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A method of ultrasonic surface plastic deformation is widely used to change the properties of the surface layers of metal products. Under the influence of this type of treatment, the structure of the material changes, microhardness increases, roughness decreases, internal tensile stresses are removed, and compressive stresses are created. Now many types of ultrasonic surface plastic deformation have been developed, which differ in the degree of impact on the material. The object of this paper is to study the change in the microgeometry of steel 45 (ASTM M1044; DIN C45; GB 45) under the action of ultrasonic plastic deformation by a free deforming element (indenter in the form of a surface rolling ball). During the study, factors that have the greatest influence on the change in the microgeometry of the sample during treatment were identified. These include the initial roughness of the sample, the number of passes of the indenter, the feed of the indenter, the force with which the indenter is pressed to the treated surface, and the amplitude of the oscillations of the ultrasonic horn. The paper presents the dependences of changes in the main roughness parameters on the above factors. The value of the initial roughness at which it is possible to obtain a uniform surface microrelief is determined. The optimization of treatment parameters providing a change in the height and step parameters of roughness was carried out. Recommendations for choosing the most effective technological modes of ultrasonic treatment of steel 45 with a surface rolling ball are given.

Aiming at the problems of large elastic deformation and low machining accuracy in cutting titanium alloy thin-walled parts, this paper establishes the finite element model of milling titanium alloy thin-walled parts, and simulates and analyses the milling process of titanium alloy thin-walled parts by the statics analysis module of ANSYS 15.0 software. The maximum deformation point of the workpiece in the milling process is determined. Then the combination of cutting parameters that can minimize the deformation is determined by the orthogonal experiments of four factors and four levels. This paper designs the single factor experiments, which study the distribution of the milling force and the deformation law of the parts in the milling process. Moreover, this paper carries out the optimal design of the cutting parameters by orthogonal experiments, which provides a reference for the selection of the cutting parameters for the bending thin-walled parts of titanium alloy.

The purpose of this paper is to develop a new technology for controlling the quenching deformation of light cast aluminum alloy wheels. First, based on the existing wheel heat treatment process, a gas–liquid–solid multi-phase flow coupling model was established through the ANSYS Workbench platform to analyze the gas–liquid phase change, heat exchange on wheel surface and quenching deformation characteristics during the process of wheel immersion into the water. The results show that heat exchange characteristics of the wheel surface are comprehensively affected by wheel structure, quenching fluid flow field and gas–liquid phase transition. There are a lot of non-uniform heat exchange areas in the outer rim, spoke area and center area, which affect the overall deformation characteristics. Affected by spoke structure, the maximum deformation occurs at the outer and inner rim end faces farthest away from the wheel. Based on the above research, this paper independently develops a new deformation control strategy of spray and water immersion composite step process. Through spraying, the influence of spoke structural stiffness on the overall deformation characteristics of the wheel is effectively reduced, and the wheel deformation control is realized by meeting the mechanical properties of the wheel, with the maximum deformation reduction of 39.2%. This study provides a new option for the integrated control of deformation and mechanical properties of aluminum alloy wheels.

Connecting a variable groove weldment is always challenging, and it is necessary to monitor the course of the work and optimize the welding process parameters in real time to ensure the final welding forming quality. Welding penetration is an important index to appraise the welding forming quality; the visual sensing method for molten pool is the main method for detecting the weld penetration, but its detection accuracy is affected by the arc light. In this paper, a welding penetration sensing method for variable groove weldments based on the welding temperature field distribution is proposed. Firstly, a set of temperature field measurement system for a weldment is developed by means of an infrared sensor. Secondly, in the direction perpendicular to the welding direction, a linear temperature distribution feature extraction algorithm based on Gaussian fitting is studied; in the direction parallel to the welding direction, the linear temperature distribution feature extraction algorithm based on the thermal cycle parameters is studied, and the feasibility of using the extracted linear temperature distribution features to identify the weld penetration of a variable groove weldment is analyzed. Finally, taking the extracted linear temperature distribution features as input, using an artificial neural network, the prediction model for the welding penetration of a variable groove weldment is established. The experimental results showed that the weld penetration sensing method put forward in this paper can realize high-precision weld penetration sensing and has high reliability, which solves the problem that weld penetration sensing is affected by arc light to a great extent.

In recent years the chlorination leaching separation process in the field of hydrometallurgy has been developed considerably. However, the development of the chlorination separation process in the field of pyrometallurgy has lagged. In this paper, the thermodynamics of vacuum chlorination volatilization of valuable metals Ni, Co, Mn, Li, Al, and Cu from spent lithium−ion batteries is investigated, and it is found that chlorination helps to achieve the trapping and separation of the singlet metals. With the help of Factsage 8.1, a theoretical map of the stable regions of valuable metal chlorides, the order of separation of each chloride at 10 Pa, and a discussion of the behavior of excess CuCl2 in the system at different temperatures were determined. This paper provides research ideas in the fields of selective separation of alloying elements in the carbothermal reduction products of waste lithium−ion batteries and one−step separation of valuable metals by carbothermal reduction.

The increasing demand for ultra-high purity aluminum for technological applications has led to the improvement of refining methods in recent decades. To achieve ultra-purity levels (>5N), the common industrial way is to firstly purify aluminum from 2N8 up to 4N8 via three-layer electrolysis, followed by fractional crystallization (usually zone melting). Since both of these methods are very cost- and time-intensive, this paper aims at providing other alternatives of purification. For this purpose, here, the purification of some selected impurities through cooled-finger fractional crystallization method and vacuum distillation have been the focus of this investigation. Both processes are more environmentally friendly than three-layer electrolysis and require less time than zone melting. In this paper, both methods were explored for the aluminum purification. Moreover, the effect of process parameters on the purification efficiency of iron, zinc, and silicon has been investigated. At the end, the effectiveness of the two processes was compared and advantages and disadvantages were summarized. The results showed that the cooling finger process effectively removed iron and silicon impurities, but the removal efficiency of zinc was low. The vacuum distillation process successfully removes zinc in the first stage of distillation. Iron and silicon removal requires additional distillation stages to achieve lower impurity levels.

