METASTABLE STRUCTURE OF AUSTENITIC MANGANESE ALLOY AND PROSPECTS FOR CREATION OF PARTS BASED ON IT

Comparative microstructural studies and mechanical tests of an experimental austenic manganese alloy and typical structural materials have been carried out. As a result of the research, relative data have been revealed, indicating high mechanical properties of the experimental alloy, which makes it possible to recommend it for machine parts operating at high load-speed operating conditions and temperature exposure up to 700 0C.

Alpine subduction zone metamorphism in the Paleozoic successions of the Monti Romani (Northern Apennines, Italy)

The hinterland of the Cenozoic Northern Apennines fold-and-thrust belt exposes the metamorphic roots of the chain, vestiges of the subduction-related tectono-metamorphic evolution that led to the buildup of the Alpine orogeny in the Mediterranean region. Like in other peri-Mediterranean belts, the tectono-metamorphic evolution of the Paleozoic continental basement in the Apennines is still poorly constrained, hampering the full understanding of their Alpine orogenic evolution. We report the first comprehensive tectono-metamorphic study of the low-grade metasedimentary (metapsammite/metapelite) succession of the Monti Romani Complex (MRC) that formed after Paleozoic protoliths and constitutes the southernmost exposure of the metamorphic domain of the Northern Apennines. By integrating fieldwork with microstructural studies, Raman spectroscopy on carbonaceous material and thermodynamic modelling, we show that the MRC preserves a D1/M1 Alpine tectono-metamorphic evolution developed under HP-LT conditions (~ 1.0-1.1 GPa at T ~400 °C) during a non-coaxial, top-to-the-NE, crustal shortening regime. Evidence for HP-LT metamorphism is generally cryptic within the MRC, dominated by graphite-bearing assemblages with the infrequent blastesis of muscovite ± chlorite ± chloritoid ± paragonite parageneses, equilibrated under cold paleo-geothermal conditions (~ 10 °C/km). Results of this study allow extending to the MRC the signature of subduction zone metamorphism already documented in the hinterland of the Apennine orogen, providing further evidence of the syn-orogenic ductile exhumation of the HP units in the Apennine belt. Finally, we discuss the possible role of fluid-mediated changes in the reactive bulk rock composition on mineral blastesis during progress of regional deformation and metamorphism at low-grade conditions.

Tests of lithium CPS on basis of carboxylic fabric, reinforced with carbon nanotubes under high thermal and radiation loads

This work is devoted to testing a lithium CPS based on carbon fabric reinforced with carbon nanotubes under conditions of thermal and radiation loads. The paper considers and analyzes: the properties of carbon nanotubes and methods of their synthesis, the nature of the interaction of carbon materials with liquid lithium at different temperatures. A description of all the main stages in the manufacture of lithium CPS based on carbon fabric reinforced with carbon nanotubes is given. Microstructural studies of a manufactured lithium CPS sample based on carbon fabric reinforced with carbon nanotubes are presented. Studies have shown that a carbon fabric with a fiber surface reinforced with carbon nanotubes is completely wetted by liquid lithium. The developed technology is fully suitable for the manufacture of lithium CPS samples for further research. The results of experiments on the interaction of lithium CPS based on graphite fabric reinforced with carbon nanotubes with hydrogen isotopes under thermal and radiation loads are presented.

Specific features of ruthenium influence on corrosion characteristics of different titanium alloys

This article discusses the results of corrosion tests and microstructural studies of forgings from various titanium alloys modified with ruthenium, of systems Ti–Al–Zr + 0.15% Ru, Ti–Al–V–Mo + 0.15% Ru, Ti–Al–V–Cr–Fe–Mo + 0.15% Ru and similar systems of basic compositions. On the basis of the performed complex of studies, the influence of the amount of the β-phase on the local content of ruthenium and, as a consequence, on the effect of cathodic protection in general was analyzed.

