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For steels of different grades, the effect of the chemical composition, structure, and surface etching on the contact potential difference is studied using the Kelvin probe method. It was shown experimentally that, with a change in the structure and chemical composition, the contact potential difference changes. Etching the surface of the steel with a 4% solution of nitric acid leads to a sharp decrease in the magnitude of the contact potential difference, which allows us to conclude that the value of the electron work function from the sample surface increases. The ability to control the composition and structure of the material by the Kelvin probe method is shown.

The microstructure of the advanced low carbon steel with a superior hardenability was studied. The steel contained the following main alloying elements, wt. %: C – 0.20; Cr – 2.0; Mn – 2.0; Si – 1.04 Ni – 1.0; Mo – 0.3. The dilatometer investigation of the steel under consideration revealed the only phase transformation occurring during continuous cooling (0.1...30 °C/s), which started at the martensite start temperature Ms. It was shown that the isothermal treatment of the studied steel led to the bainite formation above and below Ms. The temperature of the bainite morphology shift was determined.

The specimens of austenitic stainless steels were machined to different strain rates (105 s−1, 1050 s−1, 1500 s−1, 2100 s−1). These specimens were subjected to low-temperature sensitization (LTS) heat treatment. The LTS treatment was carried out at 475℃ and 575℃ for 24 h. Further, oxalic acid, double-loop electrochemical potentiokinetic reactivation (DL-EPR) were carried out. As-machined specimens were subjected to surface roughness measurements, optical microscopy, electron backscattered diffraction (EBSD), and Fourier transform infrared spectroscopy (FTIR) imaging measurements. Machined specimen exhibited more difficulty in passivation than the as-received specimen. The complete surface statistics were extracted. The specimens machined at a strain rate of 2100 s−1 were exhibited a higher degree of sensitization (DoS) at LTS of 575℃ and 475℃ for 24 h, respectively, than other specimens. It was found that specimens machined at a higher strain rate produced smoother roughness. FTIR imaging was used to extract the signal intensity of chromium oxide (Cr2O3) peak. Detected Cr2O3 peak/signal was strong for the specimen that exhibited lower DoS as estimated from FTIR-imaging.

Ordinary steels have poor corrosion resistance in chloride medium leading to a deterioration of their longevity. The present research work focuses on the deposition and characterization of a zinc layer by dip galvanizing onto low carbon steel ASTM A283M-98 in sheet form using different characterization techniques such as optical microscopy, scanning electron microscopy (SEM) coupled to energy dispersion spectrometer (EDS), atomic force microscopy (AFM) and X-ray diffraction (XRD). Optical microscopy and X-ray diffraction analyses of the steel reveal a ferritic microstructure with the presence of a small amount of pearlite. The deposited layer is composed of four Fe–Zn intermetallic phases, namely eta (η), zeta (ζ), delta (δ), and gamma (Γ). The electrochemical study in 0.5M NaCl medium indicate an enhancement of the corrosion resistance of ASTM A283M-98 steel coated with Fe–Zn multi-phased layer, characterized by a decrease in corrosion current (Icorr = 3.36μA/cm2) and corrosion rate (Cr = 0.29mm/year) compared to the bare steel (Icorr = 12.29μA/cm2 and Cr= 0.72mm/year).

Experiments were conducted to investigate the microstructural evolution of AZ31 alloy when deformed by multi-pass differential speed rolling (DSR) using the simplest modification of route A passing sequence. Microstructural observations were taken on all three planes of the sample to obtain a three-dimensional view. Based on quantitative microstructural analysis, the counts of the fine DRX grains increased with increasing number of DSR passes, while the fine DRX grains’ size was consistent in each pass. These results signified that the refinery process was attributed to dynamic recrystallization. Thermal stability was perceived by examining the evolution in microstructure and microhardness value of the 4-pass DSR sample during isochronal annealing over a range of temperature from 423 to 723 K. The increase in distortion energy with multi-pass DSR resulted in the decrease in critical temperature for the initiation of recrystallization upon annealing at 423 K, which induced an immediate drop in microhardness.

In automotive industries, employing advanced high-strength steels such as dual-phase steels by taking advantage of high dynamic force absorption during car accidents and lightweight is one of the major challenges. In this regard, the effect of resistance spot welding parameters on the above great properties of advanced high-strength DP590 steel has been studied. In this study, the effect of optimized welding (spot resistance welding) on the weld microstructure was evaluated using optical microscopy as well as scanning electron microscope equipped with electron backscatter diffraction analysis (EBSD). Also, hardness profile along with the welding section was determined as mechanical property. The results showed that the welding practice has a significant influenced on the microstructure and microhardness of welded samples. The final microstructure of the nugget consisted of lath martensite, whereas in the HAZ, the microstructure was found to be mixture of coarse and fine martensite. The hardness profile was relevant to the above phase configuration. The phase variations along with different weld region were extensively characterized and discussed using EBSD technique.

Refill friction stir spot welding (refill FSSW) is one of the most industrially promising friction stir spot welding variants. The absence of an exit hole improves the effectiveness of surface treatments and minimizes damage by fouling. Aerospace aluminium alloys AA2024-T3 and AA7075-T6 with a thickness of 2 mm were used in this investigation. A range of values for rotation speed and plunge depth were experimented to determine the most promising process parameter combination based on the cross-sectional analysis and lap shear strength. The effect of an interfacial sealant on the weld properties was determined for both alloys using the most promising process parameter combination. Fatigue life analysis and fractography using scanning electron microscopy were performed for specimens with and without sealant.

