Seznam abstraktů 2018: SEKCE E - NEŽELEZNÉ KOVY A SLITINY

Ti-35Nb-6Ta-7Zr alloy was developed more than 20 years ago for biomedical use due to its biocompatibility and low elastic modulus. Main drawback is limited strength of this material. Recently it was found that alloying by 0.7 wt. % of oxygen leads to significant (100%) strength increase. However, simultaneously, oxygen addition leads to an adverse increase of elastic modulus. It is now understood that body centred cubic beta phase shows lowest elastic modulus if the stability of the beta phase is low due to the ‘proximity’ to martensitic beta to alpha’’ transformation. Oxygen causes relative beta phase stabilization causing increased stiffness. In the present study, six different alloys with reduced niobium and/or tantalum content in order to reduce beta phase stability were prepared by vacuum arc melting. Their microstructure in beta solution treated condition was studied by scanning electron microscopy and mechanical properties were studied by microhardness measurements, measurement of elastic modulus and tensile test. Elastic modulus was found to correlate with beta phase stability, while strength remains high. Ductility is negatively affected by the coarse-grained as-cast condition of the material.

Commercially pure titanium was prepared by advanced powder metallurgy methods with the aim of producing ultra-fine grained material. To fully understand the microstructural changes during the process, detailed investigation was performed after each step.
Cryogenic attritor milling was used as a first step to refine the microstructure at liquid argon temperatures to suppress recovery and dynamic recrystallization. Spark plasma sintering was afterwards employed to produce bulk material, exploiting its ability to achieve fully dense structure in short time and thus to reduce the grain growth.
Powder morphology was changed significantly after milling, while particle fragmentation was only limited. Equilibrium grain size was found to be approx. 50 nm with texture similar to rolling texture.
Grain size after sintering was in micron scale, relatively independent of sintering conditions. Stabilization was provided predominantly by impurity inclusions from milling. Due to the shape and packing of particles, texture was retained even in the sintered samples, resembling texture after multidirectional rolling.

Metastable beta Ti alloys are perspective materials for a number of biomedical and aerospace applications. After quenching from temperatures above the beta transus, the microstructure of metastable beta Ti alloys consists of beta and omega phase. During subsequent heat treatment at lower temperatures, particles of alpha phase form and the microstructure becomes thermodynamically stable. Initial stages of alpha phase formation were characterized using advanced experimental techniques. The crystallographic relationship and the orientation of alpha lamellae with respect to beta phase matrix were studied.

A Ti15Mo metastable beta titanium alloy was subjected to high pressure torsion (HPT) and equal channel angular pressing (ECAP). A subsequent annealing at 400 °C and 500°C of these materials results in heterogeneous precipitation of the alpha phase. The morphology and the heterogeneity of the precipitation of the alpha phase has been studied using a combination of scanning and transmission electron microscopy. It was revealed that a slightly larger Mo content suppress the formation of the alpha phase, however, a high density of dislocations and grain boundaries promote the diffusion of the atoms, hence, the nucleation and growth of the alpha phase particles.

Beta titanium alloying system Ti-Nb-Zr-Ta-O has been thoroughly studied in the last two decades. This research yielded several compositions with optimized properties for the endoprostheses production requirements (high yield strength, low Young’s modulus). One of these alloys, Ti-35Nb-6Ta-7Zr-0.7O (wt. %), differs from most of them by its very high oxygen content, which provides a significant interstitial solution strengthening. However, there is a need for thermomechanical processing because of the poor fatigue resistance after casting. This is caused by a residual porosity in the ingot and large grains (size > 1 mm). Die forging was used to work the cast rod of 55 mm in diameter into rods with diameters of 35 mm and 25 mm. Resulting microstructure and mechanical properties are evaluated and discussed.

