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1
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Special Structures of Graphite Steels After High-Energy Electron Irradiation

100%
Alexandrova N.
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vol. 96
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issue 2
259-262
EN
The effect of high-energy electron irradiation on the structure and properties of the graphite steels have been investigated. It has been shown that single- and multicycle irradiation allows the improvement of hardness and ductility (≈ twice). A partial dissolution of the graphite, carbides redistribution, and refinement of the grain size allow the formation of the favorable surface structure after irradiation.
2
Content available remote

Improving the Surface Properties of Cp-Ti by Pulsed Electro-Spark Deposition

100%
Yılmaz M., Atar E., Şahin O., Kayalı E.
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vol. 125
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issue 2
593-596
EN
Al-Ti intermetallic compounds were coated by electro-spark deposition. Commercially pure titanium (Cp-Ti) (grade 2) and aluminum rods were used as substrate and electrode materials, respectively. During the electro-spark deposition experiments the following pulse parameters in a group were used: pulse current amplitude, pulse duration and pause between the pulses of a pulse group with 100-300-500 A, 50-100 μs, and 100 μs, respectively. Al-Ti coatings having a thickness range of 15-30 μm were formed on the surface of titanium substrate using electro-spark deposition process. The coating properties such as the roughness and the thickness increased with increasing pulse duration and pulse current amplitude. The mass transfer coefficient decreased with increasing pulse current amplitude and pulse duration. The quality of the adhesion characters of the coatings, determined by Rockwell-C adhesion test, becomes worse from HF-2 to HF-4, due to increase of pulse current amplitude. Depending on the electro-spark deposition process parameters, the coating formed as AlTi or as layered structure consisting of AlTi+AlTi_3 when pulse current amplitude increases. The Al-Ti coatings include some micro cracks lying throughout the coating from surface to interface which is nature of this process. The maximum cross-sectional hardness of the coatings were in the range of 800-1150 HV.
3
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Calculation of Lattice Relaxation in Some Substitutional Alloys Using a Green Function

100%
Das S., Datta Roy (Paul) S.
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vol. 95
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issue 3
359-366
EN
In this paper we calculate nearest neighbour relaxation in some dilute substitutional alloys using a lattice static Green function and the Morse potential function. Distant neighbour relaxation is calculated by invoking a continuum approximation. The potential parameters for the unlike interactions are calculated using simple interpolation formulae. Using the above relaxation, we calculate volume changes in the above alloys. It is observed that the simple model predicts values which are in reasonably good agreement with the experimental values in all cases. The calculated values are also compared with those obtained from the Vegard law. For Au-Ag alloy, our model reproduces both the correct sign and the magnitude of the volume change, whereas the Vegard law cannot even give the sign of the volume change. This shows the inherent strength of the present model.
4
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A Green Function Estimation of Correction to Vegard's Law for isovalent Substitutional Defects in Alkali Halide Crystals

100%
Datta Roy (Paul) S., Das S.
Acta Physica Polonica A
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2000
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vol. 97
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issue 4
671-679
EN
A Green function method is developed for estimation of lattice parameter r(χ) of an AX-BX solid solution over entire composition range (χ=0 to 1). The r(χ) obtained in the present method is different from the value r_{V}(χ) suggested by Vegard's law. We estimated the deviation from Vegard's law, r(χ)-r_{V}(χ), over entire composition range for isovalent substitutional defect in alkali halide crystals. When compared to X-ray diffraction measurements, we find that the deviation is in correct direction, variation of r(χ) with χ is consistent with experiment and the overall agreement is fairly good considering the accuracy of the experiment.
5
Content available remote

Long-Range Effect in Ion-Implanted Titanium Alloys

80%
Budzynski P., Sielanko J.
Acta Physica Polonica A
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2015
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vol. 128
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issue 5
841-844
EN
Surface modification of titanium alloy (Ti6Al4V) by nitrogen ion implantation and ion beam-assisted deposition (C, N) was investigated. The depth distribution of implanted nitrogen atoms was analysed using the Rutherford backscattering technique. Nitrogen implantation reduces the coefficient of friction and wear. A better effect can be obtained when nitrogen implantation is combined with carbon deposition. Based on the changes in the coefficients of friction and wear as well as profilograms of wear tracks, the improvement of the tribological properties was found at a depth exceeding nearly 5 times the range of the implanted nitrogen ions. Identification of the long-range effect for Ti6Al4V alloy was performed on the basis of tribological analyses. This study is a continuation of research conducted for AISI 316L and H11 steel.
6
Content available remote

