scholarly journals Модель растворения пор на границах зерен при отжиге ультрамелкозернистого алюминиевого сплава

2021 ◽  
Vol 47 (18) ◽  
pp. 40
Author(s):  
М.Ю. Гуткин ◽  
Т.С. Орлова ◽  
Н.В. Скиба
Keyword(s):  
Theoretical Model ◽  
Grain Boundary ◽  
Total Energy ◽  
Grain Boundaries ◽  
Ultrafine Grained ◽  
Model Pore ◽  
Ultrafine Grained Materials ◽  
Good Agreement ◽  
Zr Alloy

A theoretical model which describes the mechanism of pore dissolution at grain boundaries in ultrafine-grained materials during the ageing annealing is suggested. Within the framework of the model, pore dissolution occurs due to the emission of vacancies and the climb of grain-boundary dislocations along the grain boundary towards the pore. It is shown that in this case there is a significant decrease in the total energy of the system. The results of the model are in good agreement with the available experimental observations of pore dissolution during annealing of ultrafine-grained Al-Zr alloy.

Mechanism of Stress-Driven Grain Boundary Migration in Nanotwinned Materials

2018 ◽  
Vol 55 (1) ◽  
pp. 21-25 ◽  
Author(s):  
N.V. Skiba
Keyword(s):  
Theoretical Model ◽  
Grain Boundary ◽  
Twin Boundary ◽  
Boundary Migration ◽  
Grain Boundary Migration ◽  
High Angle ◽  
Twin Boundaries ◽  
Critical Stresses ◽  
Ultrafine Grained ◽  
Ultrafine Grained Materials

Abstract Stress-driven grain boundary (GB) migration in ultrafine-grained materials with nanotwinned structure is theoretically described. In the framework of the theoretical model, the stress-driven high-angle GB migration is accompanied by migration of twin boundaries which adjoin this GB. Energetic characteristics and critical stresses of the GB migration accompanied by the twin boundary migration are calculated.

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.

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.

scholarly journals Механизм упрочнения ультрамелкозернистого алюминия после отжига

2019 ◽  
Vol 61 (10) ◽  
pp. 1836
Author(s):  
М.Ю. Гуткин ◽  
Т.А. Латынина ◽  
Т.С. Орлова ◽  
Н.В. Скиба
Keyword(s):  
Plastic Deformation ◽  
Grain Boundary ◽  
Grain Boundaries ◽  
Quantitative Agreement ◽  
Triple Junctions ◽  
Energy Characteristics ◽  
Low Temperature Annealing ◽  
Critical Stresses ◽  
Ultrafine Grained ◽  
Sequential Transformation

A theoretical model is proposed that describes the mechanism of hardening of ultrafine-grained aluminum, obtained by severe plastic torsion deformation, after low-temperature annealing. In the framework of the model, hardening is realized due to the sequential transformation of the grain-boundary dislocation structure. In particular, plastic deformation occurs through the emission of lattice dislocations from triple junctions of grain boundaries containing pile-ups of grain-boundary dislocations, the subsequent sliding of lattice dislocations in the bulk of the grain, and the formation of walls of grain-boundary dislocations climbing along opposite grain boundaries. The energy characteristics and critical stresses for the emission of lattice dislocations are calculated. The theoretical dependences of the flow stress on the plastic deformation are plotted, which show good qualitative and quantitative agreement with experimental data.