Evolution of ω phase in metastable β-titanium alloy (Ti-15Mo) was investigated in-situ during heating by synchrotron X-ray diffraction and compared to previous measurements. The initial condition of the material contains β phase matrix and tiny uniformly dispersed athermal ω particles, which formed during quenching. The values of intensity of ω reflections decrease during heating up to about 230 °C indicating that volume fraction of ω phase also decreases. Further heating results in increase of intensity of ω reflections. Between approximately 400 and 560 °C the intensity of ω peaks again decreases, which could be caused either by decrease of volume fraction of ω phase or by sharpening of ω reflections due to increase of size of ω particles. Absence of ω and α reflections at 560 °C was observed, therefore ω particles do not serve as direct precursors for α phase precipitation. Reflections of α phase begins to appear at higher temperatures (about 580 °C).

Anomalous X-ray diffraction (AXRD) is a technique which makes use of anomalous dependence of diffracted intensity on photon energy around an absorption edge of an element present in the studied material. AXRD allows the determination of the concentration of this selected element in the sample. In this study, AXRD was measured near the MoK absorption edge (20.0 keV) in single crystals of Ti-15wt.%Mo. The measurement was carried out at selected ω and β diffraction peaks for a series of heat-treated conditions. The dependence of diffracted beam intensity on the primary beam energy was simulated by a core-shell model in which ω particles are slightly depleted in Mo, whereas the region in the immediate proximity of ω particles (shell) is richer in Mo than the average concentration in the alloy. Local elastic deformation of the β lattice arising from the presence of ω particles was also included in the model.

Ti-6Al-4V alloy is mostly used for dental and hard tissue implants, due to its high strength to weight ratio, high corrosion resistance, and relatively low elastic modulus. However, apart from health concerns of V ions release and higher Young’s modulus (~ 120 GPa) than human bone (~30 GPa), recent research indicates day-to-day cyclic loading instead of a single-load event such as a fall, might be the consequence of inherent stiffness of fixation implants. In this study, Ti-6Mo-4Zr-xSn (at. %) alloy with pliable quality was developed and fabricated to efficiently avoid the potential hazards of fragility fracture and spinal spurs that pinch the spinal cord or its nerve roots and can cause weakness or numbness in the arms or legs—has been a long-term clinical quest. The evidence of its bone matching modulus, pliable mechanical behaviour, excellent wear, corrosion and cytotoxicity properties are desirable potentials for future clinical therapy.

Aluminum-magnesium based alloys are well-known to possess excellent corrosion resistance. However, alloys containing more than 3 wt% Mg are susceptible to localized attack by intergranular corrosion and to exfoliation when they are exposed to temperatures ranging from 50 - 180 °C. This susceptibility is predominantly linked to the precipitation of highly anodic beta-phase along grain boundaries. This phenomenon is termed as sensitization. Moreover, the presence of stress along with a sensitized microstructure leads to a strong susceptibility towards intergranular stress corrosion. The continuous precipitation of beta-phase leads to accelerated failure through anodic dissolution in the presence of detrimental chemical species like chloride ions.
The nucleation and growth of boundary precipitates are strongly affected by the type of boundary because of the correlation between the Mg segregation level and grain boundary energy. Strong beta-phase continuous precipitation and subsequent corrosion attack is therefore often observed in layered pancake grain structures formed generally in rolled sheets. However, such an unwanted precipitation is highly suppressed in the same material in areas without the pancake structure containing only a random distribution of low-angle boundaries.
Direct casting of sheets to the final thickness (typically 3 - 8 mm) by continuous twin-roll casting without the necessity of using subsequent rolling steps could limit the formation of layered structures. The necessary grain refinement could be reach by severe plastic deformation methods. In the present contribution the grain-boundary segregation in Al-Mg-Sc-Zr alloy prepared conventionally by rolling is compared with this effect in twin-roll cast materials refined by constrained groove pressing.

Multi-component alloys containing at least five elements in equimolar or near equimolar ratio are commonly known as High-Entropy Alloys. Despite the complex chemical composition, with the fulfillment of specific thermodynamic parameters, they are characterized by the existence of simple phases. During designing process of such materials VEC (Valance Electron Concentration) parameter is commonly used to predict the crystallographic structure of the alloy. Calculations are based on the percentage of individual elements and the number of each valence electrons. Research presents the effect of chromium addition on the structure and microstructure of alloys from Al-Ti-Co-Ni-Fe-(Cr) system. The assumption is, that the addition of chromium will lower the value of the VEC parameter, and will results in the transition from FCC structure to FCC + BCC structure. Such crystallographic change should additionally leads to significant changes in the properties of these alloys, e.g. by hardness increasing. ACKNOWLEDGEMENT:This work was supported by the Polish National Science Centre [grant number 2017/25/N/ST8/02542].