Closed-cell aluminum foam has a porous structure and metal properties due to its unique composition. As a structural material, it has the advantages of being lightweight, having a large specific surface area, and having high specific strength and stiffness. As a functional material, it can be used for sound and noise reduction, heat insulation, electromagnetic shielding, damping, and energy absorption, but it also has poor mechanical properties and poor surface flatness, and can be easily corroded. Considering the abovementioned problems, researchers have gradually extended their research on foam materials. Under the research of many international scholars, studies have shifted from simple aluminum foam preparation to improving and optimizing aluminum foam composite structures (AFCSs). From the perspective of development prospects, AFCSs have better application prospects than single aluminum foam. In this paper, the research progress on the preparation technology of AFCSs in recent years was reviewed based on the performance enhancement mechanism of aluminum matrix composites and the structural characteristics of aluminum foam. The morphology and pore structures of closed-cell AFCSs under different preparation methods were summarized. However, due to the limitations of existing experimental conditions, this paper only considered the advantages and disadvantages of AFCS preparation methods. The improvement of AFCS preparation technology, the development of the potential properties of AFCSs, and the promotion of AFCS industrial applications were also considered.

The metal sandwich structure is characterized by light weight, high stiffness, and high-impact energy absorption capacity, which is considered a good alternative protective structure in explosion scenarios. In this paper, four design forms of the metal sandwich structure are introduced, and the dynamic response of the metal sandwich structure under explosion load is researched. Then, a new analytical method is proposed to predict the dynamic response of the metal sandwich structure under explosion load, and numerical simulations are carried out to verify the accuracy of the proposed analysis method. The proposed analytical method is designed for aerial explosions without considering the fluid–structure interaction. In addition, a series of parameter studies are carried out, including the influence of the face sheet aspect ratio, the core height, and the thickness of the face sheet and core on the dynamic response of the sandwich structure under explosion load. The research in this paper has reference value for the anti-explosion design of the metal sandwich structure and will provide a useful reference for the design and optimization of the metal sandwich structure.

The joint is a key component of the aviation piping system, with severe performance requirements and better requirements for connection technology. With a focus on the manufacturing demand of AA6061 aerospace pipe joints, as well as the characteristics of EMP forming technology, this paper investigates the deformation behavior of the EMP forming on AA6061 aerospace pipe joints, the influence of process parameters on the deformation behavior, and the deformation mechanism of the tube wall. The results show that under the conditions of this paper, with an increase in the initial tube-sleeve gap and discharge voltage, the degree of local deformation of the AA6061 tube wall and the trench embedding rate increase. Keeping the width and depth of the grooves as 1.14 mm and 0.23 mm, the embedding rate of the grooves is less than 85% under the clearance conditions of 0.11 mm and 0.5 mm, while the lowest voltage for the embedding rate of the grooves to reach more than 85% under the clearance conditions of 1 mm, 1.5 mm and 2 mm is 7 kV, 6 kV, and 5 kV, respectively. The metallographic organization of the deformation area shows that the tube is deformed by the intense shear at the edge of the groove of the tube sleeve, thereby showing streamlined organization characteristics and deformation characteristics. The electromagnetic pulse forming process of the AA6061 tube is mainly divided into two stages: free bulging and local deformation; the inertia of high-rate deformation causes the groove filling to exhibit volume deformation characteristics in the local deformation stage.

One of the most important challenges for every machining shopfloor, especially a small one, is to achieve the required productivity with minimal energy consumption and engaged power. The paper presents a way to determine the optimal combination of values of cutting parameters such as depth of cut, feed rate and cutting speed from the range of their recommended values, which are usually additionally limited by the real conditions of available machines and tools. The optimal combination is the one which ensures targeted productivity and maximum energy savings at the same time. As an example, a real practice case of external rough turning of an AISI 1045 steel workpiece is presented. The selection of the optimal combination of cutting parameter values is based on a model which is developed using in situ measurements of energy consumption and engaged power in an experiment that emulates the critical operation in terms of energy consumption. The results show that optimization of cutting parameter values that enables the minimum of total energy consumption while achieving target productivity, does not necessarily enable the maximum of energy savings for a given operation. In the example from real practice shown in the paper, this optimization approach can cause higher total energy consumption by as much as 15.9% compared to the combination of parameters that ensure maximum productivity.

The automatic classification of aluminum profile surface defects is of great significance in improving the surface quality of aluminum profiles in practical production. This classification is influenced by the small and unbalanced number of samples and lack of uniformity in the size and spatial distribution of aluminum profile surface defects. It is difficult to achieve high classification accuracy by directly using the current advanced classification algorithms. In this paper, digital image processing methods such as rotation, flipping, contrast, and luminance transformation were used to augment the number of samples and imitate the complex imaging environment in actual practice. A RepVGG with CBAM attention mechanism (RepVGG-CBAM) model was proposed and applied to classify ten types of aluminum profile surface defects. The classification accuracy reached 99.41%, in particular, the proposed method can perfectly classify six types of defects: concave line (cl), exposed bottom (eb), exposed corner bottom (ecb), mixed color (mc), non-conductivity (nc) and orange peel (op), with 100% precision, recall, and F1. Compared with the existing advanced classification algorithms VGG16, VGG19, ResNet34, ResNet50, ShuffleNet_v2, and basic RepVGG, our model is the best in terms of accuracy, macro precision, macro recall and macro F1, and the accuracy was improved by 4.85% over basic RepVGG. Finally, an ablation experiment proved that the classification ability was strongest when the CBAM attention mechanism was added following Stage 1 to Stage 4 of RepVGG. Overall, the method we proposed in this paper has a significant reference value for classifying aluminum profile surface defects.

