Electron work function at grain boundary and the corrosion behavior of nanocrystalline metallic materials

2005 ◽  
Vol 887 ◽  
Author(s):  
D. Y. Li
Keyword(s):  
Corrosion Resistance ◽  
Grain Boundary ◽  
Grain Boundaries ◽  
Work Function ◽  
Nanocrystalline Materials ◽  
Minimum Energy ◽  
Electron Work Function ◽  
Chemical Properties ◽  
Nanocrystalline Structure ◽  
Boundary Density

ABSTRACTDue to their high grain boundary density, nanocrystalline materials possess unusual mechanical, physical and chemical properties. Extensive research on nanocrystalline materials has been conducted in recent years. Many studies have shown that corrosion, one of important properties of nanocrystalline materials, is crucial to their applications. In this article, the activity of electrons at grain boundaries of metallic surfaces is analyzed based the electron work function (EWF), the minimum energy required to attract electrons from inside a metal. It is demonstrated that at grain boundaries, the electron work function decreases, indicating that at a grain boundary, electrons are more active. As a result, the surface becomes more electrochemically reactive. Such increase in electrochemical reactivity has negative effect on the corrosion resistance of nanocrystalline materials. However, for a passive nanocrystalline metal or alloy, the nanocrystalline structure is beneficial to its corrosion resistance through rapid formation of a protective passive film. The mechanisms responsible for the variation in EWF at grain boundary and effects of nanocrystallization on corrosion are discussed in this article.

EFFECT OF GRAIN SIZE ON THE ELECTRON WORK FUNCTION OF Cu AND Al

2004 ◽  
Vol 11 (02) ◽  
pp. 173-178 ◽  
Author(s):  
WEN LI ◽  
D. Y. LI
Keyword(s):  
Grain Size ◽  
Phase Transformation ◽  
Grain Boundary ◽  
Work Function ◽  
Electron Work Function ◽  
Deformation Texture ◽  
Kelvin Probe ◽  
Surface Conditions ◽  
The Mean ◽  
Sophisticated Instrument

The Kelvin probe is a sophisticated instrument which is very sensitive to changes in surface conditions, such as deformation, texture, phase transformation and contamination. Efforts have been made to use this technique to diagnose wear. In this study, the effect of the grain boundary (GB) on the electron work function (EWF) was examined with the aim of investigating the contribution of changes in grain size to total changes in the EWF during wear. Copper and aluminum were studied as examples. It was demonstrated that the EWF dropped in the vicinity of GB's and the mean EWF decreased as the grain size decreased. The mechanism responsible for the changes in the EWF with respect to the GB is discussed.

Understanding the low corrosion potential and high corrosion resistance of nano-zinc electrodeposit based on electron work function and interfacial potential difference

RSC Advances ◽  
2016 ◽  
Vol 6 (100) ◽  
pp. 97606-97612 ◽  
Author(s):  
Qingyang Li ◽  
Hao Lu ◽  
Juan Cui ◽  
Maozhong An ◽  
Dongyang (D. Y.) Li
Keyword(s):  
Corrosion Resistance ◽  
Work Function ◽  
Corrosion Potential ◽  
Electron Work Function ◽  
Coarse Grained ◽  
High Corrosion Resistance ◽  
Corrosion Behaviors ◽  
Interfacial Potential ◽  
Nano Zinc ◽  
Zinc Coatings

The corrosion behaviors of coarse-grained and nanocrystalline zinc coatings and correlated the corrosion potential with electron stability are investigated.

scholarly journals Segregation of P and S Impurities to A Σ9 Grain Boundary in Cu

Metals ◽  
2020 ◽  
Vol 10 (10) ◽  
pp. 1362
Author(s):  
Cláudio M. Lousada ◽  
Pavel A. Korzhavyi
Keyword(s):  
Grain Boundary ◽  
Grain Boundaries ◽  
Coordination Number ◽  
High Performance ◽  
Chemical Properties ◽  
Atomic Scale ◽  
Atomic Site ◽  
Segregation Energy ◽  
Physical Chemical ◽  
Symmetric Tilt

The segregation of P and S to grain boundaries (GBs) in fcc Cu has implications in diverse physical-chemical properties of the material and this can be of particular high relevance when the material is employed in high performance applications. Here, we studied the segregation of P and S to the symmetric tilt Σ9 (22¯1¯) [110], 38.9° GB of fcc Cu. This GB is characterized by a variety of segregation sites within and near the GB plane, with considerable differences in both atomic site volume and coordination number and geometry. We found that the segregation energies of P and S vary considerably both with distance from the GB plane and sites within the GB plane. The segregation energy is significantly large at the GB plane but drops to almost zero at a distance of only ≈3.5 Å from this. Additionally, for each impurity there are considerable variations in energy (up to 0.6 eV) between segregation sites in the GB plane. These variations have origins both in differences in coordination number and atomic site volume with the effect of coordination number dominating. For sites with the same coordination number, up to a certain atomic site volume, a larger atomic site volume leads to a stronger segregation. After that limit in volume has been reached, a larger volume leads to weaker segregation. The fact that the segregation energy varies with such magnitude within the Σ9 GB plane may have implications in the accumulation of these impurities at these GBs in the material. Because of this, atomic-scale variations of concentration of P and S are expected to occur at the Σ9 GB center and in other GBs with similar features.