The research problem focuses on the wires made of aluminum alloys acquired in the wire drawing process of the wire rod obtained using the Continuus Properzi method. The nature of the drawing process generates a heterogeneity of strain on the wire cross-section, which results in the formation of internal stresses. The result of drawing round wires is a parabolically shaped internal stress distribution: tensile stresses around the surface and compressive stresses around the axis of the wire.
The aim of the work was to empirically determine the distribution of internal stresses in the wires made of aluminum alloy EN AW 6101 (AlMgSi) obtained in various conditions. The internal stresses were determined through the surface treatment method. In order to achieve that, after proper preparation of the wire samples, their surface was pickled using a 20% NaOH solution. After stabilization of the thermal state, changes in length were investigated. Parallel to the internal stress tests, the macroscopic properties were characterized in a uniaxial static tensile test.

Presented paper compares fatigue behaviour of alloy AlSi9Cu3 produced by gravity casting and Selective Laser Melting (SLM). SLM is one of the additive manufacturing method. It allows a production of metal parts with complicated shape in relatively short time and without big material waste. However the quality of final material could be worse than conventionally produced one (e.g. moulded or extruded).
Acoustic emission (AE) method is used to obtain a detailed information about fatigue behaviour. Compared to previous work, the new methods of AE signal analysis is used. This method provides a more detailed AE signal analysis, in addition to number of count and events, also takes into account rise time and amplitude of the events. So we do not get only a ratio of fatigue stages but also an idea of microstructure changes during cyclical loading.
Main aims of presented study are to compare endurance limit of cast and SLM aluminum alloy using standard S-N curves and analyse the fatigue processes using AE method. Both material were tested in as-cast resp. as-built condition without any heat treatment. All samples were subjected to fatigue bending tests in high-cycle regime. Result shows that the endurance limit of the SLM material is better than the cast material with a similar chemical composition. AE signal analysis shows different ratio of fatigue stages and indicate a different mechanism of crack initiation and grow.

Twin-roll casting (TRC) allows production of sheets and strips with required thickness without subsequent homogenization or hot rolling and therefore has a high potential for industrial applications. One of the drawbacks of this method is a formation of inhomogeneous structure with central segregation. TRC prepared from 3003 aluminum alloy with 1 % Mn, 0,2 % Fe, 0,5 % Si, 0,2 % Cu and small addition of Zr (0,2 %) and Cr (0,1 %) was studied by X-ray computed tomography. Segregations in the material form as manganese, iron and silicon rich channels spread in the rolling direction. Material annealed at 450°C exhibits diffusion of alloying elements from segregations into their surroundings and formation of voids or material with lower density in the center of segregation channels due to Kirkendall effect.

The results of investigations of the structure and mechanical properties of in-situ aluminum matrix composites based on the Al-Mg-Si system reinforced with primarily crystallizing silicides Mg2Si are presented. The main advantage of such materials is the usage of relatively inexpensive initial components with absence of the necessity for the use of powders, which greatly simplifies technology and reduces the production cost of castings. However, coarse morphology of primary crystals Mg2Si and needle structure of eutectic phase Mg2Si in cast composites have negative influence on the strength characteristics of obtained products.
To control the morphology and size of endogenous Mg2Si particles, thermo-temporal treatment of the Al-Mg-Si melts has been tested. It is shown that the thermo-temporal treatment has a grain refining effect on the primary crystals of the Mg2Si reinforcing phase. With an increase in the duration of isothermal holding of the composite melt from 15 to 30 minutes at 900 °C, the average size of the reinforcing particles decreases substantially, and their total amount increases. A further increase in the holding time to 45 min leads to coarsening of the morphology and growth of the inclusions, and upon holding for 60 min the amount of primary Mg2Si crystals decreases sharply and eutectic colonies are formed. Under the conditions of the experiments, the most favorable structural characteristics and mechanical properties of cast specimens were attained by isothermal holding of the melt at 900 °C for 30 min.