Cu-containing steels can suffer from hot shortness unless Ni is added to protect them but whether this problem also influences the straightening operation is not clear. Previous work on hot ductility has found that only when the tensile samples from Cu-containing steels are oxidised can any deleterious influence of copper be found. However, this paper shows that oxidation is not essential. It is more complex than that and, as Cu has been suggested for TRIP steels at levels up to 2.5% Cu to increase their strength and ductility, a greater understanding is required, both of hot shortness and cracking during straightening. The present paper explores the hot ductility behaviour of steels alloyed with Cu and Ni in the straightening temperature range, 700–1000 °C, when tested in air and in an argon atmosphere. Segregation of Cu to the sulphides and grain boundaries occurred allowing the formation of fine Cu2S particles at the austenite grain boundaries favouring intergranular failure and this was more pronounced under oxidising conditions and required strain. It was concluded that a Cu addition, as well as causing hot shortness at higher temperatures will also cause cracking problems in the straightening temperature range in the more sensitive to cracking grades of steel and although the problems are different they are nevertheless interrelated and provided there is sufficient Ni, both may be avoided.

The paper deals with the metallographic analysis of overlapped laser welds of dissimilar materials based on galvanized and ungalvanized steels in various combinations. In addition to a gallery of metallographic sections, the paper presents the monitoring of weld defects, the measurement of selected weld geometrical characteristics and changes in weld microstructure by measuring the microhardness profile across the joint. The mixing of materials was monitored by area and line EDX analysis in the melting zone. Subsequently, the load carrying capacity of the formed joints was determined and compared with FEM simulation. Finally, the dependences of hardness and strength of welds on carbon content and carbon equivalent were determined.

The objective of the study is to improve understanding of the practical role of niobium (Nb) in the case of industrial inconsistent rolling processes such as the rolling of heavy gauge plates where a lower stored energy rolling practice will result in a less stable and less repeatable static recrystallization (SRX) activation that prevents complete recrystallization. In the current study, these variabilities are validated by comparing the mean flow stress (MFS) indirectly determined from the rolling force measured on a reverse four-high rolling mill stand. The material resistance to deformation and grain size evolution of a C-Mn steel during hot rolling was observed and validated with and without Nb addition. The pre-defined rolling schedule was predicted to exhibit incomplete recrystallization in the roughing phase due to the limited stored energy of deformation that resulted from low rolling loads and a higher number of rolling passes. The prior austenite grain size (PAGS) distribution was predicted and compared to the measured effective ferrite grain (FG) size distribution after the completion of hot rolling and phase transformation achieved using natural air plate cooling. Both the predicted PAG and measured FG distributions revealed the presence of multimodality, and both distributions were used for grain size reduction factor determination for γ → α transformation for the current study with 1.96 for 0 Nb and 1.70 for 240 Nb. The results presented in this paper are not only limited to the rolling schedule used in this paper because instabilities resulting in incomplete austenite conditioning are also observed when evaluating the cross-sections of other heavy plates and various steel grades utilizing different processing routes with comparable compositions such as modern lean abrasion-resistant steels, regular line pipe steels, and other similar grades.

This paper presents a 0.25 scale quasi-three-dimensional hydraulic model experiment of transient fluid flow phenomena during continuous casting of steel. The relationship between the continuous casting process and the hydraulic jump phenomenon is established. The casting process in the mold is divided into four stages (I–IV) from the beginning to the end of continuous casting. The filling process involves stages I–II and is investigated by high-speed camera. The filling process is part of the cast start. In this paper, the hydraulic jump behavior varies and is controlled by different spring and iron chips arrangement on the dummy bar during the filling process. A filling coefficient is proposed to judge the best filling conditions and apply them to the whole filling process. There is an optimal spring and iron chip arrangement, which can adjust the hydraulic jump to optimize the initial flow field during the filling process, even the whole continuous casting process.

This paper evaluates the effect of stress-relieving heat treatment on the AlSi10Mg alloy prepared by additive manufacturing using the Laser Powder Bed Fusion (L-PBF) with print parameters: 370 W, 1400 m/s, and 50 μm. The as-built state and four different annealing modes (240 °C/2 h, 240 °C/6 h, 300 °C/2 h, and 300 °C/2 h/water-quenched) are investigated. To determine the effect of the annealing mode on the mechanical properties of the L-PBF AlSi10Mg alloy, heat-treated samples were compared with the as-built state and with each other. The mechanical properties of the samples were determined by tensile and hardness tests. The strength in the as-built state is 488 MPa, depending on the method of heat treatment, the strength values range from 296 MPa to 417 MPa, and the HV10 hardness values are in accordance with the measured strength values. Furthermore, the microstructure of the samples was investigated by scanning electron microscopy (SEM) analysis, which was then linked to the measured mechanical properties. The composition of the microstructure of the alloy and its influence on the mechanical properties were determined by energy dispersive spectroscopy (EDS) analysis. Furthermore, the differences between the individual heat treatments in comparison with the as-built state were analyzed and the phenomenon of decomposition of the silicon network after reaching specific temperatures was discussed and confirmed. The paper evaluates the effect of dwelling time on stress relief annealing. It was found that if annealing at intermediate temperatures of 240 and 300 °C is applied, changes in structure and mechanical properties are more temperature- than dwell-time-dependent.

In this paper, the research progress on the strengthening of copper and copper alloy is reviewed. The research shows that traditional strengthening methods are often accompanied by the decrease of plasticity, and there are limitations in size, cost, and other aspects in the process. The in-situ nanoparticle strengthening and plasticizing technology proposed in recent years can avoid the above problems. In this paper, the idea of in-situ nanoparticle strengthening is introduced to realize the simultaneous enhancement of strength and ductility of as-cast pure copper and tin bronze alloys. The effects of in-situ precipitation of iron-rich nanoparticles on the microstructure, and mechanical properties of different copper alloy systems, are systematically elucidated based on the former characterization and mechanical testing results. The results show that the in-situ introduction of iron-rich nanoparticles in the copper systems induces the formation of a nano precipitate-fine grain (NPFG) structure, which greatly improves the strength and ductility of copper alloys. The evolution of size, distribution, number density, morphology evolution in iron-rich nanoparticles, and the formation mechanism of NPFG structure, as well as the mechanism of NPFG strengthening and toughening, are summarized. An industrial-applicable casting process is proposed to prepare bulk NPFG structured copper alloys with complex shape, high strength, and high ductility.

