To design and optimize liquid-assisted processes such as reactive infiltration for fabricating refractory SiC/ZrSi₂ composites, basic investigations on the interfacial phenomena occurring when liquid Si-based alloys are in contact with C and SiC substrates, are key steps. Indeed, targeted wettability studies may provide helpful indications for finding the suitable set of operating conditions to succeed the fabrication of composites via the reactive infiltration and for predicting the key influencing mechanisms. The wettability of glassy carbon (GC) by two different Si-rich Si-Zr alloys as a function of the Si-content has been investigated by the sessile drop method at T = 1450°C. The more relevant results obtained in terms of equilibrium contact angle values, spreading kinetics, reactivity and developed interface microstructures are reported in the paper and compared with the behaviour previously observed in the Si-27Zr/GC system. The increase of Si-content only weakly affected the overall phenomena observed at the interface, which from the practical point of view means that even the Si-Zr alloys with higher Si-content, as respect to the eutectic alloy (Si-27Zr), could be potentially used as infiltrant materials.

SiC is a material with excellent mechanical and thermal properties, but with a high production cost. Obtaining SiC by reactive infiltration is an attractive method and at a much lower cost than the traditional sintering process. However, the reactive infiltration process presents a serious problem, which is the high residual silicon content, which decreases its range of application. The replacement of silicon with silicides is a widely used alternative. The present investigation shows the good mechanical properties of the SiC/IrSi₃ composite material obtained by reactive infiltration of SiC/C preforms with Ir-Si alloys. The thermomechanical analysis shows a high compatibility of silicide with SiC. The presence of the silicide shows a substantial improvement against the oxidation of the SiC/Si composites.

Titanium boride (TiB2) is a material classified as ultra-high temperature ceramics. The TiB2 structure is dominated by covalent bonds, which gives materials based on TiB2 very good mechanical and thermal properties, but also makes them difficult to sinter. Obtaining dense TiB2 polycrystals requires chemical or physical sintering activation. Carbon and molybdenum disilicide (MoSi2) were chosen as sintering activation additives. Three series of samples were made, the first with carbon additives: 0 to 4 wt.%; the second with 2.5, 5 and 10 wt.%. MoSi2 and the third with both additions of 2 wt.% carbon and 2.5, 5 and 10 wt.% MoSi2. MoSi2. On the basis of dilatometric sintering analysis, all additives were found to have a favourable effect on sinterability of TiB2, and it was determined that sintering of TiB2 with carbon addition can be carried at 2100°C and with MoSi2 and both additives at 1800°C. The polycrystals were sintered using the hot pressing technique. On the basis of the studies conducted in this work, it was found that addition of 1 wt.% of carbon allows to obtain single-phase TiB2 polycrystals of high density (>90%). The minimum MoSi2 addition required to obtain dense sinters with a cermet-like microstructure was 5 wt.%. High density was also achieved by materials containing both additives. Samples with higher MoSi2 content, i.e. 5 and 10% showed densities close to 100%. Mechanical properties such; as Young's modulus, hardness and fracture toughness (KIc) of the polycrystals and composites were similar for samples with densities exceeding 95%. The Vickers hardness was 23 to 27 GPa, the fracture toughness (KIC) was 4 to 6 MPa·m0.5 and the Young's modulus was 480 to 540 GPa. The resulting TiB2-based materials showed potential in high-temperature applications.

To design properly and optimizate liquid-assisted processes such as reactive infiltration for fabricating light weight and corrosion resistant SiC/TiSi2 composites, the interfacial phenomena taking place when liquid Si-rich Si-Ti alloys are in contact with glassy carbon (GC) were investigated for the first time by wetting tests performed by both the sessile and pendant drop methods at T = 1450°C. Specifically, two different Si-rich Si-Ti alloys were selected, and the obtained results in terms of contact angle values, spreading kinetics, reactivity, and developed interface microstructures were compared with experimental observations previously obtained for the liquid Si-rich Si-Ti eutectics processed under the same operating conditions. The increase of the Si content did not affected the final contact angle values. Contrarily, the final developed microstructure at the interface as well as the spreading kinetics were observed as weakly dependent on the composition. From the practical point of view, Si-Ti alloy compositions with a Si-content falling in the simple eutectic region of the phase diagram might be potentially used as infiltrant materials of C- and SiC-based composites.

