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Additive manufacturing (AM) is an advanced manufacturing process that provides the opportunity to build geometrically complex and highly individualized lightweight structures. Despite its many advantages, additively manufactured components suffer from poor surface quality. To locally improve the surface quality and homogenize the microstructure, friction stir processing (FSP) technique was applied on Al-Si12 components produced by selective laser melting (SLM) using two different working media. The effect of FSP on the microstructural evolution, mechanical properties, and corrosion resistance of SLM samples was investigated. Microstructural investigation showed a considerable grain refinement in the friction stirred area, which is due to the severe plastic deformation and dynamic recrystallization of the material in the stir zone. Micro-hardness measurements revealed that the micro-hardness values of samples treated using FSP are much lower compared to SLM components in the as-built condition. This reduction of hardness values in samples treated with FSP can be explained by the dissolution of the very fine Si-phase network, being characteristic for SLM samples, during FSP. Surface topography also demonstrated that the FSP results in the reduction of surface roughness and increases the homogeneity of the SLM microstructure. Decreased surface roughness and grain size refinement in combination with the dissolved Si-phase network of the FSP treated material result in considerable changes in corrosion behavior. This work addresses the corrosion properties of surface treated additive manufactured Al-Si12 by establishing adequate microstructure-property relationships. The corrosion behavior of SLM-manufactured Al-Si12 alloys is shown to be improved by FSP-modification of the surfaces.

The conditions for increasing the hot workability and extending the temperature range for the safe hot working of M2 high-speed steel (HSS) were studied and revealed. This was enabled by combination of two approaches, i.e. results obtained by an analysis of so individual as well as spatial influences of chemical elements on the hot workability using a conditional average estimator neural networks in combination with the results obtained from hot-compression tests that revealed the appropriate soaking conditions. The Latin Hypercube Sampling technique was used to model the uncertainty of the collected data used in the analysis. The obtained results reveal new, surprisingly complex, typically spatial and (highly) non-linear relationships between the chemical elements and the hot workability of M2 HSS, i.e. common mutual influence of carbon, carbide-forming elements as well as elements, i.e. Si, Mn and Co, which indirectly influence the formation of carbides. Further also new allowed upper limits for contents of some harmful elements like S, P, Al, Sb, Cu, Sn, As, Ni, etc. at which transition from higher to lower workability takes place were revealed. Finally, by applying a specially developed procedure for hot-compression tests the appropriate soaking time and temperature were assessed. New findings explain and considerably improve the intrinsic hot workability and extend the temperature range for safe hot working at its upper and lower limits.

Advancing the application of safety and health (S&H) technologies is likely to remain a value in the mining industry. However, any information that technologies generate must be translated from the organization to the workforce in a targeted way to result in sustainable change. Using a case study approach with continuous personal dust monitors (CPDMs), this paper argues for an organizational focus on technology integration. Although CPDMs provide mineworkers with near real-time feedback about their respirable coal dust exposure, they do not ensure that workers or the organization will continuously use the information to learn about and reduce exposure sources. This study used self-determination theory (SDT) to help three mines manage and communicate about information learned from the CPDM technology. Specifically, 35 mineworkers participated in two mixed-method data collection efforts to discuss why they do or do not use CPDMs to engage in dust-reducing practices. Subsequently, the data was analyzed to better understand how organizations can improve the integration of technology through their management systems. Results indicate that using the CPDM to reduce sources of dust exposure is consistent with mineworkers’ self-values to protect their health and not necessarily because of compliance to a manager or mine. Keywords: Autonomous organization, Continuous personal dust monitor, Respirable coal mine dust, Safety and health management system, Self-determination theory

In recent years, numerous scientific and technological innovations have been introduced in the fields of medicine and dentistry. The application of computer-based engineering techniques has enabled significant improvement in the design and performance of biomedical components, including implants and prostheses. Innovative and flexible manufacturing methods, such as single point incremental forming (SPIF), allow the cost-effective production of these “custom-made” components. The SPIF technology has been employed to manufacture a metal denture base plate (framework) of a complete maxillary (upper) denture to replace a traditional prosthodontic procedure based on a lost-wax technique, which is time-consuming and requires much manual work. Stainless steel sheet of quality X6Cr17 and thickness of 0.5 mm was adopted due to its biocompatibility, good mechanical properties, and reasonable price. The SPIF process was completely designed in a digital environment with a focus on achieving high quality and accuracy of the part followed by experimental verification. For validation, the formed part was compared in terms of the geometry and mechanical strength with the reference one fabricated using the lost-wax technique. The results obtained confirmed the high dimensional accuracy and good strength of the SPIF-made part. The experimental investigations also included analysis of sheet thinning, surface roughness, and microstructure.

Estimating the overall floor stability in a coal mine using deterministic methods which require complex engineering properties of floor strata is desirable, but generally it is impractical due to the difficulty of gathering essential input data. However, applying a quantitative methodology to describe floor quality with a single number provides a practical estimate for preliminary assessment of floor stability. The coal mine floor rating (CMFR) system, developed by the University of New South Wales (UNSW), is a rock- mass classification system that provides an indicator for the competence of floor strata. The most significant components of the CMFR are uniaxial compressive strength and discontinuity intensity of floor strata. In addition to the competence of the floor, depth of cover and stress notch angle are input parameters used to assess the preliminary floor stability. In this study, CMFR methodology was applied to a Central Appalachian Coal Mine that intermittently experienced floor heave. Exploratory drill core data, overburden maps, and mine plans were utilized for the study. Additionally, qualitative data (failure/non-failure) on floor conditions of the mine entries near the core holes was collected and analyzed so that the floor quality and its relation to entry stability could be estimated by statistical methods. It was found that the current CMFR classification system is not directly applicable in assessing the floor stability of the Central Appalachian Coal Mine. In order to extend the applicability of the CMFR classification system, the methodology was modified. A calculation procedure of one of the CMFR classification system’s components, the horizontal stress rating (HSR), was changed and new parameters were added to the HSR.

Since 2009, the Mine Safety and Health Administration (MSHA) has required mines to install refuge alternatives (RAs) in underground coal mines. One of the biggest concerns with occupied RAs is the possible severity of the resulting thermal environment. In 30 CFR 7.504, the maximum allowable apparent temperature (AT) for an occupied RA is specified as 35 °C (95 °F). Manufacturers must conduct heat/humidity tests to demonstrate that their RAs meet the 35 °C (95 °F) AT limit. For these tests, heat input devices are used to input the metabolic heat of actual miners. A wide variety of test methods, sensors, and heat input devices could be used when conducting such tests. Since 2012, the National Institute for Occupational Safety and Health (NIOSH) has conducted over thirty 96-hour heat/humidity tests on four different RAs. This paper discusses the test equipment and procedures used during these investigations. This information is useful for RA manufacturers conducting RA heat/humidity tests, for other researchers investigating RA heat/humidity buildup, and for those who need to assess the thermal environment of any confined space where people may be trapped or are seeking refuge. Keywords: Refuge chamber, Refuge alternative, Confined space, Thermal environment, Test method, Temperature

Coal mines are continuously seeking to determine the performance of entries with different ground control products and installation methods. There are many factors that impact how an entry will perform which include but are not limited to geology, overburden, bolting type and pattern, and mine design. At the National Institute for Occupational Safety and Health (NIOSH), research has been instituted to examine the relationship of the parts of a coal mine entry as a system and not as individual components. To study this relationship, the first step in this study was to create a numeric rating system that accurately reflects visual observations of the mine entry and is easy to implement. NIOSH researchers devised this rating system to improve upon previous ideas, offering increased flexibility which can be incorporated into an overall entry condition that offers different levels of confidence based on the user’s time devoted to the inspection. This new entry rating system was implemented at three different mines over varying periods of time to evaluate the ground response to the geology, bolt installation pattern, stress changes by mining, overburden, and time dependency.

