Search Results (11,697)

In this work, the interaction of an additively produced Ti-₄Al-₃V titanium alloy with a nickel superalloy tool and the features of the stir zone formation during friction stir processing have been studied. The stop-action technique was used to produce the samples to be studied using optical and scanning electron microscopy methods, as well as microhardness measurements. As a result, it was revealed that the tool, when moving, forms a pre-deformed area in front of it, which is characterized by a fine-grained structure. The presence of an interface layer between the workpiece material and primary fragmentation by the tool was revealed. It was demonstrated that the transfer of titanium alloy material occurs periodically following the ratio of feeding speed to tool rotation rate. Metal flow around the tool can occur in both laminar and vortex modes, as indicated by the tool material stirred into the transfer layer and used as a marker. Full article

The TiNbZr/(Ti, Nb)B metal matrix composite with 2.5 vol.% of borides was produced by vacuum arc melting. The composite was then cold-rolled to thickness strains of 10, 20, 50, or 80%. In the initial condition, the composite had a network-like microstructure consisting of the soft TiNbZr matrix (dendrites) and the rigid (Ti, Nb)B shell (interdendritic space). In comparison with the as-cast condition, cold rolling increased strength by 17–35%, depending on the thickness strain. After the maximum thickness strain of 80%, yield strength and ultimate tensile strength of the composite achieved 865 and 1080 MPa, respectively, while total elongation was found to be 5%. Microstructural analysis revealed that cold rolling to 50% resulted in the formation of crossing shear bands caused by the considerable difference in deformation behavior of the matrix and reinforcements. Cold rolling to 80% led to the formation of a lamellar-like microstructure comprising the interlayers of the (Ti, Nb)B phase between the TiNbZr laths. The maximum strain (80% cold rolling) shortened the (Ti, Nb)B fibers into nearly equiaxed particles, with a length to diameter ratio of ~2. Full article

Since steel cleanness comes to the fore of steel producers worldwide, it is necessary to understand the formation mechanism and modification of non-metallic inclusions (NMIs) in more detail. One central point is the identification of the source of especially interfering NMIs to prevent their evolution in the future. The present study applies two approaches to determine the source of NMIs in Ti-stabilized ultra-low carbon (ULC) steels—the active and the passive tracing. Both approaches are applied to an industrial experiment. The active tracing technique is focused on investigating the clogging layer formation in submerged entry nozzles and, hence, the origin of alumina particles. This method adds rare earth elements (REEs) directly to the melt to mark pre-existing deoxidation products at a certain point of the steelmaking process. The main concern of the passive method, the so-called REE fingerprint, is the determination of the source of mesoscopic NMIs. For the REE fingerprint, the pre-existing concentration of REEs in different potential sources and the investigated NMIs are measured by using an inductively coupled plasma mass spectrometer (ICP-MS). The resulting patterns are compared after normalizing the contents to chondrites, and the NMIs’ origins are identified. Concerning the EDS analysis and the resulting patterns from the REE fingerprint, the mold slag and, respectively, the casting powder were the sources of the investigated NMIs. Full article

For the present, it is difficult to obtain thermodynamic data for binary liquid alloys by experimental measurements. In this study, the molecular dynamics processes of the binary liquid alloys Pb50-Sn50, Al50-Sn50, and In50-Zn50 were simulated by using the ab initio molecular dynamics (AIMD) principle, and their partial radial distribution functions (PRDF) were obtained at different simulation steps. Combined with the relevant binary parameters of the Molecular Interaction Volume Model (MIVM), Regular Solution Model (RSM), Wilson Model, and Non-Random Two-Liquid (NRTL) models. The integral terms containing the PRDF were computed using the graphical integration method to obtain the parameters of these models, thus estimating their activity and molar excess Gibbs energy. The total average relative deviations (ARD) of the activity and molar excess Gibbs energy estimates of the four models for the binary liquid alloys Pb50-Sn50, Al50-Sn50, and In50-Zn50 at full concentration when the PRDF is obtained by the symmetry method are MIVM: 21.59% and 59.35%; RSM: 21.63% and 60.27%; Wilson: 24.27% and 86.7%; NRTL: 23.9% and 83.24%. When the PRDF is obtained by the asymmetric method: MIVM: 22.86% and 68.08%; RSM: 32.84% and 68.66%; Wilson: 25.14% and 82.75%; NRTL: 24.49% and 85.74%. This indicates that the estimation performance of the MIVM model is superior to the other three models, and the symmetric method performs better than the asymmetric method. The present study also derives and verifies the feasibility of Sommer’s equation for estimating the molar excess Gibbs energy and activity of binary liquid alloy systems in the Miedema model by using different equations of enthalpy of mixing versus excess entropy given by Tanaka, Ding, and Sommer. The total ARD of Tanaka, Ding, and Sommer’s relational equations in the Miedema model for estimating the activities and molar excess Gibbs energies of the binary liquid alloys Pb-Sn, Al-Sn, and In-Zn are 3.07% and 8.92%, 6.09% and 17.1%, and 4.1% and 14.77%. The results indicate that the estimation performance of the Miedema model is superior to the other four models. Full article