It is shown from the point of view of the quasicrystalline model of metallic melts that during the liquid phase treatment by nanosecond electromagnetic pulses it may be possible the occurrence of energy fluctuations in the melt, change of short-range order structure in the atoms arrangement, reducing the cluster size and shortening their lifespan, decreasing the disordering temperature. These processes change the physical properties of the melt, crystallization parameters, physical-mechanical and operational properties of the obtained alloys.
It is theoretically justified that irradiation of the melt with nanosecond electromagnetic pulses, by reducing the surface energy of an interphase boundary "crystal-melt" and contributing to increase in degree of the melt undercooling, increases the formation rate of nucleation centers in a unit volume of the melt and provides the refinement of microstructure of resulting castings. In addition, increasing the wettability of solid particles by the melt and reducing the surface tension at the interphase boundaries leads to substantial dispersion of nonmetallic inclusions and intermetallic phases, which causes the formation of additional crystallization centers.
It is assumed that when the nanosecond electromagnetic pulses are applied to the liquid phase, the bond energy curve shifts toward a lower value of the interatomic distance, while the absolute value of the bond energy decreases. For this reason, the melt irradiation provides the possibility of an energetically and kinetically easier moving of atoms from one stable state to another, which accelerates diffusion processes and deactivates clusters.

The Diffusion welding was used to join aluminium alloy AlMg3 in order to make ultrasonic testing of diffusion bonded joints and analyse diffusion process. This ultrasonic testing should be used to compare with other non-destructive testing methods which the Institute of Manufacturing Technology of CTU in Prague develop. The paper discusses the ultrasonic testing for the diffusion bonded joints of AlMg3 and magnesium oxide which was created and which had an influence on quality of the diffusion bonded joints. The Alloy AlMg3 was selected be-cause of easy correlation with welding parameters, ultrasonic testing, metallographic examination and prepara-tion of samples for the diffusion welding.

Binary Mg-Nd (content of Nd 2 wt.%) and Mg-Y (content of Y 4 wt.%) alloys processed by hot extrusion and equal channel angular pressing (ECAP) were studied. Microstructure after extrusion and different number of ECAP passes was investigated by scanning and transmission electron microscope. Evolution of mechanical properties was tested by microhardness tests and compression deformation tests in two directions – along processing direction and transverse direction. The experimental results showed significant grain refinement in both alloys. However, heterogeneous coarsening of intermetallic phases of Mg-Nd alloy occurred, probably due to the high processing temperature of ECAP. The mechanical strength of both alloys considerably increased through ECAP. Several strengthening mechanisms, include solid solution strengthening, precipitation hardenning as well as grain boundaries strengthening positively affect the strength of alloys. Additionally, isotropic mechanical behaviour was found in X and Y direction and was discussed with regarding to microstructural development during processing.

We investigate the new alloys of Mg-Ga-Zn-X system, where X = Ca, Y and Nd. These alloys can be used as biodegradable materials due to the low cytotoxicity of Zn and Ga and effectiveness of Ga against bone resorption, osteoporosis and Paget’s disease. The microstructure and phase composition of alloys were determined using scanning electron microscopy and energy dispersive X-ray spectroscopy. The as-cast microstructure of Mg - 4 wt. % Zn - 4 wt. % Ga (Mg4Zn4Ga) alloy consist of magnesium solid solution (Mg) and two eutectic phases with composition (Mg,Ga)7Zn3 and (Mg,Zn)5Ga2. For the improvement of mechanical properties the severe plastic deformation technique named equal channel angular pressing (ECAP) was used. Microstructure, mechanical and corrosion properties of ECAP processed alloys were investigated. It was established that the grain sizes differ more than ten times in microstructure of Mg4Zn4Ga alloy after ECAP. The additions of 0.2 - 0.3 wt. % Ca, Y and Nd lead to formation of uniform-sized grains of 5 - 15 μm. Mentioned previously additions does not change the mechanical properties of Mg4Zn4Ga alloy and measured values of ultimate tensile stress (UTS) is 298 MPa, yield stress (YS) is 167 MPa and elongation (El) is 23 % of Mg4Zn4Ga alloy. The hydrogen evolution corrosion test was carried out in Hanks’ solution during 192 h. The additions of 0.2 - 0.3 wt. % Ca, Y and Nd to Mg4Zn4Ga alloy promote the increasing of the corrosion rate for about two times.

