Seznam abstraktů 2022: SEKCE E - NEŽELEZNÉ KOVY A SLITINY

Complex shearing of extruded tube (CSET) represents a new technique of producing thick-wall tubes from a bulk billet. It combines extrusion with two passes of severe plastic deformation similar to the equal channel angular processing. Additionally, the mandrel can rotate and introduce further twist deformation by friction between the rotating mandrel and the inner wall of the tube. The CSET process is decribed in detail, and the microstructure and mechanical properties of the tube fabricated of a 3003 aluminum alloy are discussed. Electron backscatter diffraction (EBSD) revealed differences in the grain size and textures between tubes processed with stationary and rotating mandrel. Kernel average misorientation maps obtained from EBSD experiments and ASTAR analysis performed in transmission electron microscopy help to identify the density and arrangement of the dislocations. As regards the rotation of the mandrel, the tube processed using a stationary mandrel showed a dynamically recovered microstructure with elongated grains separated by low-angle grain boundaries ordered in subgrains. On the other hand, the microstructure of the tube processed with a rotating mandrel was dynamically recrystallized with the grain size in submicrometer range. Vickers microhardness (HV) measurements revealed a substantial increase of HV and differences in the samples prepared using stationary mandrel and using rotating mandrel, which follow the samples' microstructure.

Additive manufacturing (AM) has been increasingly used to produce metal components in the last few decades. One of the most popular AM technologies is selective laser melting (SLM). Materials prepared by SLM technology show very good mechanical properties, even though in these materials many defects are present, such as spherical pores, keyhole pores, lack of fusion porosity or cracks. The mentioned defects can be minimized by optimizing the process parameters or changing the chemical composition of the material. Therefore, the objective of this study is to describe changes in the microstructure and mechanical properties depending on the Al alloys chemistry. Three new alloys with different chemical compositions (differs in silica content) were prepared by mechanical mixing of the conventional alloys AlSi12 and AlCu2Mg1.5Ni, and subsequently processed by SLM technology with the same process parameters. Relative density (RD), type of defects, and microstructure were studied in all cases by light microscopy (LM). Mechanical properties were determined by tensile tests performed at room temperature and by hardness tests (HV0.3). Fractographic analysis was performed on fracture surfaces after tensile tests using scanning electron microscopy (SEM). It was found that with an increasing percentage of silica, the RD increases from 95.8 % to 98.8 %. The new alloy with the highest Si content showed the highest tensile test characteristics (UTS = 453 MPa, YS = 243 MPa, and A5.65 = 7.74 %).

The AlSi10Mg alloy is widely used for the production of complex-shaped components by Laser-based Powder Bed Fusion (L-PBF). These parts, characterized by high specific stiffness and strength mainly when produced as lattice structures, are currently employed in high-performance room temperature applications in the automotive and aerospace sectors. However, in order to spread the use of the L-PBF AlSi10Mg alloy, more data concerning the high temperature mechanical behavior are needed. This study therefore aims to fulfill this lack of knowledge by investigating the tensile properties at 200 °C of the AlSi10Mg alloy subjected to a T5 heat-treatment (artificial aging at 160 °C for 4h directly after LBPF) and to an innovative T6 heat-treatment (solubilization at 510 °C for 10 min and artificial aging at 160 °C for 6 h). Microstructural and fractographic analyses were carried out to correlate the mechanical behavior of the alloy to the peculiar microstructural features of the additively manufactured alloy and to investigate the mechanisms of failure. The ultra-fine cellular microstructure, which characterizes the T5 heat treated L-PBF AlSi10Mg alloy, exhibited higher tensile strength and lower elongation than the homogeneous composite-like microstructure of the T6 heat-treated L-PBF AlSi10Mg alloy, and mechanical properties comparable to the T6 heat-treated Al-Si-Mg cast alloys widely used in the automotive and aerospace fields, such as the A356 alloy.