Physical experiments allow to obtain maximum information on a studied process at minimal cost, ensuring its higher accuracy comparing with data, obtained by mathematical simulation and avoiding risks, which can occur at industrial testing of new technological modes. Results of studies of deformation in the process of pipes production by extrusion presented. The studies were accomplished at laboratory test units, developed by specialists of the laboratory of drawing and extrusion of JSC “RusNITI”. One of the basic problems at pipes production by extrusion is ensuring minimal possible wall non-uniform thickness. It was noted that the relation between plunger die moving speeds during sleeve pressing-out and immediate pipe extrusion has a significant effect on pipe wall non-uniform thickness. Computer simulation of the pipe extrusion process, accomplished by application QForm program shown that minimal values of wall non-uniform thickness corresponded to relation abovementioned speeds as 0.5–0.8. To check the data, a physical simulation of extrusion process of lead cylinder samples, having outside diameter of 18.94 mm and wall thickness 5.19–5.32 mm was accomplished. For the extrusion, a universal servohydraulic system of dynamic test Shimadzu Servopulser was used. Within the physical experiment a dependence was established between pipe wall non-uniform thickness on relation between speeds of pressing-out and extrusion. The revealed regularity was confirmed during pilot production of a pipe lot at the 55 MN force extrusion line. Another physical simulation of extrusion of 10.0×2.0 mm pipe-samples made of C1 grade lead was accomplished with one- and twothread helical ribbing of internal surface. For its accomplishment an experimental module was designed and manufactured. It was established that rotation speed of the extrusion mandrel had no significant effect on extrusion force. Metallographic studies shown that the extrusion mandrel rotation speed contributes to considerable increase of pipes surface hardness and obtaining finer grain comparing with the classic extrusion method. The technical ability of pipes production with internal helical ribbing by hot extrusion method was confirmed. The results of the study became a base for elaboration of a technology of pipes production at Volzhsky pipe plant according to ТУ 14-3Р-157–2018 “Steel seamless hot-extruded pipes with helical ribbing of internal surface for steam boilers”. Results of physical simulation of pipe drawing process at self-adjusting mandrel with application of lubricant materials of various viscosity. The data obtained were used for elaboration of a technology for production of cold-deformed pipes with internal diameter of 6.0–12.0 mm at Sinarsky pipe plant.

A non-dendritic microstructure normally forming the products made by the controlled diffusion solidification process (CDS) has been studied. Samples from Al-4.7 wt%Cu, Al-8 wt%Cu, and Al-4.7 wt%Zn were made via the CDS process by mixing pure aluminum into Al-Cu and Al-Zn binary alloys at a different mass ratio. ANSYS software was employed to predict the distribution of the mixed alloys during the mixing step. The simulation results show that the mixed alloys breakdown to different size pockets. The higher mass pockets fall into the bottom sample after the mixing step resulting in effect the microstructure forming in the entire sample. The experimental results indicate that globular mixed with rosette and dendritic morphologies form the entire microstructure, although all the morphologies were exposed to the same thermal environment during growth. The results show that the globular morphologies form in the undercooled alloy that have a higher liquidus temperature, while the dendritic morphologies form from the alloy that has a lower liquidus temperature, which is heated during the mixing.

The oxy-acetylene torch brazing of copper tubes using silver-based filler metals (Ag-Cu-Zn-Cd) was investigated in this study. Filler metals containing silver content of 15% and 35%, designated by BR15 and BR35, were used to assess the influence of the silver content in the microstructure and mechanical performance of brazed joints. The brazed joints microstructure was analyzed by means of optical microscopy, scanning electron microscopy, and energy-dispersive spectroscopy. The microstructures of the BR15 and BR35 samples were composed mainly of Ag–Cd-rich phase, solid solution of Cu–Zn, and a eutectic structure of Ag and Cu. The increase in the Ag content changed the solidification mode from cellular to dendritic and caused an increase in the eutectic phase volume fraction. The tensile strength of the Ag–Cu–Zn–Cd filler and the phos–copper filler metals was compared. The tensile strength of silver-based filler metal was slightly higher than the phos–copper filler metal brazed joints.

The intention in this research work is to investigate the effect of welding speed in electron beam (EB) welded 18mm thick plates of AISI 321. In this work, an attempt is made to study the effect of two different welding speeds on the microstructure, mechanical properties and corrosion resistance of the welded joints. The results in the study show that bead width, reinforcement area, dendritic length and inert dendritic spacing vary for the different heat inputs. The microstructure conducted using optical microscope and scanning electron microscope (SEM) shows the presence of lathy and vermicular ferrites in the weld bead. In addition, the ferrite measurements and the X-ray diffraction (XRD) studies indicate the difference in the ferrite content of the two beads. The fusion boundary has the highest microhardness of about 171.9 HV. The maximum toughness of 129.3J was found at the top region of the weld. The percentage elongation in the tensile test had shown increase in the root region of the welds. The rate of intergranular corrosion in mm per year was calculated and was found to be 13% more in the in the welds with more heat input.

In this research, hypereutectoid Si–Mn TRIP steel was prepared via casting method followed by thermomechanical processing and different heat treatments. Subsequently, fracture behavior and mechanical properties of the prepared steel were investigated. The time–temperature–transformation curves of the specimens were predicted by a simulation software. Their mechanical properties were studied through tensile, hardness, and impact tests. The microstructure and fracture behavior of the specimens were evaluated using an optical microscope, scanning electron microscope and fractographic analysis. Results indicated that the heat-treated sample containing a multi-phase microstructure of bainite, martensite, pearlite and retained austenite, had the highest ultimate tensile strength around 1,300 MPa. The software predictions of the heat treatments were in good accordance with the microstructural results. The samples have undergone thermomechanical process and heat treatment including isothermal transformation showed brittle behavior with intergranular and cleavage fracture surfaces. In addition, the two-stage quenching cycles resulted in dual-phase microstructure composed of martensite embedded in retained austenite with a combination of brittle and ductile fracture behavior.