Several additive manufacturing processes are capable of fabricating three-dimensional parts with complex distribution of material composition to achieve desired local properties and functions. This unique advantage could be exploited by developing and implementing methodologies capable of optimizing the distribution of material composition for one-, two-, and three-dimensional parts. This paper is the first effort to review the research works on developing these methods. The underlying components (i.e., building blocks) in all of these methods include the homogenization approach, material representation technique, finite element analysis approach, and the choice of optimization algorithm. The overall performance of each method mainly depends on these components and how they work together. For instance, if a simple one-dimensional analytical equation is used to represent the material composition distribution, the finite element analysis and optimization would be straightforward, but it does not have the versatility of a method which uses an advanced representation technique. In this paper, evolution of these methods is followed; noteworthy homogenization approaches, representation techniques, finite element analysis approaches, and optimization algorithms used/developed in these studies are described; and most powerful design methods are identified, explained, and compared against each other. Also, manufacturing techniques, capable of producing functionally graded materials with complex material distribution, are reviewed; and future research directions are discussed.

Recent advances in technology and refinement of available computational resources paved the way for the extensive use of computers to model and simulate complex real-world problems difficult to solve analytically. The appeal of simulations lies in the ability to predict the significance of a change to the system under study. The simulated results can be of great benefit in predicting various behaviors, such as the wind pattern in a particular region, the ability of a material to withstand a dynamic load, or even the behavior of a workpiece under a particular type of machining. This paper deals with the mathematical modeling and simulation techniques used in abrasive-based machining processes such as abrasive flow machining (AFM), magnetic-based finishing processes, i.e., magnetic abrasive finishing (MAF) process, magnetorheological finishing (MRF) process, and ball-end type magnetorheological finishing process (BEMRF). The paper also aims to highlight the advances and obstacles associated with these techniques and their applications in flow machining. This study contributes the better understanding by examining the available modeling and simulation techniques such as Molecular Dynamic Simulation (MDS), Computational Fluid Dynamics (CFD), Finite Element Method (FEM), Discrete Element Method (DEM), Multivariable Regression Analysis (MVRA), Artificial Neural Network (ANN), Response Surface Analysis (RSA), Stochastic Modeling and Simulation by Data Dependent System (DDS). Among these methods, CFD and FEM can be performed with the available commercial software, while DEM and MDS performed using the computer programming-based platform, i.e., “LAMMPS Molecular Dynamics Simulator,” or C, C++, or Python programming, and these methods seem more promising techniques for modeling and simulation of loose abrasive-based machining processes. The other four methods (MVRA, ANN, RSA, and DDS) are experimental and based on statistical approaches that can be used for mathematical modeling of loose abrasive-based machining processes. Additionally, it suggests areas for further investigation and offers a priceless bibliography of earlier studies on the modeling and simulation techniques for abrasive-based machining processes. Researchers studying mathematical modeling of various micro- and nanofinishing techniques for different applications may find this review article to be of great help.

Vision-based welding seam tracking is an important and unique branch of welding automation. Active vision seam tracking systems achieve accurate feature extraction by using an auxiliary light source, but this will introduce extra costs and the real-time performance will be affected. In contrast, passive vision systems achieve better real-time performance and their structure is relatively simple. This paper proposes a passive vision welding seam tracking system in Plasma Arc Welding (PAW) based on semantic segmentation. The BiseNetV2 network is adopted in this paper and online hard example mining (OHEM) is used to improve the segmentation effect. This network structure is a lightweight structure allowing effective image feature extraction. According to the segmentation results, the offset between the welding seam and the welding torch can be calculated. The results of the experiments show that the proposed method can achieve 57 FPS and the average error of the offset calculation is within 0.07 mm, meaning it can be used for real-time seam tracking.

Be-Al alloy is a type of in situ metal matrix composite composed of a primary Be phase for strength and stiffness and a continuous Al matrix for ductility and toughness. Be-Al alloy (AlBe-Cast®910) has the characteristics of low density (2.17 g/cm3), high elastic modulus (193 GPa) and specific stiffness (88.94 GPa/(g/cm3)) as a preferred material for lightweight aerospace products. Investment casting technology can be employed to prepare the components with thin-walled complex structures for aerospace; however, the wide solidification range for Be-Al leads to difficulty in feeding a casting and results in extensive shrinkage and porosity in cast parts. In this paper, the characteristics of Be-Al alloy are introduced first. Secondly, the mechanisms of influence of adding elements on the casting process, mechanical properties (strength increases more than 20% by adding elements) and microstructure evolution are explained in detail. In addition, the heat treatment technology (strength increases at least 10% after heat treatment) and the repair of defects by electron beam welding are discussed. Finally, Be-Al alloy is a new type of composite material, and China is a major research and application country; this paper introduces its research status and analyzes existing problems and shortcomings and points out the direction of Be-Al alloy development in China in the next few years.

As the lightest structural materials, Mg alloys show great effectiveness at energy saving and emission reduction when applied in the automotive and aerospace fields. In particular, Zr-bearing Mg alloys (non-Al containing) exhibit high strengths and elevated-temperature usage values. Zr is the most powerful grain refiner, and it provides fine grain sizes, uniformities in microstructural and mechanical properties and processing formability for Mg alloys. Due to the importance of Zr alloying, this review paper systematically summarizes the latest research progress in the grain refinement effects of Zr on Mg alloys. The main points are reviewed, including the alloying process of Zr, the grain refinement mechanism of Zr, factors affecting the grain refinement effects of Zr, and methods improving grain refinement efficiency of Zr. This paper provides a comprehensive understating of grain refinement effects of Zr on Mg alloys for the researchers and engineers.