Characterization of New U-Ni-X₂ Splats and Study of their Physical Properties

80%
Molčanová Z., Mihalik M., Mihalik M., Reiffers M., Džubinská A., Huráková M., Kavečanský V., Paukov M., Havela L.
Acta Physica Polonica A
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2017
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vol. 131
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issue 4
994-996
EN
We explored the crystal structure, magnetic, and transport properties of UNiX₂ (X = Ge, Si) materials, which were prepared by a conventional metallurgical technique and by rapid solidification - splat cooling. The UNiSi₂ splat is mostly single phase, containing only small traces of a minority phase. Magnetic and electrical properties of the splat resemble properties of samples, which were prepared by conventional methods, exhibiting a ferromagnetic transition at about 91 K and similar temperature dependence of resistivity. The coercive field of μ₀H_c=4.25 T is much enhanced due to the magnetic anisotropy introduced by the sample preparation technique. The Barkhausen jumps were observed on the hysteresis loop. Magnetization of the sample does not saturate in fields up to μ₀H=9 T. The phase structure of UNiGe₂ splat is not completely solved and will be subject of our study in future. Our preliminary results indicate the presence of completely new phase with tetragonal crystal structure and antiferromagnetic ordering below 54 K.
7
Content available remote

Crystallisation of Amorphous Y rm_{50}Cu_{42}Al_8 Alloy

80%
Idzikowski B., Śniadecki Z., Mielniczuk B.
Acta Physica Polonica A
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2009
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vol. 115
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issue 1
147-149
EN
Amorphous Y_{50}Cu_{42}Al_8 ribbon was prepared by melt-spinning technique on the Cu wheel. The crystallisation process was analysed by differential scanning calorimetry and X-ray diffraction. Differential scanning calorimetry curves characterising two crystallisation stages of Y_{50}Cu_{42}Al_8 alloy were measured in non-isothermal dynamic mode at different heating rates. Activation energies of both steps of crystallisation process were acquired by the Kissinger method and are equal to 570± 56 and 290±29 kJ/mol for the first and second stage, respectively. By annealing the ribbon at a given temperature for various times the nanocrystalline phase grains of the sizes of about 40 nm in diameter were created. The influence of the annealing temperature on the grain size evolution was also examined.
8
Content available remote

Surface Modification of Metallic Targets with Ultrashort Laser Pulses

80%
Gakovic B., Stasic J., Petrovic S., Radak B., Krmpot A., Jelenkovic B., Trtica M.
Acta Physica Polonica A
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2009
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vol. 116
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issue 4
611-613
EN
Interaction of pulsed femtosecond Ti:sapphire laser (160 fs), operating at high repetition rate (75 MHz) at 800 nm, with nickel-based superalloy Inconel 600 and tungsten-titanium (WTi) target was studied. The WTi target was in form of thin film deposited on silicon substrate. Low laser fluence of maximum 50 mJ/cm^{2} had modified the target surface during irradiation/exposure time of seconds or minutes. The radiation absorbed from the laser beam generates at the surface a series of effects, such as direct material vaporization, formation of clusters, etc. Morphological features of the targets can be summarized as: (a) intensive removal of material and crater appearance; (b) creation of nanostructures; (c) microcracking, etc. Ablation of Inconel 600 surface is effective, resulting in formation of holes with small diameter ( ≤ 10 μm) and relatively large depth ( ≤ 50 μm). In case of WTi target/thin film, the surrounding rim is not so expressed, and crater depths are lower. It can be concluded that the average laser power of the order of watts, pulse energies of the order of nanojoules and high repetition rates (MHz range) can successfully modify metallic materials.
9
Content available remote

Activation Energies of Crystallization in Amorphous RMn_{4.5}Ge_{4.5}Fe_{1.5}Al_{1.5} (R = La, Y, Dy) Alloys

80%
Śniadecki Z., Rößler U., Idzikowski B.
Acta Physica Polonica A
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2009
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vol. 115
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issue 1
409-412
EN
The effective activation energies, characteristic crystallization temperatures and enthalpies of amorphous RMn_{4.5}Ge_{4.5}Fe_{1.5}Al_{1.5} (R = Y, La, Dy) alloys produced using melt-spinning technique were investigated by differential scanning calorimetry. X-ray diffraction measurements were performed for as-quenched and annealed samples. The crystalline structure of annealed YMn_{4.5}Ge_{4.5}Fe_{1.5}Al_{1.5} and DyMn_{4.5}Ge_{4.5}Fe_{1.5}Al_{1.5} alloys was determined as orthorhombic TbFe_6Sn_6-type with Cmcm (63) space group. The alloy with Y appears as a more useful non-magnetic analogue for DyMn_{4.5}Ge_{4.5}Fe_{1.5}Al_{1.5} than the La-based alloy. The differential scanning calorimetry curves for Dy- and Y-based alloys also exhibit similar thermal behavior. The effective activation energies E_a were determined using the Kissinger approach and high values up to 778±74 kJ/mol for La-based sample were established. The comparison of Y-, La-, and Dy-based alloys suggests improvement of thermal stability with the increase in rare-earth element atomic radius in the glassy RMn_{4.5}Ge_{4.5}Fe_{1.5}Al_{1.5} systems.
10
Content available remote