The objective of the present work is to investigate the feasibility of the synthesis of copper matrix composite reinforced with in-situ nanosized Al2O3 particle powder via combustion synthesis method from metal nitrates followed by reducing process at high temperature. The starting nitrates Cu(NO3)2.3H2O and Al(NO3)3·9H2O composition corresponds to Cu-30%Al2O3. X-ray Diffraction (XRD) patterns of the obtained powders indicated the presence of the oxides CuO and CuAl2O4. The powder had the size of 75 ± 10 nm after deagglomerating by soft ball milling for 24h. After reducing in CO at 1000oC for 3h, the peaks of the oxides were no longer observed and were replaced by the peaks of Cu and -Al2O3. The morphology of the reduced powders observed by scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS) analysis showed well distribution of the -Al2O3 particles within the Cu matrix with an average particle size of 40 nm.

A magnesium alloy AZ31 as plate of dimensions (60 x 60 x 3) mm has been constrained groove pressed (CGP) four deformation passes (16 pressings) at 250 oC by simulation and experiments. On the basis of the analysis of calculation results about the deformation distribution in the alloy AZ31 workpieces, the mechanism for its microstructure evolution during the severe plastic deformation (SPD) process was partly clarified. On the other hand, deformation heterogeneity distribution developed in the workpieces by applying CGP caused the evolution of a non-uniform microstructure. The TEM microstructure analysis results provided clear evidence that across the plate both the banded deformed microstructure where dislocation cell structure and/or partially or fully recovered polygonized subgrain microstructure are present. The recovering dynamic and local polygonization process contributes significantly to the formation of ultra-fine materials (UFG) microstructure.

The present paper is devoted to the possibilities to classify the spatial arrangement of the elements (features) of a stochastic process with geometrical objects. The fundamental quantities describing point processes were introduced. Experimental possibilities of structural objects determination, possibilities of evaluation of the size distribution of the secondary phases, testing of planar point structures (estimation of the process intensity, square method and characteristics of the second order) were estimated. Interparticle distances, namely mean interparticle distance, mean minimum distance, mean visibility and mean path of spherical contact were defined. Selected processes were described and demonstrated from simulated realizations on Al-Al4C3 dispersion strengthened material, prepared by a powder metallurgy method of reaction milling. Interparticle distances of Al4C3 particles were evaluated. Polygonal methods and quadrant counts method were used for characterization of the particle arrangement.

Dominating globally and within Ukraine, the blast-furnace practice for iron production requires iron ore sintering preparation wherein the significant amount of fossil fuel is consumed, accompanied by harmful emissions into the environment. Pursuing the purpose to mitigate this negative impact, we address the promising direction of biomass utilisation for a partial replacement of fossil fuels in iron ore sintering. This paper considers the benefits of fossil fuels substitution with biomass, the world practice of biomass utilisation in iron ore sintering and the scope of the biomass energy potential in Ukraine. The study for obtaining sinters with the use of raw biomass fuels (sunflower husk, walnut shell) and charcoal has been carried out via lab-scale sintering pot. The influence of various biomaterials types on the process of iron ore sintering have been investigated and the obtained sinter quality in comparison with the conventional types of the fuels allows establishing the feasibility of replacing 25 % of coke breeze by charcoal or by walnut shell. The sunflower husk application is possible if preliminary preparation of the material for increasing bulk density is assumed to be carried out, for instance, by pressing.

Environmental protection is a complex ecological and economic problem, including the need to develop and implement a number of environmental protection measures to mitigate the negative impact of mining waste on all natural environment components and human health. In this regard, the study purpose was to assess the impact of Pb, Cd, Cr, and As compounds on the environment and health of the population of the Solnechny miner’s village. Based on the purpose, the following tasks were set: 1) review and systematization of literature data on the problem of technogenic dust pollution; 2) assessment of the mining industrial system as a source of ecosystem pollution with toxic elements within the closed mining enterprises impact areas; 3) development of proposals for mitigating the impact of mining activities on ecosystems and human health. The paper presents the findings of the study of the elemental status of children and adolescents living within the closed town-forming enterprise JSC Solnechny GOK impact area. The relationship between the level of technogenic pollution of the natural environment and the changes in the elemental status of the children was shown. A feature of the elemental status of the children in the study group was high content of heavy metals, including Pb, Cr, and As. Our research confirmed the data that a growing child’s body actively adsorbs compounds of toxic chemical elements. Deficiency and imbalance of microelements in the body can cause ecologically-related diseases in the child population. Individual and population carcinogenic risks (CR) caused by the As, Pb, and Cr pollution were calculated. In accordance with the acceptance criteria for the risk caused by exposure to the pollutants, the individual carcinogenic risk CR (Cr) = 1,05 · 10–3 belongs to the fourth range and is unacceptable neither for the population, nor for occupational groups. This is De manifestis risk, and when it is reached, it is necessary to carry out emergency curative measures to mitigate it. The individual risks CR (As) = 7,05 · 10–4 also exceed the acceptable level for the population. This level of pollution is subject to permanent monitoring, requires development and implementation of planned curative measures to improve the indicators of the human environment, one of which is the organization of the environmental monitoring system in the study area.

This research belongs to the field of rock physics. In recent years, in solid state physics and materials science, new knowledge has emerged about microplastic strain of various materials, including rocks. These data were obtained using high-precision micro- and nanoscale strain measurements. The very fact of the existence of the poorly studied rock property in the earth sciences requires the study of the possible influence of the rock microplasticity on the propagation of seismic and acoustic waves. The studies were carried out using three alternative methods and under different observation conditions. The field measurements were carried out in the zone of low velocities in crosshole space with transmitted waves of frequency of 240–850 Hz. The laboratory measurements were carried out on sandstone samples with transmitted (6.8 kHz) and reflected (1 MHz) waves at the strain of 10−8–10−6. The manifestations of microplasticity were recorded using high-resolution recording of signals with discretization time tdiscret = 1 μs – 40 μs and 32.5 ns. The wave amplitude variation was provided in a closed cycle: discrete increasing the amplitude from minimum to maximum and return to the initial value (A1+ → A2+ → … Amax … → А2– → A1–). In this amplitude range, an amplitude hysteresis was observed, a sign of which was the inequality of wave velocities on the upward and downward amplitude courses. This effect was recorded for all three measurement methods at different frequencies. However, the amplitude hysteresis of the wave velocity was not observed only in the measurements at full water saturation of loam. The largest amplitude-dependent change in the wave velocity reached 2% (at the accuracy of 0.02%), and the change in the attenuation value amounted to 5%. The reason for this effect could be microplastic inelasticity, which manifested itself by amplitude plateaus located within the waveform. The amplitude microhysteresis forms overall picture of the amplitude dependence of the wave velocity in wide amplitude range. Proposals for the potential use of the obtained data for solving some applied problems have been presented.

This paper describes the influence of deformation by equal-channel angular pressing (ECAP) on the solid particle erosion resistance of the AlSi7Mg0.3 alloy and AlSi7Mg0.3 based composite material reinforced with the addition of 4 % of fly ash (FA) particles. Both, alloy and composite samples were produced using the compo-casting method. The samples have been subjected to ECAP in multiple passes with the rotation of samples around the vertical axis for the angle of 90° after each pass. Particles of silicon carbide (SiC) have been used as erodent while their impact angle was varied (30° and 90°). Observed samples of AlSi7Mg0.3 alloy generally showed higher wear resistance at 90° angle where material fatigue predominates, than at a 30° angle where abrasion-related phenomena predominate. On the other hand, AlSi7Mg0.3 based composite material exhibited erosion wear at 30° angle less than at 90° angle after one ECAP pass. Evaluation of the erosion resistance has been made based on mass and volume loss. After two passes of ECAP, the matrix structure of the AlSi7Mg0.3 based composite material, as well as that of the AlSi7Mg0.3 alloy was improved from the aspect of erosion resistance.