Influence of B2O3 doping on synthesis of MgTiO3 ceramics from recycled magnesia-hercynite materials

Herein, magnesium metatitanate (MgTiO3) ceramics were synthesised using recycled magnesia-hercynite (MH) bricks as the raw materials to achieve solid waste reusing of cement kiln refractories. The recycled MH materials were mixed with anatase TiO2 to investigate the effect of addition of doped B2O3 during the synthesis of MgTiO3 ceramics at 1400 °C. Phase compositions and microstructural studies were performed using x-ray diffraction (XRD) and scanning electron microscope (SEM), respectively. In addition, energy-dispersive spectroscopy (EDS) was conducted and the dielectric properties of the samples were studied. Results show that the addition of B2O3 can promote sintering, improve shrinkage, promote densification, stabilise MgTiO3 lattice, and inhibit the formation of MgTiO3. In addition, the presence of appropriate amount of B2O3 can accelerate the material diffusion and result in grain growth through the formation of intercrystalline liquid phase. Results also suggest that an increase in dielectric constant results in a decrease in dielectric loss. It was concluded that 2 wt% was the optimum amount of B2O3 required to obtain the most favourable synthesis rate of MgTiO3 (98.2%). The samples exhibited a maximum density of 3.69 g·cm−3 and excellent microwave dielectric properties at ε r = 18.28 and tanδ = 0.086.

Developing Mg-Zn-Fish Bone Derived Hydroxyapatite Composites for Biomedical Applications: In vitro Degradation Studies

The study of magnesium (Mg) based biomaterials has emerged as a potential research area in recent times. Controlling the rapid corrosion and improving the implant-tissue interface kinetics for better tissue regeneration are the prime interests behind developing novel Mg-based composites. In the current work, the metal matrix composites of Mg-Zn, dispersed with nano-hydroxyapatite derived from fish bones (fHA), were produced by powder metallurgy route. The powders were mixed with the help of ball milling in the presence of ethanol and then sintered at 440 °C. From the microstructural studies, micro-lamellar morphology was noticed for the sintered compacts due to the flake-like morphology of the milled powders. The sintered compacts were then subjected to in vitro biodegradation studies in simulated conditions for one week. From the results, the presence of fHA was found to be highly influential in increasing the rate of mineral deposition on the surface of the composites. These higher mineral depositions protected the surface of the composites from further degradation. The results demonstrate that adding fHA to Mg accelerates biomineralization and controls degradation, leading to better implant-tissue interactions.

Microstructure and Properties of the Aluminum Alloyed with ZrO Powder Using Fiber Laser

The scope of the work covers the development of the relationship between the chemical composition of surface-modified aluminium and its mechanical properties. This article presents the impact of laser alloying with ZrO powder on the microstructure and mechanical properties of pure aluminium. In order to study the phenomena occurring during the laser alloying process, microstructural studies were carried out using optical microscopy. Additionally, the properties of the obtained alloy were tested - abrasion resistance and hardness measured at low load force. As a result of the alloying process, three distinct zones were identified: the remelting zone (RZ), the diffusion zone (DZ) and the heat affected zone (HAZ). The surface modification resulting from laser alloying increases the hardness and abrasion resistance of the material.

Microstructural Tailoring and Enhancement in Compressive Properties of Additive Manufactured Ti-6Al-4V Alloy through Heat Treatment

Among laser additive manufacturing, selective laser melting (SLM) is one of the most popular methods to produce 3D printing products. The SLM process creates a product by selectively dissolving a layer of powder. However, due to the layerwise printing of metal powders, the initial microstructure is fully acicular α′-martensitic, and mechanical properties of the resultant product are often compromised. In this study, Ti-6Al-4V alloy was prepared using SLM method. The effect of heat treatment was carried out on as-built SLM Ti-6Al-4V alloy from 650–1000 °C to study respective changes in the morphology of α/α′-martensite and mechanical properties. The phase transition temperature was also analyzed through differential thermal analysis (DTA), and the microstructural studies were undertaken by optical microscopy (OM) and scanning electron microscopy (SEM). The mechanical properties were assessed by microhardness and compressive tests before and after heat treatment. The results showed that heat treated samples resulted in a reduction in interior defects and pores and turned the morphology of the α′-martensite into a lamellar (α + β) structure. The strength was significantly reduced after heat treatment, but the elongation was improved due to the reduction in columnar α′-martensite phase. An optimum set of strength and elongation was found at 900 °C.