Metals, Volume 14, Issue 6 (June 2024) – 59 articles

Physical vapor deposition (PVD) coatings could affect the friction performance at the contact interface between Ti₂AlNb alloy parts and tool couples. Suitable coating types could improve the friction properties of Ti₂AlNb alloy while in contact with WC/Co carbide. In this study, the linear reciprocating pin–disc friction tests between the Ti₂AlNb alloy and the WC/Co carbide tool couple, with the sole variation of the PVD CrAlN/(CrAlB)N/CrAlN coating were conducted within the temperature range of 25–600 °C. The antifriction properties of the Ti₂AlNb alloy were estimated using the time-varied friction coefficients, the alloy wear rate, worn surface topography, worn surface element, and wear mechanism analysis. The results showed that the PVD CrAlN/(CrAlB)N/CrAlN coating could decrease the average friction coefficient and alloy wear rate compared to the uncoated WC/Co carbide couple. The apparent adhesive wear and abrasive wear of the Ti₂AlNb alloy could be improved due to the PVD coating at evaluated temperatures. The PVD CrAlN/(CrAlB)N/CrAlN coating could be utilized to improve the antifriction properties of the Ti₂AlNb alloy, which may be deposited on the cutting tool to improve the machining performance of Ti₂AlNb alloys in future aerospace machining industry. Full article

Heat treatment is the critical step in achieving a refined microstructure and enhanced mechanical properties of TiAl-based alloys. This study investigated the influence of heat treatment temperature, cooling method, and heat treatment time on the microstructure and mechanical properties of an extruded powder metallurgy Ti-48Al alloy, and achieved the control of fully lamellar fine microstructures and the enhancement of performance through a simple heat treatment, rather than the traditional approach of homogenization followed by heat treatment. The results indicate that the heat treatment temperature determines the type of microstructure, while the cooling rate dictates the lamellar width. As the heat treatment temperature was increased from the two-phase region to the α single-phase region, the microstructure transitioned from duplex to near lamellar, and the alloy strength initially increased and then decreased, influenced by both the lamellar colony ratio and grain size. A rapid cooling rate (water quenching) induces a non-diffusive massive phase transformation, whereas a slow cooling rate (air cooling) gradually forms α₂/γ lamellar colonies. Therefore, a suitable heat treatment regime for the powder metallurgy Ti-48Al alloy was determined to be 1340 °C/5 min/air cooling. The microstructure of the alloy was near lamellar, consisting of lamellar colonies approximately 50 μm and a small number of γ equiaxed grains of about 10 μm. Subsequently, the alloy exhibited a room temperature tensile strength of 784 MPa and a yield strength of 763 MPa, representing improvements of 17.0% and 38.7% over the extruded alloy, respectively. This research provides a reference for establishing a heat treatment process for powder metallurgy TiAl alloys. Full article

This article focuses on investigating the effect of printing direction on the mechanical properties of Cu–10Sn alloys prepared by laser powder bed fusion (LPBF) technology. Specimens with different forming angles (0°, 15°, 30°, 45°, 60°, 75°, and 90°) were fabricated using LPBF technology, and their mechanical properties were systematically tested. During the testing process, we used an Instron 5985 electronic universal material testing machine to accurately evaluate the mechanical properties of the material at a constant strain rate of 10⁻³/s. The experimental results showed that the mechanical properties of the specimens were the best when the test direction was perpendicular to the growth direction (i.e., the 0° direction). As the angle between the test direction and the growth direction increased, the mechanical properties of the material exhibited a trend of first decreasing, then increasing, and then decreasing again, which was consistent with the direction of the microtexture of the specimens. The root cause of this trend lies in the significant change in the stress direction borne by the columnar crystals under different load directions. Specifically, as the load direction gradually transitions from being parallel to the columnar crystals to perpendicular to them, the stress direction of the columnar crystals also shifts from the radial direction to the axial direction. Due to the differences in the number and strength of grain boundaries in different stress directions, this directly leads to changes in mechanical properties. In particular, when the specimen is loaded in the radial direction of the columnar crystals, the grain boundary density is higher, and these grain boundaries provide greater resistance during dislocation migration, thus significantly hindering tensile deformation and enabling the material to exhibit superior tensile properties. Among all the tested angles, the laser powder bed fusion specimen with a forming angle of 0° exhibited the best mechanical properties, with a tensile strength of 723 MPa, a yield strength of 386 MPa, and an elongation of 33%. In contrast, the specimen with a forming angle of 90° performed the worst in terms of tensile properties. These findings provide important insights for us to deeply understand the mechanical properties of Cu–10Sn alloys prepared by LPBF. Full article