Three stationary hydrodynamic theoretical problems are solved, in which filtrations obey only the General nonlinear law. Simple flows occur in tasks: plane-parallel, plane-radial, and hemispherical-radial. All derived formulas – oil flow rate, filtration rate, pressure gradient, etc. – should be used to solve various practical problems of the development of these deposits and even when drawing up a project for the development of such deposits. It should be noted that a plane-parallel simple filtration flow of oil originates from a strip-like reservoir to a straight gallery. In addition, such a simple filtration fluid flow also occurs when the oil field under development has several parallel rectilinear rows of production production wells and, in some cases, there may be rows of injection water wells in the reservoir. In oil-bearing areas between parallel adjacent rows, oil filtration is also plane-parallel. Hence, the practical significance of solving the first problem of a plane-parallel oil flow in this scientific article becomes clear. Planar-radial simple filtration flow of oil originates from a circular horizontal formation to a central production well. In addition, such a simple filtration fluid flow also occurs when a strip-like oil field being developed has several (usually three or four) parallel straight rows of production production wells. In the drainage zones of these wells, a simple flat-radial filtration flow also occurs. From the foregoing, the practical significance of a radial plane oil flow becomes clear. Hemispherical – a radial simple filtration flow of oil originates from a hemispherical reservoir to a central well, barely penetrated by the reservoir by its hemispherical concave bottom. By analyzing these calculation formulas, you can identify the specific features of the development of deposits, develop and implement measures to eliminate undesirable phenomena.

Relevance of the research. Stable parameters of dumps are critical in mining operations ensuring their safety and economic efficiency. This problem is particularly acute for mining enterprises engaged in surface mining and for coal open pit mines, in particular. One of the main problems of this issue is related to the substantiation of rigorous methods for assessing stability and determining the limiting parameters of external and internal dumps filling an embankment on weak gently dipping interface. In the technical and regulatory literature, this issue has been considered for a long time. However, there are no specific recommendations for finding the most dangerous sliding surfaces on slopes, as well as methods for calculating shearing and restraining forces along these surfaces. All the signs are that the reason for the stability loss of operated dumps is the absence of theoretically substantiated design schemes, respectively, there are errors in the design of dumping. Purpose of the work is to develop reliable methods for calculating the limiting parameters of dumps on weak gently dipping interface. The main idea of the work is to apply a new, not previously used scheme for calculating the stability of dumps on weak gently dipping interface. Research methods. The work deals with the apparatus of flow mechanics and more specifically, the rigid-plastic model (the method of limit equilibrium), and the variational, integral and differential branches of calculus act as a mathematical apparatus. Results and conclusions. Based on the results of previous studies, a new scheme for calculating the stability of the dump during its destruction along weak interface was proposed, which implies the absence of a curved section of the sliding surface under the slope and the convex shape of the sliding surface under the berm. In contrast to the existing calculation schemes, such a calculation scheme predicts significantly lower values of the critical parameters of dumps. It means that the use of the proposed scheme will prevent the destruction of dumps by landslides along the dumpbasement interface and increase the economic efficiency of enterprises. Because a sufficiently large overestimation of the critical parameters of dumps at weak interface limited by current regulatory documents has been determined, it is recommended to revise these parameters for the designed and operated dumps using the proposed schemes for calculating their stability.

Relevance. The assessment of uncertainties for the calculation of hydrocarbon reserves is a timely topic. The quality of hydrocarbon reserves is declining as old oil fields are depleted. Rates of discovery are in decline since most of the territories prospectively rich in hydrocarbon resources have already been explored. Newly discovered fields are classified as small and medium in terms of the amount of hydrocarbon reserves and difficult in terms of the quality of reserves. Purpose of the research is to determine important reservoir properties that have the greatest impact on the variability of the initial hydrocarbon reserves using sensitivity analysis and conducting a probabilistic hydrocarbon reserves assessment by the Monte Carlo method. Methods of research. The probabilistic hydrocarbon reserves assessment was carried out by the Monte Carlo method with the corresponding frequency curves of the probability distribution of volumetric parameters, which were performed using the Oracle Crystal Ball application. The sensitivity analysis of volumetric parameters that have the greatest impact on the amount of the initial hydrocarbons reserves was performed using the Oracle Crystal Ball application as well. Results and their application. An assessment of uncertainties and risks is necessary both for newly discovered fields in order to negate the risk of drilling unproductive wells and mature fields for a targeted program of geological and technological measures (GTM). Conclusions. The formation of bedded sand bodies of the Vasyugan (SE11, SE12, SE13) and Tyumen (SE2) suites took place in various sedimentation conditions, which could not but affect the quality of the reservoir of the studied formations. The analysis of the sensitivity of parameters has shown that different parameters affect the amount of hydrocarbon reserves in places SE11, SE12, SE13 and place SE2 .

Relevance of the work. The Iset river basin contains the most extensive outcrops of volcanogenic formations of the Beklenishchevsky complex of the East Ural megazone, the age of which is determined as Early Carboniferous by the ratio of volcanic rocks with faunistically characterized sedimentary deposits. Volcanics here compose flows of andesite-basaltic and andesitic lavas and lava breccias. There are no geochronological dates specifying the age of the rocks, which makes it difficult to assess their role in the formation of the megazone. Therefore, isotopic dating of these formations is very important. Methods. The U – Pb age and data on the geochemistry of zircons were obtained by laser ablation (LA – ICP – MS). Purpose of the research is to study the features of the geological structure, the material composition of volcanic rocks in the Iset river basin, the geochemistry of zircons from andesites and the determination of their isotopic age. Results of the work and the scope of their application. Lava flows of andesites and basaltic andesites with minor amounts of basalts and dacites have tectonic contact with sedimentary rocks of the Early Carboniferous age. The distribution of rare elements in volcanics is typical of supra-subduction formations. Zircons in andesites are represented by prismatic and isometric crystals. Prismatic differences in the nature of the distribution of REE and the content of Li, Ti, Sr, Th, U refer to zircons of magmatic genesis, isometric – to “hydrothermal”. According to the U / Yb – Y ratios, the former correspond to the zircons of the ocean floor, while the latter are related to the continental ones. Isotopic dating of zircons from andesites was carried out for the first time. Their age was 311 million years. The data can be used in geological mapping, as well as in the compilation of large-scale geodynamic maps and diagrams. Conclusions. Volcanic rocks in the Iset river basin were formed in supra-subduction continental-marginal geodynamic conditions that took place in the Urals in the Carboniferous. The obtained value of the age of zircons from andesites, possibly, fixes the stage of their transformation. Keywords: East-Ural megazone, volcanic rocks, zircon, isotopic age.