Equilibrium Shapes of Pb Inclusions at 90° Tilt Grain Boundaries in Al

1996 ◽  
Vol 54 ◽  
pp. 364-365
Author(s):  
E. Johnson ◽  
U. Dahmen ◽  
S.-Q. Xiao ◽  
A. Johansen
Keyword(s):  
Grain Boundary ◽  
Grain Boundaries ◽  
Nearest Neighbor ◽  
Lattice Mismatch ◽  
Equilibrium Shape ◽  
Minimum Energy ◽  
Aluminum Matrix ◽  
Spherical Cap ◽  
Polycrystalline Aluminum ◽  
Aluminum Films

Ion implantation of lead in aluminum leads to spontaneous phase separation and formation of dense distributions of nanosized lead inclusions[1]. The inclusions have fee structure, and despite the large lattice mismatch (aA1 = 0.4048 nm and aPb = 0.495 nm) they grow in parallel-cube topotaxy with the matrix. Their shape is cuboctahedral with larger {111} facets and smaller {100} facets which is the minimum- energy shape for an fee crystal in equilibrium with its vapor, as calculated by considering only nearest neighbor bonds. Implantation of polycrystalline aluminum films is accompanied by preferential nucle- ation and enhanced growth of inclusions in the grain boundaries. In adapting their equilibrium shape, grain boundary inclusions will be subject to a larger number of constraints than inclusions in the bulk matrix. This may result in a variety of morphologies characteristic for different types of grain boundaries.In the present study we have used a well-defined bicrystal geometry to study the morphology and structure of lead grain boundary inclusions in mazed bicrystal aluminum films containing mainly 90°<110> tilt boundaries with fixed misorientation but variable inclination[2]. It was found that the shape, size and orientation of the inclusions in the grain boundaries depend on the inclination, i.e. the orientation of the grain boundary plane. Inclusions were all single crystalline and invariably faceted toward one aluminum grain and more rounded toward the other grain (fig.l). Independent of grain boundary inclination, the faceted side was a section of the cuboctahedral equilibrium shape of inclusions in parallel topotaxy with the bulk aluminum matrix. The rounded side, where the inclusions were rotated by 90° with respect to the aluminum lattice, approximated a spherical cap consisting partly of somewhat flatter segments with complex faceting, illustrating the lack of distinctly flat low-energy facets.

scholarly journals Effect of Grain Boundaries on the Electron Work Function of Ultrafine Grained Aluminum

2018 ◽  
Vol 57 (1) ◽  
pp. 110-115 ◽  
Author(s):  
T.S. Orlova ◽  
A.V. Ankudinov ◽  
A.M. Mavlyutov ◽  
N.N. Resnina
Keyword(s):  
Grain Size ◽  
Grain Boundaries ◽  
Work Function ◽  
High Pressure Torsion ◽  
Electron Work Function ◽  
Ultrafine Grained ◽  
Average Grain Size ◽  
Different Temperatures ◽  
First Time ◽  
Specific Length

Abstract The electron work function (EWF) of ultrafine grained (UFG) aluminum structured by high pressure torsion (HPT) has been investigated. For the first time, the dependence of the EWF on the specific length of grain boundaries (or the grain size) for UFG Al has been obtained. The change of average grain size was achieved by short term annealing of HPT-processed aluminum at different temperatures from the range 90-400 °C. It has been shown that the state of grain boundaries (GBs) affects the magnitude of the EWF. It has been found that the transformation of GBs due to annealing at 90 °C from a nonequilibrium to more equilibrium state while maintaining the specific length of GBs and their average misorientation is accompanied by a decrease in average GB specific energy by 0.3 J m-2. This transition provides a sharp increase in the EWF of the UFGAl by 0.25 eV.

