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Copyright of Proceedings in Archeology & History of Ancient & Medieval Black Sea Region is the property of Cimmeria Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In the process of small-caliber ammunition production, the quality of the setting of the deep drawing technology of CuZn30 brass and its subsequent recrystallization is essential. The quality of the setting of this technological process is also very important for the final quality of the whole ammunition, as the cartridge case, or even the projectile, is produced by the technology of deep drawing. In deep drawing technology in cartridge case manufacturing, when CuZn30 brass already reaches the value required for recrystallization, the brass structure changes the grain size of the structure. And at the same time, makes it difficult to achieve a uniform grain size in the entire cartridge case cross-section after recrystallization or after some steps of the technological process. [ABSTRACT FROM AUTHOR]

Due to their physical and mechanical properties, niobium products are used in the nuclear power industry, chemical industry, electronics, medicine and in the defence industry. Traditional manufacturing technology for these products is characterized by long production cycles and significant material losses during their surface machining. This paper presents the results of a study on the fabrication of niobium products by Spark Plasma Sintering (SPS). Structural and mechanical tests were conducted on the products obtained, as well as a comparative analysis with the properties of products obtained using traditional technology. Based on the analysis of the test results obtained, recommendations were made for the sintering of Nb powders. It was found that the optimum temperature for sintering the powder is 2000 °C as the density of the material obtained is close to the theoretical density. The microstructure obtained is comparable to samples obtained by the traditional method after recrystallization annealing. Samples obtained according to the new technology are characterized by higher mechanical properties R p0.2 and R m and the highest hardness.

This study presents a microstructural investigation of the printing parameters of an AlSi7Mg0.6 alloy produced by powder bed fusion (PBF) using laser beam melting (LB/M) technology. The investigation focused on the effects of laser power, exposure velocity, and hatching distance on the microhardness, porosity, and microstructure of the produced alloy. The microstructure was characterized in the plane of printing on a confocal microscope. The results showed that the printing parameters significantly affected the microstructure, whereas the energy density had a major effect. Decreasing the laser power and decreasing the hatching distance resulted in increased porosity and the increased participation of non-melted particles. A mathematical model was created to determine the porosity of a 3D-printed material based on three printing parameters. Microhardness was not affected by the printing parameters. The statistical model created based on the porosity investigation allowed for the illustration of the technological window and showed certain ranges of parameter values at which the porosity of the produced samples was at a possible low level.

Nickel Aluminum Bronze (NAB) and Manganese Aluminum Bronze (MAB) are high-alloyed bronzes that are increasingly employed in several industrial sectors, mainly related to hostile environments due to their excellent properties against corrosion, cavitation, erosion and improved mechanical properties in relation to other copper-based alloys. These materials are very sensitive against thermal treatments due to a multiphase microstructure in as-cast condition. To contribute to the knowledge of the behavior of both alloys, the effect of thermal treatments on the corrosion behavior of NAB (CuAl10Fe5Ni5) and MAB (CuMn12Al8Fe4Ni2) was studied. As-cast material was subjected to various combinations of quenching and quenching and tempering at 850 °C and 600 °C. Corrosion testing was carried out using simulated sea and fresh water. The microstructures of the as-cast and heat-treated samples were characterized by metallography using two chemical agents with FeCl3 and NH4OH solutions and examination by optical and scanning electron microscopy. The major effect of thermal treatments on corrosion was found in influencing the amount and distribution of β-phase, which is prone to selective corrosion in both electrolytes.

Industries demand that their products are high quality with the least number of defects due to the rapid improvement in manufacturing technology. Quality is a critical criterion for evaluation in manufacturing firms. The production of a final product that can meet customer requirements is essential in a sustainable supply chain system to reduce costs, increase productivity and provide high-quality products. The aim of the study is to identify the root cause of defects emerging in the production process of prestressed railway concrete sleepers. Ishikawa diagram and Pareto analysis were used to identify the root cause. The results showed that the cause of the faulty concrete sleeper is the breaking of the bolts, which are supplied by the external provider. Since the supplier refused to accept the complaint, chemical analysis and measuring of hardness and microhardness of bolts were realized. It showed that the hardness of the bolts does not achieve the values, which should be achieved after the declared heat-treatment. As a corrective action, the input control of bolts hardness was proposed as well as establishing the team cooperating with the supplier to improve the heat treatment process, which will be the objective of further study.

