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Volume 8 (2008): Issue 1 (March 2008)

Journal Details
Format
Journal
eISSN
2083-4799
ISSN
1730-2439
First Published
23 Sep 2008
Publication timeframe
4 times per year
Languages
English

Search

Volume 8 (2008): Issue 1 (March 2008)

Journal Details
Format
Journal
eISSN
2083-4799
ISSN
1730-2439
First Published
23 Sep 2008
Publication timeframe
4 times per year
Languages
English

Search

24 Articles
Open Access

Modification of Plastic Strain Localization Induced by Hydrogen Absorption

Published Online: 23 Sep 2008
Page range: 5 - 14

Abstract

Modification of Plastic Strain Localization Induced by Hydrogen Absorption

In order to highlight hydrogen effects on the plasticity, the slip morphology after straining (under tension up to 4% of plastic strain in ambient air) of hydrogenated (at 135 wt.ppm) and non-hydrogenated 316L stainless steel polycrystals was compared. A statistical analysis of both slip band spacings (SBS) and slip band heights (SBH) was performed using atomic force microscopy. Tensile tests were performed at low strain rate, specimens being previously charged at controlled hydrogen concentration. The plastic strain field heterogeneity in polycrystals was taken into account thanks to numerical simulation of crystalline plasticity. On each grain, the calculated plastic shear was correlated with the distribution of SBS and the average number of emerging dislocations per slip band. In comparison with uncharged specimen and for an equivalent cumulated plastic strain, the hydrogenated specimen shows an increase of the slip band spacing (SBS) and of emerging dislocations. This result confirms a plastic localization induced by absorbed hydrogen.

Keywords

  • Hydrogen
  • plastic strain localization
  • finite element calculation
Open Access

Composite Oxide Electrolytes for Electrochemical Devices

Published Online: 23 Sep 2008
Page range: 15 - 30

Abstract

Composite Oxide Electrolytes for Electrochemical Devices

This work is focused on the comparative analysis of electrical, electrochemical and mechanical properties of composite ceramic oxide electrolytes, providing a brief overview of the materials having better performance than monophase ones in various high temperature electrochemical devices such as: solid oxide fuel cells, sensors for automotive industry, oxygen probes for controlling metal processing. Introduction of Al2O3 inclusions into cubic yttria - zirconia solid solution (8YSZ) matrix, caused the improvement of electrical and mechanical properties compared to pure 8YSZ. The Nd2Ti2O7 secondary phase was also able to coexist with 8YSZ matrix and the fracture toughness KIc of 8YSZ ceramics was also significantly improved by Nd2Ti2O7 addition.

Heterophase oxide ionic conductors in the system Calcium zirconate - cubic calcia zirconia solid electrolytes seem to be promising solid electrolytes for application in electrochemical probes for controlling oxygen dissolved in molten steel. The ionic conduction limit for electrolytes based on CaZrO3 is lower than that for calcia - stabilized zirconia (13CSZ). Hence CaZrO3-based materials perform better at low oxygen concentration at molten alloys.

On the other hand composite layered ceramics involving Ce0.8Sm0.2O2/Bi0.8Eb0.2O2 or Ce0.9Gd0.1O2/BaCe0.8Y0.2O3/Ce0.9Gd0.1O1.95 system exhibited better electrolytic stability in gas atmospheres with low oxygen partial pressure at the temperatures 600-800°C. These materials are successfully tested as electrolytes in solid oxide fuel cells. The gradient ceramic oxide electrolytes seems to overcome the limitation of applying them as solid electrolytes in solid oxide fuel cells for long time performance.

Keywords

  • composite dispersed solid electrolytes
  • gradient ceramic electrolytes
  • solid oxide fuel cells (SOFC)
  • electrochemical oxygen probes
  • ceria
  • zirconia electrolyte
Open Access

Structure and Properties of Nano-Crystalline Ti-Base Alloys Obtained by Vacuum Hot Pressing

Published Online: 23 Sep 2008
Page range: 31 - 36

Abstract

Structure and Properties of Nano-Crystalline Ti-Base Alloys Obtained by Vacuum Hot Pressing

The cp-Ti and Ti-base alloys with additions of Ta and Nb were ball milled and consolidated using vacuum hot pressing. This novel technique allowed to obtain a high level of densification of milled powders up to about 98% and the nanometric grain size level. In the samples of vacuum hot compacted cp-Ti grain size of a single α phase was estimated at 140 nm. With the increase of content the β-stabilizing elements in alloys such as Ta and Nb, structure and a grain size has been changed. In the case of Ti-5Ta-5Nb alloy, also single α phase was observed but with grains size was much smaller, close to 85 nm. The further increasing of the content of Ta and Nb caused further refinement of grain size down to 60 nm and change of structure into two phase α+β and β in case of Ti-10Ta-10Nb and Ti-15Ta-15Nb alloys respectively. The hardness and Young Modulus were measured using the dynamic hardness tester and calculations of hardness and elastic modulus values were based on Oliver and Pharr model.

Keywords

  • Ti-base alloys
  • mechanical alloying
  • powder consolidation
  • TEM microstructure
Open Access

The Regularities of Phase and Structural Transformation in Binary Titanium Alloys with Metals of IV—VIII Groups of the Periodic Table

Published Online: 23 Sep 2008
Page range: 37 - 42

Abstract

The Regularities of Phase and Structural Transformation in Binary Titanium Alloys with Metals of IV—VIII Groups of the Periodic Table

Martensitic β→α′(α″) and β→ω transformation in a series of Ti-base alloys with transition metals of groups IV-VIII have been investigated using the techniques of X-ray diffraction, optical and transmission electron microscopy. Phase and structural information is given on the non-equilibrium and metastable modifications occurring in these alloys during quenching from high-temperature β-field and aging. The conditions of the orthorhombic ″-phase, ω-phase and metastable β-phase formation in binary titanium-base alloys with d-metals of V-VIII groups were investigated. It was established that the position of the alloying metal in the Periodic Table defines the presence or absence of the ″-phase in the alloy after quenching and the minimum concentration of the alloying metal necessary for formation of the ″-phase, ω-phase and metastable β-phase.