In this study, the creep behavior of base metal, weld metal, and heat-affected zone of IN738 superalloy welded by pulsed Nd:YAG laser was investigated by the newly developed small punch creep testing method in the temperature 700 °C and under the punch forces 350 N and 45N. The results of time–displacement creep behavior showed that the aging heat treatment causes a significant increase in rupture time compared to the casting specimen. This was due to an increase in the volume fraction and a decrease in the size of the γ´ particles, which create a more substantial barrier to the movement of the dislocations. On the other hand, by performing solution heat treatment before welding, phases such as γ´, γ–γ´ eutectic, Cr-Mo boride, Ni-Zr intermetallic, and MC carbide, which reduced the rupture time in the cast specimen by forming a partial liquation in the HAZ, were removed.

In this manuscript, the latest developments pertaining to sensitization are discussed. Sensitization leads to intergranular corrosion and intergranular stress corrosion cracking. The advantages and disadvantages of conventional methods to combat sensitization are elaborated. Emerging/newer techniques such as grain boundary engineering, creation of orientation gradients, and high density of twinning to improve resistance to sensitization are also covered. Detection and monitoring of deleterious phase precipitation such as carbides, nitrides, and other intermetallic phases during operation necessitate making use of nondestructive testing (NDT) methods. Possible information that we get from NDT is for material characterization includes the size, shape, and location of a defect. Herein, the significant developments for monitoring and detection of phases concerning sensitization by NDT are discussed. These range from magnetic methods to ultrasonic techniques. The multi-physics approach is essential to fully utilize NDT to ensure/predict the lifetime of the components used in the industry. Further, proper selection of suitable NDT for defect detection can avert accidents, catastrophic failures, and economic losses due to corrosion degradation. For this, the corrosion engineer/corrosionist properly apply the suitable techniques (prevention, monitoring, and assessment) to address the issues of sensitization among the wide choice available.

In this article, we review existing approaches to recycling technogenic raw materials (ore dumps, metallurgical production slag, mill tailings of ore-dressing plants, etc.), containing non-ferrous and noble metals, which are accumulated in almost non-ferrous metallurgy industries. An analysis of existing technologies for processing technogenic raw materials (pyrite cinders and flotation tailings of concentration plants), which include enrichment, pyro- and hydrometallurgical and combined ways of extracting valuable components, was conducted on the basis of a review of published sources. It was shown that enrichment (screening, desliming in a hydrocyclone, enrichment using a concentration table, magneticliquid separation, flotation), pyrometallurgical and combined ways for extracting noble metals from this type of raw materials are unprofitable. The most satisfactory results were obtained using hydrometallurgical methods to extract valuable components from technogenic raw materials. Various solvents, such as sodium cyanide, thiocarbamide, sodium thiosulphate and sodium sulphite were tested as leaching agents. Cyanation proved to be the most effective way to extract noble metals from technogenic raw materials; however, this process is characterised by a high consumption of sodium cyanide. Therefore, it is of importance to discover an approach to extracting valuable components from such problematic products in order to make their processing more cost-effective by reducing cyanide consumption while maintaining gold extraction. According to the obtained results, gold-containing raw materials are promising in terms of extraction of nonferrous and noble metals using hydrometallurgical technologies. Future research should identify rational methods for processing technogenic gold-containing raw materials in order to make the technology more profitable for extracting valuable components.

The joining of plastics is required because component geometries are severely restricted in conventional manufacturing processes such as injection molding or extrusion. In addition to established processes such as hot plate welding, infrared welding, or vibration welding, hot gas butt welding is becoming more and more important industrially due to its advantages. The main benefits are the contactless heating process, the suitability for glass fiber reinforced, and high-temperature plastics as well as complex component geometries. However, various degradation phenomena can occur during the heating process used for economic reasons, due to the presence of oxygen in the air and to the high gas temperatures. In addition, the current patent situation suggests that welding with an oxidizing gas is not permissible depending on the material. On the other hand, however, there is experience from extrusion welding, with which long-term resistant weld seams can be produced using air. Investigations have shown that the same weld seam properties can be achieved with polypropylene using either air or nitrogen as the process gas. Experimental investigations have now been carried out on the suitability of different gases with regard to the weld seam quality when welding polyamides, which are generally regarded as more prone to oxidation. The results show that weld strengths are higher when nitrogen is used as process gas. However, equal weld strengths can be achieved with air and nitrogen when the material contains heat stabilizers.

Additive manufacturing (AM) using PBF (powder bed fusion) is widely applied in industry with many advantages but also some drawbacks such as productivity rates and limited dimensions. Future implementations of AM will require a re-design of components in order to reserve AM for the particular complex geometries, to join AM subassemblies or to connect with conventional components. It brings the aspect of weldability of AM parts in the picture. This study is investigating the weldability of AM 316L components using common welding processes such as manual GTAW. Bead-on-plate tests were started as a first step to examine weldability. After satisfactory results, two AM pipe components were fabricated (PBF) in the same built to be welded to conventional 316L parts. One AM pipe component was used to characterize the mechanical properties while the other test coupon was welded to conventional pipe by manual GTAW. The test welds were submitted to a mechanical and corrosion testing program including creep rupture testing. It was decided to start the weldability analysis in the worst condition, i.e., As Build/As Welded (AB/AW) without any heat treatment nor post-processing. Based upon the results obtained for the conditions tested, it could be concluded that AM (PBF) components are weldable.

