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.

Emission Nuclear Gamma-Resonance Spectroscopy of Grain Boundaries in Coarse-Grained and Ultrafine-Grained Polycrystalline Mo

2015 ◽  
Vol 364 ◽  
pp. 147-156 ◽  
Author(s):  
Vladimir V. Popov ◽  
A.V. Sergeev ◽  
A.V. Stolbovsky
Keyword(s):  
High Pressure ◽  
Grain Boundary ◽  
Grain Boundaries ◽  
High Pressure Torsion ◽  
Boundary Segregation ◽  
Grain Boundary Segregation ◽  
Coarse Grained ◽  
Resonance Spectroscopy ◽  
Nuclear Gamma Resonance ◽  
Ultrafine Grained

Grain boundaries in coarse-grained Mo with grain boundaries of recrystallization origin and in ultrafine-grained (UFG) Mo obtained by high pressure torsion have been studied by the emission Mössbauer spectroscopy on the57Co (57Fe) nuclei. It is demonstrated that Co atoms diffuse along grain boundaries by interstitials. The temperature dependence of grain-boundary segregation factor of Co in coarse-grained Mo has been determined. It is shown that the state of Co atoms in grain boundaries and near-boundary areas in UFG Mo differs from that in coarse-grained Mo.

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 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.

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 Statistical model checking for variability-intensive systems: applications to bug detection and minimization

2021 ◽  
Author(s):  
Maxime Cordy ◽  
Sami Lazreg ◽  
Mike Papadakis ◽  
Axel Legay
Keyword(s):  
Model Checking ◽  
Statistical Model ◽  
Linear Time ◽  
The State ◽  
Coarse Grained ◽  
Bug Detection ◽  
Statistical Model Checking ◽  
Fine Grained ◽  
Type 1 Error ◽  
First Case

AbstractWe propose a new Statistical Model Checking (SMC) method to identify bugs in variability-intensive systems (VIS). The state-space of such systems is exponential in the number of variants, which makes the verification problem harder than for classical systems. To reduce verification time, we propose to combine SMC with featured transition systems (FTS)—a model that represents jointly the state spaces of all variants. Our new methods allow the sampling of executions from one or more (potentially all) variants. We investigate their utility in two complementary use cases. The first case considers the problem of finding all variants that violate a given property expressed in Linear-Time Logic (LTL) within a given simulation budget. To achieve this, we perform random walks in the featured transition system seeking accepting lassos. We show that our method allows us to find bugs much faster (up to 16 times according to our experiments) than exhaustive methods. As any simulation-based approach, however, the risk of Type-1 error exists. We provide a lower bound and an upper bound for the number of simulations to perform to achieve the desired level of confidence. Our empirical study involving 59 properties over three case studies reveals that our method manages to discover all variants violating 41 of the properties. This indicates that SMC can act as a coarse-grained analysis method to quickly identify the set of buggy variants. The second case complements the first one. In case the coarse-grained analysis reveals that no variant can guarantee to satisfy an intended property in all their executions, one should identify the variant that minimizes the probability of violating this property. Thus, we propose a fine-grained SMC method that quickly identifies promising variants and accurately estimates their violation probability. We evaluate different selection strategies and reveal that a genetic algorithm combined with elitist selection yields the best results.

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.

scholarly journals Failure mechanisms of titanium VT1−0 and zirconium alloy E110 in ultrafine-grained, fine-grained and coarse-grained states under cyclic loading in gigacycle regime

2018 ◽  
Vol 8 (3) ◽  
pp. 317-322
Author(s):  
O. B. Naimark ◽  
Yu. P. Sharkeev ◽  
A. M. Mairambekova ◽  
M. V. Bannikov ◽  
A. Yu. Eroshenko ◽  
...  
Keyword(s):  
Cyclic Loading ◽  
Zirconium Alloy ◽  
Failure Mechanisms ◽  
Coarse Grained ◽  
Fine Grained ◽  
Ultrafine Grained

scholarly journals Increasing Fatigue Life of 09Mn2Si Steel by Helical Rolling: Theoretical–Experimental Study on Governing Role of Grain Boundaries

Materials ◽  
2020 ◽  
Vol 13 (20) ◽  
pp. 4531
Author(s):  
Sergey Panin ◽  
Ilya Vlasov ◽  
Pavel Maksimov ◽  
Dmitry Moiseenko ◽  
Pavlo Maruschak ◽  
...  
Keyword(s):  
Fatigue Life ◽  
Grain Boundaries ◽  
Elastic Energy ◽  
High Strength ◽  
Coarse Grained ◽  
Material Structure ◽  
Structure Transformation ◽  
Helical Rolling ◽  
Fine Grained ◽  
Fine Grained Structure

The structure and mechanical properties of the 09Mn2Si high-strength low-alloyed steel after the five-stage helical rolling (HR) were studied. It was revealed that the fine-grained structure had been formed in the surface layer ≈ 1 mm deep as a result of severe plastic strains. In the lower layers, the “lamellar” structure had been formed, which consisted of thin elongated ferrite grains oriented in the HR direction. It was shown that the five-stage HR resulted in the increase in the steel fatigue life by more than 3.5 times under cyclic tension. The highest values of the number of cycles before failure were obtained for the samples cut from the bar core. It was demonstrated that the degree of the elastic energy dissipation in the steel samples under loading directly depended on the area of the grain boundaries as well as on the grain shapes. The fine-grained structure possessed the maximum value of the average torsional energy among all the studied samples, which caused the local material structure transformation and the decrease in the elastic energy level. This improved the crack resistance under the cyclic mechanical loading. The effect of the accumulation of the rotational strain modes at the grain boundaries was discovered, which caused the local structure transformation at the boundary zones. In the fine-grained structure, the formation of grain conglomerates was observed, which increased the values of the specific modulus of the moment of force. This could be mutually compensated due to the small sizes of grains. At the same time, the coarse-grained structures were characterized by the presence of the small number of grains with a high level of the moments of forces at their boundaries. They could result in trans-crystalline cracking.

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