical properties of HSLA steel was investigated. TMP was conducted using a laboratory open die forging machine.Multiaxial forging (MAF) and intercritical annealing methods were used. TMP is designed to obtain ultrafine grained (UFG) steels. MAF is performed on prismatic shaped samples up to nine strain forging steps to produce ultra-fine grained (UFG) ferrite-pearlite steel with higher strength as compare to as received steel.Fine grained (FG) ferrite-martensite dual phases (DP) steel was fabricated by using combined effect of warm MAF and intercritical annealing. The tensile strength of FG-DP steels was much higher than that of the coarse-grained (CG) counterpart, and the uniform elongations were significantly enhanced. This steel exhibited the superior combination of higher strength and more rapid strain hardening compared to those of CG-DP steel was explained in terms of their specific microstructural features.

Effect of Grain Boundary State on Diffusion and Diffusion-Controlled Processes in Ultrafine-Grained Materials Processed by Severe Plastic Deformation

2015 ◽  
Vol 5 ◽  
pp. 111-126
Author(s):  
Evgeny V. Naydenkin ◽  
Galina P. Grabovetskaya ◽  
I.P. Mishin
Keyword(s):  
Plastic Deformation ◽  
Grain Boundary ◽  
Severe Plastic Deformation ◽  
Grain Boundaries ◽  
Experimental Studies ◽  
Boundary State ◽  
Diffusion Controlled ◽  
Ultrafine Grained ◽  
Ultrafine Grained Materials ◽  
And Diffusion

Experimental studies on the grain boundary diffusion and processes controlled by it in the ultrafine-grained metallic materials produced by various methods of severe plastic deformation are reviewed. Correlation between the increased diffusion permeability of grain boundaries and features of recrystallization and deformation development in these materials possessing the non-equilibrium state of grain boundaries formed during severe plastic deformation in the temperature range of T < 0.35Tm is demonstrated and analyzed.

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