In this work, the industrial X-ray computed tomography was exploited for measuring maximum crack depths across the weld interfaces within resistance spot welding (RSW) specimens welded under intensive welding condition. Individual crack profiles were measured for each sample and presented in terms of the total crack length, the maximum crack depth and the median crack width. A linear trend between maximum crack depth and median crack width was observed, where the associated coefficient of determination was sufficiently high (R2 = 0.79). Hence, the crack width is proposed to predict the crack depth. Based on the experimental findings, the effectiveness of the proposed method is demonstrated through machine learning studies, and a simple relation to predict the internal crack depth from the surface crack width was further developed. Semantic segmentation results proposed an algorithm succeeded in separating enough crack areas to calculate the crack width. Since Zn-assisted liquid metal embrittlement (LME) is now accepted as an inevitable consequence with respect to RSW process, the methodology demonstrated in this work can potentially offer the insights into an effective and automatic method of quantifying LME cracks.

This study aimed to investigate the heat-affected zone (HAZ) behavior in an API 5L X70 steel welded by the gas metal arc welding process (GMAW). In the steel welding processes, this region is very critical due to microstructural and allotropic transformations that affect the mechanical properties. Three samples were welded using a robotic arm with different welding speeds, thus obtaining three different heat inputs, which were 2.0 kJ/mm, 2.5 kJ/mm, and 3.0 kJ/mm. For all heat inputs, the microstructures of the HAZ showed the Widmanstatten ferrite, Acicular ferrite, bainite, and martensite and retained austenite, which influenced the mechanical properties of this region. The electron backscattering diffraction analysis showed that the presence of low-angle grain boundaries (2–15°) increases the fracture toughness. The kernel average misorientation map and the results of the Charpy impact test showed that the heat input of 3.0 kJ/mm lead to characteristics of the HAZ that are remarkably similar to the base metal (BM).

In the present study, the effect of electromagnetic stirring parameters, including stirring time, pouring temperature and stirring frequency, on the morphology of the AM60 alloys was investigated using Taguchi-based grey relational analysis (TGRA). Each parameter of the process was analyzed at three levels. To accommodate all parameters, an orthogonal array L9 based on the Taguchi approach was used. The optimum parameters were chosen, using different microstructural responses such as shape factor, roundness, average grain size, average grain density and average aspect ratio. The optimal processing parameters were found to be 240 s, 30 Hz and 610 °C for stirring time, stirring frequency and pouring temperature, respectively. Results showed that the shape factor, roundness and average grain density were improved by 33%, 12.8% and 5.5%, respectively. Moreover, the average grain size and the aspect ratio decreased compared to those related to the preliminary set of experimental parameters, which represents the refining of the primary α-Mg phases. In addition, optimal experiment shows a dramatic improvement in tensile strength, uniform elongation and hardness compared to the initial conditions. Besides, the overall grey relational grade was compared to an initial set of experimental parameters, showing an improvement of 64%.

Synergetic double-sided probeless friction stir spot welding is a novel process proposed in this study, which is used to solve the contradiction between the improvement of metallurgical bonding and deterioration of hook defect. The effect of the coordinated movement of the tools on the joint formation was evaluated based on the coupled Eulerian-Lagrangian technique. By flexibly adjusting the welding parameters on both sides, the mechanical interlock caused by hook defect could be effectively regulated while significantly improving the metallurgical bonding, due to the enhancement of thermo-mechanical cycle along the thickness direction. According to the microstructure analysis, the interfacial evolution was ascribed to the combined effects of plastic deformation, material flow, atom diffusion, and recrystallization, as well as local abrasion. In addition, the microhardness profile exhibited a uniform distribution. Based on the above characteristics, the technology is expected to obtain higher strength joints, which will promote its applications in the manufacture fields.

This paper documents a series of experimental 4130 heats that had additions of rare earth master alloys with different rare earth oxide inclusions. Once melted, the heats were poured into keel block castings for mechanical testing and metallographic examination. Additionally, a single-thermocouple thermal analysis system was employed to examine the solidification reactions of each heat. Several interesting observations were made. First, the mechanical properties and solidification structure of the heats were similar, contrary to earlier work in 4130. Thermal analysis noted that the liquidus and peritectic did not shift with the master alloy additions. Inclusion characterization found that the inclusions in the final castings were significantly different from the ones in the master alloys. These inclusions contained low or no sulfur in them. Based on this, the author concludes that sulfur-containing rare earth inclusions are the likely nuclei in steels. This work identifies several important factors in the grain refinement of 4130. Not all rare earth inclusions cause refinement, supporting the conclusion by many that specific rare earth inclusions refine a steel’s structure by acting as heterogeneous nuclei. Sulfur-containing inclusions may be the compounds that are acting in this role. Additionally, shifts in the peritectic temperature appear related to the occurrence of refinement. No refinement in this work occurred, and no peritectic shift happened either. Other work in the literature observed an increase in the peritectic temperature and the onset of refinement. The peritectic reaction appears to play a role in steel solidification refinement.

This paper has developed a new compound curing agent powder for a modified phosphate binder (3 wt% of raw sand). This combination can be self-cured and achieve relatively high bonding strength. The optimal composition ratio of curing agent powder is fused magnesia powder:silica fume:sodium polyacrylate at a ratio of 6:6:5, respectively. In this case, the tensile strength of phosphate binder sand sample at 4 h and 24 h is 0.65 MPa and 1.27 MPa, respectively. Infrared spectroscopy and scanning electron microscopy were utilized to analyze the variation of functional groups and the morphology of bonding bridge fracture of phosphate bonded sand samples after the addition of curing agent (fused magnesia powder, silica fume and sodium polyacrylate). The result shows that fused magnesia powder, silica fume and sodium polyacrylate all participate in the polymerization and curing reaction of phosphate binder; furthermore, sodium polyacrylate can effectively mitigate the propagation of cracks on bonding film.

