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.

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.

Evaluation on Adhesion Strength of Laser Induction Hybrid Rapid Cladding Cu-Fe-Based Coatings Using Scanning Kelvin Probe

2015 ◽  
Vol 1096 ◽  
pp. 103-106
Author(s):  
Xiao Qin Dai ◽  
Sheng Feng Zhou ◽  
Zheng Xiong
Keyword(s):  
Solid Solution ◽  
Tensile Strength ◽  
Work Function ◽  
Adhesion Strength ◽  
Electron Work Function ◽  
Nondestructive Method ◽  
Kelvin Probe ◽  
Scanning Kelvin Probe ◽  
Logarithmic Relationship ◽  
Laser Induction

It is very important to effectively evaluate the adhesion strength of coating. A nondestructive method to evaluate the adhesion strength of laser induction hybrid rapid cladding Cu-Fe-based coatings was investigated. The electron work function of coatings was measured by scanning Kelvin probe. It was demonstrated that the Fe-rich particles and solid solution of Fe can increase the EWF and the tensile strength. A logarithmic relationship between the ratio of EWF to dilution and the adhesion strength was established.

Microstructure and Properties of Ultrafast Annealed High Strength Steel

2013 ◽  
Vol 753 ◽  
pp. 554-558 ◽  
Author(s):  
Roumen H. Petrov ◽  
Farideh Hajyakbari ◽  
Fernando Ramos Saz ◽  
Jurij Sidor ◽  
Maria Jesus Santofimia ◽  
...  
Keyword(s):  
Grain Size ◽  
Phase Transformation ◽  
High Strength Steel ◽  
High Strength ◽  
Deformation Texture ◽  
Point Of View ◽  
Structural Refinement ◽  
Cold Rolled ◽  
Ferrite Grain Size ◽  
Martensite Structure

The grain size, recrystallization, phase transformation and mechanical properties of a cold-rolled high-strength steel (HSS) are studied after annealing with high (~140°C/s) and ultra-high (~1500°C/s) reheating rate, followed by subsequent water quenching without isothermal soaking. By monitoring the hardness and microstructure, it was shown that the increase of the reheating rate from 140°C/s to 1500°C/s causes grain refinement from 5 µm to 1 µm in diameter and the final ferrite grain size depends significantly on the reheating temperature and reheating rate. It was observed that after an extreme reheating rate of ~1500°C/s the α-γ phase transformation starts before the completion of recrystallization in the recovered matrix. The crystallographic texture of the ultrafast reheated and water-quenched high-strength steel inherits the cold-rolled deformation texture with well pronounced RD and ND texture fibres, even after the α-γ-α′ phase transformations. It was found that the ultrafast reheating results in a very fine non-equilibrium ferrite-martensite structure with an excellent ultimate tensile strength of ~1400 MPa and an acceptable elongation at fracture. The observed data are very promising from industrial application point of view and open up possibilities for further structural refinement and alternative texture control.

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 Boundary Segregated Dopant on Phase Stability in Tetragonal Zirconia Polycrystal

2010 ◽  
Vol 654-656 ◽  
pp. 2208-2211
Author(s):  
Yorinobu Takigawa ◽  
Takahisa Yamamoto ◽  
Kenji Higashi
Keyword(s):  
Grain Size ◽  
Phase Transformation ◽  
Grain Boundary ◽  
Phase Stability ◽  
Boundary Diffusion ◽  
Tetragonal Zirconia ◽  
Transformation Behavior ◽  
Hydroxyl Ion ◽  
Boundary Stress ◽  
Tetragonal Zirconia Polycrystal

The effect of grain boundary segregated dopant on phase stability of tetragonal zirconia polycrystal (TZP) is examined by accelerated exposure tests ageing in hot water. The materials used in this study are 3 mol%Y2O3 stabilized TZP (3Y-TZP) and 0.1mol%SiO2-doped 3Y-TZP. Accelerated exposure tests in an autoclave reveal that the tetragonal phase stability of 3Y-TZP in water is highly affected by the grain boundary segregated dopant and the grain size. When the grain size of TZP is about 0.55μm, the change in phase transformation behavior with dopant is explained from the change in grain boundary diffusivity of hydroxyl ion. Grain boundary diffusion of hydroxyl ion must be blocked by the presence of some segregated ion which reduces the effective area of grain boundary diffusion. On the other hand, when the grain size is about 0.35μm, the phase transformation behavior seems to be controlled by the grain boundary stress. Decreased grain boundary stress by the segregation of some dopant must enhance the phase transformation of 3Y-TZP.