Study of Point Defect Distributions in Tantalum

80%
Djaafri A., Kadoun A., Driss-Khodja M., Elias A., Djaafri T.
Acta Physica Polonica A
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2018
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vol. 133
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issue 1
39-44
EN
We have investigated the point defect distributions in tantalum under irradiation by means of the Marlowe code based on the binary collision approximation. The study is carried out by simulating displacement cascades initiated with primary knock-on atom energies ranging from 5 to 20 keV. The Molière, Born-Mayer and average modified Lenz-Jensen potentials are used to describe the interactions between tantalum atoms. We have examined the creation of damage, the spatial defects distribution, and the vacancy clustering in tantalum. The results show that with an appropriate recombination radius, less than 16% of the created defects constitute permanent Frenkel pairs. Spatial configuration of defects indicates a separation between the two point defect types, vacancies and interstitials. The Molière potential favors the production of a greater number of displaced atoms and the development of voluminous cascades more than the other potentials. The cascade volume distributions deviate clearly from a Gaussian distribution. They are large and very stretched toward higher volumes for all used potentials. Only small vacancy clusters are formed in tantalum under irradiation and about 41% of the produced vacancies are considered as isolated
11
Content available remote

Mechanical Properties of the Stellite 6 Cobalt Alloy Implanted with Nitrogen Ions

80%
Budzyński P., Kamiński M., Wiertel M., Pyszniak K., Droździel A.
Acta Physica Polonica A
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2017
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vol. 132
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issue 2
203-205
EN
The effect of nitrogen ion implantation on Stellite 6 cobalt alloy was investigated. In this research, cobalt alloy was implanted with 65 keV nitrogen ions at the fluence of (1÷10)×10¹⁶ N⁺/cm². The distribution of implanted nitrogen ions and vacancies produced by them was calculated using the SRIM program. The surface morphology was examined and the elemental analysis was performed using scanning electron microscopy, energy dispersive X-ray spectroscopy and grazing incidence X-ray diffraction. The wear tests were conducted with the use of the pin-on-disc method. The results demonstrate that implantation with nitrogen ions significantly reduces the friction factor and wear. The friction coefficient of the implanted sample at the fluence of 1×10¹⁷ N⁺/cm² increased to the values characteristic of an unimplanted sample after 5000 measurement cycles. The depth of the worn trace was about 2.0 μm. This implies that the thickness of the layer modified by the implantation process is ≈2.0 μm and exceeds the initial range of the implanted ions by an order of magnitude. This is referred to as a long-range implantation effect. The investigations have shown that the long-range effect is caused by movement of not only implanted nitrogen atoms but also carbon dopant atoms towards the friction zone. Diffusion of carbon atoms has been documented here for the first time. Furthermore, the increased content of oxygen atoms on the track bottom indicates a dominant oxidative wear of the Stellite samples after nitrogen implantation with the energy 65 keV and the fluences of 5×10¹⁶ and 10¹⁷ N⁺/cm².
12
Content available remote

Defect Range and Evolution in Swift Xe-Ion Irradiated Pure Silver Studied by Positron Annihilation Technique

80%
Dryzek J., Horodek P., Skuratov V.
Acta Physica Polonica A
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2017
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vol. 132
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issue 5
1585-1589
EN
Variable energy positron beam and positron lifetime spectroscopy were used to study pure silver samples exposed to irradiation with swift Xe²⁶⁺ ions of energy 167 MeV with different dose: of 10¹³, 5×10¹³ and 10¹⁴ ions/cm². The positron lifetime spectroscopy revealed the presence of dislocations or vacancies associated with dislocations. They are distributed at the depth of about 6 μm, and this correlates with the ion implantation range, i.e. 9 μm. However, some defects are observed also to a depth of about 18 μm. At the depth less than 1 μm from the entrance surface strong dependence of positron diffusion length on the dose is observed. It indicates the presence of interstitial atoms and/or dislocation loops as a result of Xe²⁶⁺ ions implantation.
13
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Content available