In the present study, the effect of heat input of gas tungsten arc welding on the microstructure and mechanical properties of AZ91 magnesium alloy was investigated. The microstructural studies were performed by using an optical microscope and scanning electron microscope equipped with energy dispersive X-ray spectroscopy, and tensile test was used to evaluate the mechanical properties. It was shown that, comparing to the base metal, a fine microstructure of α(Mg) and Mg17Al12 phase is formed in the weld metal and the size of α(Mg) phase slightly increased with heat input during welding process. The results also indicated that the thickness of partially melted zone increased with heat input. Tensile strength of welded samples was lower than that of the base metal and it decreases with increasing heat input. Failure of the welded specimens accrues in the partially melted zone. Studying of fracture surface revealed that the interface of α(Mg) and Mg17Al12 compound acts as crack initiation and growth path during the tensile test. Formation of cleavage steps in the fracture surface was the dominant fracture mechanism during tensile tests.

Electrochemical corrosion tests were performed on samples of horizontally solidified Al7Si0.3Mg (wt%) alloy. The investigated solidification and corrosion parameters were growth and cooling rates (VL and TR, respectively), secondary dendritic spacing (λ2), corrosion potential, and corrosion current (ECORR and iCORR, respectively). Optical and scanning electron microscopy analysis were carried out on the samples, and typical solidification microstructure was characterized by primary and eutectic phases (Alα and Alα-eutectic+ Si+ π-Al8Mg3FeSi6+θ-Mg2Si, respectively). The results depicted a higher corrosion resistance in as-cast samples with finer dendritic microstructure, that is, for higher and lower VL/TR and λ2 values, respectively. A mathematical expression characterized the iCORR variation with VL, TR, and λ2. SEM/EDS element maps and point microanalysis showed a strong decreased of Mg and Fe elements within the interdendritic regions due to the corrosion of π and θ intermetallic phases. It was allowed to conclude that Si particles exhibit cathodic behavior in relation to the matrix as well as π and θ intermetallic compounds. A comparative analysis with the literature was also conducted.

The features of phase formation during the joint aluminothermic reduction of titanium, niobium, tantalum, and vanadium from their oxides are studied using thermodynamic modeling and differential thermal (DTA) and X-ray diffraction phase analysis. Using computer thermodynamic modeling made it possible to predict the optimal temperature conditions in the metallothermic process, the composition and ratio of the reagents in the charge, the behavior of the elements, and the sequence of the phase formation. To identify the kinetic and thermochemical components of the process, thermodynamic calculations are supplemented by differential thermal studies using combined scanning calorimetry. An analysis of the theoretical and experimental data shows that the interaction of aluminum with titanium dioxide proceeds through the stage of formation of titanium monoxide and results in the formation of TixAly intermetallic compounds of various compositions (TiAl3, TiAl, and Ti2Al) depending on the Al to TiO2 ratio in the batch. When titanium dioxide is partially replaced by niobium, tantalum, and vanadium oxides, the metallothermic process under interactions in the Al–TiO2–Nb2O5, Al–TiO2–Ta2O5, and Al–TiO2–V2O5 systems is of the similar character; enters the active phase after the formation of liquid aluminum; is accompanied by exothermic effects; and is characterized by the priority formation of titanium aluminides and binary and ternary intermetallic aluminum compounds with rare refractory metals of group V such as AlNb3, Al3Nb, Al3Ta, Al3(Ti1 – х,Taх), Al3(Ti,Ta), and Al3(Ti0.8V0.2). The joint conversion of titanium dioxide and rare refractory metal pentoxides during the reduction process is affected through sequential and parallel stages of the formation of simple and complex element oxides with low oxidation states.

The characteristics of the oxide layer deposited by microarc oxidation (MAO) on Al – Si alloys in a silicate-alkaline electrolyte are studied. The thermal conductivity of the layer at 50 – 120°C is determined using a special facility by the method of stationary heat flow. The thickness, the porosity, the elemental composition, the content of the amorphous phase, and the size of the crystallites in the oxide layer are determined. The results obtained are analyzed and the conditions for the lowest thermal conductivity of the oxide layer are determined.

Tantalum and palladium were added to Inconel 718 at the expense of Nb content to study resultant microstructure and mechanical properties in hot-worked and annealed condition. An increase in {100} peak intensity along with a concomitant decrease in {111} peak intensity was observed with decreasing Nb content. Ta-containing alloys exhibited annealing twins and annealing twin density showed a direct relationship with Ta content. Overall, alloying additions improved strength as well as ductility except the alloy containing only Ta which was less strong than Inconel 718. The alloy containing Ta as well as Pd exhibited highest toughness and lowest Rockwell hardness value.

A novel 3d transition metal high entropy alloy (3d TM HEA), CoCrCuNiTi, was exploited by Ti addition into a common 4-elemental group of CoCrCuNi. Its phase constitution, microstructure, and compressive properties in as-cast and annealed conditions were investigated. The studied alloys in both states were composed of a complex multiphase structure, including two BCC phases, one FCC phase, one cubic laves phase, and one HCP Ni3Ti phase. The two BCC phases took up around 50 vol % in total, and the other three phases occurred within the remaining regions. The majority of the BCC phases were attributed to the promising ultimate compressive strength of the studied alloys in both conditions (as-cast: 2.53 GPa, annealed: 2.22 GPa). Furthermore, an outstanding hardness of 694 HV was obtained in the as-cast alloy, implying that no strong relationship was exhibited among the hardness, phase constituent, or valence electron concentration (VEC) in the CoCrCuNi-base HEAs system.