Solid-state additive friction stir deposition (AFSD) is a thermomechanical-based additive manufacturing technique. For this study, AFSD was utilized to produce aluminum alloy 6061 (AA6061) blocks with varying layer thicknesses (1 mm, 2 mm, and 3 mm). The mechanical properties were assessed through uniaxial tensile tests and Vickers microhardness measurement, and statistical analysis was employed to investigate differences among data groups. The results revealed that the deposition layer thickness influences tensile properties in the building (Z) direction, while the properties in the X and Y directions showed minor differences across the three AFSD blocks. Furthermore, variations in tensile properties were observed depending on the sample orientation in the AFSD blocks and its depth-wise position in the part in the building direction. The microhardness values decreased non-linearly along the building direction, spread across the width of the part’s cross-section, and highlighted that the deposition layer thickness significantly affects this property. The 1 mm block exhibited lower average microhardness values than the 2 mm and 3 mm blocks. The temperature histories and dynamic heat treatment are influenced by the deposition layer thickness and depend on the location of the point being studied in the part, resulting in variations in the microstructure and mechanical properties along the building direction and across the part’s width. Full article

The elimination and retrieval of slag produced during the hot-dip galvanizing process are crucial in reducing plating defects and enhancing economic efficiency. Hot-dip galvanizing slag can be separated and purified efficiently by using graphite carbon felt filtration in a supergravity field. The effects of the gravity coefficient (G), separation temperature (T), and separation time (t) on the separation efficiency were investigated. Under the optimal conditions as G = 300, T = 460 °C, and t = 120 s, these conditions yielded filtered zinc with 0.022 wt% Fe and 1.097 wt% Al. The separation efficiencies achieved were 87% for the acquisition ratio of filtered zinc (A_Zn), 93.67% for the recovery ratio of zinc (R_Zn), and 96.01% for the loss ratio of iron (L_Fe). Based on these laboratory findings, an amplified centrifugal separation apparatus was conceptually designed for future online separation and recycle of zinc slag on an engineering scale. The filtered zinc obtained from this apparatus contained 0.027 wt% Fe and 1.844 wt% Al, while the recovery ratio of zinc (R_Zn) and the loss ratio of iron (L_Fe) achieved 85.97% and 95.47%, respectively. Full article

Radiation hardening is studied for stainless austenitic and ferritic–martensitic chromium steels after ion and neutron irradiation at various temperatures. Austenitic and ferritic–martensitic steels irradiated up to 30 dpa in various nuclear reactors and ion accelerators are studied at various temperatures. A change in Vickers microhardness is used as the radiation hardening parameter. A methodology is developed that allows one to determine the ion irradiation parameters, which ensure the radiation hardening of ferritic–martensitic and austenitic steels, as close as possible to the radiation hardening of the same steels under neutron irradiation. A transferability function is introduced to connect the irradiation temperatures for ion and neutron irradiation that provides the same radiation hardening. On the basis of the obtained experimental data, after ion and neutron irradiation the transferability functions are determined for the investigated austenitic and ferritic–martensitic steels, which connect the temperatures for ion and neutron irradiation and provide the same radiation hardening at a given damage dose. Full article

The present study focuses on the mechanical behaviour and formability of the aluminium alloy 2024-T3 in sheet form with a thickness of 0.8 mm. For this purpose, tensile tests at quasi-static and intermediate strain rates were performed using a universal testing machine, and high strain rate experiments were performed using a split Hopkinson tension bar (SHTB) facility. The material’s anisotropy was investigated by considering seven different specimen orientations relative to the rolling direction. Digital image correlation (DIC) was used to measure specimen deformation. Based on the true stress–strain curves, the alloy exhibited negative strain rate sensitivity (NSRS). Dynamic strain aging (DSA) was investigated as a possible cause. However, neither the strain distribution nor the stress–strain curves gave further indications of the occurrence of DSA. A higher deformation capacity was observed in the high strain rate experiments. The alloy displayed anisotropic mechanical properties. Values of the Lankford coefficient lower than 1, more specifically, varying between 0.45 and 0.87 depending on specimen orientations and strain rate, were found. The hardening exponent was not significantly dependent on specimen orientation and only moderately affected by strain rate. An average value of 0.183 was observed for specimens tested at a quasi-static strain rate. Scanning electron microscopy (SEM) revealed a typical ductile fracture morphology with fine dimples. Dimple sizes were hardly affected by specimen orientation and strain rate. Full article