Magnesium and its alloys are considered for specific applications in medicine such as fixation devices, screws and stents. However, release of hydrogen gas, pH increase and premature failure of the mechanical integrity of implant material are considered as the main limitations. Zinc-based alloys offer an interesting alternative choice for similar kind of applications, however, some limitations are known. First of all, the human body is able to accept significantly lower daily doses of zinc compared to magnesium. Zinc is also quite heavy metal with density and young modulus highly different from that of bones. In summary, both kinds of alloys intended for applications in medicine behave very differently. Present work characterizes the most relevant properties of both groups of alloys based on the date obtained by a substantial research at UCT Prague in cooperation with other institutions and companies. ACKNOWLEDGEMENTS: This research is funded by Czech Science Foundation (project no. GA 18-06110S) and specific university research (MSMT no. 20-SVV/2018).

This study investigates the effect of ageing (T6) and deep cryogenic (DC) treatment on wear and microstructure of magnesium alloy AZ91. To reach the objectif, a semi continous casted AZ91 alloy was subjected to T6 treatment at 400 oC for 4h, 5h and 6h and following to deep cryogenic (DC) treatment at -198oC for 48h. Scanning electron microscopy (SEM) technique with optical microscope, X-ray diffractometer (XRD), hardness tester and pin-on-disc wear test were used to characterise the specimens. The results show that T6 and DC treatments increased the hardness of magnesium alloys especially for the 5h and 6h ageing treatment times. This change was observed on the microstruture of the alloy; β phase dissolved in the magnesium matrix after treatments. In addition, increasing the treatment time decomposed the laminar α-phase rich in aluminum and increased the intensity of β-phase. In concordance with the modification of the morphology; wear rate increased with treatment time and higher wear rate was obtained particularly for 6h of treatment time.

Magnesium alloy with Zn and Nd alloying elements was processed by equal channel angular pressing (ECAP). Microstructure became ultra-fine grained after 8 passes of ECAP. Mechanical properties and microstructure was studied by microhardness measurement and electron backscatter diffraction (EBSD).

The mechanical and corrosion properties of Mg – (2.2-3.8 wt. %) Zn – (0.3-0.7 wt. %) Ca – (0-0.9 wt. %) Mn alloys for use as materials for the biodegradable implants were investigated. For improvement of microstructure and mechanical properties of alloys the Equal-channel angular pressing (ECAP) was used. The microstructure and phase composition of alloys were determined using scanning electron microscopy and energy dispersive X-ray spectroscopy. The phase diagrams sections and alloys phase composition was calculated using the Thermo-Calc software. By differential thermal analysis (DTA) the liquidus and solidus temperatures of alloys was obtained. The alloys have a wide solidification range of about 250 °C. The mechanical properties and coorosion properties of ECAP processed alloys were investigated. The Mn containing alloys phase composition consist of magnesium solid solution (Mg), manganese (Mn) and Ca2Mg6Zn3 phase. The alloys without Mn have the same phase composition but without (Mn) phase. The solute heat treatment of alloys leads to an increase of the zinc content in the (Mg). Calcium and manganese have low solubility in (Mg). The obtained samples of Mg-Zn-Ca and Mg-Zn-Ca-Mn alloys have ultimate strength (UTS) from 220 to 240 MPa, and elongation (El) from 17 to 29 % after ECAP. In vitro corrosion test by hydrogen evolution method was carried out in Hank’s solution at 37 °C during 192 h. All of investigated alloys showed approximately the same corrosion rate and manganese addition didn't affect the corrosion rate.

Acoustic emission has been used to study magnesium alloys for many years. We introduce a new method of evaluation of the acoustic emission signal and its advantages for studying mechanical and corrosion properties of magnesium alloys.