Keywords

  • titanium alloys
  • phase transformation
  • ″-phase
  • ω-phase
  • metastable β-phase
Open Access

Ocena Wpływu Parametrów Nadtapiania Laserowego w Warunkach Kriogenicznych Na Strukturę Warstwy Wierzchniej Na Stopie Ti-6al-4V

Published Online: 23 Sep 2008
Page range: 43 - 51

Abstract

Keywords

  • tytan
  • Ti-6Al-4V
  • nadtapianie laserowe
Open Access

Oxide Coatings on Titanium Produced by Oxidation in Fluidized Bed

Published Online: 23 Sep 2008
Page range: 52 - 57

Abstract

Oxide Coatings on Titanium Produced by Oxidation in Fluidized Bed

The main product of a process of titanium oxidation is titanium oxide, which covers the titanium surface. Moreover oxidation in fluidized bed in temperature range of 600-700°C influences on outer layers of titanium specimen, where a diffusion layer of oxygen is observed. Microstructures of titanium with visible oxide coatings on its surface after thermo-chemical treatment are described. Microhardness measurements of titanium surface layers after oxidation process were made with a Knoop microhardness tester and showed significant differences according to oxidation parameters. Finally, the surfaces of titanium after oxidation in fluidized bed were scratched in aim to measure their adhesion to the substrate surface.

Keywords

  • titanium
  • oxidation
  • fluidized bed
  • adhesion
Open Access

Analiza Ekonomiczna Procesu Utleniania Tytanu w Złoży Fluidalnym

Published Online: 23 Sep 2008
Page range: 58 - 62

Abstract

Keywords

  • złoże fluidalne
  • ekonomia
  • obróbka cieplna
Open Access

Wysokotemperaturowe Utlenianie Stopów Na Osnowie Fazy Gamma-TiAl: Procesy w Metalicznym Podłożu

Published Online: 23 Sep 2008
Page range: 63 - 71

Abstract

Keywords

  • intermetaliki
  • wysokotemperaturowe utlenianie
  • dyfuzja
Open Access

Cost Reduction of TiAl by Alternative Production and Integration of TiAl Scrap Recycling — Concepts and Vacuum-Metallurgical Equipment

Published Online: 23 Sep 2008
Page range: 72 - 79

Abstract

Cost Reduction of TiAl by Alternative Production and Integration of TiAl Scrap Recycling — Concepts and Vacuum-Metallurgical Equipment

Due to high corrosion resistance and low density titanium aluminides show a great potential as material for structural applications in the aerospace and automotive industry. However the high actual production costs for semi-finished products slow down a break through to mass production of TiAl. Current research projects at IME, Aachen funded by AIF "Otto von Guericke" and BMBF aim on cost reduced production methods of TiAl and on the minimisation of downgrading TiAl scrap.

This article presents firstly the state of the art of TiAl production by vacuum arc (re)melting (VAR) or induction skull melting (ISM). A comparison of new process routes under special consideration of recycling issues will follow. Innovative processing and equipment concepts are shown by intelligent combination of well known vacuum melting and remelting processes such as vacuum induction melting, specialized using ceramic lining and deoxidisation with e.g. electro slag re-melting (ESR).

For each process step and accordingly equipment the metallurgical opportunities are pointed out and the way to make use of them within the process route is described. Requirements on input material and final metal quality addicted to the processing route and refining techniques with their adjustment in respect to TiAl are mentioned. Selected results of laboratory and pilot scale experiments done at IME in Aachen and equipment needs therefore are shown.

Keywords

  • gamma-TiAl
  • Recycling
  • VIM
  • ISM
  • ESR
  • VAR
Open Access

Carbon Diffusion During Bainite Reaction in Austempered Ductile Iron

Published Online: 23 Sep 2008
Page range: 80 - 93

Abstract

Carbon Diffusion During Bainite Reaction in Austempered Ductile Iron

The paper presents an investigation of the carbon concentration in the residual austenite and the time required for the diffusion of carbon out of supersaturated sub-units of ferrite into the retained austenite. Experimental measurements of volume fraction of bainitic ferrite and volume of the untransformed austenite indicate that there is a necessity of carbides precipitation from austenite. A consequence of the precipitation of cementite from austenite during austempering is that the growth of bainitic ferrite can continue to larger extent and that the resulting microstructure is not an ausferrite but is a mixture of bainitic ferrite, retained austenite and carbides. Additionally, carbon concentration in the residual austenite was calculated using volume fraction data of austenite and a model developed by Bhadeshia based on the McLellan and Dunn quasi-chemical thermodynamic model. The comparison of experimental data with the T0, T0' and Ae3' phase boundaries suggests the likely mechanism of bainite reaction in cast iron is displacive rather than diffusional. The carbon concentration in retained austenite demonstrates that at the end of bainite reaction the microstructure must consist of not only ausferrite but additionally precipitated carbides.