In this article, we provide a morphological and typological description of mirrors of the Sargatka culture discovered in the area of the Tobol-Ishim interfluve. Similar artefacts were found in places across a significant part of Eurasia, with quantitative investigations demonstrating their preponderance in the Lower Volga basin and the Aral Sea area. 12 mirrors were analysed using the atomic emission spectroscopy, X-ray fluorescence and spectral analysis methods. Data on metal processing techniques for 11 items were obtained by visual inspection and me-tallographic analysis. The results of atomic emission spectrometry, X-ray fluorescence and metallography showed that both local, traditional and unique, rare technologies had been used in their production. Most mirrors are made of high-tin bronze alloys containing 20–30 % of tin, which imparts a golden colour and lustre to the artefacts. Working with high-tin alloys is known to require special skills, since their forging can be performed only within a narrow temperature range. Reheating and water quenching are the final operations, aimed at strengthening the product during its operation. Stable uniform techniques and temperature regimes seem to have been applied when producing the Sargatka mirrors. The use of water quenching is considered to be an innovation in this locality, which distinguishes the metalworking of the Early Iron Age from the preceding Bronze Age. This allowed us to propose that the processing techniques and the finished products could have been imported from two mirror production centres located in the areas of the Volga river basin and the Aral Sea. The similarity of the artefacts under study indicates that they could have been manufactured at a single production centre. The destination of this centre is hard to determine due to the identity of the artefacts both in terms of their composition and common production pattern, which implies the quenching of hot-forged mirrors in cold water. Taking into account the traditional contacts of the Sargatka tribes, who settled the Tobol-Ishim basin, with the population of the Volga region, as well as the geographical proximity of these territories, we tend to suppose that this centre was located on the territory of the Volga river basin. Thus, a Chinese mirror from the Chepkul 9 burial ground is likely to have been professionally manufactured using a blank wax model for casting. Han mirrors were one of the most important and popular Chinese articles exported to other cultures, including the Sargatka culture. The area of the Sargatka culture embraced the northern branch of the Great Silk Road.

In this paper we have studied the effect of magneto-static field onpropagation of thermal wave generated in metal by pulsed laser. In fact this interactiongenerate acoustic wave in different mechanisms. However, always the commonmechanism in the interactions of laser pulse and metal is the thermo-elastic wavegeneration. Applying the suitable magneto-static field on the surface of interaction oflaser pulse and metal can trap the propagation of thermal wave in thermo-elastic regime.The physical mechanism of trapping and experimental results have investigated in thispaper. We obtained maximum reduction in 2D thermal wave propagation aroundin simulation and around 5.3% by metallography.

The article presents the issues of sharpness of images of the structure of materials in metallographic studies. The use of the concept of depth of field to obtain images of the structure of various objects – fractures, microsection polished specimen, optically transparent materials is illustrated. The errors of focusing on the sharpness for metal specimens are considered; it is shown that in the case of inclined arrangement of the specimen, the zone of sharp image is a strip with parallel boundaries formed by a fuzzy visible structure. Particularities of focusing out-of-flatness samples and replicas are shown. It is noted that the location of the areas of the non-sharply visible structure in the image is the result of external influence. The possibilities of varying sharpness for the quantitative analysis of austenite grain, as well as the visualization of dendritic structures are demonstrated.

This article presents a preliminary report on the first results of the interdisciplinary project Early copper metallurgy in Ancient Egypt- a case study of the material from Agyptisches Museum - Georg Steindorff - der Universitat Leipzig, in cooperation of the Czech Institute of Egyptology, Faculty of Arts, Charles University in Prague, Institute of Chemistry and Technology in Prague and the Egyptian Museum in Leipzig. The project is focused on the analysis of a selected corpus of artefacts from ancient Egyptian and Nubian sites (fig. 1 ). The analysed material was found in greatest part at the Egyptian sites of Abusir, Abydos and Giza and at the Nubian site of Aniba (fig. 2). The artefacts represent an outline of the development of ancient Egyptian metallurgy over more than one and half millennia, from the First Dynasty (ca 3100 - 2900 BC) until almost the end of the New Kingdom (ca 1200 BC). The selected corpus of artefacts has been documented by X-ray radiography and computer tomography last year at the Institute of Mineralogy, Crystallography and Material Science of the Leipzig University. ln all, 86 artefacts were then sampled and a I most 100 samples obtained. The results of a metallography and SEMIEDS analysis of five selected artefacts, representing five different chronological stages of the corpus, are discussed in this article (Table 1 ). The first one is a Dynasty 1 vessel from Abusir South (AMUL 2162; Fig. 3). This bowl was hammered out of copper sheet, with high contents of Ni, As and Fe. Non-metallic admixtures of copper sulfides are present in the inner structure, which is highly deformed by the hammering. The second is an Old Kingdom vessel from Giza made of arsenical copper, hammered and annealed (AMUL 2169; Figs. 4-5). The third is a lugged and decorated Middle Kingdom axe blade, hammered and annealed and made of copper with admixtures of As, Fe and S (AMUL 3952; Fig. 6). The fourth is a pair of tweezers from a C-Group tumulus N83 at Aniba, which was made by the cold hammering of arsenical copper, bul with rather surprising amount (1 .0%) of tin (AMUL 4647; Figs. 7-8). The fifth is the middle part of an early Dynasty 18 dagger cast from a tin bronze alloy (AMUL 2153; Figs. 9- 1 0). A poster with the analysis of the XRF results was presented at the 41st lnternational Symposium on Archaeometry at Kalamata (Greece) and received honorable mention from The Society for Archaeological Sciences in the Best Student Poster competition (Kmošek - Odler et a/. 2016). All samples will be submitted to neutron activation analysis, and the selected corpus will be also analysed for lead isotope ratios.