To date, scholars’ research on the stability behavior of the arch structure mainly focuses on solid–web section arches, steel tubular truss arches and concrete-filled steel tubular arches, but the stability behavior of the novel spatial grid arch structure, which integrates the characteristics of grid structure and arch structure, is not yet clear. Based on the Eye of the Yellow Sea pedestrian bridge project in Rizhao, China, the stability behavior of this large-span spatial grid arch structure was studied, in this paper, by the project’s structure design team. The project is a glass covered steel arch pedestrian bridge with a span of 177 m, a height of 63.5 m, an elliptical section with a long axis of 18 m, and a short axis of 13.5 m. The elastic and the nonlinear elasto-plastic stability behavior considering different initial geometric imperfections, was analyzed by the ABAQUS finite element model. The buckling modes and the full-range load-displacement curve of the structure were analyzed, and the stress distribution, deformation mode and overall structural performance during the whole loading process were analyzed. The effects of initial imperfections, geometric nonlinearity and material nonlinearity on the ultimate load-carrying capacity of the structure were studied. The stability behavior of large-span spatial grid arch structure was studied in this paper, which provides an important reference for the design and analysis of such structures.

In this paper, four array patterns were first designed by observing the structural features of the surface microstructures of pig bones and tree frog paws on the titanium alloy surface bionically. Then, the optimal parameters for laser processing were determined experimentally, and the optimized processing parameters were used to prepare micron-scale bumps on the titanium alloy surface and to investigate the relationship between the weaving height and the processing times. Finally, multiple acid etching was used to prepare nanoscale holes on the surface of the titanium alloy. It was found that the multiple acid etching could not only prepare nanoscale holes on the surface of the titanium alloy, but could also well eliminate the slag left on the surface of titanium alloy by laser ablation. Based on the above study, this paper also analyzed the effect of micro-nano structure on the friction properties of the titanium alloy surface from three aspects—theory, hardness test and friction coefficient test—and experimentally analyzed the effect of single-factor and multi-factor coupling of structural features on the friction properties of the titanium alloy surface. It was found that the optimal mean friction coefficient was 0.0902, corresponding to the characteristic values of 0.66 for the shape, 200 μm for the edge length and 60 μm for the height.

Porous materials have significant advantages, such as their light weight and good specific energy absorption. This paper presents the designs of two ordered Voronoi structures, a truncated octahedron (Octa) and a rhombic dodecahedron (Dodeca), based on spatial Voronoi tessellation. Through a numerical analysis, the dynamic behavior, deformation and energy absorption of the two porous structures under different impact energies were explored. According to the energy-absorption index, the effects of porosity, rotating unit cell and unit-cell shape on the energy absorption of the porous structures were quantitatively evaluated. The study shows that, for Dodeca and Octa structures subjected to various impact energies, the force-displacement curves exhibit three modes. The porosity, rotational unit cell and unit-cell shape play a crucial role in affecting the impact resistance of porous structures. The work in this paper proposes an effective way to improve the energy-absorption capacity of porous structures under different impact energies. At the same time, a new understanding of the deformation mechanism of Octa and Dodeca was obtained, which is significant for the impact-resistance design and energy-absorption evaluation of porous structures.

Nowadays, advanced turning processes are extensively being adopted to perform different types of turning operations such as straight turning, taper turning on Hastelloy, Nimonic, and Inconel, stainless steel, and tool steel to fabricate better quality cylindrical and rotating parts such as miniature-bars, miniature-pins, miniature-electrodes, and miniature-tools. This paper presents a review of the previous research conducted on the turning of miniature cylindrical bars using thermoelectric-erosion based turning processes namely thermoelectric-erosion turning (TET) and wire-assisted thermoelectric-erosion turning (WTET). It also highlights work and tool electrode materials, types of dielectrics, detailed specifications of turning, types of turning, process parameters, performance measures, advantages and limitations, and key findings. The paper ends with conclusions and future research directions. This paper aims to facilitate researchers and scholars by highlighting the potential and capabilities of TET and WTET processes and providing relevant information for ease of fabrication of miniature parts and components from a wide range of difficult-to-machine materials.

The wetting behavior of water on metal surfaces is important for a wide range of industries, for example, in the metallurgical industry during the preparation of metallic nanoparticles or electrochemical or electroless coating preparation from aqueous solutions, as well as in the construction industry (e.g., self-cleaning metal surfaces) and in the oil industry, in the case of water–oil separation or corrosion problems. Wettability in water/metal systems has been investigated in the literature; nevertheless, contradictions can be found in the results. Some papers have reported perfect wettability even in water/noble metal systems, while other researchers state that water cannot spread well on the surface of metals, and the contact angle is predicted at around 60°. The purpose of this paper is to resolve this contradiction and find correlations to predict the contact angle for a variety of metals. In our research, the wetting behavior of distilled water on the freshly polished surface of Ag, Au, Cu, Fe, Nb, Ni, Sn, Ti, and W substrates was investigated by the sessile drop method. The contact angle of the water on the metal was determined by KSV software. The contact angle of water is identified as being between 50° and 80°. We found that the contact angle of water on metals decreases linearly with increasing the atomic radius of the substrate. Using our new equation, the contact angle of water was identified on all of the metals in the periodic table. From the measured contact angle values, the adhesion energy of the distilled water/metal substrate interface was also determined and a correlation with the free electron density parameter of substrates was determined.

In recent decades, the electromagnetic induction quenching approach has been widely applied in the surface treatment process of steel engine parts such as crankshafts. In this paper, the strengthening effect of this approach was selected to be the object of study. First, the multi-physics coupling phenomenon was established by a 3D finite element simulation approach. Then, the fatigue property of the crankshaft was predicted based on the combination of the residual stress field obtained in the previous step and a chosen multi-axial fatigue damage model. Finally, a corresponding experiment verification was carried out to check the accuracy of the prediction. The results showed that the method proposed by this paper can provide high enough accuracy in predicting the fatigue property of two types of commonly used steel crankshafts.

