List of Abstracts 2018: POSTER SESSION
Date: November 14, 2018
The work deals with the studies on electrolytic-plasma polishing (EPP) of the surface of Ti-6Al-4V alloy with ultrafine-grained (UFG) structure produced by equal channel angular pressing. Possibility to use the regime (electrolyte composition and temperature, voltage) developed earlier for coarse-grained structure alloy is estimated. The electrolyte temperature range and working shift voltages of EPP are proposed to ensure the polishing effect in Ti-6Al-4V with UFG structure. The results of the studies on topography and chemical composition of the alloy surface in CG and UFG states by scanning electron microscopy are presented. The impact of EPP duration on surface roughness and metal removal rate are demonstrated. The perspectives of the EPP process applied to a surface treatment of medical implants and items for mechanical engineering are discussed;
ACKNOWLEDGEMENTS: The work was conducted with the support of the Russian Science Foundation under grant No. 16-19-10356 in USATU.
This research concerned the whole production of UFG materials, using Severe Plastic Deformation (SPD). These new technologies for production of semi-finished products with ultra-fine grained structure differ from conventional technologies. One of them is new type of equipment DRECE (Dual Rolling Equal Channel Extrusion), designated for obtaining UFG structure and increase of mechanical properties in strip of sheet. The main goal of the paper is a review of current achieved results obtained by processing of Cu based materials by DRECE method, the equipment of which was put in service towards the end of 2009 at the Department of mechanical technology, Faculty of mechanical engineering, VŠB - Technical University of Ostrava. Cu-based materials - technical pure Cu (99.3% purity) - is used as experimental material. Experiments with use of the formed structural material - copper was made on the forming device in order to achieve grain refinement in the strip of sheet (Cu 99,3% purity) with dimensions 58 x 2 x 1000 mm The paper describes results of determination of an influence of number of passes on resulting mechanical and micro-structural properties of the processed Cu-based materials.
This research primarily focuses on improving the strength of Al-3%Mg aluminium alloy by processing using ECAP equipement and post ECAP ageing. The microstructure evolution in Al-3%Mg, subjected to Room Temperature ECAP was analysed. ECAP was carried out using an optimized die with Channel angle ‘ϕ’ = 120°and corner angle ‘Ψ’ = 20° through processing route A. Optical Microscopy, Scanning Electron Microscopy (SEM)/X-Ray Energy Dispersive Spectroscopy (EDS), X-Ray Diffraction (XRD), dilatometric analysis and Vickers hardness tests were used to evaluate the microstructural and mechanical properties.
The Al-Mg alloys are widely used in the automotive and marine industry due to their excellent properties such as corrosion resistance, good weldability and intermediate mechanical properties along with their low price. Magnesium has a high solubility in the aluminium ~17.35 wt. %. Its addition increases the work-hardening ability, thus an essential work hardening can be expected in those alloys. Refining the grain size of the aluminium-magnesium alloys to the ultra-fine (<1 µm) and even nanometric scale using severe plastic deformation processes become the most effective strategy to increase their mechanical strength, whereas the post plastic deformation treatments are strategies to increase ductility. Experiments were conducted to evaluate the mechanical behaviour of an AlMg5 alloy after ECAP processing and subjected to the post-ECAP annealing treatment. The initial grain size was ~270 µm and this was reduced to ~20 µm by ECAP and post-ECAP annealing treatment at 350 °C for 30 min. The annealing treatment led to some sort of bimodal grain mixture with the larger grains embedded in the original UFG structure that provide an excellent combination of strength and ductility.
The rapid progress that has been made in the field of nanotechnology, particularly in the last sixteen years, has made it possible to develop new technologies for preparing nanoscale objects, including composite, polymeric and ceramic one-dimension nanoaterias with small diameters of just several nanometers. Materials in the form of nanofibers, nanowires or nanorods are characterised by a considerable length and a small cross-section whose diameter may be approximately 100 times smaller than their length. The most effective technology of production of 1D nanomaterials is producing fibres in the electrostatic field, which does not require complicated procedures and expensive equipment. This type of process allows to produce polymer and composite nanostructures on an industrial scale relatively easily and quickly. The electrospun 1D nanostructures were studied using scanning electron microscope (SEM) and transmission electron microscope (TEM) to analyse the influence of used temperature on the morphology and structures obtained ceramic nanomaterials. In order to examine the chemical structure of nanowires, the energy dispersive spectrometry (EDS) was used.. Optical property analysis was performed on the basis of UV-Vis spectra of absorbance as a function of wavelength. Using the modified Swanepoel method which the authors proposed and the recorded absorbance spectra determined banded refractive index n, real n' and imaginary k part of refractive index as a function of wavelength, complex dielectric permeability ε, real and imaginary part εr and εi of the dielectric permeability as a function of the radiation energy of the produced ceramic nanowires.
Residual stresses remaining after severe plastic deformation processes can negatively influence the quality and behaviour of the work-pieces. However, the determination of the stress distribution is not straightforward and needs the combination of the results from several material characterization methods. In this study, commercially pure (CP) titanium (Ti) grade 2 subjected to one to three passes of CONFORM ECAP (C-ECAP) method was investigated by neutron diffraction (ND), X-ray diffraction and electron back-scatter diffraction (EBSD) methods in the transverse direction of the specimens. ND measurements revealed the residual strain distribution in three perpendicular orientations (axial, radial and hoop). Moreover, local X-ray texture measurements helped to construct the orientation distribution function (ODF) and thanks to EBSD observations, grain shapes and grain sizes of the investigated regions were determined. The residual stress calculation was based on the modified Kröner model and on previous experimental results. After the first and second C-ECAP pass, the residual stress distribution, with a mainly compression character, shows symmetric distribution around the centre of specimens with large stress gradients from edges toward the centre in axial and hoop orientations. In radial orientation, the distribution seems very homogeneous with compression character. After the third C-ECAP pass, the stress distribution is very inhomogeneous without any symmetry. These results help to enlighten the conditions which prevail in the processed material and consider the further processing steps.
This paper is focuses on study of a hot extruded AZ31 magnesium alloy processed by severe plastic deformation method TCAP (Twist Channel Angular Extrusion) at different temperatures. In order to characterize processing temperatures and the resulting structure and properties, the speimens were processed by 4 passes at 250°C, 230°C and 200°C. Microstructure and mechanical characterization was performed by Vickers hardness testing and metallographic analysis on an optical microscope.
Laser quenching is a modern technology of material processing. High speed of process, extremely high speeds of heating (in order of 1000°C/s) and absence of cooling medium after heating are the biggest advantages of heat treatment by unconventional technology. Moreover, laser quenching could be in some cases only one possible way, how to heat treated the material’s surface.
This article deals with the problematics of laser spots overlap during square parts quenching. It is necessary to set optimal distance between two neighboring tracks. If this distance is too low, the second pass of laser can temper previously hardened track. On the other hand, the stripe completely without heat treatment remains in the surface, if too long distance between quenching tracks is used. Optimal distance of laser spots at quenching of 1.7225 steel was searched under present research. It was verified that at least 4 mm overlap is needed.