The Effect of Grain Boundary Sliding and Strain Rate Sensitivity on the Ductility of Ultrafine-Grained Materials

2010 ◽  
Vol 667-669 ◽  
pp. 677-682 ◽  
Author(s):  
Nguyen Q. Chinh ◽  
Tamás Csanádi ◽  
Jenő Gubicza ◽  
Ruslan Valiev ◽  
Boris Straumal ◽  
...  
Keyword(s):  
Grain Boundary ◽  
Strain Rate ◽  
Strain Rate Sensitivity ◽  
Rate Sensitivity ◽  
Grain Boundary Sliding ◽  
Room Temperature Ductility ◽  
Ultrafine Grained ◽  
Boundary Sliding ◽  
Ultrafine Grained Materials ◽  
High Strain Rate Sensitivity

Most ultrafine-grained (UFG) materials produced by severe plastic deformation (SPD) exibit only limited ductility which is correlated with the low strain rate sensitivity (SRS) of these materials. Recently, it was demonstrated that SPD is capable of increasing the room temperature ductility of aluminum-based alloys attaining elongations up to 150%, together with relatively high strain rate sensitivity. In the present work, additional results and discussions are presented on the effect of grain boundary sliding (GBS) and SRS on the ductility of some UFG metals and alloys. The characteristics of constitutive equations describing the steady-state deformation process are quantitatively analyzed for a better understanding of the effects of grain boundaries and strain rate sensitivity.

Grain Boundary Design of Bulk Nanomaterials for Advanced Properties

2015 ◽  
Vol 5 ◽  
pp. 43-54 ◽  
Author(s):  
Ruslan Z. Valiev
Keyword(s):  
Plastic Deformation ◽  
Grain Boundary ◽  
Severe Plastic Deformation ◽  
Grain Boundaries ◽  
Metals And Alloys ◽  
New Approach ◽  
Petch Relation ◽  
Ultrafine Grained ◽  
Grain Boundary Segregations ◽  
Bulk Nanomaterials

Nanostructuring of metals and alloys by severe plastic deformation techniques is an effective way of enhancing their mechanical and functional properties. The features of the nanostructured materials produced by severe plastic deformation (SPD) are stipulated by forming of ultrafine-sized grains as well as by the state of grain boundaries. The concept of grain boundary (GB) design of ultrafine-grained metals and alloys is developed for enhancement of their properties by tailoring grain boundaries of different types (low-angle and high-angle ones, special and random, equilibrium and nonequilibrium) and formation of grain boundary segregations and precipitations by SPD processing. The paper presents experimental data demonstrating the super-strength and “positive” slope of the Hall-Petch relation when passing from micro-to nanostructured state in a number of metallic materials subjected to severe plastic deformation. The nature of the superior strength is associated with new strengthening mechanisms and the difficulty of generation of dislocations from grain boundaries with segregations. This new approach is used for achieving the enhanced strength in several commercial Al and Ti alloys as well as steels subjected to SPD processing.

The Role of Grain Boundaries and other Defects on Phase Transformations Induced by Severe Plastic Deformation

2015 ◽  
Vol 5 ◽  
pp. 77-92 ◽  
Author(s):  
Xavier Sauvage ◽  
Yana Nasedkina
Keyword(s):  
Plastic Deformation ◽  
Severe Plastic Deformation ◽  
Phase Transformations ◽  
Grain Boundaries ◽  
Mechanical Mixing ◽  
Ultrafine Grained ◽  
Ultrafine Grained Materials ◽  
Underlying Mechanisms ◽  
Scientific Questions

During the past two decades, processing of ultrafine grained materials using severe plastic deformation techniques has attracted great interest in the scientific community. Although the up-scaling of processes and the lack of ductility of ultrafine grained alloys are still some important challenges, these techniques look promising because they produce bulk materials free of porosities. More recently, some strategies to combine precipitation hardening and ultrafine grained structures have been proposed. It has also been shown that nanoscaled composite materials could be successfully processed. This experimental work rose however some very fundamental scientific questions about the influence of severe plastic deformation on the precipitation mechanisms or on the formation of supersaturated solid solution through mechanical mixing. The driving force and the thermodynamics of these phase transformations are of course affected by the high amount of energy stored in severely deformed alloys, especially as interfacial energy. But grain boundaries, with the help of dislocations and point defects, also play an important role in the kinetics. In this paper, it is proposed to shortly review these phenomena and the underlying mechanisms with a special emphasis on the contribution of grain boundaries.

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