Relevance and purpose of the work. Currently, the area of development of Tomsk is increasing. New neighborhoods are growing on previously undeveloped land (for example, on the left bank of the river Tom). The central part of the city is being redeveloped and reconstructed. It is impossible to develop a high-quality territory without taking into account the dynamics, mechanisms, factors and patterns of development of dangerous natural and technological processes, the forecast of their development. The purpose of the work is to establish the patterns of gully erosion, assess the intensity of its development, and predict the probability of its occurrence within the new city boundaries. Methods of research. We performed an assessment and forecast of the development of gully erosion in Tomsk using GIS technologies, which are an important tool in the city management process due to their ability to process and analyze multidimensional data about the geological environment. We compared the traditional model of data-driven frequency ratio (FR) and expert-based multi-criteria assessment, i.e. analytical hierarchical process by weighting of gulley conditioning factors. Results of the work. We constructed a map of the distribution of gullies on the territory of the city, including 23 polygons. These polygons were then randomly divided into training (16 polygons or 70%) and validation data (7 polygons or 30%). We used seven gulley-conditioning factors for the two models to produce gulley susceptibility maps: slope angle, slope aspect, curvature, elevation, geological structure of the territory; types of filtration sections; distance to the river, to analyze the spatial patterns that determine the development of gully erosion. The spatial correlation between gulley locations and the conditioning factors were identified using GIS-based statistical models. We constructed gulley susceptibility maps based on the ranking of each factor by two methods using a training data set. Receiver operating characteristics (ROC) were used to validate the resulting susceptibility maps. The area under the curve (AUC) was 0.905 for the AHP model and 0,800 for the FR model, respectively, which indicates excellent and high quality of forecast maps. We proved that both methods are beneficial for assessment the susceptibility of the territory to gully erosion. We recommend using the constructed maps for regional planning and hazard mitigation, as well as in education by teaching the discipline “Engineering geodynamics”.

The effective reinforcement of two or more overlying layers of mine openings in a single installation is usually done by coupling of two standard rock bolts mainly during the extraction of medium-thick coal seams. However, field observations show that the couplers of multiple bolts often degrade or break mostly at their connections. These types of failures can be avoided by strengthening the couplers of such multi-bolts assemblies. To achieve this, a novel threaded coupler system with an expansion shell was suggested in this paper. The newly designed coupler consists of a threaded tapered-plug-cum-connector with an expansion shell for connecting and tightening two standard rock bolts. An analytical model for evaluating the load distribution along the coupler subject to axial load was derived. Numerical analysis was performed to analyse the load transfer, deformation, and strains across the coupler including the factor of safety for the bolt-coupler-resin and bolt-coupler-expansion shell. The results validated the analytical model of the proposed coupler design, which provides better anchorage near the interface of the host rock mass. Thus, the developed coupler design would reduce the failures of the proposed coupler and stabilize laminated roof strata above the medium-thick coal seams in underground mines.

Fe–10Cr–10Ni cryogenic maraging steel is one of the key candidate materials applied in harsh cryogenic condition due to its high strength and good cryogenic toughness. In this study, the effect of aging temperature on its microstructure and mechanical properties was systematically studied based on austenite reversion and nano-precipitation. It shows that a desirable combination of high strength (834 MPa, 25 °C) and excellent cryogenic impact toughness (164 J, −196 °C) can be obtained by aging treatment at 500 °C. Multi-scale characterizations were conducted to reveal the microstructure characteristics of the steel. It was found that obvious film-like reversed austenite nucleate and grow at the high-angle grain boundaries of martensite matrix in the steel aged at 500 °C, whereas the higher aging temperature resulted in a larger content of blocky reversed austenite in martensite blocks. Austenite reversion mechanism was proposed based on the double-spherical-cap model and diffusion kinetics of Ni element. Besides, it was found that the precipitation sites of Ti-rich particles are not only distributed in matrix but also located at the dislocations, and they were identified as the clusters of Ni3Ti precipitates. Finally, the origin of the above cryogenic toughness includes the transformation-induced plasticity (TRIP) effect from the soft film-like austenite, higher density of high angle grain boundaries of martensite and fine nanoscale precipitates. Moreover, the precipitation strengthening from the clusters of Ni3Ti precipitates contributes to the high strength of the steel aged at 500 °C.

Blasting of rocks has intrinsic environmental impacts such as ground vibration, which can interfere with the safety of lives and property. Hence, accurate prediction of the environmental impacts of blasting is imperative as the empirical models are not accurate as evident in the literature. Therefore, there is need to consider some robust predictive models for accurate prediction results. Gene expression programming (GEP), adaptive neuro-fuzzy inference system (ANFIS), and sine cosine algorithm optimized artificial neural network (SCA-ANN) models are proposed for predicting the blast-initiated ground vibration in five granite quarries. The input parameters into the models are the distance from the point of blasting to the point of measurement (D), the weight of charge per delay (W), rock density (ρ), and the Schmidt rebound hardness (SRH) value while peak particle velocity (PPV) is the targeted output. 100 datasets were used in developing the proposed models. The performance of the proposed models was examined using the coefficient of determination (R2) and error analysis. The R2 values obtained for the GEP, ANFIS, and SCA-ANN models are 0.989, 0.997, and 0.999, respectively, while their errors are close to zero. The proposed models are compared with an empirical model and are found to outperform the empirical model.

This research presents a high energy ball milling method for producing supersaturated solutions of the Ti100-xMgx (x = 10, 15, 20) composite powders containing a process control agent (PCA) under an argon atmosphere at an ambient temperature. The microstructure of the Ti–Mg solid solution during milling was analyzed by scanning electron microscope, and an X-Ray diffraction. A particle size analyzer was employed to investigate the average particle size at different milling times (12 h, 20 h, 32 h). After milling for 32 h of Ti100-xMgx (x = 10, 15, 20) composite powders, the solid solubility of the Mg in Ti reached about 0.5 wt.%, 1.14 wt.%, and 1.92 wt.%, respectively. It was found that the crystallite size of the milled powder decreased by increasing the milling time and reached the value of 4–11 nm after 32 h of milling. Moreover, the addition of the process control agent after 12 h and 20 h significantly reduced the agglomeration by cold welding. As a result, the average particle size of the dispersed composite powder Ti100-xMgx (x = 10, 15, 20) was refined to about 1 μm which indicated that the Ti controlled the final size as being a major alloying element. The maximum value of the density of green compacts was found to be 2.69 g/cm3 for Ti–10Mg.

To develop a clean and sustainable carbon anode material derived from biomass with desirable properties for lithium-ion batteries (LIBs), bio-nitrogen (N)-doped composite carbon nanofibrous mats (CNFMs) were made using natural cellulose (CE) and chitosan (CS) by means of two different electrospinning ways (single-nozzle and coaxial-nozzle) coupled with pyrolysis. The conventional CNFMs that had a CE/CS ratio of 5:5 showed the best electrochemical performance, corresponding to a high specific capacity of 327 mAh g−1 at 100 mA g−1, good rate performance with specific capacity of 399 mAh g−1 at 30 mA g−1 and 210 mA g−1 at 1000 mA g−1, as well as excellent cycling stability after 300 cycles. The core–shell CNFMs with a thick outer layer of CS and large average fiber diameter (316 nm) at the same CE/CS ratio had higher pyridinic-N and pyrrolic-N contents but a lower degree of graphitization and BET surface area compared to the conventional CNFMs. It was concluded that the bio-N in CS was more uniformly doped into the CNFMs by the single-nozzle electrospinning way than by the coaxial one, and thus more effectively promoted a comprehensive electrochemical performance.