The copper precipitation offers possibility of effective and easily achievable ferrite strengthening. There is reported yield point rise by 150 MPa thanks to formation of nanometric copper precipitates in ferrite for Cu content 1.5 wt.%. Such rise of yield strength is most significant for soft and ductile materials, containing free ferrite. Ferritic-martensitic dual steels are example of such material. They are widely used for their favourable combination of strength and ductility. Their yield strength is defined by the soft phase, the ferrite. Ferrite strengthening in these steels is achieved mainly by grain refinement and by solution strengthening caused by substitutional alloying elements. This article describes preparation of dual phase structure in 0.2% C steel alloyed by Cu, Mn, Ti and B. Dual phase structure was prepared by controlled rolling with rolling finishing temperatures in the intercritical region. Samples were analysed by light and scanning electron microscopy. Hardness was measured and tensile tests were performed.
Nano-crystalline (nc) Cu with Cr2O3 dispersoid (~4 vol. %) was successfully made by reactive-milling at 210 K with a mixture of elemental Cu, Cu2O, and Cr powder. The milled powders were vacuum hot pressed (HP) at 1123 K and 50 MPa for 2h to consolidate for further analysis. TEM (Transmission Electron Microscopy) observation showed that the HPed materials were comprised with a mixture of nc-Cu and homogeneous and bimodal distribution of Cr2O3 dispersoids. The microstructure and Vickers hardness of the as-milled powder and the HPed materials were measured by standard metallographic techniques. The grain size of the nc-Cu was measured using Scherrer’s formula (XRD) and direct TEM observation; the Cr2O3 dispersoid size was estimated from the HADDF (High Angle Annular Dark Field) images and element mapping by STEM-EDS (Scanning Transmission Electron Microscopy-Energy Dispersive Spectroscopy) works. The formation kinetics and coarsening of the dispersoids were discussed in terms of the relationship between the microstructure and hardness value, using XRD, TEM, and thermodynamic calculation.
In this work, we have been interested in the characterization of the effect of heat treatment and mechanical treatment on the crystallinity of a polylactic acid (PLA) film by two techniques, DSC and Raman spectroscopy. the results obtained by the dsc for the stretched film shows the appearance of a broad peak of crystallization around 120 ° C, a rise in melting peak in a significant way, which shows that the uniaxial stretching has increased the crystallinity of the PLA, whereas for the annealed film appearance of a double melting peak. The results obtained by Raman spectroscopy show new peak appears at 922 cm−1 after stretching process, indicating crystallization process occurs.
The purpose of this study is to compare corrosion resistance of the joints between commercially pure titanium (Grade 2) and stainless steel (X5CrNi18-10) bonded by interlayers made of pure metals. Three different interlayers were used in the study, which were made of aluminium (Al 99.5), copper (Cu 99.99) and nickel (Ni 99.6). The diffusion bonding process has been employed to join those dissimilar materials. The microstructure of the joints were investigated using scanning electron microscopy equipped with an energy dispersive X-ray system (EDS). The phases of the reaction layers in the diffusion zone were identified by means of an X-ray diffraction (XRD).The structures of the joints varied importantly depending on the interlayer. The galvanic corrosion test was carried out in two solutions one in a 3,5% NaCl and second one in 1M Na2SO4 solution. The potentiodynamic polarization curves in a 3,5% NaCl solution show that the higher corrosion potential as well as a lower corrosion current were registered for the joints performed by nickel. The test carried out in 1M Na2SO4 solution show that that the lowest corrosion current was registered for the joints performed by copper and also all investigated samples have a tendency towards passivation.
In the present investigation, transient liquid-phase bonding was performed between pure titanium (Grade 2) and stainless steel (X5CrNi 18-10) using nickel foil as an intermediate material. The process was carried out at the temperatures of: 950, 975 and 1000 ⁰C for 60 minutes under the compressive stress of 2 MPa in a vacuum. The microstructure was investigated using light microscopy and scanning electron microscopy equipped EDS. The metallographical examination shows that the diffusion interfaces are free from cracks. However, Kirkendall voids were observed at the borders of materials. Especially large voids were formed in middle section of the joint prepared using the highest bonding temperature. The structure of the joints on the titanium side was composed of the eutectoid mixture αTi+Ti2Ni and layers of intermetallic phases Ti2Ni, TiNi and TiNi3. The nickel interlayer blocked the diffusion of titanium to stainless steel side at 950 °C bonding temperature and prevented from formation of the Fe-Ti intermetallic layers. The layer of a solid solution γFe+Ni between nickel and stainless steel was observed at the 950°C processing temperature. The mixture of λ+FeTi+Ti, FeTi+Ti, λ+αFe and λ+χ+αFe phases was formed at 975 and 1000 °C at the nickiel-stainless steel interlayer.
At present time the importance of indentation measurements once again increases. As modern and perspective measurement method it allows to measure various mechanical properties while only needing micro and nano volumes of materials.
While standard hardness measurement methods examine only the plastic response of sampled material, Depth Sensing Indentation (DSI) testing is founded on real-time recording of applied force and resulting travel of indenter. This allows to evaluate both plastic and elastic response of examined material during the indentation process which in turn allows for calculation of various static material properties in very small volumes of samples.
The big advantage of this approach is saving of time (especially on sample preparation), however the data analysis - and thus results - could be influenced by certain factors. Those worth noting are surface quality of the sample, wear of the indenter head, its shape and material, and also the pliability of testing machine’s frame.
If we consider the frame of testing machine being pliable, inevitably there will occur not only displacement of indenter but also displacement of frame itself, especially noticeable while using high loads. This negatively influences the results of such measurement.
This work’s aim is to calculate the pliability of test machine’s frame using Finite Element Method model and 1 mm in diameter steel ball indenter.
The result of this work is addition of virtual spring to the FEM model and fine tuning of its stiffness. This should allow us to minimize the influence of frame’s pliability on the results of future measurements.
Most cryogenic systems failures are generally caused by incorrect choice of construction materials or neglect change of some physical property from the atmosphere to low temperatures.
For example, the property of ductility of the material requires careful consideration since the low temperature has the effect of making some structural materials brittle or less malleable.
The aim of our work is to study the behavior of two metals at low temperatures: Austenitic Stainless Steel 304 and Aluminum Alloy 5083, especially their behavior in the hardness and resilience tests. The samples (16 for each metal) are cut in pipes formed by two pieces welded steel and subjected to hardness tests which are applied in 15 points distributed in three areas of the sample : the base metal; the heat affected zone and the molten zone representing the welding metal. Other samples (also 16 for each) were subjected to Charpy tests and the absorbed energy were recorded. The tests were conducted on the prepared samples from ambient (25°C) to low temperature of ( -150 ° C). In total seven different temperatures were used in this study (25, 0, -30, -60, -90, -120 and -150 ° C). Results of the resilience and hardness tests for each temperature were analysed. It was confirmed that at low temperatures the behaviour of the austenitic Austenitic Stainless Steel 304 is more adequate than Aluminium Alloy 5083.