Rare-earth containing magnesium alloy AE42 was prepared by powder metallurgy technique of spark plasma sintering. The effect of sintering parameters on the microstructure, precipitation of secondary particles and mechanical properties was investigated. The gas-atomized AE42 alloy powder was sintered at three different temperatures of 450 °C, 500 °C and 550 °C for three minutes, which was sufficient to achieve almost full density. Despite the negligible effect of the sintering temperature on the grain size, sintering had a pronounced effect on the Al11RE3 secondary phase particles. Fine eutectic lamellae structure of Al11RE3 in gas-atomized powder transformed to almost globular particles during SPS and size of these precipitates increased with increasing sintering temperature. As the result, SPS temperature had significant effect on the mechanical strength of the material via altering size and morphology of Al11RE3 precipitates. Sintered material was compared with the gas-atomized powder subsequently annealed at 550 °C. It was found that the kinetics of the globularization of the Al11RE3 precipitates is much faster during spark plasma sintering than during conventional annealing at the same temperature. This can be associated with increased diffusivity along the matrix/precipitate interface or possibly by locally increased temperature due to electron transport.

Experimental study and numerical model for the thermo-mechanical properties in continuous casting of Cu-Al alloys is presented. This is a prerequisite basis for further development of the Cu based shape memory alloys (SMA) with various alloying elements (like Ni or Mn). A coupled thermo-mechanical numerical simulation of the continuous casting process is implemented and applied to the full non-equilibrium process conditions. In the experimental part we have used simple yet effective vertical continuous casting system. For the quantitative comparison we have implemented special temperature measurement system within graphite crystallizer that enables us to monitor temperature profile at several spots around solidification front in real time. Present analysis of the various process parameters effect on the solidification process include: casting speed, thermal contact conductivity, liquid metal temperature and cooling system set up. For microstructural examination we have prepared samples from rods that were subsequently investigated by optical microscopy, scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDXS) analysis. Comparisons of the experimental results and numerical simulation have been carried out. We have developed comprehensive numerical simulation model that quantitatively describes non-equilibrium time dependent temperature profile, solid fraction and microstructure features in as cast state. Results from the coupled thermo-mechanical and microstructural simulations compare favorably with experimental data suggesting the casting speed as a key parameter in process optimization. Acknowledgments: This work has been supported by Croatian Science Foundation under the project (IP-2014-09-3405).

Biodegradable implants are characterized by high biocompatibility, specific corrosion rate in the human body, good mechanical properties and lack of harsh reactions of the organism to the corrosion products. In recent years, zinc alloys have become more and more popular among biodegradable metallic materials with potential application for short-term implants or stents. It should be highlighted that pure zinc possesses desirable corrosion rates and does not pose a health issue in regard to corrosion product toxicity on the human organism. As it has been reported in the literature, the brittleness and poor mechanical properties of pure zinc can be improved by alloying with biocompatible elements, through proper forming methods and plastic deformation processes. The aim is to achieve finer grains in the microstructure so as to increase the yield point and strength of zinc, in accordance with the Hall-Petch equation. Based on this, the presented research includes the characterization of the effect of zirconium microadditions on indirectly extruded zinc alloys. Microstructural and mechanical property analyses, as well as preliminary corrosion test results show the influence of two meaningful factors responsible for increasing the strength of metals, i.e. alloying element introduction and hot deformation process. The obtained grain refinement via zirconium additions and the resulting improvement in strength and ductility indicate that new biocompatible Zn-Zr alloys could be a good candidate for bioresorbable implant materials.

Presented research characterizes Zn-0.5Cu alloy that was investigated in as-cast, homogenized state and after carrying out Equal Channel Angular Pressing (ECAP) four times at room temperature via route BC. The microstructural analysis obtained using light and scanning electron microscopy show the typical as-cast microstructure, equiaxed grains after annealing and ultrafine-grained microstructure after the ECAP process. Mechanical characterization was performed at room temperature via uniaxial tensile and compression tests and also Vickers hardness. To analyze the main deformation mechanism SEM/EBSD analysis were made. Ultrafine-grained microstructure allows to obtain superplastic flow at room temperature what was observed for the first time for Zn-Cu alloys.