The paper is devoted to an experimental study of the effect of an electric discharge energy and the conditions of its flow (in air and using distilled water) on the geometrical parameters of a single well obtained on a sample of U8A steel, as well as the microhardness of its surface layer. The questions of the technique for carrying out experimental studies are described, including a description of the device for obtaining single holes on the surface of a steel sample, as well as the means and methods for measuring their geometric parameters and microhardness of the surface layer. The results of studies that made it possible to quantify the effect of the energy of an electric discharge and its flow conditions on changes in the geometric parameters of a single well and the microhardness of its surface layer are presented and analyzed. It is established that with increasing energy of an electric discharge, the dimensions of geometrical parameters of a single well increase, and simultaneously the microhardness of its surface layer increases. In this case, in comparison with treatment in air, the use of distilled water leads to a decrease in both the geometric dimensions of the well and the microhardness of its surface layer.

The Akko Tower Wreck is ently the remains of a 25-m-long merchant brig, dated to the first half of the nineteenth century. During the 2015 underwater excavation, a piece of brass sheet was retrieved from the shipwreck and its surface and bulk were examined by metallurgical analyses. The examinations revealed a unique example of almost two hundred years’ natural etching, which took place in the sea underwater environment. The surface of the sheet was covered with different copper and zinc oxides, which were identified by XRD analysis. Observation of the naturally etched surface with multi-focal light microscopy and SEM-EDS analysis indicated a microstructure of annealed α-brass, similar to that of its bulk. S-OES chemical analysis of the bulk revealed a composition of 65.0 wt% Cu, 34.4 wt% Zn and 0.6 wt% Pb. Based on the thickness of the sheet and its good state of preservation, it is suggested that it was used as sheathing to protect the hull against marine organisms, and to improve the sailing qualities of the ship. The results provide further information about the Akko Tower shipwreck; and expand our knowledge regarding the corrosion processes and preservation of brass during a long burial period in marine environments.

Most of the nonferrous metals cannot be hardened to a significant degree by the techniques used for hardening steels because most other metals and alloys do not undergo martensitic transformations. Continuing Education Units: PDH 1.5/CEU.15 On Demand ASM Digital Short Course - Types of Corrosion Most environments are corrosive to metals and alloys but the susceptibility to corrosion varies from metal to metal, alloy to alloy, and environment to environment. Understanding the fundamentals of corrosion, is necessary not only for identifying corrosion mechanisms, but also for preventing corrosion and for predicting the corrosion behavior of materials under various service conditions. Continuing Education Units: 2.0 On Demand ASM Metallurgy for the Non-Metallurgist™ Online Course This course presents a brief history of metals, providing insight into the discovery and use of pure metals and alloys thousands of years before the modern era. [Extracted from the article]

The article analyzes the methods of modernization of optical microscopes to obtain digital images and simplifies their subsequent analysis while conducting basic metallographic examinations of deposited metal specimens. Two main methods of modernization were considered: with the help of a camera, equipped with special adapters, which is attached to the tube of the microscope eye-piece and with the help of a video eyepiece, which is installed instead of a standard microscope eyepiece. The main advantages and disadvantages of each method were noted. Using MIM-7 metallographic microscope, Canon 650D camera, SIGETA MCMOS 3100 video eyepiece, as well as specimens of microsections with a deposited layer of semi-heat-resistant steel of C – Cr – Mo – W – V alloying system, comparative metallographic examinations were performed. It is shown that the use of a special video eyepiece SIGETA MCMOS 3100 allows obtaining better digital images of metal microstructures. As an illustration of the main advantages of the work, provided by the use of the equipment modernized in this way, the results of metallographic examination of metal, deposited by electric arc method using flux-cored wire PP-NP-120V3KhMF, were provided. It was experimentally established that the Toupview software, supplied with the eyepiece SIGETA MCMOS 3100, used in these examinations, allows easy processing of the obtained digital images, which greatly expands the capabilities of basic metallographic analysis. [ABSTRACT FROM AUTHOR]