This research investigates the nickel content added by 1.1wt%, 2.2wt%, 3.7wt% and 4.5wt% on the microstructure and mechanical properties in the nodular cast iron. The results demonstrate that the microstructure of nickel addition consists of nodule graphite, ferrite and pearlite phase while nickel was added to 4.5 wt% the microstructure becomes ferrite transform to fully pearlite phase. In addition the ductile iron has the highest nodularity (0.79%), followed by 1.1%Ni (0.75%), 2.2%Ni (0.71%), 3.7%Ni (0.69%) and 4.5%Ni (0.58%). The hardness and tensile strength increase when increasing the nickel content. Elongation is enhanced with nickel increasing and reaches a maximum of 12% at 1.1 wt% Ni, then decreases with the further increase of nickel.

The main mechanisms of structure formation in zones of welded joints of unlike metals (steel – aluminum) obtained by friction stir welding in the mode of structural superplasticity are considered. Sheet billets of different steels (St3ps, 12Kh18N10T) and deformable aluminum alloys (AD1, AMg6) with a thickness of 3 mm are butt- and lap-welded by the friction stir technique. The microstructures, the phase components and the mechanical properties of the welded joints are determined.

A comprehensive study of the features of physical and mechanical processes occurring in the deformation zone of metal during continuous extrusion is carried out with rectangular Cu-ETP buses 10 × 60 mm in size. With the use of finite element computer simulation, values of the power parameters of the extrusion process are obtained. It is noted that the values of the torque and force increase until the free space of the press chamber is filled with metal, reaching maxima of 12.26 kN m and 1.54 MN, respectively. As a result of an analysis of the stress-strain state of metal in the deformation zone, the fields of distribution of equivalent strain, strain rate intensity, and average stresses are obtained and the graph of change in the metal temperature with the time of the extrusion process is plotted. The maximum of the equivalent strain and compressive stresses are observed in the region of contact between the workpiece and the abutment of the press container. That is also where the most intense deformation-induced heating of the metal occurs. A comparison of the results of modeling and microstructural studies indicates that a significant part of work on refining the cast structure takes place at the entrance to the deformation zone and in the abutment region, where the level of compressive stresses is the highest. Plastic deformation of the metal passing through the die leads to the formation of an oriented crystal structure with a grain size of 25 to 30 µm. The results of measuring the hardness of the samples are very consistent with the results of analyzing the structure in the studied regions of the deformation zone. When the workpiece passes through the abutment region of the press container, deformation-induced heating occurs, which leads to a decrease in the hardness from 93 to 67 HV. After the metal passes through the die, recrystallization processes continue in it, leading to a slight increase in grain size and, accordingly, a decrease in the hardness from 79 to 74 HV, which lasts until the bus comes into contact with a cooling medium.

Long-length bimetallic conductors with a copper core and a shell from an aluminum alloy up to 2.4 mm in diameter with enhanced strength are obtained by swaging. The effect of the swaging strain on the structure, phase composition and mechanical properties of the bimetallic conductors is studied.

Aluminum alloys have always been the material of choice for the aircraft industry owing to their versatile attributes, such as excellent strength to weight ratio, good corrosion resistance, thermal conductivity, and low production cost after wood. However, these days composite materials, carbon fiber reinforced plastic and fiber metal laminate are substituting aluminum alloys mainly because of their incapability to work at high temperatures. Nonetheless, continuous research in these aluminum alloys will effectively combat with those modern polymer composites and carbon fiber reinforced plastic. And so forth, mechanical and tribological properties of aluminum alloys can nowadays be enhanced by adding a suitable reinforcement in an appropriate volume fraction. Reinforcements like micro or nano sized SiC, Al2O3, TiC, B4C, SiO2 and iron powder when used, can alter the microstructural characteristics that develop excellent physical and mechanical properties in aluminum alloys, primarily for aerospace applications. These alloys are being used in different aircraft components that have a relative motion, like actuators and track roll units of a control surface. Stress and wear are generated due to the relative motion of these components during take-off and landing, causing a rise in temperature. And hence, a brief study on moving components used in aircrafts and tribological behaviour of aircraft components is presented in the literature. Also considering that the selection of an appropriate material for the proper functioning of an aircraft component is critical, three most important properties viz. strength, fatigue and corrosion resistance of an aircraft have been provided. Therefore this review article emphasizes on the following topics: (1) aluminum alloys in the aerospace industries, (2) aircraft components with relative motion, their working and material being used, (3) substantial properties of aircraft components viz. strength, fatigue resistance and corrosion resistance, (4) tribological aspect of an aircraft, (5) elevated-temperature behaviour of aluminum alloys, and (6) role of reinforcement for improving properties. This review article is beneficial for those researchers and academicians who want to seek the understanding, pertaining to the usefulness of the aluminum in the aircraft industry.

The parameters of the process of production of flawless bimetallic billets from powder steel R6M5 (the external layer) and 5KhNM (the core) are assessed by mathematical simulation. The bimetal has mechanical properties comparable to those of cast and deformed high-speed steel, a more homogeneous structure, and a much lower cost.

The methods of transmission and scanning electron microscopy are used to study the evolution of the structure of a welded joint of steels 32G2 and 40KhN in the thermomechanically affected zone (TAZ) under rotary friction welding (RFW). EBSD analysis is used to certify the microstructure in different parts of the TAZ and to calculate the densities of the low- and high-angle boundaries. It is shown that complex processes of dynamic recrystallization combining several mechanisms develop in all these regions of the TAZ. Typical differences in the structures of the mobile (steel 40KhN) and immobile (steel 32G2) parts of the billets are described.