Keywords

  • carbon diffusion
  • decarburization
  • bainite
  • ductile iron ADI
Open Access

Neural Network Analysis of Tensile Properties of Austempered Ductile Iron

Published Online: 23 Sep 2008
Page range: 94 - 104

Abstract

Neural Network Analysis of Tensile Properties of Austempered Ductile Iron

Austempered ductile iron is an excellent material and it possesses attractive properties as high strength, ductility and toughness. In this paper the neural technique was applied to the analysis of the ultimate tensile strength, the yield strength and elongation of austempered ductile iron (ADI). Estimation of the mechanical properties of austempered ductile cast iron (ADI) was curried as a function of chemical composition and heat treatment conditions (austenitizing temperature, austenitizing time, austempering temperature and austempering time). A ‘committee’ model was used to increase the accuracy of the predictions. The model was validated by comparison its predictions with data of tensile tests experiments on austempered samples of ductile cast iron. The model successfully reproduces experimentally determined ultimate tensile strength and elongation and it can be exploited in the predictions of tensile properties in the design of chemical composition of cast irons and their heat treatments.

Keywords

  • ADI
  • elongation
  • tensile strength
  • neural network
Open Access

Hydride Formation at Cathodic Charging of α-Ti

Published Online: 23 Sep 2008
Page range: 105 - 114

Abstract

Hydride Formation at Cathodic Charging of α-Ti

The hydrogen absorption and the formation of the hydride phase at cathodic polarization of annealed α-Ti have been studied by the kinetic hydrogen extraction and by the X-ray diffraction methods. The electrochemical parameters of cathodic hydrogen charging have been selected in order to obtain the hydrogen present in the solid solution of α-Ti lattice and the hydride phase to be formed. In 2M NaOH solution, the hydride phase has been already formed at cathodic polarization lower than 1 mA/cm2. In the case of 0.1M NaOH, the polarization regions (i) of hydrogen dissolution in the solid phase (ii) of hydride precipitation and (iii) of formation the increased amount of hydride phase have been distinguished in the course of application of increased cathodic polarization. Hydrogen dissolved in the metal lattice produces its dilatation, whereas presence of hydride phase causes the contraction of Ti lattice. Increased cathodic polarization causes the increase it the amount of hydride phase and the increase in the hydrogen content in TiHx phase as well.

Keywords

  • X-ray diffraction
  • hydrogen thermal extraction
  • NaOH solutions
  • hydrogen solid solution
  • TiH
Open Access

Effect of Surface Modification of α-Ti on Internal Friction

Published Online: 23 Sep 2008
Page range: 115 - 123

Abstract

Effect of Surface Modification of α-Ti on Internal Friction

The measurements of the internal friction were done using the RAK -3 relaxator at the bending mode oscillation of the acoustic frequency. The annealed α-Ti and α-Ti with the surface modified by the pulse mechanical grinding, by the plasma assisted formation of the layer of Ti-Al intermetallics and by the electrochemical hydrogen charging have been studied. The Young modulus and the attenuation of samples were measured at the heating of specimens between 200 and 600 K. In the studied temperature range, some relaxation processes occurred in the modified specimens. The values of the Young modulus and of the internal friction background have been also found to depend on the state of the Ti surface. The possible effects of the phase composition and the stress state on the obtained results have been discussed.

Keywords

  • internal friction
  • resonance frequency
  • relaxation processes
  • surface modification
  • Ti-Al intermetallics
  • hydride
Open Access

Kinetic Measurements of Hydrogen Distribution between Different States in Exploited Steels

Published Online: 23 Sep 2008
Page range: 124 - 129

Abstract

Kinetic Measurements of Hydrogen Distribution between Different States in Exploited Steels

The Hydrogen Analyzer AV-1 equipped with the high resolution registration system has been used to measure the kinetics of hydrogen extraction and thus to distinguish the different states of hydrogen in metals. The hydrogen distribution between the various energetic states as measured in the pipe line ferrite-pearlite steels being in service for different time has been shown to depend on conditions and on time of exploitation. Results of such measurements may be used for assessing the life time of industrial installations.

Keywords

  • hydrogen kinetic and static vacuum extraction
  • hydrogen trapping
  • ferrite-pearlite pipe line steels
Open Access

High Temperature Corrosion of TialCrNb Alloy with Tial2 Out-Of-Pack Coating in N2-O2-SO2-HCl Environments

Published Online: 23 Sep 2008
Page range: 130 - 137

Abstract

High Temperature Corrosion of TialCrNb Alloy with Tial<sub>2</sub> Out-Of-Pack Coating in N<sub>2</sub>-O<sub>2</sub>-SO<sub>2</sub>-HCl Environments

In this article results of microstructural analysis and corrosion resistance tests of 48-2-2 alloy (TiAlCrNb) with and without protective coating were presented. The aluminide coating was deposited by out-of-pack method on the base alloy. The thickness of the coating was 10μm and it was composed of TiAl2 phases. The corrosion resistance tests of the base alloy with and without the protective coating have been conducted at 600°C in the atmosphere containing nitrogen, with the addition of 9% of O2, 0,08% of SO2 and 0,20% of HCl. The tests lasted for 1250h. The aim of the conducted tests was to determine the mass gain of the samples in the given conditions and to identify the corrosion products, using X-ray phase analysis and EDS chemical content microanalysis. The detailed investigation has been done after 25, 50, 100, 150, 250, 500, 750, 1000 and 1250h of testing. As clearly indicated by the results of investigations, aluminide coating improves the corrosion resistance of TiAl alloy in the conditions of the performed test. The corrosion-resistance-enhancing effect of this type of diffusion coatings was attributed to the surface layer consisting of TiAl2.