The conductor aluminum alloys Al-0.25wt.%Zr doped additionally with Х = Er, Si, Hf, and Nb were the objects of investigations. The fine-grained microstructure in the alloys was formed by Equal Channel Angular Pressing and Rotary Swaging. The thermal stability of the microstructure, specific electrical resistivity, and microhardness of the novel conductor aluminum alloys was investigated. The mechanisms of nucleation of the Al3(Zr,X) secondary particles during annealing the fine-grained aluminum alloys were determined using Jones-Mehl-Avrami-Kolmogorov equation. Using Zener equation, the dependencies of the mean secondary particle sizes on the annealing time were obtained on the base of analysis of the data on the grain growth in the aluminum alloys. The secondary particle nucleation during long-time low-temperature annealing (300 оC, 1000 hrs) was shown to go preferentially at the cores of the lattice dislocations. The Al-0.25%Zr-0.25%Er-0.20%Hf-0.15%Si alloy subjected to long-time annealing at 300 оC has the optimal combination of the microhardness and electrical conductivity (59.8%IACS, Hv = 480 ± 15 MPa).

The influence of the grain structure on the tensile deformation strength is studied for precipitation-strengthened Cu-0.2%Zr at 673 K. Subgrains and grains are formed by ECAP and annealing. The fraction of high-angle boundaries increases with prestrain. Subgrains and grains coarsen during deformation. This leads to softening in the quasi-stationary state. The initial quasi-stationary state of severely predeformed, ultrafine-grained material exhibits relatively high rate-sensitivity at relatively high stresses. This is interpreted as result of the stress dependences of the quasi-stationary subgrain size and the volume fraction of subgrain-free grains.

An oxidation resistant coating on cemented tungsten carbides is characterised in this work. Cemented tungsten carbides (cWCs) are routinely used in mining and manufacturing but are also candidate materials for compact radiation shielding in fusion power generation. In both environments, cWCs will suffer significant degradation due to oxidation at relatively low temperatures. In a recent study, a Si-deposition coating method was demonstrated to improve the oxidation resistance of cWCs by up to a factor of 1,000. This work focusses on the growth kinetics, phase composition, and mechanical properties of these coatings. By combining quantitative X-ray diffraction, electron microscopy and nanoindentation, we show that the coating layer has a 20 % higher hardness than the substrate, which was explained on the basis of a previously-unknown presence of a fine distribution of very hard SiC laths. To interpret the coating stability, a coating growth map is developed. The map shows the structure is stable under a broad range of processing temperatures and composite compositions, demonstrating the potential application of these coatings in a variety of nuclear shielding cWCs.

The sepiolite/ZrO2 composites were prepared by sepiolite (Sep) modification with zirconium propoxide in toluene, at room temperature for 24 h (Sep –ZrI) or 95 °C for 4h (sample Sep –ZrII). The efficiency of the obtained adsorbents for the removal of phosphate from aqueous solutions at initial pH = 4 and pH = 8, was investigated. Characterization of the samples showed that higher temperature of synthesis for shorter time provided slightly higher content of amorphous Zr-phase, which was deposited on sepiolite fibers as a thin layer and agglomerated nanoparticles. Compared to Sep, the composites had lower point of zero charge and higher specific surface area and pore volume. The adsorption kinetics follows the pseudo second-order model. The adsorption capacities of the composites were approximately the same at both initial pH and higher at initial pH = 4 than at pH = 8. The XPS and ATR-FTIR of Sep-ZrI before and after adsorption identified the formation of inner-sphere complexes as the mechanism of phosphate adsorption. The slow release during desorption with NaOH solution confirmed strong bonds of phosphates with the surface of the composites.