Sterilization of ultra-high molecular weight polyethylene (UHMWPE) based composites used for acetabular cup liner via UV or gamma-irradiation before surgery is inevitable. Thus, understanding the alteration of mechanical properties and wear resistance of cup liner via irradiation process requires investigation. This paper aims to understand the effect of UV (0.03 J/cm2) and gamma (25 kGy) irradiation on mechanical properties and scratch resistance of compression molded UHMWPE composites reinforced with alumina (Al2O3), hydroxyapatite (HAp) and carbon nanotubes (CNTs). After irradiation, nearly 100% increased crystallinity of polyethylene, due to recrystallization, helped in enhancing the hardness and elastic modulus by ~1.5 times compared to that of as-processed UHMWPE (Hardness: ~70 MPa and Elastic modulus: ~1.25 GPa). The recrystallization was not favored by the presence of nano-reinforcements in irradiated UHMWPE based nanocomposites, and caused deterioration in the mechanical properties. The micro-scratch results revealed the remarkable wear resistance (i.e., 1.5 to 2 times lower wear rate) of irradiated samples than that of as-processed samples. Mouse fibroblast L929 in vitro cell culture test confirmed the cytocompatibility of irradiated samples. This study indicated that the UV and gamma irradiated UHMWPE nanocomposites are the challenging candidates as acetabular cup liner.

Dissimilar TC4 titanium alloy and 316L stainless steel were successfully joined utilizing thermoplastic bonding (TPB) with a Ti-based bulk metallic glass (BMG) as the filler. Good physical pre-bonding and metallurgical bonding were successively achieved through superplastic flowing in the superliquid region and solid-sate atomic diffusion and reaction. The experimental results indicated that the superplastic flow of BMG in the superliquid region greatly promoted void shrinkage in the interfaces. Hence, a compact contacting was obtained at temperature much lower than the melting point of the filler metal, which is beneficial to the atomic diffusion between the filler metal and base metals as temperature increased. After holding for some time below the melting point of the filler metal, three different reaction layers derived from the atomic diffusion and reaction between the base metal and filler metal were formed in the interfacial regions. A series of irregular bulky and small plate-shaped fine phases were formed and uniformly distributed in the interfacial regions and intermediate region. The shearing tests showed that a high strength of 225 MPa was obtained after diffusing at 695 °C for 60min. The fracture surface of the joint shifted from the 316L interface to then central crystallization layer as temperature increased.

Residual stresses (RS) induced in machined components have substantial impact on the quality and lifetime of the final products. There are several cutting parameters and conditions that affect the generation of RS, so understanding the relationship between the RS generation and those parameters to minimize the induced tensile RS is a crucial issue. This paper presents a study on the utilization of artificial intelligence-based methods to model the RS generation during dry turning of DT4E pure iron. The experiments were designed based on central composite design method. The effects of the cutting parameters such as cutting speed, feed and cutting depth on the generated RSes in both circumferential and radial directions are investigated. Two hybrid artificial neural network (ANN) models are used to predict the process responses after training them using the experimental results. The prediction accuracy of the two models are enhanced via integration with two different metaheuristic optimization algorithms, namely particle swarm optimization (PSO) and flower pollination algorithm (FPA). These optimization algorithms are used as subroutine algorithms to determine the optimal parameters of the ANN model. The predicted results by the proposed models were compared with the experimental results as well as those obtained by standalone ANN. The accuracy of all models was evaluated using different statistical measures. The ANN-FPA had the best prediction accuracy followed by ANN-PSO. The coefficient of determination of ANN-FPA has high values of 0.996 and 0.997 for radial RS and circumferential RS, while they were 0.971 and 0.992 for ANN-PSO and 0.649 and 0.815 for standalone ANN.

In the present study, the microstructure, toughness and cracking behavior of a batch of X12CrMoWNbVN10-1-1 martensitic heat resistant steels used for manufacturing steam turbine blades in power plant were investigated. The manufacturing route of the X12CrMoWNbVN10-1-1 martensitic steels was casting, forging and heat treatment. These martensitic steels were taken from different positions in the same ingot, but they exhibited different toughness, which were marked as two groups: (i) the matrix located in the core of the ingot, hereinafter referred to sample A; (ii) the matrix located in the edge of the ingot, hereinafter referred to sample B. Impact toughness was characterized by Instrumented Charpy impact test, fracture toughness was determined by single edge notch tension (SENT) test in terms of double-clip gauge method, and crack propagation behavior was observed by in-situ single edge notch bend (SENB) test. Optical microscopy (OM), scanning electron microscopy (SEM) and high-resolution energy dispersive X-ray spectrometry (EDX) were used to examine the microstructure and cracking features. The impact toughness of sample A was much lower than that of sample B, which was proved to be attributed to the large amount of NbC precipitation in sample A. The clustered NbC particles could induce brittle cracking and thus significantly reduced absorbed energy for stable crack propagation, resulting in the poor impact toughness of sample A. It was believed that the large amount of NbC in sample A was precipitated directly from liquid metal during casting process, which might be related to the high niobium content of the core of the ingot due to the low cooling rate. The results revealed that the large number of clustered NbC particles formed in the casting process not only cannot promote precipitation-induced reinforcement, instead might be detrimental to toughness.

The solidification microstructure of 8Cr13MoV martensitic stainless steel electroslag remelting (ESR) ingot is observed by scanning electron microscopy (SEM) and field emission scanning electron microscopy (FE-SEM). The results show that eutectic carbides in ESR ingot are composed of three types of morphology, which are clustered blocky, fibrous and cerebriform. Transmission electron microscopy (TEM) results indicate that the eutectic carbides are M7C3 carbides. Electron backscattered diffraction (EBSD) results show that although the morphology of eutectic M7C3 carbides is diverse, they are composed of three carbide substructures, which are bulky carbides, fibrous carbides and spherulitic carbides, respectively. Eutectic M7C3 carbides in the center of the ingot are general carbide clusters composed of bulky carbide grains, fibrous carbide grains and a small amount of spherulitic carbide grains. However, eutectic M7C3 carbides at the edge of the ingot edge are almost cerebriform carbides composed of fibrous carbide grains and spherulitic carbide grains. Microsegregation promotes the formation of heterogeneous nuclei Al2O3-(Ti,V)N at the solidification end, which promotes the formation of bulky carbides. In the meanwhile, microsegregation also substantially increases the supersaturation of the residual liquid and drives the morphology evolution of eutectic carbides from bulky to fibrous and spherulitic. The cooling rate increase restrains carbide growth, intensifies the solute enrichment in the residual liquid, obviously increases the supersaturation and finally promotes the morphology change from bulky to fibrous and spherulitic. Furthermore, microsegregation and the cooling rate change have less effect on the agglomeration and coalescence behaviors of carbide substructures.

High-strength titanium (Ti) alloys are progressively demanded for structural applications in weight-critical aerospace industry. Improving mechanical properties of the alloys are thus exploited in response to the requirement. In this study, a strategy of through-transus thermomechanical forging was applied to the Ti–10 V–2Fe–3Al metastable β-Ti alloy, and the resulting microstructures and mechanical properties were systematically investigated in comparison to the conventional (α+β) dual-phase field forging. It is found that the through-transus thermomechanical forging significantly enhances strength, ductility and strain hardening capacity, while it is the inferior combinations of mechanical properties in the alloys subjected to the (α+β) dual-phase field forging. Microstructural characterization reveals that the former renders the hierarchical microstructure composed of intergranular αp-necklaces, and intragranular αp-rods as well as αs-lamellae in the β-matrix. The superior combinations of mechanical properties are conferred by good strain compatibility of these microstructural constituents. By contrast, the latter renders the network microstructure comprised of intergranular globular αp-phase and continuous grain boundary (GB) αGB-films as well as the intragranular αs-lamellae. Local deformation-damage is more preferred to initiate in the intergranular network structure. These findings provide fundamental understanding on the correlation between mechanical properties and microstructures, facilitating manufacturing high-performance β-Ti alloys at an industry scale using commercially available thermomechanical processing.