Investigations of Au Segregation in AuNi Alloys by the Line Shape Analysis of Photoelectron Spectra

80%
Lesiak B., Biliński A., Jóźwik} A.
Acta Physica Polonica A
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2006
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vol. 109
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issue 6
701-714
EN
The surface segregation of Au in Au5Ni95 polycrystalline alloy is studied applying the line shape analysis, known as the fuzzy k-nearest neighbour rule, to the selected X-ray photoelectron and X-ray induced Auger spectra. Each line, characterised by the kinetic electron energy exhibited in the particular transition, samples the depth described by the mean escape depth depending on the inelastic mean free path of electron in the investigated material and the geometry of the measurement. The following electron transitions in the electron kinetic energy range 216.6-1486.6 eV are analysed: Au N_5N_{67}V, Ni 2p, Ni L_2M_{23}M_{45}-Ni L_3M_{45}M_{45}, Au 4d, Au 4f and the valence band transitions (overlapping Au 5d6s and Ni 3d4s transitions). The results of the quantitative analysis using the fuzzy k-nearest neighbour rule are compared to the results of quantitative analysis by the multiline approach which applies the Au 4f and Ni 2p photoelectron transitions. Both methods demonstrate Au surface segregation starting at the temperature above 200ºC. The line shape analysis was shown to be applicable for quantification of the surface region with possibility of investigating the in-depth non-uniform concentration profiles.
14
Content available remote

PSG Method for Simulating Agglomeration of Al₂O₃ Inclusions in Liquid Steel

80%
Kalisz D., Żak P.
Acta Physica Polonica A
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2016
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vol. 130
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issue 1
157-159
EN
A quantitative description of the non-metallic inclusions removal from liquid steel is the most important element of secondary metallurgy. Authors made an attempt at calculating balance of Al₂O₃ particles during turbulent flow, which represents the steel refining conditions. For this purpose a special program was worked out. The agglomeration of non-metallic inclusions in liquid steel was modeled with the particle grouping method. Calculations were performed for steel with 300 and 500 ppm oxygen content. Then the quantity of generated aluminum oxide was calculated. Various mixing rates of the melt, corresponding to the actual conditions in the ladle, were applied. Simulations were performed for 6 groups of particles for the initial size of inclusions 1, 3, and 5 μ m. The size interval for each group was predefined very strictly. The diameter increase and particle number reduction of the successive groups were graphically presented in plots. In the initial phase the rate of particle removal was very high, especially when high mixing energies were involved. This calculation procedure realistically describes the agglomeration and elimination of non-metallic inclusions in the secondary metallurgical processes and can be implemented for modeling this type of processes.
15
Content available remote

Hydrogen Release and Microstructure of MgH_{2} Based Composite Powders Containing a Relevant Amount of LaNi_{5}

80%
Abazović N., Aurora A., Contini V., Mancini M., Montone A., Vittori Antisari M.
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issue 5
841-848
EN
Micro-composite materials based on MgH_{2} with the addition of a relevant amount of LaNi_{5} have been synthesized by reactive ball milling. The powder microstructure has been studied by a combination of X-ray diffraction and scanning electron microscopy, while the decomposition behaviour and the hydrogen release properties have been obtained by differential thermal analysis and thermo-gravimetric measurements. Both temperature scans and constant temperature isotherms have been used to this purpose. Experimental results allow identifying optimum processing condition for synthesis of material that shows the onset of hydrogen release at temperatures as low as 450 K. The decomposition kinetics has been studied by isothermal measurements which show that the whole process cannot be described by just one mechanism limiting the reaction velocity. In fact in the first decomposition step the reaction is kinetically limited by the second phase nucleation, while, for partially decomposed samples the bulk diffusion appears to limit the process. On the basis of the experimental results we propose a mechanism of phase transformation where a percolating network of the two phases is formed.
16
Content available remote

Substructural Strengthening of Medium-Carbon Alloyed Steel with Preliminary Thermomechanical Processing

80%
Kodzhaspirov G., Rudskoy A.
Acta Physica Polonica A
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2015
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vol. 128
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issue 4
527-529
EN
Substructural strengthening result in preliminary thermomechanical processing, when applied cold deformation with the combination of post deformation annealing and induction hardening based on the of dislocation structure inheritance effect on the mechanical properties such as torsion static strength has been studied. Final heat treatment with the use of post deformation tempering followed by induction hardening and low temperature tempering demonstrated the highest static torsion strength in consequence of the inheritance of polygonal dislocation substructure of ferrite arised at the proper post deformation annealing temperature at preliminary thermomechanical processing by dislocation structure of austenite formed under followed induction hardening heating and then by dislocation substructure of martensite formed result in following quenching.
17
Content available remote