The study analysed pre‐Hispanic gold objects found within a surprising archaeological finding of a structure that likely served as a funeral pyre in Medellín, Colombia. 14C analyses of the site's organic materials dated the structure to the fifth century ce. The metal objects were subjected to X‐ray diffraction (XRD), energy‐dispersive X‐ray fluorescence (EDXRF), scanning electron microscopy‐energy dispersive X‐ray (SEM‐EDX), density measurement by the Archimedes method, and metallographic analysis. The measurements by EDXRF and SEM‐EDX showed that the pieces were composed mostly gold and silver. The XRD results indicated that the microstructure of the objects corresponded to a single phase of gold and silver. The images obtained by the metallographic microscope showed equiaxial grains with some twins, a structure consistent with annealed metals. The different colours observed correspond to different grain orientations. Pre‐Hispanic objects from a second archaeological site in the municipality of Amalfi (Department of Antioquia) were also analysed for comparative purposes. The results showed that the gold objects were not subjected to any alloying process, but were instead manipulated in their original form (native gold). The shape of the objects and their microstructural results suggested that the pieces were manufactured by casting, mechanical deformation and then annealing. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Polytechnic is the property of Journal of Polytechnic and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The article analyzes the methods of modernization of optical microscopes to obtain digital images and simplification of their subsequent analysis during basic metallographic examinations of deposited metal specimens. Two main methods of modernization were considered: with the help of a camera, equipped with special adapters, which is attached to the tube of the microscope eyepiece and with the help of a video eyepiece, which is mounted instead of a standard microscope eyepiece. The main advantages and disadvantages of each method were noted. With the help of the metallographic microscope MIM-7, camera Canon 650D, video eyepiece SIGETA MCMOS 3100, as well as specimens of microsections with a deposited layer of semi-heat-resistant steel of C-Cr-Mo-W-V alloying system, comparative metallographic examinations were performed. It is shown that the use of the special video eyepiece SIGETA MCMOS 3100 allows obtaining digital images of metal microstructures with a higher quality. As an illustration of the main advantages of the work, provided by the use of the equipment modernized in such a way, the results of metallographic examination of the metal, deposited by electric arc method using flux-cored wire PP-Np-120V3KhMF, were provided. It was experimentally established that the software Toupview, supplied with the eyepiece SIGETA MCMOS 3100, used during these examinations, allows easy processing of the obtained digital images, which greatly expands the capabilities of basic metallographic analysis. 10 Ref., 7 Figures. [ABSTRACT FROM AUTHOR]

Modern lightweight car bodies are becoming more and more complex in comparison with previous constructions. Various materials are used in particular areas of car bodies, serving different purposes. Constructions made of aluminium alloy sheets are widely used in car body production to reduce the total car weight. However, resistance spot welding is not applicable for joining aluminium alloy sheets. Therefore, alternative joining methods are being developed. One of the alternatives is mechanical joining - clinching. The paper focuses on the evaluation of the properties of joints made by clinching. Aluminium alloy sheets EN AW 5754 of hardness H11, H22 and H24 and EN AW 6082 were used for experiments. The tensile test and a metallographic observation were used to evaluate the properties of the clinched joints. Clinching proved to be a suitable technique for joining the observed aluminium alloy sheets. [ABSTRACT FROM AUTHOR]

The paper presents the research results of the micro- and nanostructure of the type 30Х13 (AISI 420S) stainless steel based on the atomic force microscopy (AFM) investigations. Using the AFM images, the phase composition of AISI 420S steel is identified by the scanning and optical electron microscopes. The grain size of carbide inclusions and their structural properties are studied in this paper. [ABSTRACT FROM AUTHOR]

The temperatures of phase transformations and the oxidation-reduction reactions occurring under heat treatment of composite Al – Si + flux brazing metal used for brazing of Al alloys and produced by the TRILLIUM™ Technology are determined. It is shown that the melting mechanism is stepped and is accompanied by a chemical reaction between the flux and the oxide film and by diffusion transfer of silicon into the substrate. The heat treatment temperature is shown to affect the microstructure in the zone of contact between the brazing metal and the substrate. [ABSTRACT FROM AUTHOR]

We consider the results of studies on the choice of material of the lower radial bearing of the pump designed to circulate lead–bismuth coolant. The circulation of the liquid coolant is provided by a vertical axial pump having a "long" shaft. In this design, it is necessary to provide for the lower bearing the lubrication carried out with lead–bismuth coolant. Having analyzed the operating conditions of the axial pump, we decided to carry out the lower bearing in accordance with the scheme of a hydrodynamic sliding bearing. The materials of friction pairs in such a bearing must withstand the stresses arising from the operation of the pump, as well as the aggressive conditions of the coolant. Nonmetallic materials—ceramics and carbon-based composite materials—were selected on the basis of the study of published data for experimental research on the corrosion and heat resistance in the lead–bismuth environment. [ABSTRACT FROM AUTHOR]

The heterogeneity of the structural state of a VT41 pseudo-α-titanium alloy after hot upset is studied. The analysis of the distribution of deformation upon upset and characteristic features of the formation of each of the structural components of the specimen is performed. Globular grains are deformed by the mechanism of intergranular slipping. β grains and α plates make the greatest contribution to plastic deformation. Lamellar grains of the α phase undergo recrystallization in the zone of localization of deformation. The dimensions of the zone where the recrystallization occurs coincide with the zone of localization of deformation estimated by the macrostructure. When quenching the billet, the β phase breaks down into α plates in the center of the specimen and into smaller grains that probably are needle-like β-titanium martensite in the near-surface regions. A decrease in the microhardness in the central regions may be due to both recrystallization and the fact that the surface layers are subjected to martensite quenching. [ABSTRACT FROM AUTHOR]