The work is aimed on the coatings used as a barrier against Heavy Liquid Metal (HLM) influence and coated material behaviour under mechanical loading. The comparison of two kinds of coatings deposited on two different steels is examined: ferritic-martensitic steel T91 coated with AlTiN and austenitic steel 316L coated with Al2O3. Both samples underwent tensile tests with constant extension rate in the HLM autoclave-cell for material testing. The testing environment in the cell was liquid PbBi eutectic at the temperature of 550 °C. The examination by Scanning electron microscopy and Energy-dispersive X-ray spectroscopy followed after exposure. The yield strength of the steel was exceeded in both cases, cracks and adhesion were studied in depth to characterize their resistance to the simultaneous effect of load and environment. Both coatings offered protection against corrosion; however, localized cracking gave rise to the damage of the substrate. These coatings provided a corrosion barrier, which once damaged is not able of self-healing.
This paper demonstrates that the diffusion bonding method can be used to join AlSi11 alloy to AM60 alloy. The microstructure of the bonding zone in such joints was examined using optical and scanning electron microscopy. Its chemical composition was determined through energy dispersive X-ray microanalysis. The experimental results show that the microstructure of the bonding zone is dependent on the parameters of the diffusion bonding process. In an AlSi11-AM60 bimetallic joint fabricated at 420 oC, the bonding zone had a thickness of about 50 µm and it was composed of Mg-Al intermetallic phases with irregularly distributed Mg2Si phase areas. When the heating temperature was 440 oC, the bonding zone was about 150 µm thick. Mg2Si was the predominant phase and were distributed more regularly over Mg-Al phases matrix. The microhardness measurements of this joint showed that the bonding zone containing hard phases had much higher hardness than either of the alloys joined.
Cost F steel structure was characterized by advanced scanning electron microscopy (SEM) technique. The SEM instrument is equipped with a concentric backscatter detector (CBS), which enables effective energy and angular separation of the backscattered electrons (BSE). Filtering of the BSE signal enables improving and/or diminishing of selected type of contrast. The samples (after standard and accelerated) creep test were imaged by the CBS detector and the low energy micrographs created by the in-elastically scattered BSEs show clear contrast of the Laves phase. The images were used as an input data for image analysis and the specimen after standard creep test and the specimen after accelerated creep test were compared. Statistical data about the Laves phase area fraction, size and shape were obtained. The specimen after accelerated creep test contains significantly lower content of the Laves phase and its size and shape is also different in comparison with the specimen after standard creep test.
Growth of share renewables in the field of electric power supplier and a lack of mechanism to cover shortage, force standard supplier of energy to stabilize the electrical grid. This situation is then demonstrated by increase of hot-start and cold-starts. But there is a lack for robust tool for qualitative assessment of residual life of the turbine shaft and for design of such a component. The goal of this paper is to present influence of the holding period on low-cycle fatigue (LCF), thermo-mechanical fatigue (TMF) and the so called Damage Operator Approach (DOA) by Nagode, which were used as a new approach for design of turbine shaft in Doosan Škoda Power. Experimental program was used in order to identify material parameters and to verify numerical simulations.
The effect of cobalt substitution for Fe on the magnetic properties (magnetic saturation, magnetic remanence, coercivity, power losses) and structural properties of high induction Fe84.5Nb5B8.5P2 alloys was studied. For various Co content the amorphous and nanocrystalline samples in the form of the ribbons were prepared via melt-spinning method. The crystalline form of the obtained ribbons were verified using the X-ray diffraction method. Therefore the crystallization temperature as well as crystallization kinetics have been examined by use of differential scanning calorimetry (DSC). Basing on the DSC studies the temperatures and times of thermal treatment of wound toroidal cores have been optimized. It was found that the substitution of 5 wt% Co for Fe enhanced the magnetic properties at 50 Hz and the magnetic saturation of >1.7T is reached at 500 A/m with the power losses of 1 W/kg. Then the magnetic properties of the optimized samples have been corelated with calorimetric (kinetic of crystallization parameters) and diffraction results (crystallinity ratio and crystalline size of the α-Fe phase).
This article helps to look at the problem of quality and using properties increasing of cast iron castings. One of the most actually stream in this area is optimization of existing processes and integration new processes of furnace out treatment of the melts. At now, the theory and the practice status of using compounds modifiers shows the necessity for preparing and applying some new materials, such as nanomaterials. In this case using of high-reactive nanosized substances, such as all types of the nanocarbon, is more perspective from materials production side. These materials have high mechanical and usage properties. This article shows the results of high-strength cast iron researches with adding of complex modifiers. The compound modifier is discovered and it consist of standard modifier for high-strength cast iron and nanocarbon components. That modifier is high effective. In result, the number of graphite inclusions has increase and their size has decrease with a lower concentration of the modifier.
This work aims to study the microstructures of two deformed stainless steels 316Ti and 904L which are used in the petroleum industry. The two steels have been cold rolled with two width reductions of 50 and 95%. Microstructural analysis has been conducted before and after the cold deformation by using an optical microscope and revealed different morphologies. Results of the microhardness measurements performed on the two steels indicated that the 316L stainless steel is harder than the 904L stainless steel. In addition, the higher the deformation amount the higher the microhardness values for the two steels. X-ray diffraction analysis based on the Rietveld refinement method has been conducted and reveled a decrease of the size of the coherent domain of diffraction as a function of the deformation. This decrease is accompanied by an increase of the dislocation density. A correlation with microhardness and a comparative discussion between the two steels is presented in this sudy.
Aluminum alloys have become a standard application in automotive industry due to their strength to weight ratio and corrosion
properties. Aluminum alloys based on Al-Mn (class 3XXX) that are
applied as components in air conditioning modules in automotive as well as in construction and consumer industries are often submitted to vibrations which can eventually lead to fatigue cracks and in the end to complete failure of the components. The study of fatigue failures of cyclic loaded Al-Mn alloy was performed using fractographic analysis on scanning electron microscope JEOL JSM-649OLV. The loading was realised from 100,000 to 1,369,000 cycles at room temperature. The features of fatigue fracture surfaces were discussed comparing different states of the A3003 alloy, specifically in the state 1/4 hard (H12) and full soft (O). The results for corresponding loading cycles were compared. Areas close to the crack initiation were characterized by radial marks corresponding to fatigue propagation. Fracture was propagated through the growing lines in form of fine striations with secondary cracks and microcracks between them. The striations were arranged to bands and corresponded to crack propagation at each loading cycle. For final fracture the typical quasi-cleavage morphology was observed.
This contribution is focused on the issue of Environmentally Assisted Cracking (EAC). For EAC testing in low pressure superheated hydrogen steam environments a special corrosion apparatus is being built in cooperation with University of Manchester and Škoda JS. The whole concept is being prepared for the MEACTOS project. One section concerns the problems with determining an environment with a mixture of hydrogen, argon and steam. The presented equations are necessary for controlling the environment and for the settings of the area of test interest. The test instrumentation is described.