The natural fiber reinforced polymeric composites have found to be an excellent substitute for synthetic fiber based polymeric composites and are being widely utilized in several advanced engineering applications. The present experimental work deals with randomly oriented Indian mallow fiber/polyester (IMFP) composites which are fabricated by compression moulding method by varying the fiber wt. % from 10 to 50%. The prepared IMFP specimens were evaluated through various mechanical and thermal properties and the results showed that better properties were obtained in specimens with 50 wt. % fiber content. The optimum tensile strength and modulus was about 46 MPa and 3.56 GPa respectively, while the elongation at break was 1.39%. The optimum flexural and impact strength are estimated to be around 111 MPa and 14 kJ/m2 respectively. The heat deflection test (HDT) displayed that temperature withstands up to 84 °C at 50 wt. % of fiber content. The surface morphologies of the fractured composite specimens were characterized by scanning electron microscopy (SEM) analysis. The overall results confirmed the suitability of the present specimens to be employed in various light weight applications.

Pure nanocrystalline akermanite was successfully synthesized by mechanical activation and heat treatment of talc, calcium carbonate, and silicate. Powders were characterized by thermogravimetric analysis (TGA), x-ray diffractometry (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The formation mechanism was studied in depth. These results showed that akermanite was produced by the formation and consumption of transitionary compounds such as enstatite, wollastonite, larnite, and merwinite. Pure akermanite was synthesized with a crystalline size of 34 nm after ball milling for 20 h and subsequent heat treatment at 900 °C for 1 h.

The boriding of 4Cr5MoSiV1 steel was performed in the temperature range of 860°C–980 °C to examine the influence of boriding conditions on the boride layers. The experimental results show the formation of FeB and Fe2B layers with the predominant saw-tooth morphology. The boride layer depth increases with increase the boriding temperature and time. Thick and compact boride layers could be obtained at temperatures higher than 900 °C. The growth kinetics of boride layers is characterized by a parabolic curve. FeB and Fe2B exhibit a hardness of 1600HV0.1 and 1300HV0.1, respectively, which is 4 and 3 times that of the substrate. A diffusion model, based on the boron concentration profiles of the surface layers and the parabolic growth law, was established to predict the growth kinetics of the boride layers including both the FeB and the Fe2B layer. A satisfactory agreement between the model and experimental results was obtained. The work thus provides an approach to investigate and to predict the boride layer growth of 4Cr5MoSiV1 steel in the boriding process.

It is a challenging and valuable work to synthesize surface enhanced Raman scattering (SERS) substrate with low cost and high performance by simple methods, and use it to detect pesticide residues in food. Here, Ferrero® chocolate-like Cu2O@Ag microspheres (FRC-Cu2O@Ag) were fabricated by a facile in-situ redox reaction. Cu2O directly acted as templates and reducing agents to induce the nucleation and growth of Ag nanoparticles on the microspheres surfaces. The prepared semiconductor-noble metal hybrids of Cu2O@Ag were utilized as SERS substrates to detect 4-mercaptobenzoic acid (4-MBA) and thiram molecules. The distinguished SERS effect was achieved when target molecules absorbed on the FRC-Cu2O@Ag composite. The substrate presented excellent sensitivity and reproducibility for the detection of 4-MBA and thiram with the limit of 10−10 and 10−9 M, respectively. Due to combining both advantages of electromagnetic enhancement of Ag metals and chemical enhancement of Cu2O semiconductors, the obtained FRC-Cu2O@Ag microspheres provided a SERS platform to conveniently detect molecules with thiol groups. When it was applied to detect thiram residues on apple peel and the detection limit was 1.2 × 10−7 M, low than maximal residue limit (MRL) of 7 × 10−6 M in fruit prescribed by the U.S. Environmental Protection Agency (EPA).

Clove essential oil (CEO) was immobilized in mesoporous silica nanoparticles (MSN) (0, 1, 2, and 3 wt%) and incorporated into poly(lactic acid) (PLA) matrix via a casting method. The functional properties including mechanical property, thermal property, antimicrobial property, and CEO release behavior of the PLA nanocomposite film were investigated. The compatibility of CEO-loading MSN with PLA was verified by scanning electron microscopy analysis. The tensile strength, tensile module, and glass transition temperature of the MSN/CEO/PLA composite film was improved with the increase in MSN content. The release study indicated that the MSN/CEO/PLA composite films exhibited sustained release profile of CEO. The MSN/CEO/PLA films demonstrated efficient antimicrobial activity. The results indicated that CEO immobilized MSN incorporated PLA nanocomposite film showed promising features for active food packaging material.

In this study, the development of surface features of Inconel 718 samples fabricated by selective laser melting under different laser powers and scanning speeds has been studied and correlated with the powder melting behaviors through both experimental and modeling approaches. The interaction between laser beam and powder particles was studied by a three-dimensional model using the height function-lattice Boltzmann method. Different process parameters were introduced to perform the simulations, revealing the underlying physics of the surface morphology. Through the calculation of the surface forces, some new insights were given about the powder melting behaviors and the resultant surface features. It was found that the surface tension rather than recoil pressure pulled the melted powder into the molten pool during the SLM process. As for low energy input, the powder tended to fuse together with the neighboring particles before entering the molten pool, which was found to be the main cause of the formation of surface fluctuations and the subsequent surface pores. To some extent, the existence of recoil pressure was favorable for a relatively stable flow and a flat surface morphology. The simulation results of the top surface morphology were compared with experimental results, and they were in good agreement.

In multi-seam mining, the interlayer rock strata between the upper coal seam (UCS) and the lower coal seam (LCS) appear damage and strength weakening after mining the UCS. Ground stability control of the gob-side entry retaining (GER) under the gob with close distance coal seams (CDCS) is faced with difficulties due to little attention to GER under this condition. This paper focuses on surrounding rock stability control and technical parameters design for GER under the gob with CDCS. The floor rock strata damage characteristics after mining the UCS is first evaluated and the damage factor of the interlayer rock strata below the UCS is also determined. Then, a structural mechanics model of GER surrounding rock is set up to obtain the main design parameters of the side-roadway backfill body (SBB) including the maximum and minimum SBB width calculation formula. The optimal SBB width and the water-to-cement ratio of high water quick-setting material (HWQM) to construct the SBB are determined as 1.2 m and 1.5:1.0, respectively. Finally, engineering trial tests of GER are successfully carried out at #5210 track transportation roadway of Xingwu Colliery. Research results can guide GER design under similar mining and geological conditions.

Inorganic perovskite nanostructures based on neodymium (Nd) were processed in form of nanostructures for bi-functional electrocatalytic reactions. The active role of Co ions in influencing the material characteristics of Nd-ferrite (NdFeO3) were investigated in detail. The nanostructural characteristics were adjudged through the aid of diffraction and high-resolution microscopic studies. Evidences relating to the co-occurrence of neodymium oxides (Nd2O3) were also noticed. The valency of Nd, Co and Fe ions and their nature of interaction in the ferrite architecture was studied through X-ray photoelectron spectroscopy. Here, convincing affirmations relating to the partial substitution of Co ions in place of Nd and Fe sites were also made. NdFeO3 and NdxCo1-xFeO3 nanostructures were studied for their electrocatalytic functions under varied alkaline pH (10 and 14) conditions. The improved conductivity studied via electrochemical impedance analysis in Co incorporated ferrites were noted to accelerate oxygen/hydrogen production in the corresponding electrodes. The overpotential values corresponding to oxygen evolution reactions reduced to 198 mV from 227 mV, while hydrogen evolution reactions lowered to 206 mV from 239 mV upon Co substitution. Similarly, the related Tafel slope values got improved in Co substituted ferrite matrix. The overall stability related electrochemical data suggested the processed ferrites as viable bi-functional electrocatalysts possessing essential features required for effective oxygen and hydrogen evolution reactions.