During quasi-stationary tensile deformation of ultrafine-grained Cu-0.2 mass%Zr at 673 K and a deformation rate of about 10⁻⁴ s⁻¹ load changes were performed. Relative load reductions by more than about 25% to relative loads R < 0.75 initiate anelastic back flow. Subsequently the creep rate turns positive again and goes through a relative maximum. This is interpreted by a strain rate contribution ε ̇− from recovery of dislocations. Back extrapolation indicates that ε ̇− contributes about (20 ± 10)% to the quasi-stationary strain rate. The stress dependences of the recovery-strain rate ε ̇− and the rate ε ̇+ related with generation and storage of dislocations are discussed in terms of thermally activated processes characterized by different kinetics.

The thermal conductivity of the products of the interaction of molten core with concrete was derived using number theory. A formula has been found that describes the thermal conductivity of ZrO₂, ZrSiO₄, (U,Zr)SiO₄ and UO₂ over a wide temperature range. Formula is expressed in terms of the atomic numbers of elements, their valencies, the crystal structure of substances, and the thermal conductivities of individual chemical elements of the corium.

The microstructure evolution and grain refinement kinetics of a solution treated Cu – 0.1Cr – 0.06Zr alloy during equal channel angular pressing (ECAP) at a temperature of 673 K via route B_C were investigated. The microstructure change during plastic deformation was accompanied by the microband formation and an increase in the misorienations of strain-induced subboundaries. The refinement of initial coarse grains was considered as a result of continuous dynamic recrystallization. The dynamic recrystallization kinetics was discussed in terms of grain/subgrain boundary triple junction evolution. The strain dependence of the triple junctions of high-angle boundaries can be expressed by a modified Johnson-Mehl-Avrami-Kolmogorov relationship with a strain exponent of about 1.49. Severe plastic deformation by ECAP led to substantial strengthening of the Cu-0.1Cr-0.06Zr alloy. The yield strength increased from 60 MPa in the initial state to 445 MPa after the total strain of 12.

Research on the development of new lightweight Al-Li alloys using selective laser melting pro-cess has great potential for industrial applications. This paper reports on the development of novel aluminum-lithium alloys using selective laser melting technology. Al-Cu-Li-Mg-Ag-Sc-Zr pre-alloyed powders with lithium contents of 1 wt.%, 2 wt.% and 3 wt.%, respectively, were prepared by inert gas atomization. After SLM process optimization, the microstructure and me-chanical properties of the as-formed specimens were investigated. The densification of the three newly developed alloys are 99.51 %, 98.96 % and 92.01 %, respectively. They all have good form-ability, with the lithium loss rate about 15 %. The as-formed alloy with 1% Li content presents good comprehensive properties with a yield strength of 412.6 ± 16.0 MPa, an ultimate tensile strength of 461.1 ± 11.7 MPa, and an elongation of 13.6 ± 1.1%. The three alloys exhibit a layered molten pool stacking morphology and have a typical heterostructure. The columnar crystals and equiaxed fine grains are alternately arranged, and most of the precipitated phases are enriched at the grain boundaries. The change of Li content mainly affects the precipitation of Cu-containing phase. When the Li content is 1 wt.%, there are θ phase, T1 phase and TB phase. When Li increased to 2 wt.%, T1 and T2 phases precipitated together. When Li reaches 3 wt.%, δ' phase precipitates with T2 phase. This study provides useful guidance for the future SLM form-ing of new crack-free and high-strength Al-Li alloys.