Laser shock peening (LSP) is an innovative surface treatment technique for strengthening metallic materials. The treatment improves fatigue performance and is achieved by introducing compressive residual stresses into the material surface layer. The compressive stresses are created over a significant surface area by means of high pressure shock waves, which are generated by confining the laser-induced plasma. In the present study, the LSP effect on fatigue life of austenitic stainless steels was investigated by changing the laser parameters. The tested material was austenitic stainless steel 08CH18N10T. The influence of LSP treatment on the fatigue life was examined through the three-point bend fatigue test.
The stresses induced by laser cutting in the non-oriented fully processed electrical FeSi sheets were investigated using X-ray diffraction, Mössbauer spectroscopy and magnetic measurements. The magnetic measurements were used for studies of changes in magnetic properties due to changes in stresses. The original laser cut samples were compared with those after heat treatment. The magnetic measurements appeared as the most sensitive method among those selected for the present study. The influence of stresses has an impact on the shape of the hysteresis loops and the permeability in dependence on excitation magnetic field. The selected heat treatment caused decrease of stresses and improvement of magnetic properties of the sheets.
Steel welds are still being used in vehicle constructions. Welding technology introduces local geometry changes into structures, undesirable residual stresses, changes the microstructure of the material in the heat-affected area. The weld acts as a structural-technological notch that degrades the fatigue properties of the base material. Until recently, this has limited the use of high-strength steels in vehicle construction. Increased yield strengths and strength limits could be used only for static load components, but not with time-varying loadings.
However, for some welded nodes, increased fatigue strength can be achieved if one of the HFMI (High Frequency Mechanical Impact) technology is applied. This is especially important for details made of high-strength steels. For harmonic loading, this improvement is clearly defined (increasing fatigue strength and shifting the S-N curve to higher lifetimes). In operation, however, most vehicles are exposed to loads that are random in nature. Of course, the manufacturer is interested in whether the application of a more sophisticated technology will be beneficial for real vehicle operation. What is the increase in the expected service fatigue life or what is allowed to increase the maximum service stresses in the structural node under consideration. Therefore, a parametric study was carried out which used the knowledge about stress spectra in the buses (trolleybus) constructions and the recommendations of the International Institute of Welding for improving the fatigue strength of welded joints with HFMI treatment.
In the article presented the results of studies of strength characteristics (yield strength- δy, ultimate strength δuts, power exponent- n) and fracture toughness (JR, JIC) determined on the specimens of steel S235 taken in the rolling and perpendicular direction. Standard strength characteristics are similar for the specimens in both directions. However, there occurs an essential difference in fracture toughness characteristics for the specimens from different directions. To determine (explain) factors that cause this phenomenon performed some metallographic studies and the analysis of local stress and strain distributions in front of the crack.
In the present work, results of tests conducted on thin welded steel-concrete stubs are presented. The studied section was made of two cold formed steel plates with U shape and welded to form an I steel section. The cross section dimensions were: 100x70x2 mm. A total of 24 stubs were tested under axial compression. The columns are divided in two groups. In the first group, A total of 8 stubs were tested, 4 were empty, 4 filled with normal concrete. In the second group, a total of 16 columns partially filled by the ordinary concrete, and were tested at 28 days after the date of casting, eight columns had shear connecters welded along the centreline of the web, and 8 had steel rods welded between the tips of opposing flanges on both sides. According to these results, we concluded that the bearing capacity was increased with the addition of shear connectors and local-buckling resistance of the flanges was increased with the addition of the transverse link. More experiment is needed to investigate the effect of the spacing of the transverse link on increased confinement for concrete and the mode steel local-buckling, of partially concrete filled thin welded steel stubs.
Mechanical alloying is a powder metallurgy processing technique involving cold welding, fracturing, and rewilding of powder particle in a high energy. It has been used to obtain nanocrystalline alloy. Fe 53%atm. Si 28%atm B19% atm. alloys were synthesized using a planetary ball mill (Retsch PM400). X-ray diffraction was used to identify and characterise various phase during the milling process. We used the hyperfrequence and the electromagnetic methods, to characterize the variation of structure and their influence. The shape of hyperfine field distributions used is discussed. It is shown that the FeSi solid solution was formed after 4 hours milling. The study state grain size is about 13 nm.
The paper presents the results of the bending tests performed on sling hooks. The hooks are produced of S235JR steel for the power industry. Because of the loading mode, the bending was conducted in two directions: along the axis of the hook and perpendicular to the hook axis. The data on the force values allowed determining the capacity of the slings and the maximum values of breaking forces.
The paper presents experimental results of investigations on deep drawing process of cylindrical drawpieces without collar in four drawing steps (single draw and three redraws). The research involved the use of EN AW-1050A aluminum blanks with diameter D = 66 mm. The material was prepared by rolling with different percent deformations (z = 5%; 10%; 15% and 20, respectively) at rolling mill DUO-100 and blanking process. In investigations of deep drawing, experimental force waveforms as the function of displacement for different percent deformations of sheet metal made from aluminium were obtained.
The efficiency of monitor and control of the technological process of hot rolling steels on strip mills depends largely on the accuracy of calculating the deformation resistance of the rolled metal the value of which is determined by the deformation parameters and depends on the steel chemical composition and the structural transformations of rolled products. This paper proposes a mathematical model for forecasting the deformation resistance of carbon and low-alloyed steels during hot rolling on a strip mill; the model makes it possible to take into account, along with deformation parameters, the content of chemical elements in steel and the metal recrystallization processes during deformation and during pauses between reduction steps. The model was verified by comparing the results of calculating deformation resistance with the experimental data obtained by rolling 100 strips 2-12 mm thick from 16 grades of carbon and low-alloy steels on a wide-strip mill 2000. The influence of dynamic, metadynamic and static recrystallization on the deformation resistance of carbon and low-alloy steels in mill stands is estimated. It is shown that taking into account the recrystallization processes of deformed metal makes it possible to significantly increase the accuracy of forecasting the value of the deformation resistance.
The indentation test is a simple, rapid and reliable tool that allows the mechanical properties of materials to be obtained from experimental load-penetration curves using inverse computation methods. Through this approach and using Berkovich and spherical indenters, the creep and elasto-plastic properties of the polymers have been estimated. A finite element analysis is carried out to simulate the mechanical behaviour of the polymers which is defined by the Young's modulus E and the parameters (K, n) which define the hardening of the polymers for large deformations. Simulations of the elasto-viscoplastic behaviour of polymers under nanoindentation tests were performed. The functions obtained by the simulations were validated by nanoindentation tests and compression tests for the studied materials.