Deformation on the macro scale is governed behaviour of grains. In this study creep was investigated in differently oriented grains of pure zinc using nanoindentation creep test. Creep was investigated by indenting along three different directions viz.,<0001>,<112 ̅0> and <101 ̅0>. Results have shown different creep behaviour for different orientations suggesting a strong creep anisotropy. Basal grains had a higher creep rate as compared to other orientations. Although basal grain showed higher creep, the depth recovery observed was highest for this orientation. The creep deformation mechanisms observed through AFM were different for different orientations. Twinning was observed when indented along <112 ̅0> and <101 ̅0>. Stress exponent values obtained for different orientation suggests different creep mechanisms.

Fe-Al-based superalloys containing sub-micron Fe2AlTi cuboids coherently embedded into a disordered Fe-Al solid solution are intensively studied as materials for high-temperature applications. We focused on the Fe71Al22Ti7 alloy composition for which the transmission electron microscopy (TEM) revealed the superalloy nano-structure and the energy-dispersive X-ray (EDX) technique detected the composition of individual phases. Subsequent quantum-mechanical calculations predicted these two phases to be elastically very different. The differences in the elastic response were detected also experimentally by roomtemperature quasistatic nano-/micro-indentation and nano-scale dynamic mechanical analysis (nanoDMA). Regarding high-temperature macro-scale measurements, small-punch testing was performed and the data were analyzed using a rheological model.

Cobalt based ternary metal borides are high-tech valuable boron-based materials with a high application potential in wide range of multi-functional areas. Although there have been comprehensive research reports on binary metal-boron systems in local and international literature, the syntheses and general properties of ternary metal borides have not been well worked out and established, yet.
In this study, synthesis of cobalt-iron-boron ternary metal boride powders was carried out via inorganic molten salt technique at low temperatures. Powder mixtures of anhydrous CoCl2, FeCl3 and NaBH4 were used as starting materials along with eutectic composition of KCl-LiCl. The reaction medium was prepared in an argon-filled glovebox and the reactants were heated in a vertical furnace (under argon) to a maximum temperature of 850°C. The unwanted alkali metal chlorides were removed by hot water leaching after the reaction. Effects of NaBH4 amounts and reaction conditions (e.g. temperature, time) on the formation, microstructure, particle size and production efficiency of the boride powders were investigated. Phase, chemical, microstructural and thermal characterizations of the synthesized powders were conducted using X-ray diffractometer (XRD), X-ray fluorescence spectrometer (XRF), differential scanning calorimeter (DSC) and scanning electron microscope / energy dispersive X-ray spectrometer (SEM/EDX). Particle size and distribution were determined by means of a Zetasizer dynamic light scattering (DLS) technique. Semi-crystalline CoFeB ternary was obtained in high purity and nano-scale after a reaction at 750°C for 2 h by using excess amount of NaBH4.

The effect of chemical composition on hot tearing susceptibility of a polycrystalline industrial gas turbine blade during casting process has been investigated. Five master melts from two different nickel base superalloys by nearly similar chemical composition have been used for this purpose. The results show that in IN738-LC alloy, hot tear sensitivity has a direct relation with Zr content, but in Rene80 the amount of Zr, doesn’t have any obvious effect on the hot tearing
susceptibility of alloy. It could be related to lower HSC parameter in Rene80 alloy in comparison with that in IN738LC. Besides the amount of Cr and Al which are the most segregating elements next to eutectic phase, in the IN738LC are higher than that in Rene80 alloy.

One of the alternative and topical ways of intermetallic and nonferrous materials application is a metal hydrides formation. Metal hydrides allow storage of hydrogen; carry out gas purification and compression.
Development of powder metallurgy provides new possibility for investigations in the field of alternative way of hydrogen storage. Solid form of hydrogen storage with the possibility of reversible sorption, gives opportunity for creation autonomous energy storage systems and use hydrogen like an modern energy carrier.
Lanthanum-nickel based alloys allow hydrogen storing at ambient temperatures and pressure not higher than 15 bar, which makes the application of these alloys quite practical. The disadvantages of these alloys are the high cost of the initial powdered pure metals and the relatively low mass content of hydrogen in the final alloy. Despite this, La-NI alloys are quite interesting and prospects for further study and modifications.