Keywords

  • TiAl alloys
  • TiAl
  • protective coatings
  • corrosion in HCl
  • aluminides
Open Access

Cena Dokładności Tytanowych Odlewów Endoprotez

Published Online: 23 Sep 2008
Page range: 138 - 143

Abstract

Keywords

  • endoprotezy
  • precyzyjne odlewy tytanowe
  • dokładność
Open Access

Energy Dispersive X-Ray Analysis and Micro-Raman Studies of Poly (3,4-Ethylenedioxythiophene) Modified by Metal Hexacyanoferrates

Published Online: 23 Sep 2008
Page range: 144 - 151

Abstract

Energy Dispersive X-Ray Analysis and Micro-Raman Studies of Poly (3,4-Ethylenedioxythiophene) Modified by Metal Hexacyanoferrates

Hybrid conducting films, obtained by modification of poly(3,4-ethylenedioxytiophene) doped with Fe(CN)64-/3- ions by multi-cyclic polarization in aqueous FeCl3, NiCl2, and CoCl2 electrolytes, were examined by Energy Dispersive X-ray (EDX) and Micro-Raman measurements. EDX analysis allows to propose composition of metal hexacyanoferate (Mehcf) obtained inside polymer matrix as follows: Fe4[Fe(CN)6]3, Co3[Fe(CN)6]2, NiFe[Fe(CN)6] for materials modified in FeCl3, CoCl2 and NiCl2 aqueous electrolytes respectively. Micro-Raman measurements show that the signal from CN is hindered for hybrid systems in comparison with inorganic Mehcf.

Stoichiometry of inorganic part of the hybrid materials has been established by means of EDX measurements.

Keywords

  • conducting polymers
  • poly(3,4-ethylenedioxythiophene)
  • metal hexacyanoferrates
  • energy dispersive X-ray (EDX)
  • micro-Raman spectroscopy
Open Access

Stabilization of the Titanium Vibration Damping Wires in the Steam Turbine Blades System

Published Online: 23 Sep 2008
Page range: 152 - 157

Abstract

Stabilization of the Titanium Vibration Damping Wires in the Steam Turbine Blades System

Damping wires are usually used for damping of vibration blades in the steam turbines. Chromium steels or titanium alloys are still applied materials for producing the vibration damping wires. In this paper the stabilization method of the titanium vibration damping wires in the steam turbine blades system is performed. Microstructure and mechanical properties of the damping wires made of WT3-1 titanium alloy after cold and hot bending processes were presented. Analysis of the investigation results cold and hot bended vibration damping wires suggest, that stabilizing by hot bending of the titanium wires in the steam turbine blades system can be used in practice with successful.

Keywords

  • steam turbines
  • titanium vibration damping wires
  • hot bending
  • mechanical properties
Open Access

Microstructure and Corrosion Properties of the (Mn-N-O-P) Type Layers Created on Aluminium Alloys

Published Online: 23 Sep 2008
Page range: 158 - 165

Abstract

Microstructure and Corrosion Properties of the (Mn-N-O-P) Type Layers Created on Aluminium Alloys

The microstructure, chemical and phase composition as well as corrosion investigations of the (Mn-N-O-P) type surface layers in comparison to uncoated an aluminium alloy have been performed. An elaborated multiplex surface treatment of aluminium alloys enables forming of phase composition in the several zones of the (Mn-N-O-P) type layers. The zone microstructure with phases consisted of nitrogen, oxygen and phosphorus has fundamental influence on the hardnes and corrosion resistance of aluminium alloys.

Keywords

  • aluminium alloys
  • (Mn-N-O-P) type layer
  • microstructure
  • microhardness
  • corrosion resistance
Open Access

FEM Approach to Estimate the Behaviour of Biocomposite Metal-Surface Coating Systems

Published Online: 23 Sep 2008
Page range: 166 - 172

Abstract

FEM Approach to Estimate the Behaviour of Biocomposite Metal-Surface Coating Systems

A three dimensional (3D) model of biocomposite metal-surface coating system, which is influenced by known external forces, is proposed. This model consists of the metallic substrate (Ti6A14V) and the hydroxyapatite (HA) coating. Using FEM (finite element method), strain-stress maps of model were generated for investigating relations between the extreme stress of HA coating and the magnitude of external force and the thickness of the coating. The analysis of numerical simulations results confirms that the system with the greatest coating thickness (i.e. 10-3 m) has the least extreme stress in this surface coating.

Keywords

  • biocomposite
  • FEM analysis
  • simulation
  • hydroxyapatite
Open Access

Cavitation Erosion of X5CrNi18-10 Austenitic Stainless Steel Alloyed with TiC

Published Online: 23 Sep 2008
Page range: 173 - 179

Abstract

Cavitation Erosion of X5CrNi18-10 Austenitic Stainless Steel Alloyed with TiC

This work presents investigations of cavitation resistance of X5CrNi18-10 austenitic stainless steel after alloying its surface by CO2 laser beam. Laser beam machining was performed in two variants. In the first case, surface layer was enriched with TiC in amount of 1.55 % wt. and in the second one in amount of 3.97 % wt. The obtained results revealed that content of 3.97 % wt. TiC caused an increase of plastic deformations resistance of surface under the cavitation loading and simultaneous increase in embrittlement of alloyed layer.

Keywords

  • cavitation
  • erosion
  • laser beam processing
  • austenitic stainless steel
Open Access

Spawanie Elektronowe I Spawanie Tig Blach Z Tytanu Technicznego

Published Online: 23 Sep 2008
Page range: 180 - 185

Abstract

Keywords

  • spawanie elektronowe
  • spawanie TIG
  • badania metalograficzne
  • tytan
Open Access

Review of Titanium and Steel Welding Methods

Published Online: 23 Sep 2008
Page range: 186 - 194

Abstract

Review of Titanium and Steel Welding Methods

The paper presents review of methods of titanium and steel welding. On basis of professional literature it was stated that titanium can be joined with steel by means of explosive welding or brazing. Joining titanium with steel by TIG welding and friction welding methods is possible with the use of copper and tantalum or vanadium interlayer.

Keywords

  • titanium
  • stainless steel
  • TIG welding
  • explosive welding
  • friction welding
  • brazing
Open Access

The Degradation of Metal Implants

Published Online: 23 Sep 2008
Page range: 195 - 199

Abstract

The Degradation of Metal Implants

The presence of metal implants in the human body causes some dangers, which result from introducing another object into organism. There may occur a biocorrosion, which causes different modifications of implant surface.