In the present work, an Al-Cu-Si-Ni-Mg brazing filler metal was developed for the joining of 6063 aluminum alloy and graphite metallized with Ag-Cu-Ti paste. The joint microstructures were studied by means of SEM and EDS. Results show that joints with a good quality can be produced at a brazing temperature of 550 °C for 10 min. TiC was formed at the graphite/active Ag-Cu-Ti paste interface due to the reaction between Ti and C, and thus, the wettability on the graphite was improved. Compared to the metallization stage, more diffusions of Al, Ag, Ti, and Cu from interlayer to graphite are observed. The bonding area mainly consists of α-Al, Ag rich phase, α + Al2Cu + Si, Al2Cu, and TiC. It is shown that joints with good quality can be produced and the average shear strength of the joints is 21 MPa.

Experimental studies have been carried out with theoretical calculations of wave synthesis in the Ni–Al–Cu system using a mathematical model. Approximate analytical formulas are obtained for synthesis performance evaluation. The inverse problem method was used to get kinetic constants that determine process dynamics based on the experimental data and analytical relationships. It is shown that the combustion front propagation velocity increases monotonically with an increase in the reaction sample relative density in the range of relative density values of 0.4 to 0.6. The depth of copper-melt penetration from the center of the sample into the nickel–aluminum matrix depends on the relative density of the sample and diameter of the copper wire: higher densities and larger diameters lead to an increase in the liquid-phase impregnation area. The rate of nickel and aluminum powder frame wetting with copper melt is limited by the synthesis wave speed. Based on the experimental data and analytical ratios, we estimate the effective kinetic constants describing the high-temperature synthesis of the Ni + Al reaction mixture in the presence of copper additives. The thermal effect of the NiAl intermetallic formation reaction and the preexponential factor in the chemical transformation equation are calculated, the exponent value in the ratio for the mixture thermal conductivity is established, and a constant determining the process of nickel–aluminum matrix impregnation with copper melt is found. The macroscopic approach used to analyze the NiAl intermetallic synthesis makes it possible to determine all the desired physicochemical characteristics and model parameters. The mathematical model is suitable for predictive estimates and experimental data analysis in the macroscopic approximation. Approximate analytical formulas are obtained for calculating the NiAl intermetallic synthesis characteristics. They allow for calculating the through channel characteristics and can be used in the design of NiAl products.

Examination of fractures of rolling bearings from steel 8Kh4V9F2-Sh (EI347-Sh) is used to assess the effect of production factors on the operating capacity of bearings under elevated loads. The microstructure and fractures of the steel are analyzed. The compressive stresses and the contents of the general and diffusion-mobile hydrogen are determined. It is shown that a fatigue crack appears in the material of the bearing in service in the case of an elevated hydrogen content and an unfavorable fiber structure.

At the Navoi Mining and Metallurgical Combine, which uses a large number of machine parts for mining operations, the issue of optimizing the compositions of wear-resistant chromium cast irons while maintaining their operational characteristics has arisen. The paper presents the results of studying the phase composition of the cast alloy, as well as the effect of heat treatment of cast iron with a high chromium content on its structure and properties. As heat treatment operations, quenching in various modes and low tempering were used. The study made it possible to systematize the known literature data on the heat treatment parameters of a group of wear-resistant chromium cast irons, as well as to optimize their heat treatment modes for parts operating in mining and processing industry.

An approach to description of the structural types of phases is suggested, in accordance with which the structural types A15, C15 and C14 of Frank–Kasper phases are described as the densest packing of chains of special unions of tetrahedrons-tetrablocks. A tetrablock is a seven-vertex union of four tetrahedrons over faces. For the packing to be the densest, the ideal tetrahedrons in the tetrablocks should undergo a minimum possible deformation. Since a tetrablock is a natural structural unit of one-dimensional chains, the approach developed may be used for plotting structural models of phase transitions where the transformation develops within linear substructures. Chains of tetrablocks may also be structural components of metallic melts and glasses.

The present work was undertaken with the aim of studying the microstructural changes and intermetallic phases in Al-Si base 413.0 alloys as well as variations in tensile properties, including ultimate stress, yield strength and elongation at rupture, resulting from the addition of alloyed elements: strontium (Sr), magnesium (Mg), copper (Cu), silver (Ag), zinc (Zn) and nickel (Ni), to the base alloy 413.0, under different conditions of heat treatments, i.e., solutionizing and artificial aging (in the temperature range of 155 °C–240 °C). The results obtained in relation to microstructural observations and tensile tests reveal that the addition of alloying elements, in particular Mg, Cu, Ag, Ni, Zn and Sr, leads to an increase in the ultimate stress and yield strength values with a decrease in the strain levels of the base alloy 413.0, following hardening during artificial aging. Both Ag and Zn do not form specific phases during solidification at a slow rate of ~ 0.8 °C/s but only segregate to the α-aluminum cell boundaries. Addition of 0.73% Ag improves the values of yield strength at all aging temperatures. Also, it enhances the alloy resistance to softening during aging in the temperature range 200–240 °C. Similar behavior was exhibited by the addition of 2.5% Zn.

The microstructure, the phase composition, the microhardness and the wear resistance of hypoeutectic white cast irons with different contents of chromium are studied. It is shown that the wear resistance of the iron depends substantially on the type of the carbide phase and on the morphology of the ledeburitic eutectic, which is determined in its turn by the content of chromium.