The paper proposes partially connected steel plate shear walls, in which the infill plates and frames are connected by discretely distributed fish plates at the corners and at the centers. The high lateral resistance of a steel plate shear wall has led to its widespread use in the design of structural shear resistance. In this paper, finite element models of the partially connected steel plate shear walls are established by the finite element method, and the effect of the different partial connections on the shear strength is firstly investigated. Moreover, the variation of the shear strength with the plate-to-frame connectivity ratio is analyzed numerically, and the effect of the connectivity ratio on the development of the tensile field is studied. Based on the numerical analysis results, the effect of the connectivity ratio on shear strength is evident at low levels. When the connectivity ratio is over 80%, the shear strength of the partially connected steel plate shear wall can reach 95% of that of the fully connected steel plate shear wall. When the connection ratio is at a low level, the advantages of the central connection on the shear strength of the structures are higher than those with corner connections. Furthermore, the fitting formula for the partially connected steel plate shear wall is obtained by changing the connectivity ratio and width-to-height ratio of the examples, which can predict the shear capacity of the partially connected steel plate shear wall with different partial connections.

The airworthiness certification of military aircraft requires a durability analysis be performed using linear elastic fracture mechanics (LEFM). Furthermore, such analyses need to use a valid small crack growth equation. This paper focuses on the effect of rough surfaces and the effect of machining the surface on the durability of AM parts using LEFM and a valid small crack growth equation for the material. To this end, this paper analyses the effect of surface roughness on wire and arc additively manufactured (WAAM) Ti-6Al-4V titanium parts and the effect of machining on the durability of a part. The analysis reveals that the life of the component is a relatively strong function of the degree of surface roughness, and that the durability of a specimen is a strong function of the local radius of the curvature of the trough. It also appears that surfaces with tall narrow roughness will not overly benefit from partial machining of the surface.

This paper describes an experimental and numerical study of the hysteretic behavior of side-reinforced joints of a steel frame manufactured from Q345B steel and welded using an E5015 electrode. The objectives of this study were to observe the mechanical behavior of side-plate reinforced joints under cyclic loads; identify their plastic hinge, skeleton curve, stiffness degradation, ductility, and energy dissipation capacity; and provide useful test data for future damage analysis of steel frames with side-plate reinforced beam–column connections. Two specimens were designed, and both were tested under cyclic loads. The test setup consisted of one beam at the end and a column connected by three groove welds. The cyclic loads were applied to the beam’s free end, and the sizes of the beams and the columns of the two specimens were held constant because the only element studied in the present work was the side-plate reinforcement. In this paper, the responses of these two joints are discussed in terms of their experimentally and numerically obtained failure modes, hysteretic curves, plastic hinge, skeleton curve, stiffness degradation, ductility, and energy dissipation capacity. The results show that the steel frame’s side-plate reinforced joints, compared with normal joints, have smaller plastic hinge displacement and deformation, and higher bearing capacity. Furthermore, if designed according to code, all these welded joints perform satisfactorily.

This paper presents a comprehensive framework for the reliability analysis of ship local structures. Existing reliability analysis of ship local structures relies on empirical analysis without experimental validation. The presented framework improves the probabilistic simulation process by combining finite element analysis and the Kriging surrogate model to increase the computational efficiency in uncertainty quantification. In addition, ultimate strength test data are introduced to update the prior distribution based on Bayesian data fusion. A cross-deck structure of a ship is studied in detail to present the application of this work. The framework provides a valuable reference for the reliability analysis of ship local structures and promotes the development of reliability-based design code. The novelty of this paper is that it introduces the combination of testing and probabilistic simulation into the reliability analysis of ship local structures.

This paper investigates the manipulation of chemical composition of a laser weld by dissimilar filler material and its effect on residual stress. The aim is to minimize residual stresses in the weld seam. In order to negate residual stresses, dissimilar combinations of low-carbon manganese steel (S235JR) base material with high-alloyed solid filler wires (G19 9 and G25 20), as well as similar combinations with low-alloyed solid filler wire G3Si1 are analyzed. The goal of the paper is to show that the so-called low-transformation-temperature effect can be used to induce residual compressive stresses in a weld without the use of specially manufactured filler wires. Chemical compositions are generated within a laser-beam-welding process by means of dilution, proving that the concept of in situ alloying is usable in order to affect the martensite formation on a weld. Dilatometry measurements show that a varying Cr and Ni content in a weld reduces the phase-transformation temperature and increases dilatation. EBSD analysis indicates that a fully martensitic weld with a negligible amount of retained austenite is created while the base material preserves its ferritic-pearlitic microstructure. Residual stress measurements with the hole-drilling method demonstrate a reduction in longitudinal tensile residual stresses, whereby the magnitude of the induced residual compressive stresses depend on the Ms temperature. As a result of this research, it was proven that a reduction in tensile residual stress by means of targeted alloying with conventional materials in low-carbon manganese steel is possible. Under the experimental conditions, residual stress in the weld seam could be reduced to 0 MPa. In some cases, even compressive residual stress in the weld could be achieved.

In this paper, a new low-carbon alloy gear steel is designed via Si/Al alloying. The carburizing and austempering, at a temperature slightly higher than the martensitic transformation point (Ms) of the surface and much lower than the Ms of the core, for different times, were carried out on the newly designed gear steel. After heat treatment, a series of different microstructures (superfine bainitic ferrite + retained austenite, superfine bainitic ferrite + martensite + retained austenite, and martensite + retained austenite) were obtained on the surface, whilst the low-carbon lath martensitic microstructure was obtained in the core. The microstructure of the surface was examined using optical microscopy (OM), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The phase composition was analyzed using X-ray diffraction (XRD). The hardness and wear resistance of the surface as well as the hardness distribution of carburizing layer of the samples with different microstructures were studied. The results show that the Si/Al-rich gear steel, after carburizing and austempering at 200 °C for 8 h, not only has excellent mechanical properties but also has high wear resistance, which meets the technical requirements of heavy-duty gear steel. The research work in this paper can provide a data reference for the application of carburized steel with mixed microstructures of bainitic ferrite and martensite in the design of heavy-duty gear.