The most important aspect of this study is that the effect of Hypnum cupressiforme Hedw. which is a bryophyte species as a "green inhibitor" on the corrosion behavior of mild steel in 1.0 M HCl solution at 298 K is being examined for the first time. The inhibitory effect of moss extract was investigated applying the electrochemical impedance spectroscopy (EIS) technique. Nyquist diagrams were performed by EIS to examine the variation of the different concentrations of the extract with some immersion-time parameters. Also, the surface charge of the metal in terms of the inhibition mechanism was determined by the EIS technique and as a result, it was found that the protonated inhibitor molecules were adsorbed directly onto the metal surface. The surface morphology studies of working electrodes were performed using field emission scanning electron microscope (FESEM) and optical metal microscopy techniques. Electrochemical tests and surface analysis studies support each other. [ABSTRACT FROM AUTHOR]

This manuscript summarizes recent investigation of the authors into the solidification and shrinkage defect formation of ductile and compacted graphite cast irons. The study makes use of the DAAS (direct austempering after solidification) technique, developed earlier by some of the authors, to reveal the solidification grains. In addition, color metallography is used to reveal the microsegregation pattern. The formation of shrinkage defects is related to both the solidification macrostructure and the microsegregation pattern. The examination of the macrostructure shows that large solidification grains, composed by dendritic austenite and graphite, characterize the solidification of compacted graphite irons of carbon equivalent values ranging from hypoeutectic to hypereutectic. Similar results are observed for ductile iron, but in this case, the hypereutectic irons display a finer macrostructure. The characteristics of the primary austenite dendrites are revealed by the microsegregation pattern, which is exposed by the color etching reagent. This pattern also clarifies the nature of the interaction between the growing austenite and the compact and spheroidal graphite particles. The microshrinkage cavities in both ductile and compacted graphite irons form at the interior of the austenite grains, where fluid feeding cannot compensate the contraction of the last-to-freeze portions of the melt. Schematics of the solidification of ductile and compacted irons are proposed, accounting for the experimental observations. [ABSTRACT FROM AUTHOR]

The main objective of the present work is to explore the morphological changes in the eutectic silicon particles associated with the increase in the solution treatment time up to 400 h by quantifying the characteristics of the eutectic silicon particles at different durations of solution heat treatment. Thermal modification of silicon particles proved to be more effective in the Sr-modified alloys rather than their Sr-free counterparts. The evolution of silicon particles during extended solution treatments followed the same trends and sequences for non-modified and Sr-modified 354-type and 356 alloys, at different evolution rates. The coarsening of eutectic Si particles occurred through particle coalescence and Ostwald ripening mechanisms. While both mechanisms were active at the same time, however, they operated independently and additively. The pinholes observed in the silicon particles derive from the impression or imprint left behind from the diffusion of small particles into larger particles. [ABSTRACT FROM AUTHOR]

This paper reports a comparative study of the polymeric materials operating in conjugation with steel. In agricultural engineering, a significant role in structural materials belongs to polymer composites. This type of material is characterized by the low price, small technological cost, as well as acceptable processing characteristics. It has been found that it is necessary to form, for each type of mated parts, a set of materials that could maximally meet the operational conditions. To describe the operating conditions in more detail, they need to be generalized for the specific tribological and loading characteristics. Based on this, such load regimes were selected that correspond to the movable mated parts in sowing complexes. For these mated parts, it was necessary, in the course of the tribological study, to choose a material with minimal technological deviations but with enhanced tribotechnical characteristics. The result of this study has established that under the predefined conditions a polymer-composite material with the high-modulus filler PA-6.6+30 % F demonstrates the best tribophysical characteristics compared to the material PA-6.6. The proposed material, in conjugation with steel 1.1191, has a friction coefficient that is 38...41 % lower, while the temperature in the contact area is 8...12 % less, than that in conjugation with the material PA-6.6. Based on the metallographic analysis of friction surfaces, one can argue that a polymer composite with a high-modulus filler creates favorable conditions for their implementation in the moving units of machines. The results reported here make it possible to analyze and synthesize composite materials primarily for agricultural engineering, taking into consideration their tribological properties. The findings may be particularly interesting for service departments and enterprises producing parts for sowing complexes. [ABSTRACT FROM AUTHOR]