A multi-functional composite coating was fabricated on magnesium (Mg) AZ31 alloy through micro-arc oxidation (MAO) combined with self-assembly technology. Polyethyleneimine (PEI) as a medium was assembled on MAO coating based on the chemical bonding and electrostatic interactions. Adhered PEI successfully mediates the self-assembly of functional silver nanoparticles (Ag NPs) with a formation of Ag NPs/PEI/MAO (APM) composite coating. The morphology and microstructure of as-prepared APM coating were characterized by using of different technologies (e.g. scanning electron microscopy, energy dispersive X-ray spectroscopy, X-ray diffraction and X-ray photoelectron spectroscopy). Its corrosion behavior in simulated body fluid and the corresponding antibacterial performance against Staphylococcus aureus (S. aureus) were also investigated. The potentiodynamic polarization results showed that the corrosion current density of APM coated AZ31 decreased more than three orders of magnitude in comparison with that of uncoated AZ31, indicating an enhanced anticorrosive ability. Electrochemical impedance spectroscopy results further revealed that the improvement of corrosion resistance was attributed to a synergistic effect of Ag NPs/PEI and MAO. The hydrogen evolution tests confirmed that APM coating provided AZ31 an excellent corrosion protection during a relatively long term. And the antibacterial research showed that APM coated AZ31 had a great antibacterial activity. This study presents a promising approach to fabricate a multi-functional composite coating on Mg alloy, which improves the anticorrosive performance of the substrate and endows it an antibacterial activity to meet a better demand in the applications.

Relevance. When mapping the vast areas of the Precambrian polymetamorphic complexes in the North Yenisei Ridge, there is a problem of metamorphism interpretation and phasing of geological development of a particular area along with thrust tectonics. The solution of these issues is also of great importance for the purposes of areas delineation of metamorphic rocks that are favorable for the detection of high-alumina (andalusite, kyanite, sillimanite) schists. Purpose of the work: to substantiate and itemize some geological prospecting, mineralogical and petrological indicator criteria for the development of high-alumina garnet-kyanite-staurolite blastomylonites of dislocation metamorphism formed by andalusite-bearing rocks of regional metamorphism. Research methodology: detailed mapping of structural-metamorphic zoning of dislocation (collisional) metamorphism in the Mayakon key area with sampling of polymetamorphic rocks for petrographic studies of mineral parageneses. Investigation of polished thin sections of polymetamorphic rocks by microprobe analysis with elucidation of minerals zoning, their chemical composition, calculation of the Р–Т paths of metamorphism and determination of the absolute age of blastomylonite formation based on the 40Ar/39Ar dating of biotite. Analysis and generalization of the results obtained for the Mayakon area and their comparison with other key areas of the North Yenisei Ridge. Results. At the Mayakon potential area, a progressive metamorphic zoning of kyanite-bearing blastomylonites has been identified, and the transitional I, outer II, middle III, and inner zones are determined as the dislocation metamorphism intensifies towards the Panimba thrust fault. Based on the compositions of garnets, biotite, and plagioclase, the P–T paths of the early regional metamorphism of andalusite-sillimanite type and late local kyanitesillimanite type were calculated. A list of geological prospecting, petrological and isotope-geochronological criteria for recognizing blastomylonites among rocks of regional metamorphism in thrust zones has been substantiated and itemized. Conclusions. Method of polymetamorphism reconstruction in the North Yenisei Ridge shows that tectonic inversion conditions took place in the Neoproterozoic, in the late Tonian era (~850 Ma ago In terms of occurrences, they are related to the final stage of the Grenville orogeny (1.1–0.85 Ga). The formation of blastomylonites of dislocation (collisional) metamorphism by metapelites of regional metamorphism in thrust zones is accompanied by an increase in the number of mineral phases and leads to a reduction in usable space of high-alumina andalusite schists.

The target of this research study was to evaluate the shear-tensile and fatigue behavior of aluminum 6061 alloy welds, in two different heat treatment conditions, joined by the recently developed intermediate layer friction stir spot welding (FSSW) technique. The keyhole, which is the disadvantage of the conventional FSSW process, was avoided using an additional intermediate layer (IL) accompanied by a simple tooling. Shear-tensile experiments demonstrated acceptable mechanical performance of IL-FSSW joints in comparison with that obtained using alternative methods. Fatigue behavior of the joints revealed a dependency to pre-processing temper especially at high cyclic load levels with improved life for the aged condition. Observations on the failure regions under shear-tensile experiments exhibited plug type and shear-plug type fracture modes for the aged and annealed conditions, respectively. In contrast, the fracture mode showed variation with respect to the load level but not to the type of temper during cyclic loading.

In order to study the factors of columnar to equiaxed transition (CET) of high-Nb TiAl alloys, Ti46Al7Nb0.4W0.6Cr0.1B alloy has been fabricated by cold crucible directional solidification (CCDS) technique under different pulling rate from 3.3 μm/s to 16.7 μm/s. The marco/micro-structure and phase composition near solid–liquid interface have been characterized. Results show that the CET of the high-Nb TiAl alloy occurs with the increase of the pulling rate at the constant temperature gradient. The microstructure of the columnar grain is composed of α2/γ lamellar matrix and a coupling structure of striped-like B2+γ phases. The lamellar colonies in a columnar grain possess the same orientation, while the arrangement direction between the striped-like B2 phase and growth direction is 0° or 45°. A solidification map for CCDS is established which predicts columnar or equiaxed morphology according to the growth rate (R) and temperature gradient (G). The dendrite morphology at the solid–liquid interface after quenching and the CET is controlled by the actual temperature gradient at the tip of the dendrite. Meanwhile, the increase of growth rate and the satisfaction of heterogeneous nucleation conditions are the main factors for CET. The decrease of actual temperature gradient caused by quenching or the increase of liquidus gradient caused by increasing growth rate can increase the maximum supercooling degree ΔTC. When it reached the supercooling degree ΔTN required to form a new nucleus, equiaxed grains will be produced. In addition, the boride in this alloy can act as a heterogeneous nucleation core to promote CET.

In the loose and fractured coal seam with particularly low uniaxial compressive strength (UCS), driving a roadway is extremely difficult as roof falling and wall spalling occur frequently. To address this issue, the jet grouting (JG) technique (high-pressure grout mixed with coal particles) was first introduced in this study to improve the self-supporting ability of coal mass. To evaluate the strength of the jet-grouted coal-grout composite (JG composite), the UCS evolution patterns were analyzed by preparing 405 specimens combining the influential variables of grout types, curing time, and coal to grout (C/G) ratio. Furthermore, the relationships between UCS and these influencing variables were modeled using ensemble learning methods i.e. gradient boosted regression tree (GBRT) and random forest (RF) with their hyperparameters tuned by the particle swarm optimization (PSO). The results showed that the chemical grout composite has higher short-term strength, while the cement grout composite can achieve more stable strength in the long term. The PSO-GBRT and PSO-RF models can both achieve high prediction accuracy. Also, the variable importance analysis demonstrated that the grout type and curing time should be considered carefully. This study provides a robust intelligent model for predicting UCS of JG composites, which boosts JG design in the field.

The films of alizarin yellow GG (AYGG)–CuCl2 blended with polyvinyl alcohol (PVA) have been successfully synthesized by casting method. The results show that the dielectric properties of AYGG–Cu(II) blended with PVA are enhanced by lowering selected frequency while σac(ω) increases monotonically with frequency, acting in accordance with the correlated barrier hopping model. At low temperature, the DC electrical resistivity of AYGG–Cu(II) blended with PVA film is temperature independent, while it is decreasing with high temperature. Al/(AYGG – Cu(II) blended with PVA)/ITO is fabricated as organic photovoltaic cell, concluding that there are many mechanisms can control the current flow. Al/(AYGG – Cu(II) blended with PVA)/ITO solar cell under illumination of green light be most effective compared to illuminations of others. It is concluded that Al/(AYGG – Cu(II) blended with PVA)/ITO solar cell is very important, with potential advantages such as low cost and low-temperature fabrication processes. It is recommended that this material can be used in different applications such as temperature sensors, inrush current limiters, thermistors, and NO2 sensor.