The phenomena of solid solution lamonation, spinodal decomposition observed in the form of separation in β phase, were found in titanium alloys with high concentration of β stabilizers. The theoretical description of the observed phenomena is faced with great difficulties, so new experimental facts describing the variety of possible thermodynamically unstable states are needed to clarify the theory guidelines. The present study primarily focuses on lamination in β phase of Ti-5553 titanium alloy. High-strength titanium alloy Ti-5553 is widely used in the aircraft industry for parts such as the chassis and structural elements. Microstructure and chemical composition of Ti-5553 alloy after heat-treatment was investigated by electron microscopy (SEM, TEM), x-ray diffraction (XRD) and energy dispersive x-ray analysis (EDX). It was revealed that after annealing and slow cooling from β phase field the β phase separated into β-enriched and β-lean regions. Observed phase separation not influenced on decomposition during further ageing.
The paper focuses on the numerical investigation of the Al2O3 precipitation behaviour at the steel-slag phases interface. Several assumptions were made to simplify the process in order to prepare its description. A mathematical model of the steel-slag-precipitation system was introduced. The model base on the equation of motion, and takes into account forces balance of buoyancy force, added mass force, drag force and rebound force. Mentioned forces act in the same direction which is perpendicular with the steel-slag interface surface, but is positive or negative. The precipitation initial velocity can be calculated on the base of steel and inclusion density, liquid steel viscosity and particle radius. The numerical model based on the firstly prepared mathematical model was presented. Results of the computations show what is the precipitation radius size influence on particle movement and its assimilation to the slag.
The Co43Fe20Ta5.5B31.5 amorphous ribbon as the initial material form for final powders was prepared via melt spinning technique. Then, the high energy ball milling and subsequent sieving process has been done to obtain amorphous powders. The XRD and DSC studies have been performed to verify the amorphous state, the interatomic correlations as well as crystallization temperature and the crystallization kinetic parameters. The thermoplastic polymer (PVDF) has been used for further studies as a powder binder. For wound toroidal core and powder composite cores the magnetic measurements at 50 Hz have been performed. The magnetic saturation, magnetic remanence, coercivity, power losses as well as complex permeability value for composite cores have been correlated with the polymer content and the Co43Fe20Ta5.5B31.5 powders grain sizes.
Selective laser melting is an advanced manufacturing technology providing alternative method of producing complex components directly from 3D computer models. The paper is focused on problems related with selective laser melting technology (SLM) used for preparing titanium based implants. Two series of ten samples were mechanically tested in tension and compression respectively before and after heat treatment. Annealing under argon atmosphere consisted of solution treatment at 955 °C followed by furnace cooling to 855 °C with water quenching and ageing at 600 °C with air cooling. A fractographic study of fracture surfaces was performed using scanning electron microscopy and the observation was correlated with structural and mechanical properties of the SLM specimens in the condition as-received or heat treated. The failure features of as-received specimens corresponded to the microstructure with relatively high porosity, martensite needles, microcracks and residual stresses. The heat treatment resulted to the transformation of martensite to (alpha+beta) lamellar structure improving plastic properties that corresponded to the morphology of fracture surfaces. In spite of the porosity occurrence both specimen series exhibited high mechanical properties in tension as well as in compression.
The main aim of this paper was to investigate the effect of reinforcement particle size on the properties of Cu-Al2O3 composites. The starting materials for obtaining the composites were commercial powders: Cu and Al2O3. Experiments were performed using specimens containing 2.5, 5, 7.5 and 10% of alumina. The average particle sizes of alumina were 3.5, 22.5, and 65 μm. Before the sintering process, single pressing was performed with a hydraulic press at a compaction pressure of 620 MPa. The obtained sinters were subjected to the compaction process at a pressure of 620 MPa, and then again sintered at 900 °C for 60 minutes. The sintering process was carried out for 60 minutes at a temperature of 900 °C. The sintered compacts were subjected to the following tests: measurement of density, hardness and electrical conductivity. Observations of the microstructure on metallographic specimens made from the sintered samples were also performed using a scanning electron microscope (SEM). The density of all the composites increased when the particle size of alumina was reduced. Higher hardness were observed in samples containing finer Al2O3 particles. The electrical conductivity of the fabricated composites increased with the reduction of the alumina particle size.
The paper presents the results of research on the production of a sintered Cu-SiO2 composites fabricated by powder metallurgy. The starting materials for obtaining the composites were commercial powders: Cu and SiO2. SiO2 particles were introduced into a copper matrix in the amount of 2.5%, 5%, 7.5% and 10% by weight. Finished powders mixtures were subjected to single pressing with a hydraulic press at a compaction pressure of 620 MPa and then subjected to sintering process at 900 °C in an atmosphere of dissociated ammonia. The sintering time was 60 minutes. The sintered compacts were subjected to the following tests: hardness, measurement of density, electrical conductivity and abrasion resistance. The highest density was obtained for a composite containing 2.5% SiO2 which was 7.94 g/cm3. The highest hardness was obtained for a composite containing 10% SiO2 which amounted to 56.8 HB. For the composite containing 2.5% SiO2 the highest electrical conductivity was obtained which was 47.1 MS/m. The highest abrasive wear resistance was obtained for a composite containing 10% SiO2. Both density and electrical conductivity decreased along with the increase of SiO2 content in composites.
CuAl10Fe3Mn2-intermetallic phases laminated composites have been fabricated through reactive bonding at 875°C in vacuum using bronze foils (0.3 mm thick) and Ti foils with different initial thickness (0.05, 0.1 and 0.15 mm). The titanium layers were completely consumed during reaction resulting in microstructure of well-bonded bronze-intermetallics composites. The mechanical properties and fracture behavior of the fabricated composites were examined under different loading conditions through tension and impact tests. The results of investigations indicated that tensile properties of the composites strongly depended on the proportion between thickness of individual bronze layers and the thickness of intermetallics. The impact tests showed that when the load was applied perpendicular to the laminates, the composites displayed superior impact toughness. The toughness increased with increasing of remaining bronze thickness. The failure during impact testing occurred by cleavage mode for the specimens loaded parallel to the laminated composites and showed extensive plastic deformation for specimens loaded perpendicularly.
The main goal of this study is to show the effect of the advancing side (AD) and the retreating side (RT) position on the Residual stresses and local mechanical behavior of dissimilar friction stir welds of aluminum alloys AA2024-T3 and AA7075-T6. Different samples were produced by varying the rotational speed of the tool (1200 and 1400 rpm) and the alloy position regarding the advancing side of the tool. Ultrasonic Method has been used to evaluate Residual Stresses. This method is based on the acoustoelastic effect, which measures the velocity variation of the elastic waves according to the stress state of the material. This can be achieved through a calibration test, which permits the determination of the acoustoelastic coefficient (K). The results show a tensile stresses in the melted zone (MZ), the heat affected zone (HAZ) and a compression stresses in the base metal (BM). Increasing the rotational speed reduces the amplitude of the longitudinal residual stresses with a high reduction in the case where AA7075 - T6 is in the Retreating side. This has been directly associated to the increase in the heat input and the reduction of the thermal mismatch between different areas of the weld. The microstructure effect of aluminum alloy position acts on the acoustoelastic constant K. The choice of t0 corrects the overestimated residual stresses in the (HAZ) and (MZ).
