Effect of radiation exposure on the structure and diffusion in the near-surface layer of ultrafine-grained nickel

2021 ◽  
pp. 88-93
Author(s):  
G.P. Grabovetskaya ◽  
◽  
I.P. Mishin ◽  
E.N. Stepanova ◽  
A.D. Teresov ◽  
...  
Keyword(s):  
Surface Layer ◽  
Grain Boundary ◽  
Boundary Diffusion ◽  
Diffusion Annealing ◽  
Nickel Surface ◽  
Near Surface ◽  
Pulsed Electron Beam ◽  
Ultrafine Grained ◽  
Isothermal Diffusion ◽  
And Diffusion

The effect of irradiation with a pulsed electron beam (PEB) in the mode of surface melting absence on the copper diffusion in the near-surface layer of ultrafine-grained (UFG) nickel has been studied. The profiles of the copper concentration distribution over depth after isothermal diffusion annealing and annealing under PEB irradiation of the UFG nickel surface are determined. It has been established that as a result of PEB irradiation, the coefficient of grain-boundary diffusion of copper in nickel increases and the mode of grain-boundary heterodiffusion changes in the near-surface layer of nickel in comparison with isothermal diffusion annealing.

scholarly journals Nd-Fe-B Magnets: The Gradient Change of Microstructures and the Diffusion Principle after Grain Boundary Diffusion Process

Materials ◽  
2019 ◽  
Vol 12 (23) ◽  
pp. 3881 ◽  
Author(s):  
Yaojun Lu ◽  
Shuwei Zhong ◽  
Munan Yang ◽  
Chunming Wang ◽  
Liuyimei Yang ◽  
...  
Keyword(s):  
Surface Layer ◽  
Grain Boundary ◽  
Diffusion Process ◽  
Shell Structure ◽  
Boundary Diffusion ◽  
Diffusion Mechanism ◽  
Temperature Stability ◽  
Grain Boundary Diffusion ◽  
Core Shell ◽  
Core Shell Structure

The diffusion of Tb in sintered Nd-Fe-B magnets by the grain boundary diffusion process can significantly enhance coercivity. However, due to the influence of microstructures at different depths, the coercivity increment and temperature stability gradually decreases with the increase of diffusion depth, and exhibit good corrosion resistance at a sub-surface layer (300–1000 μm). According to the Electron Probe Micro-analyzer (EPMA) test results and the diffusion mechanism, the grain boundary and intragranular diffusion behavior under different Tb concentration gradients were analyzed, and the diffusion was divided into three stages. The first stage is located on the surface of the magnet, which formed a thick core-shell structure and a large number of RE-rich phases. The second stage is located in the sub-surface layer, forming a uniform and continuous RE-rich phase and thin core-shell structure. The third stage is located deeper in the magnet, and the Tb enrichment only existed at the triangular grain boundary.

A Model for the Effects of Strain Rate and Temperature on the Deformation Behavior of Ultrafine-Grained Metals

2011 ◽  
Vol 291-294 ◽  
pp. 1173-1177
Author(s):  
Zi Ling Xie ◽  
Lin Zhu Sun ◽  
Fang Yang
Keyword(s):  
Grain Boundary ◽  
Strain Rate ◽  
Deformation Behavior ◽  
Boundary Diffusion ◽  
Rate Sensitivity ◽  
Grain Boundary Sliding ◽  
Dislocation Slip ◽  
Deformation Response ◽  
Ultrafine Grained ◽  
Boundary Sliding

A theoretical model is developed to account for the effects of strain rate and temperature on the deformation behavior of ultrafine-grained fcc Cu. Three mechanisms, including dislocation slip, grain boundary diffusion, and grain boundary sliding are considered to contribute to the deformation response simultaneously. Numerical simulations show that the strain rate sensitivity increases with decreasing grain size and strain rate, and that the flow stress and tensile ductility increase with either increasing strain rate or decreasing deformation temperature.

Constrained Grain Boundary Diffusion In Thin Copper Films

2004 ◽  
Vol 821 ◽  
Author(s):  
Markus J. Buehler ◽  
Alexander Hartmaier ◽  
Huajian Gao
Keyword(s):  
Thin Films ◽  
Theoretical Analysis ◽  
Grain Boundary ◽  
Grain Boundaries ◽  
Boundary Diffusion ◽  
Grain Boundary Diffusion ◽  
Atomic Scale ◽  
Diffusional Creep ◽  
Copper Films ◽  
And Diffusion

AbstractIn a recent study of diffusional creep in polycrystalline thin films deposited on substrates, we have discovered a new class of defects called the grain boundary diffusion wedges (Gao et al., Acta Mat. 47, pp. 2865-2878, 1999). These diffusion wedges are formed by stress driven mass transport between the free surface of the film and the grain boundaries during the process of substrate-constrained grain boundary diffusion. The mathematical modeling involves solution of integro-differential equations representing a strong coupling between elasticity and diffusion. The solution can be decomposed into diffusional eigenmodes reminiscent of crack-like opening displacement along the grain boundary which leads to a singular stress field at the root of the grain boundary. We find that the theoretical analysis successfully explains the difference between the mechanical behaviors of passivated and unpassivated copper films during thermal cycling on a silicon substrate. An important implication of our theoretical analysis is that dislocations with Burgers vector parallel to the interface can be nucleated at the root of the grain boundary. This is a new dislocation mechanism in thin films which contrasts to the well known Mathews-Freund-Nix mechanism of threading dislocation propagation. Recent TEM experiments at the Max Planck Institute for Metals Research have shown that, while threading dislocations dominate in passivated metal films, parallel glide dislocations begin to dominate in unpassivated copper films with thickness below 400 nm. This is consistent with our theoretical predictions. We have developed large scale molecular dynamics simulations of grain boundary diffusion wedges to clarify the nucleation mechanisms of parallel glide in thin films. Such atomic scale simulations of thin film diffusion not only show results which are consistent with both continuum theoretical and experimental studies, but also revealed the atomic processes of dislocation nucleation, climb, glide and storage in grain boundaries. The study should have far reaching implications for modeling deformation and diffusion in micro- and nanostructured materials.