Keywords

  • degradation
  • metal implants
24 Articles
Open Access

Modification of Plastic Strain Localization Induced by Hydrogen Absorption

Published Online: 23 Sep 2008
Page range: 5 - 14

Abstract

Modification of Plastic Strain Localization Induced by Hydrogen Absorption

In order to highlight hydrogen effects on the plasticity, the slip morphology after straining (under tension up to 4% of plastic strain in ambient air) of hydrogenated (at 135 wt.ppm) and non-hydrogenated 316L stainless steel polycrystals was compared. A statistical analysis of both slip band spacings (SBS) and slip band heights (SBH) was performed using atomic force microscopy. Tensile tests were performed at low strain rate, specimens being previously charged at controlled hydrogen concentration. The plastic strain field heterogeneity in polycrystals was taken into account thanks to numerical simulation of crystalline plasticity. On each grain, the calculated plastic shear was correlated with the distribution of SBS and the average number of emerging dislocations per slip band. In comparison with uncharged specimen and for an equivalent cumulated plastic strain, the hydrogenated specimen shows an increase of the slip band spacing (SBS) and of emerging dislocations. This result confirms a plastic localization induced by absorbed hydrogen.

Keywords

  • Hydrogen
  • plastic strain localization
  • finite element calculation
Open Access

Composite Oxide Electrolytes for Electrochemical Devices

Published Online: 23 Sep 2008
Page range: 15 - 30

Abstract

Composite Oxide Electrolytes for Electrochemical Devices

This work is focused on the comparative analysis of electrical, electrochemical and mechanical properties of composite ceramic oxide electrolytes, providing a brief overview of the materials having better performance than monophase ones in various high temperature electrochemical devices such as: solid oxide fuel cells, sensors for automotive industry, oxygen probes for controlling metal processing. Introduction of Al2O3 inclusions into cubic yttria - zirconia solid solution (8YSZ) matrix, caused the improvement of electrical and mechanical properties compared to pure 8YSZ. The Nd2Ti2O7 secondary phase was also able to coexist with 8YSZ matrix and the fracture toughness KIc of 8YSZ ceramics was also significantly improved by Nd2Ti2O7 addition.

Heterophase oxide ionic conductors in the system Calcium zirconate - cubic calcia zirconia solid electrolytes seem to be promising solid electrolytes for application in electrochemical probes for controlling oxygen dissolved in molten steel. The ionic conduction limit for electrolytes based on CaZrO3 is lower than that for calcia - stabilized zirconia (13CSZ). Hence CaZrO3-based materials perform better at low oxygen concentration at molten alloys.

On the other hand composite layered ceramics involving Ce0.8Sm0.2O2/Bi0.8Eb0.2O2 or Ce0.9Gd0.1O2/BaCe0.8Y0.2O3/Ce0.9Gd0.1O1.95 system exhibited better electrolytic stability in gas atmospheres with low oxygen partial pressure at the temperatures 600-800°C. These materials are successfully tested as electrolytes in solid oxide fuel cells. The gradient ceramic oxide electrolytes seems to overcome the limitation of applying them as solid electrolytes in solid oxide fuel cells for long time performance.

Keywords

  • composite dispersed solid electrolytes
  • gradient ceramic electrolytes
  • solid oxide fuel cells (SOFC)
  • electrochemical oxygen probes
  • ceria
  • zirconia electrolyte
Open Access

Structure and Properties of Nano-Crystalline Ti-Base Alloys Obtained by Vacuum Hot Pressing

Published Online: 23 Sep 2008
Page range: 31 - 36

Abstract

Structure and Properties of Nano-Crystalline Ti-Base Alloys Obtained by Vacuum Hot Pressing

The cp-Ti and Ti-base alloys with additions of Ta and Nb were ball milled and consolidated using vacuum hot pressing. This novel technique allowed to obtain a high level of densification of milled powders up to about 98% and the nanometric grain size level. In the samples of vacuum hot compacted cp-Ti grain size of a single α phase was estimated at 140 nm. With the increase of content the β-stabilizing elements in alloys such as Ta and Nb, structure and a grain size has been changed. In the case of Ti-5Ta-5Nb alloy, also single α phase was observed but with grains size was much smaller, close to 85 nm. The further increasing of the content of Ta and Nb caused further refinement of grain size down to 60 nm and change of structure into two phase α+β and β in case of Ti-10Ta-10Nb and Ti-15Ta-15Nb alloys respectively. The hardness and Young Modulus were measured using the dynamic hardness tester and calculations of hardness and elastic modulus values were based on Oliver and Pharr model.

Keywords

  • Ti-base alloys
  • mechanical alloying
  • powder consolidation
  • TEM microstructure
Open Access

The Regularities of Phase and Structural Transformation in Binary Titanium Alloys with Metals of IV—VIII Groups of the Periodic Table

Published Online: 23 Sep 2008
Page range: 37 - 42

Abstract

The Regularities of Phase and Structural Transformation in Binary Titanium Alloys with Metals of IV—VIII Groups of the Periodic Table

Martensitic β→α′(α″) and β→ω transformation in a series of Ti-base alloys with transition metals of groups IV-VIII have been investigated using the techniques of X-ray diffraction, optical and transmission electron microscopy. Phase and structural information is given on the non-equilibrium and metastable modifications occurring in these alloys during quenching from high-temperature β-field and aging. The conditions of the orthorhombic ″-phase, ω-phase and metastable β-phase formation in binary titanium-base alloys with d-metals of V-VIII groups were investigated. It was established that the position of the alloying metal in the Periodic Table defines the presence or absence of the ″-phase in the alloy after quenching and the minimum concentration of the alloying metal necessary for formation of the ″-phase, ω-phase and metastable β-phase.