In the present study, the solidification pathway, microstructure and thermal conductivity of Fe-rich Al–x Si (x = 5, 7, 9, wt%, the same below) alloys were systematically investigated. The results showed that the thermal conductivity was firstly improved and then decreased with Fe content increasing. The improvement and decreasing rate of thermal conductivity was related to the Si content. The change of thermal conductivity was closely related to the change of microstructure and solidification pathway. The addition of Fe element resulted to the precipitation of ternary β (Al5SiFe) phase (βT) and binary β phase (βB). The precipitation of βT was benefited to improve the thermal conductivity. On the contrast, the precipitation of βB was prone to deteriorate the thermal conductivity. The precipitation amount of βT phase and βB phase was related to the critical value of Fe content (Fecrit). The calculation results showed that the Fecrit of Al–x Si alloys was about 0.20% (5% Si), 0.29% (7% Si) and 0.38% (9% Si), respectively. When the Fe content was less critical value (Fecrit), the precipitation amount of βT phase was increased by Fe increasing. Furthermore, when the Fe content was more than Fecrit, the precipitation amount of βT phase was changed slightly, and the precipitation amount of βB phase continued to increase with Fe content increasing.

The methods of scanning electron microscopy and x-ray diffractometry are used to study the microstructure and mechanical properties of welded joints from alloy Ti60 after laser welding and subsequent heat treatment (PWHT). It is shown that the microstructure of the welded joint consists of three zones, i.e., a fusion zone (FZ), a heat-affected zone (HAZ) and base metal (BM). The PWHT lowers considerably the hardness in the FZ and in the internal HAZ, which results in a more homogeneous hardness profile as compared to the post-welding condition. After the heat treatment, the ultimate strength of the welded joint is 980 MPa at room temperature and 728 MPa at 600°C, the elongation is 10.9% at room temperature and 18.3% at 600°C.

With China’s bauxite resources depleting year by year, high-alumina fly ash has been regarded as a potential secondary aluminum resource, with alumina content as high as 40–60%. In view of recognized problems, such as large amounts of circulating acid and environmental pollution in the process of extracting alumina from high-alumina fly ash, Northeastern University has proposed a new electrotransformation method. This method has the main advantages of slag reduction, no waste acid, no waste alkali, and recycling. In this study, the effects of diffusion were examined during electrotransformation, in terms of electrode spacing and concentration difference on solution pH and temperature. In addition, the phase, FT-IR results, roasting weight loss rate of products, D(50), D(90), isothermal adsorption and desorption curves, BET surface area, pore volume, impurity chlorine content of roasted products, and Al recovery rate were investigated. The results showed that pH and temperature increased with prolonged electrotransformation time. And that these products were all amorphous containing-carbon aluminum salt precipitation. Roasted products were all alumina (Al2O3) with a steep broad X-ray diffraction peak. The effects of electrode spacing and concentration difference on isothermal adsorption and desorption curves, BET surface area, and pore volume were not clear. With decreased electrode spacing, the Al recovery rate increased and impurity chlorine content decreased. With increased concentration difference, the Al recovery rate tended to first decrease and then increase, while the impurity chlorine content increased. In other words, small electrode spacing and high concentration difference were beneficial for improving the Al recovery rate.

The phase transformation behavior of lead and zinc in the high-lead slag reduction process was reported in this article. First, the occurrence state of lead and zinc in the slag and the phase transformation behavior of lead and zinc during reduction were investigated. Following, the thermodynamic modeling calculation for the reduction process was constructed and discussed. The results indicated that the zinc in the high-lead slag mainly existed in the form of zinc ferrite and silicate while the lead mainly existed in a silicate form. The XRD patterns of the reduced slag at different coal ratios demonstrated that the lead existing in the high-lead slag in a silicate form could be reduced into the metal phase while the zinc existing in the high-lead slag in the form of zinc ferrite (ZnFe2O4) could be converted into zinc silicate (Zn2SiO4), as the coal ratio increased. The thermodynamic modeling calculation results showed an agreement with the experiment analysis.

The effect of heat treatment parameters (the temperature of 850 – 930°C and the cooling rate of 1 – 20 K/min) on the microstructure and mechanical properties of carbon steel with 1.95 wt.% C is studied. The temperatures of the phase transformations in the steel are determined. X-ray diffractometry is performed. A heat treatment mode preventing the formation of ledeburite in the structure of the steel and promoting a uniform distribution of carbide particles in the matrix is suggested.

An unalloyed thin-wall ductile cast iron with the chemical composition of C = 3%, Si = 4.15%, Mn = 0.36%, Mg = 0.04%, and carbon equivalent of 4.39% was cast by both conventional and ablation casting in sections of nominal thickness 1, 2, 4, 8 mm. The effect of various commercial inoculants (based on Zr, Sr, and Ba) on microstructure and mechanical properties of the samples was investigated. In the ablation casting, the mold is eroded away by water, and the water becomes responsible for the heat transfer from the casting. In our work, ablative cooling could not be applied quickly enough to have any influence on the microstructure of the 1 mm thick cast section. In the 2-mm-thick specimen, ablation increased the nodule count from 497 to 1484 and graphite nodularity from 76 to 93%. In the 8 mm section, the tensile yield strength increased from 539 to 624 MPa and elongation was increased from 4.9 to 10.2%.

In this study, Ti5Si3/Ti3Al composite was successfully vacuum-brazed with Ti-33Zr-16Cu-13Ni (wt.%) filler alloy. The typical interfacial microstructure of the joints presented a symmetrical characteristic, which mainly consisted of Ti3Al, Ti2Ni, and α-Ti phases. The effects of brazing temperature and holding time on the interfacial microstructure and mechanical properties of the joints were investigated in details. The optimized average shear strength of 224 MPa was obtained when brazing at 900 °C for 5 min. The high temperature shear strength of the joints reached 377 and 405 MPa at 600 and 650 °C, respectively. In addition, the microstructure evolution mechanism of the joints was put forward based on the experimental analysis.