A two-layer Fe-Cr-Al-Zr surface alloy was synthesized on a zirconium substrate by magnetron sputtering and subsequent low-energy high-current electron-beam (LEHCEB) processing. Thicknesses of the top Fe69Cr20Al11 (at.%) relatively large-grained (~1 µm) and transition Fe-Zr Cr-Al amorphous layers were about 0.7 and 0.6 µm, respectively. In turn, the amorphous layer consisted of two Fe64–54Zr8–22Cr21–17Al8–7 and Fe40–16Zr42–78Cr12–4Al6–2 (at.%) sublayers, differing in both zirconium and iron concentrations in wide ranges, which were separated by another nanocrystalline interlayer. The Fe-Cr-Al-Zr surface alloy serve as a diffusion barrier, preventing interaction of the zirconium substrate with oxygen from an environment. It was thermally stable up to ≈1173 K.

A homogenization of billets from Al-Cu-Li-Mg-Sc-Zr alloys should be accomplished at high annealing temperatures exceeding 500 °C. This type of aluminum alloy is susceptible to the depletion of surface layers from Li. Therefore, choosing a suitable homogenization temperature and duration is a crucial step in assuring a homogeneous distribution of alloying elements and optimal exploitation of the potential of the alloy. In-situ heating in an electron microscope was performed on a twin-roll cast Al-Cu-Li-Mg-Sc-Zr alloy to understand the peculiarities of the homogenization process. Four types of primary phase particles rich in Cu, Li, Mg, and Fe were identified in the as-cast material. They appear as coarse particles at the boundaries of eutectic cells. Their partial dissolution occurs at temperatures above 450 °C. They are almost fully dissolved at 550 °C, except for complex phases containing Fe and Cu. Small dimensions of eutectic cells in the range of 10 µm assure a homogeneous distribution of main alloying elements within the matrix after 20 min of annealing. Direct comparison with the same material prepared by mold-casting indicates that such short annealing times result in the dissolution of main primary phase particles but do not assure a homogeneous distribution of alloying elements in the whole volume of the specimen.

Thin twin-roll cast strips from a model Al-Cu-Mg-Li-Zr alloy with a small addition of Sc were prepared. A combination of a fast solidification rate and a favorable effect of Sc microalloying impacts the size and distribution of primary phase particles and the dimension of eutectic cells. Small interdendritic spacing in the range of 10-15 um enables substitution of the initial long-term homogenization annealing by a two-step annealing at 300 and 450 °C and a short solution treatment at 530 °C before quenching and the final age-hardening procedure. A dense dispersion of small Al3(Sc,Zr) precipitates intensively inhibiting recrystallization forms during this treatment. Further refining and fragmentation of the structure were performed using constrained groove pressing before the solution treatment. Small pre-straining of quenched specimens and subsequent age-hardening simulating T8 temper were used to promote the formation of a homogeneous distribution of strengthening particles and to suppress preferential heterogeneous precipitation on subgrain and grain boundaries. Microstructural features and microhardness evolution during annealing were critically examined and confronted with microstructural characteristics observed on reference mold cast alloy or alloys without Sc alloying. The proposed treatment represents a model near net shape procedure for manufacturing thicker sheets for the aerospace industry.

The article focuses on the galvanic replacement synthesis of Ti-Ni and Zr-Ni metal systems with the "core-shell" structure which are potential precursors for intermetallics. The authors defined the effective synthesis parameters and the formation features of polymetallic systems character-ized by granulometric, phase and elemental composition. The X-ray fluorescence and X-ray phase analysis methods showed that the deposition of nickel on dispersed titanium and zirconium leads to the production of test samples with phase composition representing a mechanical mixture of Ni and Ti, Ni and Zr. The method of X-ray fluorescence analysis showed that the presence of hy-drofluoric acid with a 0.5-1.5 M concentration results in the formation of fixed quantitative ratios of elements in the precipitate, which allows the quantitative composition of dispersed systems "titanium - nickel", "zirconium - nickel" to be regulated within a relatively wide range. Scanning electron microscopy proved that all synthesized systems are characterized by a highly porous structure that follows the titanium and zirconium particle surface contour and the presence of spherical nanoscale subunits on the formed particle surface.