Sub-grain Boundary Spacing in Directionally Crystallized Si Films Obtained via Sequential Lateral Solidification

2000 ◽  
Vol 621 ◽  
Author(s):  
M. A. Crowder ◽  
A. B. Limanov ◽  
James S. Im
Keyword(s):  
Energy Density ◽  
Grain Boundary ◽  
Film Thickness ◽  
Grain Boundaries ◽  
Directionally Solidified ◽  
Boundary Density ◽  
Straight Line ◽  
Preliminary Model ◽  
Sequential Lateral Solidification ◽  
Si Films

ABSTRACTIn this paper, we report on the average linear density of sub-grain boundaries that are found in directionally solidified microstructures obtained via sequential lateral solidification of Si thin films. Specifically, we have characterized the dependence of the sub-grain boundary density on the film thickness, incident energy density, and per-pulse translation distance. The investigation was confined to analyzing directionally solidified microstructures obtained using straight-line beamlets. It is found that the average spacing of the sub-grain boundaries depended approximately linearly on the film thickness, where it varied from 0.28m at a thickeness of 550Å to ∼0.75μm at 2,000 Å. In contrast, variations in either the energy density or the per-pulse translation distance within the investigated SLS process parameter domain were found to have a negligible effect on the spacing. Discussion is provided on a preliminary model that invokes polygonization of thermal-stress generated dislocations, and on implications of the dependence of device performance on the film thickness.

Effects of interrupted aging on the intergranular corrosion behavior of Al–Cu–Mg–Ag heat-resistant alloy

2016 ◽  
Vol 13 (6) ◽  
pp. 476-481 ◽  
Author(s):  
Ruijie Zhang ◽  
Xiaoyan Liu ◽  
Zhaopeng Wang ◽  
Fei Gao
Keyword(s):  
Corrosion Resistance ◽  
Grain Boundary ◽  
Grain Boundaries ◽  
Corrosion Behavior ◽  
Intergranular Corrosion ◽  
Al Alloy ◽  
Content Type ◽  
Heat Resistant Alloy ◽  
Resistant Alloy ◽  
Heat Resistant

Purpose The purpose of this study is to research the effects of interrupted aging on the corrosion behavior of Al–Cu–Mg–Ag heat-resistant alloy by means of intergranular corrosion (IGC) testing, potentiodynamic polarization combined with optical microscopy and transmission electron microscopy. Design/methodology/approach The results show that the IGC began on the grain boundaries and continued along the grain boundary. The corrosion resistance property of Al–Cu–Mg–Ag alloy was enhanced by interrupted aging. The precipitations of the interrupted aged sample both in the grains and on the grain boundaries were fine, and the chain-like phases on the grain boundary were distributed nearly continuously. Findings The corrosion resistance of Al–Cu–Mg series Al alloy with equilibrium phase (Al2Cu) is notably determined by precipitation-free zone (PFZ) as the self-corrosion potentials of (Al2Cu), PFZ and the matrix satisfied the relation EPFZ < Eθ<EMatrix. Originality/value The connections of the PFZ on both sides of the grain boundary decreased the corrosion resistance of Al–Cu–Mg–Ag alloy treated by the single aging.

An abnormal correlation between electron work function and corrosion resistance in Ti-Zr-Be-(Ni/Fe) metallic glasses

2020 ◽  
Vol 165 ◽  
pp. 108392 ◽  
Author(s):  
Jia-Lun Gu ◽  
Yang Shao ◽  
Heng-Tong Bu ◽  
Ji-Li Jia ◽  
Ke-Fu Yao
Keyword(s):  
Corrosion Resistance ◽  
Work Function ◽  
Metallic Glasses ◽  
Electron Work Function

scholarly journals The Evolution and Distribution of Microstructures in High-Energy Laser-Welded X100 Pipeline Steel

Materials ◽  
2019 ◽  
Vol 12 (11) ◽  
pp. 1762 ◽  
Author(s):  
Gang Wang ◽  
Limeng Yin ◽  
Zongxiang Yao ◽  
Jinzhao Wang ◽  
Shan Jiang ◽  
...  
Keyword(s):  
Grain Boundary ◽  
Laser Welding ◽  
Grain Boundaries ◽  
Welded Joints ◽  
Pipeline Steel ◽  
High Energy ◽  
Electron Backscattered Diffraction ◽  
Boundary Density ◽  
Energy Beam ◽  
X100 Pipeline Steel

High-energy beam welding was introduced for pipeline steel welding to reduce pipeline construction costs and improve the efficiency and safety of oil and gas transportation. Microstructures and their distribution in X100 laser-welded joints, which determine the joints’ strength and toughness, are discussed in this paper. Welded joints were prepared by an automatic 10,000-watt robot-based disc laser-welding platform for 12.8 mm thick X100 pipeline steel. Then, the grain, grain boundary, orientation, and distribution pattern of each zone of the welded joints were studied by optical microscopy (OM), scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS), and electron backscattered diffraction (EBSD) analysis techniques. The results showed that the grain boundary density, contents of the high-angle and low-angle grain boundaries, distribution states, and evolution trends of coincident site lattice (CSL) grain boundaries were essentially the same in each zone from the base metal (BM) to the weld of the X100 pipeline steel laser-welded joint. The relative content of grain boundaries above 55°, which were composed of the Σ3 type CSL grain boundary, showed a considerable impact on the mechanical properties of the joint. The content of twin grain boundaries was closely related to the thermal cycles of laser welding, and the effect of the cooling rate was greater than that of the process of austenization.

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