TiNi shape memory alloys with a superelastic effect are widely used in tribological interfaces requiring high wear resistance. One of the common approaches to reducing the wear of various metals is the application of severe plastic deformation (SPD), resulting in structural refinement and corresponding hardening. This paper investigates the tribological behaviour of a nanostructured Ti49.3Ni50.7 shape memory alloy produced using SPD. The friction and wear characteristics of the alloy at room temperature are compared in the coarse-grained, nanostructured, and nanostructured aged states. Through hardness measurement and transmission electron microscopy, it is shown that the transformation of a coarse-grained state into a nanostructured state increases wear resistance and hardness, reduces the coefficient of friction, and changes the friction mechanism. Formed nanoparticles during ageing in a nanostructured state further increase wear resistance.

In this paper, the microstructure and mechanical properties at the interface of Incoloy825/X65 bimetallic composite pipe achieved by explosive welding were systematically studied. Results show that a periodic wavy bonding interface was formed between the Incoloy825 and X65 due to the jets caused by the high-impact stresses during explosive welding, which was beneficial for improving the bonding strength of the Incoloy825 and X65. Atomic diffusion and localized melting occurred near the interface during explosive welding. Some fine crystal grains were generated in the vicinity of the interface due to the strong plastic deformation and dynamic recrystallization, whereas some elongated grains growing in the perpendicular direction to the interface were found in the wider localized melted zone. Room temperature nanoindentation test showed that due to the existence of fine grains resulting from the recrystallization at the interface, the hardness of the interface was higher than that of the base metals. Voids and defects were prone to appearing in the vortex regions near the interface, where the weak point in the interface was located.

This paper presents equations derived from thermodynamic equations for calculating the liquidus and solidus temperatures, the liquidus slope, and the partition ratio for solidification simulations. The constants of these equations can be easily determined from measurement data obtained by digitalisation from known diagrams or can be calculated using a CALPHAD-based software. ESTPHAD has a hierarchical system; the developed functions of the binary systems are used in the calculation of the functions of the ternary systems, the functions of the ternary systems in the calculation of the function of quaternary systems, and so on. The developed method is demonstrated by processing the liquidus and solidus of Si–Ge isomorphous and Al–Mg and Al–Si eutectic equilibrium phase diagrams. The use of this method for calculating the functions of ternary systems will be shown in Part II. The advantages of this method are that the equations are simple, can be determined very quickly, and can be built into the simulation software very easily. The most significant advantage is that the calculation time is shorter by some order of magnitude than that of a CALPHAD-type calculation.

Additive manufacturing (AM) is a rapidly developing technical field that is becoming an irreplaceable tool to fabricate unique complex-shaped parts in aerospace, the automotive industry, medicine, and so on. One of the most promising directions for AM application is the design and production of multi-material components with different types of chemical, structural, and architectural gradients that also promote a breakthrough in bio-inspired approaches. At the moment there are a lot of different AM techniques involving various types of materials. This paper represents a review of extrusion-based AM techniques using metal-polymer composites for structural metal parts fabrication. These methods are significantly cheaper than powder bed fusion (PBF) and directed energy deposition (DED) techniques, though have a lower degree of part detail. Thus, they can be used for low-scale production of the parts that are not rentable to produce with PBF and DED. Multi-material structures application in machinery, main aspects of feedstock preparation, the subsequent steps of extrusion-based 3D printing, and the following treatment for manufacturing single-metallic and multi-metallic parts are considered. Main challenges and recommendations are also discussed. Multi-metallic extrusion-based 3D printing is just a nascent trend requiring further wide investigation, though even now it shows pretty interesting results.

The Al-Si alloy prepared by the traditional powder metallurgy method has the problems of difficult sintering and low mechanical properties. In this paper, rotary extrusion combined with rapid solidification/powder metallurgy technology (RS/PM) is proposed and designed to produce an Al-10Si alloy. In subsequent sintering at different temperatures, better metallurgical bonding between particles can be achieved to fulfil the aim of improving the mechanical properties of the material. Additionally, the continuous preparation of materials can be achieved. Finally, it is verified that the density of the Al-10Si alloy sintered at 525 °C is 2.61 g/cm3, reaching 97.0% of the theoretical density, and the tensile strength reaches 336 MPa, which is much higher than that of the alloy prepared by the traditional casting method and powder metallurgy method.

The work described in this article is aimed at investigating the properties of a group of Ti-Zr-Nb alloys. In modern orthopedics and traumatology, the use of materials for bone implants with a minimum modulus of elasticity is becoming increasingly important. This is due to a number of advantages that allow for better integration of the implants with the bone tissue, including the reduction in the detrimental effect of the load-shielding effect, a better load distribution, and stress distribution, which allows for increasing the life of the implant. It is known that the lowest modulus of elasticity in titanium alloys at normal temperature is achieved by the phase composition consisting of metastable β-phase. It is possible to achieve the desired structure by a combination of alloy composition selection and heat treatment. Quenching of titanium alloys allows for the high-temperature β-phase to be fixed. This paper provides justification of the choice of compositions of the studied alloys by calculation methods. The structure of alloys after melting in a vacuum electric arc furnace in an argon environment was studied. The ingots obtained had a dendritic structure. Homogenizing annealing in a vacuum furnace at 1000 °C for 4 h was used to equalize the composition. The structure of the alloyed sheets after hot rolling and hot rolling and quenching was investigated. The microstructure of the plates in both variants had uniform grains of polyhedral shape. X-ray phase analysis of the plates showed that the content of metastable β-phase was 100% before and after quenching. Microhardness testing of the plates showed no significant effect of quenching. The result of the mechanical properties study showed an increase in the plasticity of the material after quenching, with the tensile plots of the samples after quenching reflecting the area where the reverse phase transition of β’ α’’ occurs. Mechanical studies by cyclic loading showed the presence of a superelasticity effect. The Young’s modulus study gave a result of 51 GPa for one of the compositions studied. The combination of properties of the materials under investigation has the potential for promising use as a basis for bone implants.