The Valaisan-type armband (a specific type of bracelet) is a typical metallurgical production from the western area of Switzerland belonging to the classic phase of the Aare-Rhone group (BzA2a, ca. 2000–1800 BC). This investigation aims to (i) characterize the metal composition, (ii) reconstruct the thermomechanical treatments applied during the manufacturing process, and (iii) gather information on the possible exploitation of the local ores coupling metallography and chemical analysis. The results show that each armband is manufactured from a hammered sheet of copper-based alloy, containing either tin (up to 3.0 wt.%) or a combination of antimony, nickel, and silver. In several cases, it is assumed that minor elements are already part of the original ore, suggesting a conscious selection of copper veins. In other armbands, a direct addition of cassiterite (SnO2) to the copper matrix is hypothesized based on the material composition and features of the inclusions. Microstructural features are coherent with a procedure that combines mechanical deformation (with a total deformation degree between 70 and 76%), annealing, and quenching, coherently with more recent productions (Late Bronze Age). The analysis of inclusions, rarely performed during metallographic investigations, provides precious evidences on thermal treatments applied during the manufacturing process and shows that annealing was carried out at low temperatures. [ABSTRACT FROM AUTHOR]

Components produced from sintered titanium alloys are increasingly used in mechanical engineering but need to be protected for operation in corrosive environments because of porosity. Nitriding is one of the effective protection methods. The objective of the study was to analyze the nitriding kinetics of a sintered VT1-0 titanium alloy at atmospheric (105 Pa) and reduced (1 Pa) nitrogen pressure at 800, 850, and 900°C for 5, 10, and 20 h versus a wrought titanium alloy of the same composition. The study employed discrete gravimetry, hardness measurement, optical and electronic metallography, profilometry, and X-ray diffraction. The nitriding kinetics of the VT1-0 titanium alloy sintered from titanium powder alone and from a mixture of titanium and titanium hydride powders was studied in comparison with wrought titanium. Under the nitriding parameters in question, the weight gain of all samples was described by a parabolic law and the weight gain of the sintered samples was higher than that of the wrought ones. The kinetic parameters of nitriding for the sintered and wrought VT1-0 titanium alloys were determined for the first time in the test temperature–time and gas dynamic conditions. Changes in the surface and near-surface layers depending on metal porosity were shown. After nitriding, the surface microhardness of the sintered titanium was lower than that of the wrought titanium samples because of porosity, and the strengthened surface layer was thicker. The nitride film formed on the sintered titanium alloy was thinner and less distorted than that on the wrought titanium alloy. The results can be used to develop nitriding conditions for sintered VT1-0 titanium products. [ABSTRACT FROM AUTHOR]

The recognitions of phases and precise grain boundaries based on metallographic images are useful for conducting micromechanical simulations, such as finite element analysis and peridynamics. In this work, those processes are automatized by using a Sobel operator for identifying edges, which is normalized by different proposed Gaussian filters (on intensity, rugosity, or both). After that, a threshold is used to discretize the edges. Different neighboring pixel configurations, sensitive to edge intensity, are proposed for thinning and cleaning the discretized edges, and hence, grain boundaries with a one-pixel thickness are obtained. Then, the phase is selected by averaging color of each delimited grain. Finally, the precision on the phase recognition was found to increase from 75.61 to 83.6% for the unmodified and the normalized Sobel operator, respectively. [ABSTRACT FROM AUTHOR]

Inconel 718 alloy fabricated by selective laser melting (SLM) (or laser powder-bed fusion (LPBF)) has been post-process heat-treated by stress-relief anneal at 1065 °C; stress-relief anneal (1065 °C) + solution treatment (at 720 °C) + aging (at 620 °C); hot isostatic pressing (HIP) (at 1120-1200 °C); stress-relief anneal + HIP; and stress-relief anneal + HIP + solution treatment + aging. Microstructure analysis utilizing optical metallography revealed primarily equiaxed grain structures (having average diameters ranging from ~30 to 49 microns) containing annealing twins, and a high concentration of carbide precipitates in all HIP-related treatments in the grain boundaries and intragrain regions. However, no precipitates nucleated on the {111} coherent annealing twin boundaries because of their very low interfacial free energy in contrast to regular grain boundaries. The mechanical properties for the as-fabricated Inconel 718 exhibited a yield stress of 0.64 GPa, UTS of 0.98 GPa, and elongation of 26%. Following stress-relief anneal at 1065 °C, the yield stress dropped to 0.60 GPa, while the elongation increased to 43%. The associated grain structure was an irregular, somewhat elongated, recrystallized structure. This structure was preserved at a stress anneal at 1065 °C + solution treatment + aging, but grain boundary and intragrain precipitation resulted in a doubling of the yield stress to 1.3 GPa and a reduced elongation of 12.6%. The results of HIP-related post-process heat treatments involving temperatures above 1060 °C demonstrated that the yield stress and elongations could be varied from 1.07 to 1.17 GPa and 11.4% to 19%, respectively. Corresponding Rockwell C-scale hardness values also varied from 33 for the as-fabricated Inconel 718 to 53 for simple post-process HIP treatment at 1163 °C. [ABSTRACT FROM AUTHOR]