Surface Treatment of Materials with High Current Pulsed Electron Beam

2005 ◽  
Vol 475-479 ◽  
pp. 3959-3962 ◽  
Author(s):  
Sheng Zhi Hao ◽  
B. Gao ◽  
Ai Min Wu ◽  
Jian Xin Zou ◽  
Ying Qin ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Surface Layer ◽  
Electron Beam ◽  
Surface Treatment ◽  
Short Pulse ◽  
Research Work ◽  
High Current ◽  
Near Surface ◽  
Pulsed Electron Beam ◽  
Dynamic Stress Field

High current pulsed electron beam (HCPEB) is now becoming a promising energetic source for the surface treatment of materials. When the concentrated electron flux transferring its energy into a very thin surface layer within a short pulse time, superfast processes such as heating, melting, evaporation and consequent solidification, as well as dynamic stress field induced by an abrupt thermal distribution in the interactive zone impart surface layer with improved physicochemical and mechanical properties. The present paper reports mainly our experimental research work on this new-style technique. Investigations performed with a variety of constructional materials (aluminum, carbon and mold steel, magnesium alloys) have shown that the most pronounced changes of composition, microstructure and properties occur in the near-surface layers, while the thickness of the modified layer with improved mechanical properties (several hundreds of micrometers) is significantly greater than that of the heat-affected zone due to the propagation of stress wave. The surfaces treated with either simply several pulses of bombardment or complex techniques, such as rapid alloying by HCPEB can exhibit improved mechanical and physicochemical properties to some extent.

Nanostructure of 45# Carbon Steel by High Current Pulsed Electron Beam

2009 ◽  
Vol 79-82 ◽  
pp. 317-320
Author(s):  
Hui Zou ◽  
H.R. Jing ◽  
Sheng Zhi Hao ◽  
Chuang Dong
Keyword(s):  
Surface Layer ◽  
Electron Beam ◽  
Electron Microscope ◽  
Carbon Steel ◽  
Short Pulse ◽  
White Layer ◽  
High Current ◽  
Near Surface ◽  
Pulsed Electron Beam ◽  
Modified Surface

When high current pulsed electron beam (HCPEB) transferring its energy into a very thin surface layer within a short pulse time, super fast processes such as heating, melting, evaporation and consequent solidification, as well as dynamic stress induced may impart the surface layer with improved properties. In this paper, HCPEB modification of 45# carbon steel with working parameters of electron energy 25 kV, pulse duration 3.5µs, and energy density 4 J/cm2 was investigated. The microstructures of modified surface were analyzed by scanning electron microscope (SEM) of type JSM 5310 and transmission electron microscope (TEM) of type H-800. It is found that the modified surface layer can be divided into three zones: the white layer or melted layer of depth 3 to10µm, the heat and stress effecting zone 10 µm below and about 250 µm, then matrix, where a nanostructure and/or amorphous layer formed in the near-surface region. It is proved that the whole treatment process is not complex and cost-effective, and has a substantial potential to be applied in industries.

Oxygen Diffusion along Symmetric [0001] Tilt Grain Boundaries in α-Alumina

2006 ◽  
Vol 317-318 ◽  
pp. 415-418 ◽  
Author(s):  
Tsubasa Nakagawa ◽  
Isao Sakaguchi ◽  
Katsuyuki Matsunaga ◽  
Takahisa Yamamoto ◽  
Hajime Haneda ◽  
...  
Keyword(s):  
Grain Boundary ◽  
Grain Boundaries ◽  
Oxygen Diffusion ◽  
Isotopic Exchange ◽  
Boundary Diffusion ◽  
Depth Profiling ◽  
Grain Boundary Diffusion ◽  
Symmetric Tilt ◽  
And Diffusion ◽  
Diffusion Properties

Grain boundary diffusion coefficients of oxygen (δDgb) at 1793K in high purity α-alumina bicrystals with Σ7{2 _ ,310}/[0001] and Σ31{7 _ ,1140}/[0001] symmetric tilt grain boundaries were measured by means of the isotopic exchange and diffusion depth profiling using SIMS. δDgb of both grain boundaries were determined to be 7.1x10-24 [m3/sec] for Σ7 grain boundary and 5.3 x10-24 [m3/sec] for Σ31 grain boundary, respectively. These results indicate that Σ values do not directly relate to grain boundary diffusion properties.

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.

Threshold Character of Zn Diffusion into InP

1998 ◽  
Vol 527 ◽  
Author(s):  
A.V. Kamanin ◽  
Yu.A. Kudryavtsev ◽  
N.M. Shmidt
Keyword(s):  
Surface Layer ◽  
Near Surface ◽  
Zn Diffusion ◽  
Diffusion Stage ◽  
Threshold Character ◽  
Isothermal Diffusion ◽  
Diffusion Temperature ◽  
Heavily Doped

ABSTRACTThe initial diffusion stage (lIDS) of Zn in InP from polymer spin-on films has been investigated. The threshold diffusion temperature of 375°C has been established. It has been found that the heavily-doped near-surface layer, that consisted of electrically neutral zinc-containing complexes, was formed at IDS, while a low part of Zn was electrically active. The Zn diffusivity during IDS has been found to be at least two orders of magnitude more than the Zn diffusivity obtained after an isothermal diffusion.

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