Evaluation of Fracture Toughness of Thermal Sprayed and Hard Chrome Coated Aluminium-Zinc Alloy

80%
Altuncu E., İriç S.
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EN
The determination of fracture toughness of aluminium alloy aviation parts, exposed to cyclic mechanical loading, is an important engineering issue. The service life and crack resistance of such unprotected metallic parts is limited under corrosive operating conditions. The resistance against fracture cracking and corrosion resistance can be increased by the surface coatings. The scientific research of fracture toughness of coated metallic parts is being carried out in a comprehensive way. In this research, fracture toughness behaviour of high velocity oxy-fuel (HVOF) spray coated and conventional hard chrome plated aluminium-zinc alloy parts were compared and the results are discussed. The fracture surfaces are investigated and fracture toughness values are calculated. Electron microscopy analysis revealed significant differences in crack growth morphology and toughness values. As a result, the fracture toughness value is higher in hard chrome plated parts.
18
Content available remote

Determination of the Young Modulus of Ti-TiAl₃ Metallic Intermetallic Laminate Composites by Nano-Indentation

80%
Yener T., Güler S., Siddique S., Walther F., Zeytin S.
Acta Physica Polonica A
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2016
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vol. 129
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issue 4
604-606
EN
Nano-indentation is an important technique to determine the Young modulus of multiphase materials where normal tensile tests are not appropriate. In this work, Ti-TiAl₃ metallic-intermetallic laminate composites have been fabricated successfully in open atmosphere using commercial purity Al and Ti foils with 250 μm and 500 μm initial thicknesses, respectively. Sintering process was performed at 700°C under 2 MPa pressure for 7.5 h. Mechanical properties including the Young modulus were determined after manufacturing. The Young moduli of metallic and intermetallic phases were determined as 89 GPa and 140 GPa, respectively. Microstructure analyses showed that aluminum foil was almost consumed by forming a titanium aluminide intermetallic compound. Titanium aluminides grow up through spherical shaped islands and metallic-intermetallic interface is a wavy form in Ti-Al system. Thus, the final microstructure consists of alternating layers of intermetallic compound and unreacted Ti metal. Microstructure and phase characterizations were performed by scanning electron microscopy, energy dispersive spectroscopy, and X-ray diffraction. Hardness of test samples was determined as 600 HV for intermetallic zone and 130 HV for metallic zone by the Vickers indentation method.
19
Content available remote

Slow Positron Beam Studies of the Stainless Steel Surface Exposed to Sandblasting

80%
Horodek P., Dryzek J., Kobets A., Kulik M., Lokhmatov V., Meshkov I., Orlov O., Pavlov V., Rudakov A., Sidorin A., Siemek K.
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vol. 125
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issue 3
714-717
EN
The paper presents slow positron beam studies of the stainless steel grade 304 AISI samples annealed in the flow N_2 atmosphere and sandblasted under different pressure from 1 to 7 bar. Heating of specimens caused formation of an additional layer on the surface which can be identified as oxides. Sandblasting reduces the thickness of the oxide layer and also defects concentration (vacancies as we suppose) decreases in dependence on pressure applied during blasting. Additionally, the atomic concentrations of oxygen have been obtained using nuclear methods (Rutherford backscattering and nuclear reactions) in the near surface layers of the studied samples.
20
Content available remote

Influence of High Energy Heavy Ions on Magnetic Susceptibility of Soft Magnetic Metallic Glasses

71%
Pavlovič M., Miglierini M., Mustafin E., Seidl T., Šoka M., Ensinger W.
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vol. 126
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issue 1
54-55
EN
This contribution presents experimental data concerning the influence of fast heavy ions on magnetic susceptibility of VITROVAC®6025 and VITROPERM®800 metallic glasses. Samples of magnetic ribbons were irradiated with Au, and Ta ions at 11.1 MeV/A (energy per nucleon), and U ions at 5.9 MeV/A. The irradiation fluences varied from 5×10^{10} up to 1.2×10^{13} ions/cm^{2}. Relative change of the samples' magnetic susceptibility after and before irradiation was measured and evaluated as a function of the irradiation fluence. Measurements were done with a commercial Kappa-bridge device. We observed that VITROPERM® showed less change of magnetic susceptibility in comparison with VITROVAC® and this change occurred at higher fluences. This indicates higher radiation hardness of VITROPERM® compared with VITROVAC® against high-energy heavy ions. In addition, heavier ions caused larger change of magnetic susceptibility than the lighter ones and the effect could be roughly scaled with the level of electronic stopping.
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