The article considers the results of metallographic studies and endurance tests with regards to droplet impact erosion of nitrided samples of 12Kh13, 20Kh13, 15Kh11MF, and EI961 blade steels, as well as stellite. Data on the effect of ion-plasma nitriding of the surface on the erosion resistance of the tested blade steels are presented. The authors consider the prospects of using the applied hardening method as alternative passive protection of the rotor blades of wet-steam turbine stages or a method of a joint application of nitriding with widely used stellite overlays. [ABSTRACT FROM AUTHOR]

The purpose of this case study is to determine the cause of failure of DIN 1.4435 BN2 (AISI 316L with very low ferrite contents) clamp ferrules applied in pharmaceutical systems. Leakage was observed during operation in the clamp pipe connections of the ultra-pure fluid delivery systems. The surface of clamp ferrules showed remarkable discoloration and cracking. It was identified that the failure was caused by defects related to the autogenous laser conduction welding procedures. The intragranular cellular welded structures, which solidified with austenite as the primary product of solidification, showed a complete absence of hot cracks, minor delta ferrite, and minimum microsegregation. The welded components failed eventually owing to unstable welding profiles and significant porosity. Recommendations were given to prevent the recurrence of similar failures. [ABSTRACT FROM AUTHOR]

Gilded copper hollow spherical pendants known as gombiky (s. gombik) were examined to identify the technology of gilding and the material chosen as the substrate. The examined ornaments dating from the ninth and tenth centuries AD were recovered from elite graves of two major political, ecclesiastical and economic centres of the Early Medieval period located in the territory of the present-day Czech Republic: Mikulčice and Prague Castle, major sites of Moravia and Bohemia, respectively. Taking into account the state of degradation and possible bias due to earlier restorations, surface and bulk characterisation of the gilded material has been performed combining optical observation, X-ray radiography, metallography, scanning electron microscopy with energy-dispersive spectrometry (SEM/EDS analysis) and focused ion beam (FIB) milling mounted on FEG-SEM. The manufacturing procedure was reproduced by experimental archaeology. A detailed investigation of the gilded artefacts revealed several types of gombik construction involving different mounted elements, including the main body parts and the suspension system elements joined by hard soldering. The different constitutive parts are made with almost pure copper or low-purity copper. The systematic use of fire gilding (mercury amalgam gilding) was documented. Differences in the materials that were used and technical quality show the coexistence of finely produced objects by highly skilled and knowledgeable jewellers alongside more coarsely manufactured imitations. These variations are discussed in terms of different workshops in a possible relationship with their origin of manufacture. [ABSTRACT FROM AUTHOR]

Pearlite refining is one of the most used methods to increase the strength of cast irons, and it can be achieved using different strategies. In this work, three strategies to obtain pearlite refining were applied to a given hypoeutectic gray cast iron centrifuged in a coated steel mold: (1) increasing the Cu, Mo and Cr contents; (2) intensifying the cooling rate of the metallic mold; and (3) cooling of the cast iron with forced air. Strategies 2 and 3 aimed to increase the cooling rate during the eutectoid reaction. Then, four experiments were conducted: a reference experiment and other three applying separately the strategies above. Materials samples were characterized by optical metallography, chemical analyses, microhardness, pearlite interlamellar spacing measurements and tensile tests. The metallographic examination did not show any important change in the graphite morphology. The pearlite interlamellar spacing and microhardness were computed as distribution curves from at least thirty measurements in the materials matrices. These curves showed a decrease in pearlite interlamellar spacing and an increase in pearlite microhardness for the three materials in which the pearlite refining strategies were applied as compared to the reference material. The mean pearlite interlamellar spacings were reduced from 0.10 μm for the reference material to 0.07 μm, 0.08 μm and 0.08 μm for the materials in which strategies 1, 2 and 3 were applied, respectively. The UTS increased from 378 MPa for the reference material to 423 MPa, 418 MPa and 390 MPa for the strategies 1, 2 and 3, respectively. [ABSTRACT FROM AUTHOR]

Ductile iron nodularity is of critical importance to its quality, but nodularity determination by metallographic analysis can be problematic. The widespread practice of estimating nodularity via comparator chart is highly subjective and prone to unacceptably high variation. An improvement over visual metallographic estimates is digital image analysis (IA) by which subjectivity can be greatly reduced, but the more reliable results obtained from IA are time-consuming and difficult to implement in a production environment. For this paper, the use of ultrasonic velocity testing via a standard coupon was evaluated as a possibly more reliable technique for determining front-end (real time) nodularity. Major results are presented herein along with details necessary for implementation of front-end ultrasonic nodularity determination using standard coupons as standard practice. [ABSTRACT FROM AUTHOR]