Al-Li based alloys are an attractive material for aircraft and aerospace applications. Preparation of these alloys by twin-roll casting (TRC), which combines rapid metal solidification and subsequent plastic reduction in a single processing step, could improve the properties of the alloys compared to materials prepared by conventional direct-chill casting. For the identification of formed phases, a commonly used approach is a chemical analysis by energy dispersive spectroscopy (EDS). More accurate results can be achieved by combination of the method with diffraction analysis. This process can be considerably simplified in microscopes equipped with automated crystal orientation and phase mapping (ACOM-TEM). Al-Cu-Li-Mg-Zr alloy was prepared by twin-roll casting. A combination of TEM and STEM images with chemical analysis by EDS and ACOM-TEM was used to obtain complex information about phases of boundary primary particles. The efficiency of the individual methods for the phase identification in TRC Al-Li based alloys is discussed.Al-Li based alloys are an attractive material for aircraft and aerospace applications. Preparation of these alloys by twin-roll casting (TRC), which combines rapid metal solidification and subsequent plastic reduction in a single processing step, could improve the properties of the alloys compared to materials prepared by conventional direct-chill casting. For the identification of formed phases, a commonly used approach is a chemical analysis by energy dispersive spectroscopy (EDS). More accurate results can be achieved by combination of the method with diffraction analysis. This process can be considerably simplified in microscopes equipped with automated crystal orientation and phase mapping (ACOM-TEM). Al-Cu-Li-Mg-Zr alloy was prepared by twin-roll casting. A combination of TEM and STEM images with chemical analysis by EDS and ACOM-TEM was used to obtain complex information about phases of boundary primary particles. The efficiency of the individual methods for the phase identification in TRC Al-Li based alloys is discussed.

Transformation of Fe- and Cu-rich primary phase particles was studied in an Al-Li-based alloy prepared by TRC. Thin foils for combined STEM and SEM experiments were prepared by electrolytic twin-jet polishing. They were in-situ heated in a TEM heating stage and observed at 200 kV in the JEOL JEM 2200FS electron microscope equipped with STEM HAADF and BF detectors and SEM BSE and SE detectors working both in composition and topographic modes. The resulting structures were combined with EDS mapping performed directly in the heating holder. Dissolution and transformation of Cu- and Fe-rich particles occur above 500 °C. EDS maps acquired on the foil cooled down to room temperature show that Cu and Fe are both still present in newly formed particles, indicating most probably the presence of the Al7Cu2Fe phase.

Aluminium-steel clad materials combine advantages of both monomaterials - strength of steel and ductility and corrosion resistance of aluminium. Final properties of the material are governed by the intermetallic phase layer, which forms at the aluminium-steel interface upon annealing. The limiting thickness of the layer is 10 um, larger layer deteriorates mechanical properties. The layer is composed by two main phases - orthorhombic Al5Fe2 and monoclinic Al13Fe4.

Aluminium based alloys have been widely used in the automotive, aircraft and defense applications because of good thermal and electrical conductivity, high tensile strength-to-weight ratio, high hardness and ductility properties. Graphene, is an allotrope of carbon, attracts great attention worldwide due to its sp2-hybridized two-dimensional honeycomb structure, low weight, thermal, electrical and mechanical properties. In the present study, high purity few-layered graphene (FLG) which was synthesized via electric arc discharge method (EAD) were reinforced to the Al-5Cu alloy matrix using various weight fraction of 0, 0.1, 0.3, and 0.5, by mechanically alloying. These nano-composite powders were consolidated by cold pressing under 450 MPa and they were subjected to sintering at 570°C and 580°C for 3 hours under Argon atmosphere. The microstructure of composites materials was studied by optical microscope and scanning electron microscopy. The FLG was observed to be dispersed homogeneously in the Al-5Cu alloy matrix. An increase in the micro hardness for Al-5Cu alloy with 0.5 wt% FLG (123 HV) by 45% was observed compared to pure Al-5Cu alloy (85 HV) sintered at 570°C. Moreover, wear properties of these composite materials were investigated by means and analysis of variance (ANOVA).