scholarly journals Analysis of the microstructural influence by laser cutting velocity

2020 ◽  
Vol 25 (4) ◽  
pp. 513-518
Author(s):  
Rodolfo Rodríguez Baracaldo ◽  
Mónica López Camargo ◽  
Aldemar Martin-Buitrago
Keyword(s):  
Grain Size ◽  
Phase Transformation ◽  
Heat Affected Zone ◽  
Laser Cutting ◽  
Low Carbon Steel ◽  
Cutting Parameters ◽  
Low Carbon ◽  
Cutting Velocity ◽  
The Mean ◽  
Good Relation

This research evaluates the influence of the CO2 laser cutting velocity in the heat-affected zone in a low- carbon steel. The control of laser cutting parameters is essential to ensure that the properties required in the material have not been affected, and avoid additional grinding processes on the cut surfaces. Morphologic, mechanic and microstructural tests were used to prove the influence of cutting process and its velocity on heat-affected zone. Transformation from ferritic into pearlitic structure and reduction in grain size were analyzed. Also, was evaluated a rise in hardness due to phase transformation. Better cutting conditions were evidenced in samples using a cutting velocity of 80 mm/s because the mean hardness obtained allow infer a good relation of properties and a smaller heat affected zone.

Interpretation of Profile and Intercept Counts in Microstructure Characterization

2008 ◽  
Vol 604-605 ◽  
pp. 403-410 ◽  
Author(s):  
Ivan Saxl ◽  
Vaclav Sklenička
Keyword(s):  
Grain Size ◽  
Grain Boundary ◽  
Unit Volume ◽  
Structural Characteristics ◽  
Mean Value ◽  
Careful Consideration ◽  
Boundary Area ◽  
Mean Grain Size ◽  
The Mean ◽  
Size Dispersion

The results of intercept and profile counts are commonly interpreted as a suitable estimates of the mean grain size as represented e.g. by the grain density V. The term grain size is not explicitly defined even when some relation to grain volume and/or mean grain breadth (the mean Ferret diameter) is tacitly assumed. However, the intercept count L is directly related to the mean value of grain boundary area per unit volume SV and the profile count A is, under relatively general assumptions, directly related to the mean value of grain junctions per unit volume LV. Their relation to V can be generally written as V = c¢(A)3/2 = c²(L)3, but the coefficients c¢ and c² strongly depend on the structural characteristics like grain size dispersion, anisotropy etc. and their evaluation is far from being simple. Consequently, whereas the reliable estimates of SV and LV result from intercept and profile counts, the estimate of grain density based on them requires a careful consideration.

Phase Transformation In Ti-6al-4v Alloys

1972 ◽  
Vol 30 ◽  
pp. 584-585
Author(s):  
Shiro Fujishiro
Keyword(s):  
Phase Transformation ◽  
Grain Boundary ◽  
Cryogenic Temperature ◽  
Β Phase ◽  
Heat Treated ◽  
Mixed Microstructure ◽  
Ductile Behavior

The Ti-6 wt.% Al-4 wt.% V commercial alloys have exhibited an improved formability at cryogenic temperature when the alloys were heat-treated prior to the tests. The author was interested in further investigating this unusual ductile behavior which may be associated with the strain-induced transformation or twinning of the a phase, enhanced at lower temperatures. The starting materials, supplied by RMI Co., Niles, Ohio were rolled mill products in the form of 40 mil sheets. The microstructure of the as-received materials contained mainly ellipsoidal α grains measuring between 1 and 5μ. The β phase formed an undefined grain boundary around the a grains. The specimens were homogenized at 1050°C for one hour, followed by aging at 500°C for two hours, and then quenched in water to produce the α/β mixed microstructure.

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