Titanium-containing carbide slag (TCS) is the product obtained by high-temperature carbothermal reduction in Titanium-bearing blast furnace slag (TBFS), which contains a large amount of TiC phase with excellent electrical conductivity. In this paper, conductive cement mortar was prepared with TCS as an aggregate and graphite as a conductive phase. The content of graphite on the compressive strength and electrical resistivity of the prepared cement mortar was investigated. The results showed that the replacement of standard sand with TCS as an aggregate not only significantly reduced the electrical resistivity of the cement mortar, but also improved its compressive strength. When the graphite content was 10 wt%, the cement mortar with TCS as the aggregate exhibited excellent comprehensive performance with the 28d compressive strength of 34.0 MPa and the electrical resistivity of 2.9 Ω m in dry condition, respectively. The results of this paper provided a new way both for the utilization of TBFS and the preparation of conductive cement mortars.

In order to solve the problem of solid waste pollution of basic oxygen furnace (BOF) slag in the metallurgical process, this paper took BOF slag as the research object, and carried out oxidation reconstruction of BOF slag and alcohol wet magnetic separation recovery of iron phase, so as to efficiently recover and utilize BOF slag. In the early stages, the research group realized the transformation from weak magnetic iron oxide to strong magnetic magnesia-iron spinel phase in BOF slag through oxidation reconstruction experiments under different technological parameters. On this basis, different conditions in the magnetic separation process were adjusted to achieve the optimal iron recovery rate and grade in this paper. The experimental results show that, under the appropriate reconstruction temperature, with the increase of reaction time, gas flow rate and magnetic field intensity, the iron recovery will increase and the iron grade will decrease. The most suitable magnetic field intensity is 75 mT, the magnetic material yield is 46.00%, the iron grade is 29.10%, and the iron recovery is 64.12%. Compared with the initial steel slag, the iron grade increased by 8.22%, and the iron recovery increased by 46.38% compared with the direct magnetic separation without oxidation.

This paper aims to provide a better understanding regarding the effects of shot peening (SP), surface mechanical attrition treatment (SMAT), laser shock peening (LSP), surface mechanical rolling treatment (SMRT), and ultrasonic nanocrystal surface modification (UNSM) on the fatigue properties of metals in high-cycle fatigue (HCF) and very-high-cycle fatigue (VHCF) regimes. The work in this paper finds that SMRT and UNSM generally improve the high-cycle and very-high-cycle fatigue properties of metals, while SP, SMAT, and LSP can have mixed effects. The differences are discussed and analyzed with respect to the aspects of surface finish, microstructure and microhardness, and residual stress. SMRT and UNSM generally produce a smooth surface finish, while SP and SMAT tend to worsen the surface finish on metals, which is harmful to their fatigue properties. In addition to inducing a plastic deformation zone and increasing microhardness, surface treatments can also generate a nanograin layer and gradient microstructure to enhance the fatigue properties of metals. The distribution of treatment-induced residual stress and residual stress relaxation can cause mixed effects on the fatigue properties of metals. Furthermore, increasing residual stress through SP and SMAT can cause further deterioration of the surface finish, which is detrimental to the fatigue properties of metals.

Repairing the worn surfaces of wear-resistant workpieces, such as rollers, is one of the main application fields of surface treatment, but the repairing time is often not considered. In fact, the repairing time is very important, since it affects the repair quality and service life of wear-resistant workpieces. In this paper, a remelted gradient coating was prepared on a ductile iron plate by plasma transferred arc to simulate the repair treatment of wear-resistant workpieces. First, two positions in the remelted gradient coating were defined, i.e., the top of the gradient remelted layer was defined as M1, and the position where the hardness was two-thirds of the top of the remelting layer was defined as M2. Next, the time taken to repair the workpiece when the working surface reached M2 was proposed. Finally this method was verified by a comparative study on the microhardness and wear resistance of the M1 and M2. In this paper, the M2 was located at a ~0.5 mm from the top of the remelted gradient layer. The results show that the microhardness of the position of the M1 was higher than that of the position of the M2. However, the wear resistance of the M1 was worse, as confirmed by the wear rates. At the same time, cracks and fragments were observed on the worn surface of the M1 and M2 positions. Furthermore, the coefficient of friction (COF) of the position of M1 was noted to be first higher and subsequently lower than that of the position of M2, owing to the grinding ball entering the substrate. The abrasion mechanisms of both regions were observed to be complex, including oxidative wear, adhesive wear, delamination wear, and/or fretting wear. The experimental data indicate that it is feasible to determine the repair time according to the microhardness of workpieces.

Ti-6Al-4V (Ti64) alloy is one of the most widely used orthopedic implant materials due to its mechanical properties, corrosion resistance, and biocompatibility nature. Porous Ti64 structures are gaining more research interest as bone implants as they can help in reducing the stress-shielding effect when compared to their solid counterpart. The literature shows that porous Ti64 implants fabricated using different additive manufacturing (AM) process routes, such as laser powder bed fusion (L-PBF) and electron beam melting (EBM) can be tailored to mimic the mechanical properties of natural bone. This review paper categorizes porous implant designs into non-gradient (uniform) and gradient (non-uniform) porous structures. Gradient porous design appears to be more promising for orthopedic applications due to its closeness towards natural bone morphology and improved mechanical properties. In addition, this paper outlines the details on bone structure and its properties, mechanical properties, fatigue behavior, multifunctional porous implant designs, current challenges, and literature gaps in the research studies on porous Ti64 bone implants.