Keywords

  • titanium alloys
  • phase transformation
  • ″-phase
  • ω-phase
  • metastable β-phase
Open Access

Ocena Wpływu Parametrów Nadtapiania Laserowego w Warunkach Kriogenicznych Na Strukturę Warstwy Wierzchniej Na Stopie Ti-6al-4V

Published Online: 23 Sep 2008
Page range: 43 - 51

Abstract

Keywords

  • tytan
  • Ti-6Al-4V
  • nadtapianie laserowe
Open Access

Oxide Coatings on Titanium Produced by Oxidation in Fluidized Bed

Published Online: 23 Sep 2008
Page range: 52 - 57

Abstract

Oxide Coatings on Titanium Produced by Oxidation in Fluidized Bed

The main product of a process of titanium oxidation is titanium oxide, which covers the titanium surface. Moreover oxidation in fluidized bed in temperature range of 600-700°C influences on outer layers of titanium specimen, where a diffusion layer of oxygen is observed. Microstructures of titanium with visible oxide coatings on its surface after thermo-chemical treatment are described. Microhardness measurements of titanium surface layers after oxidation process were made with a Knoop microhardness tester and showed significant differences according to oxidation parameters. Finally, the surfaces of titanium after oxidation in fluidized bed were scratched in aim to measure their adhesion to the substrate surface.

Keywords

  • titanium
  • oxidation
  • fluidized bed
  • adhesion
Open Access

Analiza Ekonomiczna Procesu Utleniania Tytanu w Złoży Fluidalnym

Published Online: 23 Sep 2008
Page range: 58 - 62

Abstract

Keywords

  • złoże fluidalne
  • ekonomia
  • obróbka cieplna
Open Access

Wysokotemperaturowe Utlenianie Stopów Na Osnowie Fazy Gamma-TiAl: Procesy w Metalicznym Podłożu

Published Online: 23 Sep 2008
Page range: 63 - 71

Abstract

Keywords

  • intermetaliki
  • wysokotemperaturowe utlenianie
  • dyfuzja
Open Access

Cost Reduction of TiAl by Alternative Production and Integration of TiAl Scrap Recycling — Concepts and Vacuum-Metallurgical Equipment

Published Online: 23 Sep 2008
Page range: 72 - 79

Abstract

Cost Reduction of TiAl by Alternative Production and Integration of TiAl Scrap Recycling — Concepts and Vacuum-Metallurgical Equipment

Due to high corrosion resistance and low density titanium aluminides show a great potential as material for structural applications in the aerospace and automotive industry. However the high actual production costs for semi-finished products slow down a break through to mass production of TiAl. Current research projects at IME, Aachen funded by AIF "Otto von Guericke" and BMBF aim on cost reduced production methods of TiAl and on the minimisation of downgrading TiAl scrap.

This article presents firstly the state of the art of TiAl production by vacuum arc (re)melting (VAR) or induction skull melting (ISM). A comparison of new process routes under special consideration of recycling issues will follow. Innovative processing and equipment concepts are shown by intelligent combination of well known vacuum melting and remelting processes such as vacuum induction melting, specialized using ceramic lining and deoxidisation with e.g. electro slag re-melting (ESR).

For each process step and accordingly equipment the metallurgical opportunities are pointed out and the way to make use of them within the process route is described. Requirements on input material and final metal quality addicted to the processing route and refining techniques with their adjustment in respect to TiAl are mentioned. Selected results of laboratory and pilot scale experiments done at IME in Aachen and equipment needs therefore are shown.

Keywords

  • gamma-TiAl
  • Recycling
  • VIM
  • ISM
  • ESR
  • VAR
Open Access

Carbon Diffusion During Bainite Reaction in Austempered Ductile Iron

Published Online: 23 Sep 2008
Page range: 80 - 93

Abstract

Carbon Diffusion During Bainite Reaction in Austempered Ductile Iron

The paper presents an investigation of the carbon concentration in the residual austenite and the time required for the diffusion of carbon out of supersaturated sub-units of ferrite into the retained austenite. Experimental measurements of volume fraction of bainitic ferrite and volume of the untransformed austenite indicate that there is a necessity of carbides precipitation from austenite. A consequence of the precipitation of cementite from austenite during austempering is that the growth of bainitic ferrite can continue to larger extent and that the resulting microstructure is not an ausferrite but is a mixture of bainitic ferrite, retained austenite and carbides. Additionally, carbon concentration in the residual austenite was calculated using volume fraction data of austenite and a model developed by Bhadeshia based on the McLellan and Dunn quasi-chemical thermodynamic model. The comparison of experimental data with the T0, T0' and Ae3' phase boundaries suggests the likely mechanism of bainite reaction in cast iron is displacive rather than diffusional. The carbon concentration in retained austenite demonstrates that at the end of bainite reaction the microstructure must consist of not only ausferrite but additionally precipitated carbides.

Keywords

  • carbon diffusion
  • decarburization
  • bainite
  • ductile iron ADI
Open Access

Neural Network Analysis of Tensile Properties of Austempered Ductile Iron

Published Online: 23 Sep 2008
Page range: 94 - 104

Abstract

Neural Network Analysis of Tensile Properties of Austempered Ductile Iron

Austempered ductile iron is an excellent material and it possesses attractive properties as high strength, ductility and toughness. In this paper the neural technique was applied to the analysis of the ultimate tensile strength, the yield strength and elongation of austempered ductile iron (ADI). Estimation of the mechanical properties of austempered ductile cast iron (ADI) was curried as a function of chemical composition and heat treatment conditions (austenitizing temperature, austenitizing time, austempering temperature and austempering time). A ‘committee’ model was used to increase the accuracy of the predictions. The model was validated by comparison its predictions with data of tensile tests experiments on austempered samples of ductile cast iron. The model successfully reproduces experimentally determined ultimate tensile strength and elongation and it can be exploited in the predictions of tensile properties in the design of chemical composition of cast irons and their heat treatments.