Metastable β-type Ti alloys that undergo stress-induced martensitic transformation and/or deformation twinning mechanisms have the potential to simultaneously enhance strength and ductility through the transformation-induced plasticity effect (TRIP) and twinning-induced plasticity (TWIP) effect. These TRIP/TWIP Ti alloys represent a new generation of strain hardenable Ti alloys, holding great promise for structural applications. Nonetheless, the relatively low yield strength is the main factor limiting the practical applications of TRIP/TWIP Ti alloys. The intricate interplay among chemical compositions, deformation mechanisms, and mechanical properties in TRIP/TWIP Ti alloys poses a challenge for the development of new TRIP/TWIP Ti alloys. This review delves into the understanding of deformation mechanisms and strain hardening behavior of TRIP/TWIP Ti alloys and summarizes the role of β phase stability, α″ martensite, α′ martensite, and ω phase on the TRIP/TWIP effects. This is followed by the introduction of compositional design strategies that empower the precise design of new TRIP/TWIP Ti alloys through multi-element alloying. Then, the recent development of TRIP/TWIP Ti alloys and the strengthening strategies to enhance their yield strength while preserving high-strain hardening capability are summarized. Finally, future prospects and suggestions for the continued design and development of high-performance TRIP/TWIP Ti alloys are highlighted. Full article

Today, parts made by additive manufacturing (AM) methods have found many applications in the medical industry, the main reasons for which are the ability to custom design and manufacture complex structures, their short production cycle, their ease of utilization, and on-site fabrication, leading to the fabrication of next-generation intricate patient-specific biomedical implants. These parts should fulfill numerous requirements, such as having acceptable mechanical strength, biocompatibility, satisfactory surface characteristics, and excellent corrosion and wear performance. It was known that AM techniques may lead to some uncertainties influencing part properties and causing significant evaluation conflicts in corrosion outcomes. Meanwhile, the corrosion and wear behavior of additively manufactured materials are not comprehensively discussed. In this regard, the present work is a review of the state-of-the-art knowledge dedicated to reviewing the actual scientific knowledge about the corrosion and wear response of additively manufactured biomedical components, elucidating the relevant mechanism and influential factors to enhance the performance of AM-manufactured implants specifically for the physiological human body fluids. Furthermore, there is a focus on the use of reinforced composites, surface engineering, and a preparation stage that can considerably affect the tribocorrosion behavior of AM-produced parts. The improvement of tribocorrosion performance can have a key role in the production of advanced AM implants and the present study can pave the way toward facile production of high-throughput AM biomedical parts that have very high resistance to corrosion and wear. Full article

Printed circuit boards (PCBs) make up 3 to 5% of all electronic waste. The metal content of spent PCBs can reach 40%. They usually contain valuable metals, such as Ag, Au, and Pd, as well as other metals such as Cu, Sn, Pb, Cd, Cr, Zn, Ni, and Mn. However, the metallic part of a whole PCB is 40–60% including the Cu layers between the fiberglass–polymer layers. The paper describes the economics of the valuable metal (Ag, Au, Pd)-containing concentrate preparation from a raw PCB. We considered the influence of the pre-treatment method of PCBs before the extraction of valuable metals on the extraction self-cost change. The disintegration method is based on the high-energy impact of the particles of the material to be ground, thus causing the separation of the metallic components of the PCB. In the course of the work, single and double direct grinding using the method of disintegration was studied. For the calculation, the test batch of 10,000 kg of two types of PCB was taken for estimation of the self costs and potential profit in the case of complete valuable metals (Ag, Au, Pd) plus Cu extraction. It was shown that from 10,000 kg of studied PCB, it is possible to obtain 1144 and 1644 kg of metal-rich concentrate, which should be further subjected to electro-hydrochlorination for metals leaching. The novelty of this research lies in the fact that a technical and economic analysis has been carried out on a newly developed combined technology for processing electronic waste. This included mechanical processing and electrochemical leaching with the help of the active chlorine that is formed in situ. The real (not specially selected or prepared) waste PCBs were used for the process’s economical efficiency evaluation. The main findings showed that despite the high content of Cu in the studied PCBs, the commercial value was insignificant in relation to the total income from the Ag, Au, and Pd sale. A correlation was established between the self-cost decrease after separative disintegration of PCBs by metal content increase (by specific metals such as Au, Ag, Pd, and Cu) with the metal potential yield after extraction. Full article