Functionally graded materials (FGMs) are advanced engineering materials developed due their superior properties where traditional composite materials are not sufficient. Nowadays, the development and application of these materials for the potential areas have attracted much more attention. Aluminum (Al) is preferred for physical and mechanical properties such as lightweight, high specific strength, high specific modulus, and low thermal expansion coefficient in these potential applications. Graphene attracts great attention worldwide due to its superior mechanical, electrical and thermal properties. In the current study, few-layered graphene (FLG) produced with high purity electric arc discharge method were used to reinforce the Al matrix using various weight fraction of 0, 0.1, 0.2, 0.3, 0.5, and 0.7 FLG by mechanically alloying. Composite powders were consolidated by cold pressing with a layer by layer under 450 MPa. Al-FGM composites were designed including six layers and they were subjected to sintering at approximately 590°C under Argon atmosphere. The microstructure of Al-FGM was investigated by optical microscopy and scanning electron microscopy (SEM). It was observed that the FLG placed between the grains and acts as a barrier through the gradation improving the mechanical properties of the Al-FGM. Hardness value of the layer with the highest graphene content was measured as 113 HV. An increase in the Vickers hardness by 18% was observed in the last layer with FLG content of 0.7wt% compared to the first layer.

High strength and low density requirement is the fundamental issue in aerospace industry. Many new engineering materials have been focused in recent years. After the Second World War, 2050 aluminum alloys, which have low density, high fatigue resistance and excellent corrosion resistance, have become the focus of attention with their lighter weight, although they show high performance based on strength values as other using aluminum alloys in aerospace structural parts such as heavy plate applications, fuselage frames, wing skins and bulkheads. In addition to the strength values of materials used, when they show during machining, the reactions can change the desired strength values and geometrical dimensions.
In this study; feed rates, spindle speed, and radial depth of cut which directly affect the machining distortion, were optimized with the usage of the Box-Behnken experimental design method on 2050 aluminum alloy. Based on the optimum cutting parameters obtained from the experimental design studies, materials were machined in a milling center with using a carbide end mill. Depending on the optimum parameters, cutting speed, material removal rate, and spending time are calculated for mass production terminology. Also, with the optimum parameters, on the machined part; geometric dimensioning and tolerance data such as perpendicularity, parallelism and flatness were examined, the distortion values on the workpiece were obtained. Based on the distortion analysis, enhancement have been observed on the workpiece by using optimum cutting parameters which are compared with generally using cutting parameters.

Processing of polymetallic ores, especially deep sea nodules, is always considered as extraction of individual metals. This work brings a new approach, i.e. to reduce the ore in a single step without any separation process. Such new metallurgical approach does not only save the costs, but also generates whole new alloys. The properties of these new alloys were tested as sole materials and also as the additive for aluminium alloys.

Currently, biosoluble materials are widely used for the manufacture of implants, among which the most promising are magnesium alloys. Magnesium is a natural element of the body - it is contained in bone and muscle tissue, is involved in various metabolic processes. In addition, magnesium and its biocorrosion products have excellent biocompatibility. The main advantage of magnesium alloys is the positive effect of magnesium on the human body, but their quality does not meet the requirements for their use in the human body. It is possible to increase the properties of magnesium alloys as a result of improving the processes of refining and modification of liquid melt.
The technology of modification of cast magnesium alloys of Mg-Zr-Nd system by dispersed graphite powder is proposed. It is shown that
the optimal carbon additive in the amount of 0.05…0.1 % improves the mechanical properties due to grain grinding and additional strengthening of structural components. A complex filter containing equal amounts of magnesite, graphite and limestone is proposed, which provides an increased level of refining of the melt to obtain high quality casting. It is shown that the use of a complex carbon-containing filter provides not only efficient refining of the melt, but also its additional modification. In the structure of the alloy there is an increased amount of intermetallic γ-phase, which increases the microhardness of the structural components of the alloy and improves its physical and mechanical characteristics.