Sealing system for high temperature flanging joints includes the pressed sealing from the expanded graphite with higher thermal resistance, which is located in exactly defined groove, this groove has been formed by spacer rings made from nickel alloys.
MITes FS - sealing system, which was tested for use in the equipment which works with molten salt. The profile of the flange joints needs to be modified for this seal. The modification involves adding one spacer ring in inner side, or two spacer rings in inner and outer sides made from nickel alloys (INCONELL, HASTELLOY…). The spacer rings have to made from material which have during working condition (600°C - 800°C) min. Rp0,2 - 150 MPa
The sealing material of this sealing system is expanded graphite with a higher thermal resistance. The inner spacer ring is used among other things as barrier against the direct action inner media to the sealing ring. The outer spacer ring is used among other things as barrier against the oxidation of the sealing ring.
Further, this sealing system can be equipped with an active atmosphere-maintaining system for which it is needed a special modification of the outer spacer rings to which are connected capillaries with high temperature resistance which are connect the exposed flange connection to the ambient environment in which the pressure source is located.
We conduct molecular dynamics (MD) simulations of pearlitic steel in which iron and carbon atoms are included. The paper aims at clarifying micro- or nano-sized mechanism of plastic deformation of pearlitic steel in wiredrawing process. By using embedded atom method (EAM) potential, we construct a nano-sized computational wiredrawing model of pearlitic steel where lamellae structures of ferrite and cementite phases are attached to each other and it is subjected to conventional drawing condition using hollow die. Basically, diffusion of carbon atoms around the ferrite-cementite interface is observed during plastic deformation. In order to recognize probable mechanisms by which carbon atoms migrate from cementite to ferrite, dislocation emission and movement are observed in detail. Besides, the plasticity in pearlitic steel is also discussed in this research by using nano-indentation model where a nano-sized spherical indenter compresses lamellae structures of cementite and ferrite.
Today finite elements method (FEM) modeling and calculation are used for analysis current state and forecasting reliability lifetime period of components and constructions. Essential issues for correctness of obtained results in FEM analysis are: proper interpretation of boundary conditions and right constitutive equation of material in terms of high stresses and strains. Standard procedure obtaining of material constitutive relation directly from experimental tensile test data does not proper result for every type of material. Method of constitutive equation creation for elastic-plastic material for a high level of plasticity based on data obtained during tensile test is presented. The proposed calibration method was verified on materials with different levels of strength and plasticity characteristics: S355JR and 42CrMo4 steels and ADI cast iron. Plastic deformation level, triaxiality stress state parameter and Lode factor were taken into account during created of the constitutive equation.
The C enrichment of austenite is of great importance to different kinds of transformation-induced plasticity-aided steels. Particularly, quenching and partitioning - a two-step heat treatment process, which involves the partial transformation to martensite and the subsequent C partitioning to austenite and its concomitant stabilization - has received considerable attention in recent years. The present work assesses the applicability of commercial software packages (DICTRA and MatCalc) to predict the interplay of C enrichment of austenite and concomitant C depletion of martensite. Results are additionally compared to calculations based on the “constrained carbon equilibrium” (CCE) and, moreover, to experiments conducted for two exemplary material conditions. DICTRA simulations extend the CCE calculation in terms of time dependence and allow to account for the possible displacement of the phase boundary, but lack the implications of the martensitic structure. Predictions based on MatCalc more accurately reflect experimental observations. Data gained allows for the evaluation of the predictive capabilities of commercial simulation packages corresponding to a prerequisite for the industrial implementation of novel heat treatment strategies and the required process control.
The paper deals with set of surface temperature of roll during hot rolling of tubes in stretch reducing mill in Zeleziarne Podbrezova. In the article was trying to solve the surface temperature of selected roll in comparison with the simulation of stretch reducing process. Temperature of the tubes after rolling in stretch reducing mill should be higher than Ar3 as much as 30 ÷ 50 °C. The article deals the surface temperature of roll and was compared with simulation of the transition of hollow with the real measured temperature. The surface temperature of the B-roll used the contact measurment system for temperature. The peripherally condition of simulation for the process was set up such as the system in the stretch reducing mill according to rolling of the tubes. All conditions from the system were in the simulation from the output temperature of hollow to reduction of stands for selected diameter kept.
Bulk ultrafine-grained (UFG) materials produced by severe plastic deformation (SPD) have recently been one of the most active and developing fields in modern materials science. However, UFG materials prepared by main popular SPD methods (like an equal-channel angular pressing) also have some problems with industrial implementation, notably the small dimensions limit their practical applications. One of most big part of metallic products industry - flat sheet production. Most reasonable way to intensify total strain in case of flat rolling is make asymmetry along deformation zone by different dimensions or different speed of rolls in simple case. This paper shows analysis of FEM-simulation of various scheme asymmetric rolling, when metal flow asymmetry provides by 2 factors in 2 directions - conic shape of rolls makes asymmetry along deformation zone and shift of rolls axis makes additional asymmetry effect across deformation zone. Simulation shows increase of nonlaminarity of metal flow and increase of total strain in models with shift of cone rolls, but this scheme have some problems with the shape of sheets, which could be solved by additional pass in conventional rolls. Simulated scheme shows possibility of good refinement of metal structure and substantiate experimental setup development on the next step.
The processing maps (i.e. power dissipation maps superimposed over instability maps) can be used as a very convenient tool in case of an optimizing of hot forming processes. In this research, processing maps of C45 medium-carbon steel were assembled on the basis of an experimental flow stress dataset. This dataset was acquired via series of uniaxial hot compression tests in the temperature range of 1173 K - 1553 K and the strain rate range of 0.1 1/s - 100 1/s. In addition, a predicted flow stress dataset was created with use of an artificial neural network approach - it allowed extending of the experimental dataset with additional temperature levels. The experimentally compiled processing maps have been subsequently enhanced by this additional dataset to encourage the overall information capability. The results have showed that the predicted dataset was useful to reveal additional instability regions in the experimentally assembled processing maps.
Fused Deposition Modelling (FDM) is one of the most common methods of 3D printing used in many fields of industry, especially in development departments. Since plastics are fundamental materials for electronics industry, the aim of this work is to examine dielectric properties of objects printed from such materials. This work’s contribution is the evaluation of the dependency of the printed objects properties on printing quality and the use of 3D printed plastic components in electronics.
For the experiment, three commonly used materials in FDM were chosen - PLA, ABS and PET-G. The materials were pure without any additional admixtures and the relevant test samples were printed with different printing resolution (height of one layer). The following properties were examined - permittivity, dissipation factor and dielectric strength. The results showed that permittivity slightly decreased with increasing height of one layer. Dissipation factor varied significantly in the measured range and there was no apparent dependency on the printing resolution. Rather, it was an indicator of the printing quality. Dielectric strength also slightly decreased with the decreasing resolution; however this parameter was governed primarily by the employed material. Generally, an improvement of the dielectric properties of these materials is required due to a relatively small dielectric strength, for example by adding admixtures to the base material or better printing quality.