Keywords

  • ADI
  • elongation
  • tensile strength
  • neural network
Open Access

Hydride Formation at Cathodic Charging of α-Ti

Published Online: 23 Sep 2008
Page range: 105 - 114

Abstract

Hydride Formation at Cathodic Charging of α-Ti

The hydrogen absorption and the formation of the hydride phase at cathodic polarization of annealed α-Ti have been studied by the kinetic hydrogen extraction and by the X-ray diffraction methods. The electrochemical parameters of cathodic hydrogen charging have been selected in order to obtain the hydrogen present in the solid solution of α-Ti lattice and the hydride phase to be formed. In 2M NaOH solution, the hydride phase has been already formed at cathodic polarization lower than 1 mA/cm2. In the case of 0.1M NaOH, the polarization regions (i) of hydrogen dissolution in the solid phase (ii) of hydride precipitation and (iii) of formation the increased amount of hydride phase have been distinguished in the course of application of increased cathodic polarization. Hydrogen dissolved in the metal lattice produces its dilatation, whereas presence of hydride phase causes the contraction of Ti lattice. Increased cathodic polarization causes the increase it the amount of hydride phase and the increase in the hydrogen content in TiHx phase as well.

Keywords

  • X-ray diffraction
  • hydrogen thermal extraction
  • NaOH solutions
  • hydrogen solid solution
  • TiH
Open Access

Effect of Surface Modification of α-Ti on Internal Friction

Published Online: 23 Sep 2008
Page range: 115 - 123

Abstract

Effect of Surface Modification of α-Ti on Internal Friction

The measurements of the internal friction were done using the RAK -3 relaxator at the bending mode oscillation of the acoustic frequency. The annealed α-Ti and α-Ti with the surface modified by the pulse mechanical grinding, by the plasma assisted formation of the layer of Ti-Al intermetallics and by the electrochemical hydrogen charging have been studied. The Young modulus and the attenuation of samples were measured at the heating of specimens between 200 and 600 K. In the studied temperature range, some relaxation processes occurred in the modified specimens. The values of the Young modulus and of the internal friction background have been also found to depend on the state of the Ti surface. The possible effects of the phase composition and the stress state on the obtained results have been discussed.

Keywords

  • internal friction
  • resonance frequency
  • relaxation processes
  • surface modification
  • Ti-Al intermetallics
  • hydride
Open Access

Kinetic Measurements of Hydrogen Distribution between Different States in Exploited Steels

Published Online: 23 Sep 2008
Page range: 124 - 129

Abstract

Kinetic Measurements of Hydrogen Distribution between Different States in Exploited Steels

The Hydrogen Analyzer AV-1 equipped with the high resolution registration system has been used to measure the kinetics of hydrogen extraction and thus to distinguish the different states of hydrogen in metals. The hydrogen distribution between the various energetic states as measured in the pipe line ferrite-pearlite steels being in service for different time has been shown to depend on conditions and on time of exploitation. Results of such measurements may be used for assessing the life time of industrial installations.

Keywords

  • hydrogen kinetic and static vacuum extraction
  • hydrogen trapping
  • ferrite-pearlite pipe line steels
Open Access

High Temperature Corrosion of TialCrNb Alloy with Tial2 Out-Of-Pack Coating in N2-O2-SO2-HCl Environments

Published Online: 23 Sep 2008
Page range: 130 - 137

Abstract

High Temperature Corrosion of TialCrNb Alloy with Tial<sub>2</sub> Out-Of-Pack Coating in N<sub>2</sub>-O<sub>2</sub>-SO<sub>2</sub>-HCl Environments

In this article results of microstructural analysis and corrosion resistance tests of 48-2-2 alloy (TiAlCrNb) with and without protective coating were presented. The aluminide coating was deposited by out-of-pack method on the base alloy. The thickness of the coating was 10μm and it was composed of TiAl2 phases. The corrosion resistance tests of the base alloy with and without the protective coating have been conducted at 600°C in the atmosphere containing nitrogen, with the addition of 9% of O2, 0,08% of SO2 and 0,20% of HCl. The tests lasted for 1250h. The aim of the conducted tests was to determine the mass gain of the samples in the given conditions and to identify the corrosion products, using X-ray phase analysis and EDS chemical content microanalysis. The detailed investigation has been done after 25, 50, 100, 150, 250, 500, 750, 1000 and 1250h of testing. As clearly indicated by the results of investigations, aluminide coating improves the corrosion resistance of TiAl alloy in the conditions of the performed test. The corrosion-resistance-enhancing effect of this type of diffusion coatings was attributed to the surface layer consisting of TiAl2.

Keywords

  • TiAl alloys
  • TiAl
  • protective coatings
  • corrosion in HCl
  • aluminides
Open Access

Cena Dokładności Tytanowych Odlewów Endoprotez

Published Online: 23 Sep 2008
Page range: 138 - 143

Abstract

Keywords

  • endoprotezy
  • precyzyjne odlewy tytanowe
  • dokładność
Open Access

Energy Dispersive X-Ray Analysis and Micro-Raman Studies of Poly (3,4-Ethylenedioxythiophene) Modified by Metal Hexacyanoferrates

Published Online: 23 Sep 2008
Page range: 144 - 151

Abstract

Energy Dispersive X-Ray Analysis and Micro-Raman Studies of Poly (3,4-Ethylenedioxythiophene) Modified by Metal Hexacyanoferrates

Hybrid conducting films, obtained by modification of poly(3,4-ethylenedioxytiophene) doped with Fe(CN)64-/3- ions by multi-cyclic polarization in aqueous FeCl3, NiCl2, and CoCl2 electrolytes, were examined by Energy Dispersive X-ray (EDX) and Micro-Raman measurements. EDX analysis allows to propose composition of metal hexacyanoferate (Mehcf) obtained inside polymer matrix as follows: Fe4[Fe(CN)6]3, Co3[Fe(CN)6]2, NiFe[Fe(CN)6] for materials modified in FeCl3, CoCl2 and NiCl2 aqueous electrolytes respectively. Micro-Raman measurements show that the signal from CN is hindered for hybrid systems in comparison with inorganic Mehcf.