Recently, reversible solid-state metal hydrides offer significant advantages, such as high volumetric and high gravimetric storage capacities compared to hydrogen stored in its liquid or gaseous state.
Magnesium alloys are accomplished materials for hydrogen storage in the form of solid-state. For instance, the magnesium hydride, MgH2, has the highest storage capacity (7.6 wt.% H) among the reversible hydrides.
Despite Mg passing many commandments required for practical applications, it cannot be used onboard due to the following principal reasons: first of all, the hydrogenation dehydrogenation reaction for pure magnesium is very slow; secondly, it occurs only at a high temperature in the range of 350 - 400 ℃ and a hydrogen pressure of more than 3 MPa.
For improving the sorption characteristics of the Mg-based alloys, efforts have been made to reduce the desorption temperature beside accelerating the re/dehydrogenation reactions, which can be influenced by using Severe Plastic Deformation methods (SPD).The SPD methods can produce ultrafine-grained materials, high plastic strain structures, favorable texture, and increase the surface-volume ratio, so they have been considered promising to improve the kinetic and thermodynamic of absorption hydrogen..
In this paper, the process of pure Mg for hydrogen storage applications has been studied, which was subjected to equal channel angular pressing (ECAP) for 8 passes using route Bc at room temperature that resulted in an excess free volume of ~0.063% and excellent mechanical properties with ultimate tensile strength, the yield stress, and an elongation to failure of 223 MPa,170 MPa, 8% after 4 passes, respectively.
Enhanced H-sorption properties were observed for the sample processed by the ECAP process, and these properties were explained by the increase of free volume and stronger (0002) texture following ECAP at room temperature.

Traditional methods of fighting metal fires are not always safe for firefighters; Sand and salts that are thrown onto the fire to suffocate the flames can lead to splashes of molten metal, putting the firefighters and the surroundings at risk, even more so when the materials contain moisture. A novel process is described where magnesium fires are brought under control on a simple two-step process: First, coated cellulose flakes, which contain approx. 30% of inorganic salts, are blown onto the fire from a distance of several meters. Due to the low bulk density, the material settles smoothly on the fire and immediately covers the flames for several seconds. Before the hot, covered metal can break through the cover, in a second step a fine water mist is applied to the now-covered fire. That water mist wettens the top layer of the cellulose flakes, which have started to become charred from the bottom. The water will evaporate within the cellulose flake layer, withdrawing heat. It was observed that no hydrogen is formed and that the fire can be controlled in this way. 90kg of flakes could safely bring a pile of 75kg of burning Mg flakes under control. By using a pneumatic conveying unit for the flakes, firefighters can effectively and efficiently cover the flames from a safe distance. The novel method can be recommended to fire fighters in industrial magnesium processing plants, and to local fire fighters in the vicinity of such plants.

At the same time, iron-containing raw materials are essential for Uzbeksteel JSC, and this material can be extracted from copper slags. In this regard, the relevance of this work is undeniable. The problem of processing slags of metallurgical plants is the most acute in both ferrous and nonferrous metallurgy. This problem has not been practically solved in any country in the world. Slags, accumulating around metallurgical plants, create substantial environmental issues for enterprises. The tightening of environmental legislation and the consequent payment of significant fines force enterprises to seek alternative solutions.