Zirconium based alloys are commonly used as material for fuel claddings in the light water reactors. Claddings act as first metallic barriers against loss of fission products during the nuclear power plant operation, intermittent storage or final dry storage. During the reactor operation, claddings are subjected to different stress levels at high temperatures as well as neutron radiation. This results in their corrosion, hydrogen diffusion, hydrogen embrittlement and creep. And the integrity of claddings is always critical issue for during reactor operation, loss of coolant accidents and during storage of spent fuel. There exists no standard for testing for fuel claddings to determine the mechanical properties in hoop direction due to their geometry and limited wall thickness (app 0.6 mm).
In this work, ring compression testing method developed is applied to study hydrogen embrittlement, to evaluate the stress–strain behavior and hoop fracture properties of E110 (Zr-based) fuel claddings. Tests were performed on un-irradiated fuel claddings with varying hydrogen concentration between 0 to 393 ppm (0, 189, 217, 328 and 393ppm) at 380°C. Further the stress – strain curves were calculated and mathematical models were used to determine the collapse load and ultimate tensile strength. The results show that the collapse load and the tensile strength values depend strongly on hydrogen concentration. In particular, tensile strength experiment data shows significant change in its trend after reaching the maximum hydrogen solubility limit at 380°C. Furthermore RCT method showed to be simple-effective, removes complexity of specimen preparation, reduce the amount of radioactive waste and reproducible for evaluating the strength and loss of ductility of irradiated cladding's in hot cells at varying conditions.

Today neodymium plays a very important role as a main component of NdFeB magnets; which are indispensable for clean energy application. Therefore, the short information about neodymium and its production in the last years are presented. The article briefly gives also the short characteristics of NdFeB magnets , as well as their application and methods of obtaining. For these magnets, the amount of production was compared in 1997-2015, together with the main producers in 2012 and 2015. Perspectives for the production of NdFeB in the following years, together with the availability of situation of the demand for rare earth metals were also shown; mainly taking into account the dominant producer and monopoly of China. The review of available methods of recycling NdFeB magnets are presented focusing on hydrometallurgical and pyrometallurgical methods.

The ore raw materials of Au, Mo producing industry are predominantly sulphide. Technologies for their processing include the oxidation stage, for which chlorine, oxygen, ozone, nitric acid, Mn(IV), Fe(III), NaCiO are used. The nature of the oxidant and ligand of metal ions determines the kinetics of dissolution of minerals. Gravimetric, Redox-measurements with gold-bearing ore and concentrate of the Kokpatas field and dissolution electrokinetic using a rotating disk electrode, with chalcopyrite-mineral of Cu-Mo ores of Almalyk field are conducted. Dissolution of sulfide mineral under the Redox potential or its equal anodic polarization is represented by steps: - dissolution of the outer layer of the mineral; - diffusion of Cu(II), Fe(III) ions out its volume, - enrichment of the interphase boundary with sulfur (passivation). Electrokinetic measurements with chalcopyrite revealed a similarity of the processes of its reagent and anodic dissolutions in an acid medium: both were accompanied by passivation of the surface. For chalcopyrite the diffusion coefficient of Fe (III), Cu (II) ions in its solid state was calculated.

While working on the possibilities of utilization of the fly ash generated in our sponge iron & power plant, I have developed a very economical & eco-friendly process for Extraction of Aluminium from Fly Ash (fly ash contains 25 to 28% Al2O3) as well as other resources of Alumina like Bauxite, high silica bauxite, clays etc.
This process replaces both the Bayer's Process for extraction of pure Alumina (Al2O3) as well as Hall-Heroult's Process of Electrolysis of molten Alumina. (Already lot of research is being done all over the world to find alternatives to these processes due to their limitations in modern context.)
This process envisages extraction of Aluminium by Thermo-Chemical Reduction & as no electrolysis is involved, the process is very economical & eco-friendly as well as energy saver. I have already applied for a patent of this process in India.