The project 3D COVER investigates and develops material specific basics for the process of powder bed based additive manufacturing (AM) by laser beam (selective laser melting). Due to the technical complexity and the high potential provided by this young production technology, the AM technology is intensively investigated on a national and EU-level and worldwide. The collaboration of the research institutes, located in the Czech - Bavarian region, forms a unique combination of expertise and infrastructure within the program area, which sets remarkable impulses for the innovation power of the region. 3D COVER creates research basics for the entire process chain of this manufacturing method, which will be in near future similar important to conventional methods. 3D COVER attempts, to develop specific materials and characterize them over the whole process chain, to use and to qualify innovative characterization methods, by an integral solution approach. The major objective of this project is to create a material specific knowledge base for the SLM technology.
Components from the materials MS1 (1.2709) and AlSi10Mg were fabricated by selective laser melting (SLM) additive manufacturing. As-built and heat-treated components were analysed in terms of mechanical properties and microstructure. The heat treatment of the material MS1 was performed by a solution annealing at 850°C for 1 hour, ageing temperature at 480°C for 3 hours and air cooling. The heat treatment of the AlSi10Mg was performed by stress relieve at 300°C for 2 hours. Ostbayerische Technische Hochschule Amberg-Weiden carried out tensile tests of as-built and heat-treated samples. Samples were afterwards analysed in COMTES FHT a.s. for further tests of porosity and microstructure using optical and scanning electron microscopy. The aim of the present work is to show the change of mechanical properties and the microstructure with a heat treatment after the SLM process.
Titanium and its alloys are very popular for many applications. They are the most widely used materials for biomedical applications. Titanium-based materials have shown excellent biocompatibility, mechanical properties and corrosion resistance. The high fatigue life of this material is often demanded, therefore fatigue testing is concern. Additive manufacturing (AM) is innovative, widely investigated method for the production of metal components. AM allows the possibility of production accurate components. This research explores the fatigue behaviour of titanium alloy Ti6Al4V using selective laser melting (SLM). The SLM belongs to the most promising AM techniques. Different conditions and surface preparations on additive manufactured specimens were investigated by fatigue testing and compared to each other. The aim of this research is to explore the influence of surface machining and processing by hot isostatic pressing (HIP).
Numerical studies targetted to increasing power supersonic jets in oxygen converter during slag splashing process have been presented in this paper. The calculations are based on a special design of the gas-cooled lance, in which the structure was simplified, as compared with a water-cooled lance. Importantly, the sprayed slag with nitrogen and magnesium-containing (MgO) powder were used in the study. The maximum heating temperature in lance nitrogen was equal to 493 °С. The work was preceded by laboratory studies conducted for convertor slag received in one of the European plants. The following studies have been conducted: fluorescence analysis (XRF) of convertor slag samples and scanning microscopy as well as an X-Ray microanalysis of the isolated phases.
The analysis of the computation results shows that the cooling of the lance with gas leads to the heat recuperation, which increases the temperature of the injected mixture, so that the kinetic energy of the outflowing jet in the converter increases about 3.5 times, and the slag is splashed higher than in the case of a conventional water-cooled lance.
The introduction of yttrium as an alloy additive to steel is connected with the formation of non-metallic inclusions resulting in the losses of this element. The presence of yttrium is expected to minimize the precipitation processes caused by sulphur and oxygen in steel. Therefore the order in which the additives are introduced during refining processes decides about yttrium final content in steel in bounded and dissolved form. For defining the amount of the generated non-metallic phase and kinetics of deoxidation and desulphurization processes authors used a non-commercial computer program based on the worked out calculation models. The process was analyzed in view of the order of introducing additives: Al, Y and Ca to preliminarily deoxidized steel. It was revealed that yttrium dosing is connected with the formation of oxide and sulfide phases. The introduction of yttrium prior to aluminum brings about huge losses, mainly as far as oxides formation is concerned. In the case of higher participation of sulphur, this effect is even stronger. When yttrium is introduced after aluminum and calcium, yttrium is used for the formation of its sulfide, and in this way the manganese sulfide formation is reduced. The simulations showed that yttrium should be introduced at the end of the refining process after adding aluminum and calcium. In this case the yttrium losses for the formation of its sulfide and oxide and least.
This paper presents a study of surface layers produced by electro-spark deposition (ESD) using Alloy 400 electrode on the carbon steel. In the electro-spark deposition process, the electrode is the anode and the work piece is the cathode. The layers were investigated with metallographic methods. Microscopic examination was carried out to examine the structure of formed layers. Image analysis methods were used to observe the cross-section of the layer. For diffusion observations, ESD analyzes were performed on the cross-section of the produced layer. Scanning electron microscope (SEM) and energy-dispersive X-ray spectroscopy (EDX) analysis was conducted to characterize the microstructure and composition of the coating. The results of investigations showed that there is a possibility of obtaining the satisfying quality superficial layer on the carbon steel using Alloy 400 electrode.
This paper deals with the results of testing elements made of 145Cr6 steel after heat treatment. The elements have been machined with various abrasive materials (such as: quartz sand, two corundum sizes and two amounts of Brown Fused Alumina) with the use of abrasive blasting. The treatment of all types of abrasives took place at the same working pressure of 0.55 MPa. The 2D and 3D roughness parameters obtained after the abrasive blasting were analyzed. Roughness measurements were made using the Talysurf CCI Lite optical profilometer. Microscopic observations were carried out on the Nicon Eclipse MA 200 inverted microscope.
The article presents the proposal of using grounded zeolite rocks for container processing. Effectiveness of removing corrosion and geometric structure of the surface changes of objects made of carbon steel were investigated. Specified mass losses depending on the length of the vibratory machining process and changes in the geometric structure of the surface. The results were compared to analogous processes carried out with the use of ceramic abrasive media
The aim of research was to obtain fabricated new Fe/Al2O3 composite foam with controlled mechanical properties. Composite foams of iron and aluminum oxide were prepared by sintering techniques. Al2O3 microsphere powders, added during Fe foam formation were used as a base materials. During research samples containing various compositions were prepared and the amount of AL2O33 microspheres bonding in Fe foam was changed. The metallic porous structure was obtained by sintering on the basis of iron-based powder mixtures with the addition of a copper catalyst and Fe (III) oxide as a space carrier. Sintering was carried out at 1130°C and 50 minutes long, in a dissociated ammonia protective gas. Observation of the microstructure and phase identification of the synthesized samples was carried out using optical microscopy (OM), scanning electron microscopy (SEM) and energy dispersion spectroscopy (EDS). The porosity of the Fe/Al2O3 composite products for the three different compositions was measured by means of the Cavalleri principle on transverse samples prepared from sintered materials. Fabricated Fe/Al2O3 composite foam can be used to build elements that allow for kinetic energy dissipation.