Stoichiometry of inorganic part of the hybrid materials has been established by means of EDX measurements.

Keywords

  • conducting polymers
  • poly(3,4-ethylenedioxythiophene)
  • metal hexacyanoferrates
  • energy dispersive X-ray (EDX)
  • micro-Raman spectroscopy
Open Access

Stabilization of the Titanium Vibration Damping Wires in the Steam Turbine Blades System

Published Online: 23 Sep 2008
Page range: 152 - 157

Abstract

Stabilization of the Titanium Vibration Damping Wires in the Steam Turbine Blades System

Damping wires are usually used for damping of vibration blades in the steam turbines. Chromium steels or titanium alloys are still applied materials for producing the vibration damping wires. In this paper the stabilization method of the titanium vibration damping wires in the steam turbine blades system is performed. Microstructure and mechanical properties of the damping wires made of WT3-1 titanium alloy after cold and hot bending processes were presented. Analysis of the investigation results cold and hot bended vibration damping wires suggest, that stabilizing by hot bending of the titanium wires in the steam turbine blades system can be used in practice with successful.

Keywords

  • steam turbines
  • titanium vibration damping wires
  • hot bending
  • mechanical properties
Open Access

Microstructure and Corrosion Properties of the (Mn-N-O-P) Type Layers Created on Aluminium Alloys

Published Online: 23 Sep 2008
Page range: 158 - 165

Abstract

Microstructure and Corrosion Properties of the (Mn-N-O-P) Type Layers Created on Aluminium Alloys

The microstructure, chemical and phase composition as well as corrosion investigations of the (Mn-N-O-P) type surface layers in comparison to uncoated an aluminium alloy have been performed. An elaborated multiplex surface treatment of aluminium alloys enables forming of phase composition in the several zones of the (Mn-N-O-P) type layers. The zone microstructure with phases consisted of nitrogen, oxygen and phosphorus has fundamental influence on the hardnes and corrosion resistance of aluminium alloys.

Keywords

  • aluminium alloys
  • (Mn-N-O-P) type layer
  • microstructure
  • microhardness
  • corrosion resistance
Open Access

FEM Approach to Estimate the Behaviour of Biocomposite Metal-Surface Coating Systems

Published Online: 23 Sep 2008
Page range: 166 - 172

Abstract

FEM Approach to Estimate the Behaviour of Biocomposite Metal-Surface Coating Systems

A three dimensional (3D) model of biocomposite metal-surface coating system, which is influenced by known external forces, is proposed. This model consists of the metallic substrate (Ti6A14V) and the hydroxyapatite (HA) coating. Using FEM (finite element method), strain-stress maps of model were generated for investigating relations between the extreme stress of HA coating and the magnitude of external force and the thickness of the coating. The analysis of numerical simulations results confirms that the system with the greatest coating thickness (i.e. 10-3 m) has the least extreme stress in this surface coating.

Keywords

  • biocomposite
  • FEM analysis
  • simulation
  • hydroxyapatite
Open Access

Cavitation Erosion of X5CrNi18-10 Austenitic Stainless Steel Alloyed with TiC

Published Online: 23 Sep 2008
Page range: 173 - 179

Abstract

Cavitation Erosion of X5CrNi18-10 Austenitic Stainless Steel Alloyed with TiC

This work presents investigations of cavitation resistance of X5CrNi18-10 austenitic stainless steel after alloying its surface by CO2 laser beam. Laser beam machining was performed in two variants. In the first case, surface layer was enriched with TiC in amount of 1.55 % wt. and in the second one in amount of 3.97 % wt. The obtained results revealed that content of 3.97 % wt. TiC caused an increase of plastic deformations resistance of surface under the cavitation loading and simultaneous increase in embrittlement of alloyed layer.

Keywords

  • cavitation
  • erosion
  • laser beam processing
  • austenitic stainless steel
Open Access

Spawanie Elektronowe I Spawanie Tig Blach Z Tytanu Technicznego

Published Online: 23 Sep 2008
Page range: 180 - 185

Abstract

Keywords

  • spawanie elektronowe
  • spawanie TIG
  • badania metalograficzne
  • tytan
Open Access

Review of Titanium and Steel Welding Methods

Published Online: 23 Sep 2008
Page range: 186 - 194

Abstract

Review of Titanium and Steel Welding Methods

The paper presents review of methods of titanium and steel welding. On basis of professional literature it was stated that titanium can be joined with steel by means of explosive welding or brazing. Joining titanium with steel by TIG welding and friction welding methods is possible with the use of copper and tantalum or vanadium interlayer.

Keywords

  • titanium
  • stainless steel
  • TIG welding
  • explosive welding
  • friction welding
  • brazing
Open Access

The Degradation of Metal Implants

Published Online: 23 Sep 2008
Page range: 195 - 199

Abstract

The Degradation of Metal Implants

The presence of metal implants in the human body causes some dangers, which result from introducing another object into organism. There may occur a biocorrosion, which causes different modifications of implant surface.

Keywords

  • degradation
  • metal implants

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