Plan view pattern control (PVPC) is a highly effective means to improve the rectangularization of products and increase the yield of plate mills. By optimizing the parameters of PVPC, the effect of PVPC can be further improved. In this paper, a digital model for predicting and controlling crop patterns of plates is proposed based on the radial basis function (RBF) neural network optimized by the dung beetle optimizer (DBO) algorithm. Machine vision technology is used to obtain a digital description of the crop pattern of the rolled plates. An automatic threshold adjustment algorithm is proposed for the image processing of plate pattern photos during the rolling process. The error between the pattern data calculated through machine vision technology and the measured pattern data does not exceed 3 mm. The spread parameters of the RBF are optimized using DBO, and the digital model structure is established. The goodness of fit (R²) and the mean absolute error (MAE) are used as evaluation indicators. The results show that the digital model established based on DBO-RBF has good predictive and control performance, realizing intelligent prediction of the crop pattern of plates and the parameter optimization of PVPC. In practical applications, the crop cutting loss area of irregular deformation at the end of the plate can be reduced by 31%. Full article

In the petroleum industry, the casing steel is fixed with a cement sheath to ensure reliable service in demanding conditions characterized by high temperature, high pressure, and exposure to multiple types of media. After the hydration of the cement, a porous material is produced with a highly alkaline solution filling the pores, commonly referred to as the pore solution. The casing will form a protective passive film when in contact with a highly alkaline pore solution. Nevertheless, once the cement sheath cracks, chloride ions in the stratum will pass through the cement sheath to the surface of the casing. When chloride ions accumulate to a certain concentration, the passive film will be destroyed, without exerting a protective influence on the substrate. After chloride ions come into direct contact with the casing, the casing is prone to severe failure due to corrosion perforation. The casing failure can cause a blowout outside the casing and even scrapping of the oil well. Controlling casing corrosion and ensuring casing integrity relies on understanding the critical chloride ion concentration that can cause the degradation of the passive film. Therefore, to assess the electrochemical properties and analyze the damage process of the passive film under varying chloride ion concentrations, several characterization techniques were employed. These included potential–time curves (E-t), polarization curves, electrochemical impedance spectroscopy (EIS), and Mott–Schottky curves. In addition, the composition of the passive film on the surface of the P110 casing steel was qualitatively analyzed using X-ray photoelectron spectroscopy (XPS). To further understand the surface morphology of the P110 casing steel, scanning electron microscopy (SEM) was used. Full article

The production reality of sheet steels from casting to the end product is such that in the cases of ultra- and advanced high-strength steels, we have to deal with the segregation of elements on macro- and microlevels. Both can have a significant impact on the microstructure formation and resulting properties. There are several production stages where it can influence the transformations, i.e., casting, hot rolling process and annealing after cold rolling. In the present work, we focus on the latter, and more specifically, the transformation from ferrite–cementite to austenite, especially the nucleation process, in cold-rolled material. We vary the levels of two substitutional elements, Mn and Si, and then look in detail at the microsegregation and nucleation processes. The classical nucleation theory is used, and both the chemical driving force and strain energy are calculated for various scenarios. In the case of a high Mn and high Si concentration, the nucleation can thus be explained. In the cases of high Mn and low Si concentrations as well as low Mn alloys, more research is needed on the nuclei shapes and strain energy. Full article

Nickel-based alloys that contain chromium are widely used in corrosion-resistant applications in industry, but they are sensitive to the environment when the passive chromium oxide layer is damaged. In Ni600 and Ni625 alloys, precipitates can deplete the surface layer of chromium oxide. To better characterize and analyze the nickel alloy surfaces and their chromium carbides, chemical etching with different etchants and electrolytic etching were applied to sample surfaces. This paper revealed their efficacy in etching various carbides within the nickel alloys, and orange phases ranging from 2 to 20 μm in optical micrographs were identified as titanium-containing compounds. Carbides located on the grain boundaries were determined to be Cr23C6 and were surrounded by chromium-depleted zones. The findings and figures in this paper provide a more intuitive reference for future analysis of carbides and titanium nitrides, enhancing the understanding of their impact on the corrosion resistance of these alloys, which will not only contribute to the material science field but also aid in developing the Ni-based alloys for industrial applications. Full article