In the conventional powder metallurgy (PM) process route, finished components are produced from metallic powder materials by pressing at room temperature followed by pressureless sintering in a furnace. This simple method for fast and cost-effective processing is not suitable for gamma-based titanium aluminides. Due to their brittleness, these cannot be compacted in the conventional way. In order to qualify this group of alloys for the PM route, a possible solution is to add elemental powder. The basis is commercially available, pre-alloyed TiAl44-4Nb-0.7Mo-0.1B (TNM) powder, which has a high application potential for example in the aerospace industry. In this study, investigations are carried out to determine the influence of different admixtures of elemental powders on the compaction result and the obtained mechanical properties. The TNM powder is mixed with its powder main alloying elements, titanium and aluminium, and pressed into a compact using graphite as a common tool lubricant. The results show that the admixture of elemental powders enables the consolidation of TNM powder. However, depending on the applied pressure, a certain minimum amount of the respective elemental powder is necessary to produce a compact. Furthermore, a significant influence on the relative density as well as the strength of the pressed product can be observed.

The new approach for the preparation of ternary Mn2FeSi alloy by the powder metallurgy route was proposed and verified. The powder mixture of pure elements was submitted to the mechanical milling for 168 h at different ball to powder ratio (BPR = 10:1 and 4:1) followed by the annealing at 1223 K for 1.5 h. The microstructure, chemical composition, spatial distribution of elements and phase composition of powders were comprehensively investigated using the SEM/EDX and XRD analysis. The chemical analysis of powders resulted in the mean composition of 49.0 at.% Mn, 25.6 at.% Fe and 25.4 at.% Si (BPR = 10:1) and 49.9 at.% Mn, 25.3 at.% Fe and 24.8 at.% Si (BPR = 4:1), respectively. The XRD analysis of both powders confirmed inverse-Heusler (XA) structure with the lattice parameters of 0.5677 nm (BPR = 10:1) and 0.5675 nm (BPR = 4:1), which are in a good agreement with the theoretically obtained value of 0.560 nm. The presence of minor oxidation phases was also observed in the particle structure of powders. Magnetic properties were analyzed at low, room, and elevated temperatures. Both alloys exhibit paramagnetic behaviour at room temperature (RT) confirmed by transmission Mössbauer spectroscopy measurements. Temperature-induced structural transformations are detected below RT.

With the electrification of the road vehicles in recent years, the development of electric motors strives towards smaller and more efficient designs. In order to push the current limits of the electric and magnetic properties, e.g. magnetic saturation, of the ferromagnetic parts in the motor, novel materials must be developed. In the paper, the comparison of different materials (C45 steel, FeSi and FeCo alloys), used in the rotor magnetic structure of an electrically-excited synchronous motor, is made. The materials were evaluated by measuring their electrical conductivity and static B-H curve. It is shown that the materials with improved magnetic properties allow improvements in the electric motor design, leading to the enhanced performance, which is reflected in lower energy consumption (higher efficiency) and/or lower mass (higher compactness).

This article deals with the issue of the ballistic resistance of composite panels, which were made of para-aramid fiber. For the shooting tests was used Twaron CT 747 with epoxy matrix LG 700. This material is used for soft and hard ballistic protection. The composite panels were impacted by the missile 5.56 x 45 mm NATO FMJ M139 and by the missile 5.56 x 45 mm NATO FMJ SS109. To provide the required ballistic resistance in accordance with the US STANDARD NIJ 0101.06, the composite panels were impacted by the missile 7.62 x 51 mm NATO FMJ M80. The ballistic resistance of composite panels was verified through shooting tests in the experimental ballistics laboratory. Based on the ballistic tests, we monitored the extent of the damage, the spread of cracks and delamination of layers, which allowed the evaluation of the damage of these panels. The result of the shooting tests was the determination of limit thicknesses, in which the panels will not be penetrated. These results provide essential aspects for the development of new composite armor.

This article presents the history of tin metallurgy in Rwanda, its current state and future development prospects on the example of the Luna Smelter plant. The authors of the article pay special attention to the issues of successful restoration of production in the closed in 1994 plant, the impact on the labour market in Kigali, the creation of new commercial and economic ties, the geological prospecting of cassiterite ore deposits, the improvement of production lines and the optimization of technological parameters of smelting and refining.