This work is aimed at solving the challenging problem of developing an approach to determining the representative volume of an Al/SiC metal matrix composite material (MMC) with 55 vol % silicon carbide synthesized by a unique squeeze casting technology. This volume is referred to as representative volume element (RVE). Initially, the minimum unit cell size was found by a metallographic method. The RVE of the MMC, where the average filler content is equal to the average filler content in the composite material, begins with a 40 × 40-μm region. The RVE is determined by the finite element method. To perform numerical RVE calculations, we solved the two-dimensional problem of tension an element in the cross section of the MMC consisting of hard SiC particles and a pure aluminum matrix. A stress–strain curve recorded during uniaxial tension is used as the response of MMC to an external action. The problems with regions of 40 × 40, 50 × 50, 70 × 70, 100 × 100, 200 × 200 and 400 × 400 μm are solved. The results of the numerical calculations demonstrate that the minimum RVE of the Al/SiC MMC with 55 vol % silicon carbide is 200 × 200 μm. In addition, depth-sensing indentation is recommended as an experimental method for estimating RVE. When a pyramidal indenter is pressed into the surface of an MMC sample, the indentation diagram reflects the influence of both the composite matrix and silicon carbide particles. The indentation force (correspondingly, surface area) used in experiments is such that the influence of the site of indentation on the indentation diagram is minimal. Instrumented indentation used to determine RVE demonstrates that it is 200 × 200 × 200 μm. [ABSTRACT FROM AUTHOR]

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Superheater tubes are the most critical components of a power plant's boiler. Due to operation in high-temperature and -pressure conditions, platen superheater (primary superheater) tubes in thermal power point boilers are exposed to breakdowns such as creep failure and overheating. Therefore, identifying the causes of these failures and its maintenance is very important. Platen superheater tubes have failed in several similar power plant units at the same specific area. This problem is analyzed by three methods to find out the reason. These methods are metallography, measuring oxide layer thickness and CFD. These methods prove that the temperature difference between tubes is the cause of failure at the critical area. Length difference between tubes is the reason of the temperature raising in this case. Then, three solution methods are presented, namely (1) changing tubes material, (2) balancing tubes length and redesigning the platen superheater and (3) replacing the failed tube with new one. For comparing the methods, balancing tube's length and redesigning is selected. The selected solution introduces three proposed plans. These plans will be alternative for the failed platen superheater. A comparison made between three proposed design and platen superheater indicates that all of the three proposed designs are better in temperature side than the existing platen superheater. After that, the best design is chosen by the CFD results. The selected design here is the proposed plan 2 because it reduces the 25 K temperature difference of the platen superheater to 5 K and this will prevent this kind of failing. [ABSTRACT FROM AUTHOR]

This study applied piston-valve coating for an engine that worked 100% on biodiesel fuel and investigated the wear characteristics after the experiment. The plasma spraying method was used as the coating method. Al2O3 and ZrO2 ceramics, which are the most frequently used ones in the literature, were selected as coating material. The deformations on the coated and uncoated surfaces were determined after running the engine at different time intervals. The deformations on the piston surfaces were interpreted by conducting SEM and EDX analyses. In particular, the deformation on the coating material, thermal fatigue cracks, abrasive wear and elements that clang to the piston surface after combustion were determined. Additionally, post-combustion engine oil analysis was carried out to determine the elements that were released as a result of the thermal wear in connection to combustion. The relationship of the coating with thermal efficiency was investigated for all types of coatings by determining temperatures from a certain point on the engine by using a thermal camera and a surface temperature measurement device. As a result of the SEM, EDX and engine oil (ICP) analyses, it was seen that the elements that are released as a result of wear such as Al, Fe and Cr had lower quantities with the aluminum oxide (Al2O3) coating with the Nickel–Chromium (Ni–Cr) bonding agent in comparison to the other coating materials. Additionally, as a result of oil analyses, the coated engine was observed to have more positive outcomes in comparison to the uncoated engine. [ABSTRACT FROM AUTHOR]

The article provides information on the advantages of scanning electron microscopes including examination options of qualitative metallography, description of the structure of the metals and monitoring of manufacturing processes. Topics include welding technology, optimization of existing alloys and base materials.

Using electron beam surfacing, the specimens of products of titanium alloy of various shapes using the wire of grade Ti6Al4V were produced. In the deposited layers no defects were detected. In the course of the work, the investigations of microstructure, phase composition and mechanical properties of the specimens were carried out. For the weld metal, the structure consisting mainly of lamellar-acicular ɑ'-phase is typical. The structure contains a small amount of β-phase, which lies in the form of thin layers between the acicular precipitations of ɑ'-phase. It is not detected using the optical microscope, however can be detected applying electron microscopy and X-ray examinations. The microstructure of the deposited metal is mostly equilibrium and granular, gradient in sizes and microhardness. The microhardness of the boundary zones diff ers from the microhardness of the grain matrix, which may be associated with the diff erence in the content of alloying elements. Towards the top of the built specimen, the hardness decreases slightly. [ABSTRACT FROM AUTHOR]