The article concerns the assessment of the intersection structure of copper samples after abrasive waterjet (AWJ) cutting. The surface quality of the processed material was tested on a macroscopic and microscopic scale. The assessments of surface quality was carried out in three characteristic areas of the cutting surface. The macroscopic studies concerned the evaluation of post-treatment cutting traces, with particular emphasis on the trajectory of the stream in the bottom edge of the cut. Microscopic study of the geometric structure of the surface included the assessment of the conditions of impact of individual abrasive grains with the surface treated by using AWJ cutting. Characteristic orientations of machining traces were observed on the treated surface. The surface of the cutting zone located at the inlet of the stream to material is characterized a better cutting quality with visible of a privileged direction of traces of the impact of abrasive grains on the machined surfaces. As a result of the decrease of the kinetic energy of the cutting jet along with material penetration the surface at the outlet of the stream from the cut material, a surface characterized by the occurrence of multi-directional traces of abrasive grains. In this area are visible traces of decohesion of the workpiece in the form of microgrooves. In the studied areas, the effect of embedding fragments of crushed grains on the surface of the processed material was observed.
Fe79.8-xCo2CuxMo0.2Si4B14 alloys with variable Cu content were prepared using melt spinning method. The amorphous state of samples was verified using X-ray diffraction (XRD) method. It was noticed, that the ribbons with copper addition above 1.5% at. were partially crystalline. For amorphous alloys differential scanning calorimetry (DSC) was used to describe crystallization kinetics. Two exothermal peaks were observed. On the basis of analysis of XRD patterns it was noticed, that the first peak on DSC curves is associated with crystallization of the α-Fe phase, whereas second peak with formation of the Fe2B phase. Moreover, performed analysis of average Avrami exponent allowed to state that the crystallization of the α-Fe phase is the diffusion controlled growth with decreasing nucleation rate and the Fe2B interface controlled growth with increasing nucleation rate. The isothermal annealed alloys exhibit high saturation magnetization (above 1.55 T), low core loss (below 0.5 W/kg) and relatively low coercivity (below 10 A/m). The process of the α-Fe phase formation was studied using the Mössbauer spectroscopy and the high resolution transmission electron microscopy. It was noticed, that for the optimal thermal treatment parameters, the α-Fe nanocrystallites with size below 10 nm in amorphous matrix are obtained.
Cavitation wear resistance, of four different nickel-based alloy during the incubation period was investigated with the use of stream-impact device and results are presented in this paper. Four nickel alloys with excellent resistance corrosion very high corrosion resistance and very good mechanical properties were selected for the tests: Monel 400, Inconel 600, Incoloy 800H and Hasteloy C22. Nickel alloys examined for the period of 600 minutes. Mechanism
of formation and destruction of the surface layer under working liquid influence is described.
It was noticed, that first microcracks are formed on the grain boundaries, especially in the triple contact points. Effects of plastic strain were also noted on the surface of samples as a uplifting and collapsing in boundary area. It was stated, that among nickel alloys examined, a better resistance to cavitational erosion in initial period of cavitation damage has the alloys: Hasteloy C22 and Incoloy 800H.
After the Fukushima accident in 2011, development of so-called Accident Tolerant Fuels started. These advanced fuels should provide additional coping time in case of a severe accident in a nuclear reactor. VVER reactors utilize E110 alloys as nuclear cladding. These alloys have been modified by applying coatings with specific functions on their outer surface. The cladding materials with enhanced accident tolerance have been tested and optimized. Recent results of multilayer cladding will be presented inluding testing in normal operation and accidental conditions.
The ferromanganese industry is currently strained by the cost of production. Alternative reductants are being sought to try and alleviate the production costs namely solar energy, wind and biomass. Some studies on the possible use of biomass using the South African manganese ores were conducted and preliminary results were generated. The South African manganese industry has focused more on the pre-reduction. The current paper focuses on the use of raw macadamia nut shells for the reduction of manganese ore in the presence of carbon monoxide. The feed and products were characterized using XRD, XRF as well as SEM and compared to products currently obtained using conventional reductants. The basicity of the feed was kept at around 1. The temperature was set at 1450oC, a graphite crucible placed in a silica crucible to prevent any spillages. Establishment of comparisons between products obtained when raw macadamia nut shells and conventional reductants were used was done. It was found that macadamia nut shells have great potentials of replacing the conventional reductants used so far. The separation of slag from the metal needs imporvement as the slag structure was more needle-like and some metal entrapments were noticeable as compared to conventional process.
Conventional reductants have been and are still being used for most of the high temperature reduction processes. However, new reductants are being sought for. Macadamia nut shells were used as reductant in this investigation and their effect on the slag. Cassiterite containing Nb and Ta have been used in this investigation. The basicity of the feed was kept at 1 through the addition of CaO-bearing material as a flux. The raw macadamia nut shells were characterized using proximate and ultimate analysis, XRF, XRD, SEM-EDS and FTIR. The ore and flux were analyzed using XRF, XRD and SEM-EDS. Experiments were conducted using an alumina tube furnace. The temperature was set at 1450 oC, a graphite crucible placed into a silica crucible was used for the experiments. Reduced products were characterized and compared to the products currently obtained using conventional reductants. Products obtained when raw macadamia nut shells were used and when using coke were compared. Results show that macadamia nut shells present great potential to use as reductants in tin industry on condition of further investigations on optimization. The slag produced presented a more needle-like structure as opposed to the conventional process that presented a glassy slag.
Innovative bioplastics blends and composites can be realized by extrusion. Interestingly poly(Lactic acid) (PLA) toughness can be improved by following two different strategies: the use of elastomeric additives such as poly(butylene adipate-co-terephtahale) (PBAT) or the use of rigid fillers, such as calcium carbonate. In both cases the combination with plasticization can be synergistic. The modulation of mechanical properties thanks to the knowledge of structure-properties relationships opened the possibility of exploiting these materials in a wide range of applications: packaging, automotive, personal care, cosmetics and biomedical devices.
The preparation and selection of biobased materials compatible with skin in the framework of European H2020 POLYBIOSKIN project is essential for producing innovative healthy and highly ecofriendly products for the personal care sector. Functional treatments can be applied to make bioplastics suitable for specific goals (anti-microbial, anti-oxidant, anti-inflammatory, etc.). Testing the compatibility of the developed materials with cells is fundamental to evidence their potential compatibility with human body and eventual anti-microbial activity.
Ultrafine-grained (UFG) Al 7050 alloy of the 7xxx series demonstrates very high strength at room temperature with UTS=845 MPa and hardness Hv=255, which considerably exceeds the value after conventional heat treatment T73, i.e. Hv=165. It is also revealed that with increasing temperature the alloy exhibits rather high ductility with elongation to failure δ=170% at 120 °C and strain rate of 5×10-4 s-1 and typical superplastic behavior with δ=480% and δ=690% at temperatures 170 °C and 200 °C correspondingly. Such values of superplasticity (SP) temperature are considerably lower than that typical of this alloy with micron-sized grains (TSP=450-500 °C). Such reduction in superplasticity temperature made it possible to preserve ultrafine grains in the alloy structure and provide its high-strength state after SP straining.