In the present investigation, nanochitosan-polyurethane dispersions (NCS-PUs) were prepared via polymerization process and applied on polyester cotton fabric (PCF) as a finishing agent. A prepolymer of PU with NCO functionality was synthesized using isophorone diisocyanate (IPDI), polyethylene glycol (PEG) and DMPA (2, 2-dimethylol propionic acid) was extended with NCS. The structural characterization of NCS-PUs was monitored by FTIR analysis. Pad dry cure technique was adopted for the application of NCS-PUs on pre-dyed and printed PCF samples. The PCF samples (dyed and printed) were tested for antibacterial activity, Ultraviolet protection factor (UPF) and tear & tensile strength properties. The UPF values in case of 10% PUB1 to PUB6 application was recorded to be 40.5, 42.30, 44.10, 47.50, 54.30 and 37.80, respectively, whereas the tensile strength improved up to 8.1% in case of 10% NCS-PUs application and these value was increased when 20% NCS-PUs was applied. Antimicrobial activity was evaluated against Gram positive and negative strains (S. aureus and E. coli). The PCF samples finished with NCS-PUs showed higher antimicrobial activity, protection against UV and tensile strength versus unfinished sample with NCS-PUs. Results revealed that the NCS-PUs significantly improved the properties of PCF (both of dyed and printed samples), hence, the NCS-PUs can be applied as finishing agent to enhance the antimicrobial activity along with protection from UV radiation.

Relevance of the research. Construction sands are the largest functional group of sands widely used in construction industry. This natural material is one of the most demanded for the production of manufactured products in the construction industry of the region. Purpose of the researchis to study the engineering-geological conditions of construction sands deposit for the production of the manufactured products of OAO Sebryakovsky plant of asbestos-cement products, as well as for construction organizations of the region. Research methods. Based on the analysis of extensive collection materials using laboratory and statistical methods, as well as the results of additional research, the physical-geographical, engineering-geological and technogenic conditions of the study area were examined. Results and their application. The useful stratum of the deposit is composed of Upper Quaternary alluvial sands, the average thickness of which is 8.6 m, penetrated thickness is up to 12.3 m. Overburden within the study area is represented by the soil-vegetation horizon – up to 0.2 m. The extracted raw materials are used in the production of mortars, which is confirmed by tests of a cement-sand grout, and as a filler in fine-grained concrete. The reserves of the deposit are calculated in categories A + B + C1 in the amount of 2313.2 thousand m3. The development of the deposit is recommended by the open method. Explored and recoverable reserves will ensure the operation of the enterprise with an annual demand of 100 thousand m3 per year for a period up to 2030. Conclusions. Based on the results of the studies, it should be noted that the Sidorsky deposit of construction sands is assessed as profitable and competitive in relation to the exploited deposits of sand in the Volgograd region.

This paper presents a novel approach to investigate the relations between drilling signals and bit wear condition in real world full-scale mining operations. This research addresses the increasing demand for automation in mining to increase the efficiency, safety, and ability to work in harsh environments. A crucial issue in fully autonomous unmanned drilling is to have a system to detect the bit wear condition through the drilling signals analysis in real time. In this work, based on extensive field studies, a novel qualitative method for tricone bit wear state classification is developed and introduced. The relations between drilling vibration as well as electric motor current signals and bit wear are investigated and bit failure vibration frequencies, regardless of the geological conditions, are introduced. Bit failure frequencies are experimentally investigated and analytically calculated. Finally, the effect of bit design parameters on the failure frequencies is presented for the application of bit wear condition monitoring and bit failure prediction.

Soft zone formation in dissimilar Cr–Mo welding occurs during post weld heat treatment that could compromise the integrity of the weldment. The decomposition of martensite could cause this formation at the weld heat affected zone adjacent to the fusion boundary. There could not yet determine the actual width of this zone. The extent of martensite decomposition in soft zone Cr–Mo steel dissimilar weld was observed in semi in-situ stages using the x-ray absorption spectroscopy (XAS) at Synchrotron facility. 2.25Cr–1Mo was welded using ER90S–B9 using GTAW process. PWHT was performed at 730 °C for 0.5 h and 2.0 h in a chamber with opening for Synchrotron light analysis at various locations away from the fusion boundary. This was complemented by microstructure and grain size analysis. The results showed the decomposition of martensite started at the fusion boundary and could extend beyond 1000 microns covering both CGHAZ and FGHAZ. Since the experiment was performed in normal atmosphere, the oxide film could form during PWHT on the surface of the specimen. More oxide formed was observed more in the location with high carbide contents. There was more oxide formation at the locations further distance from fusion boundary due to less martensite decomposition. Therefore, the extent of the phenomena could be stated by using information from oxide formation and martensite decomposition which could help to determine the risk on both creep life and oxidation.

High-speed impact tests were conducted in transverse direction with strain rates (SRs) ranging from 1000 s−1–6000 s−1 to investigate the deformation mechanism and adiabatic shearing behavior of extruded Mg-8.0Al-0.1Mn alloy in as-extruded (AE), low temperature solution-treated (ST1) and high temperature solution-treated (ST2) states. At SR of 6000 s−1, the flow stress exhibits a slight drop after reaching its peak, except that of the ST2 sample. The highest strain rate hardening results in the highest peak stress of the ST1 sample. Deformation is first dominated by basal slip, and then gradually converts to be dominated by a coordinated mechanism between basal slip and twinning. In late stage, it shifts to be dominated by non-basal slip supplemented with twinning and basal slip, and then by a coordinated mechanism between non-basal slip and dynamic recrystallization (DRX). Heat treatment only affects the scope of the dominated mechanism. The adiabatic shear band occurs only at SR of 6000 s−1 with strain of 0.30, which strongly affects the crack propagation and DRX. Interestingly, the DRX only occurs in the AE sample due to the combined effect of adiabatic temperature rise and pre-existing twins.

Magneto-optical Kerr effect (MOKE) microscopy is a versatile technique to image magnetic domains and evaluate the behavior of magnetic materials. However, MOKE has been rarely applied to the research of low magnetic steels with complex microstructure including micron-sized features. This study reveals the potential of implementing MOKE microscopy for analyzing the microstructure and stress state of martensitic steels with high carbide density (example conducted on AISI M2 steel grade). For the first time, the resulting MOKE domain images are used to analyze the size and morphology of martensite lath structures without chemical etching of the material's surface. Furthermore, MOKE microscopy allowed the confirmation and volumetric fraction estimation of retained austenite, despite the small size and volumetric fraction of under 1%. The validity of the MOKE microscopy analysis is cross-checked with scanning electron microscopy of etched samples and X-ray diffraction. Finally, MOKE microscopy in combination with Vickers indentation is applied to determine the residual stress state of the selected steel, which was varied by processing the steel material with conventional heat treatment scheme and heat treatment including deep cryogenic treatment (DCT). The method is proven effective in indicating the residual stress qualitatively. The measurements proved, that the residual stresses are significantly reduced in DCT steel samples, as theoretically anticipated. The conducted pioneering work provides important research towards the application of MOKE microscopy for the research of steel microstructure, properties and residual stresses as well as delivers a new perspective for determining the effectiveness of DCT on the steel properties.