In situ X-ray diffraction (XRD) was used to compare nitrogen low-energy ion implantation (LEII) into austenitic stainless steel 316Ti and super austenitic stainless steel 904L. While the diffusion and layer growth were very similar, as derived from the decreasing intensity of the substrate reflection, strong variations in the observed lattice expansion—as a function of orientation, the steel alloy, and nitriding temperature—were observed. Nevertheless, a similar resulting nitrogen content was measured using time-of-flight secondary ion mass spectrometry (ToF-SIMS). Furthermore, for some conditions, the formation of a double layer with two distinct lattice expansions was observed, especially for steel 904L. Regarding the stability of expanded austenite, 316Ti had already decayed in CrN during nitriding at 500 °C, while no such effect was observed for 904L. Thus, the alloy composition has a strong influence only on the lattice expansion and the stability of expanded austenite—but not the diffusion and nitrogen content. Full article

Rare earth elements (REEs) are key materials for the development of renewable energy devices such as high-power magnets for wind turbines, electric vehicles, or fuel cells for hydrogen generation, aiming to fulfill the objectives of the European Green Deal for a carbon-neutral economy. The increased demand for REEs and their criticality strongly require the improvement of their extraction technologies from primary resources and the enhancement of their circularity reuse rate from secondary resources. The aim of this paper is to focus attention on the possibilities offered by emerging methods such as microwave (MW) treatment and mechanochemistry in waste electric and electronic equipment (WEEE) processing and the reuse of end-of-life (EoL) magnets, directed toward the tailoring of rational REE material flows. The discussed investigation examples explore some key features of conventional and new methods for efficient, environmentally friendly, and scalable REE extraction and reuse, with the final goal of producing recycled NdFeB powders, with potential use in the redesign and fabrication of new REE-based magnets. Full article

Recycling lithium-ion batteries provides sustainable raw materials. Crushing and separation are necessary for extracting metals, like lithium, from batteries. Crushing a battery carries a risk of fire or explosion. Fully discharging the battery is crucial for safe production. Discharging batteries in a salt solution is a simple and cost-effective large-scale process. However, it is important to note that there is a potential risk of corrosion and loss of battery elements when batteries are immersed in a salt solution. The purpose of this study is to investigate the effectiveness of two distinct methodologies at enhancing the voltage drop of a cylindrical battery when immersed in a salt solution while preventing corrosion. These techniques involve the application of iron and copper accelerators. A 20 wt.% salt water solution was chosen based on the research of several researchers. As the current flows through the metal parts, it encounters electrical resistance and forms an electric circuit with the electrolyte solution. This interaction converts electrical energy into various physical–electrical–electrochemical phenomena, leading to a decrease in battery voltage. Research revealed that the battery can be discharged up to 100% within 4 h without causing corrosion to its components. Another point to note is that if copper conductors are used, it is possible to decrease the battery voltage by around 90% within 8 h. The gap between the copper conductor and the battery had a direct impact on the battery’s discharge rate. Reducing the distance significantly increased the discharge rate, as confirmed by experimental evidence. This discharge mechanism was thoroughly described in a schematic, and, to further explain the electrochemical reaction, the Pourbaix diagram was utilized for both the Fe-Na-Cl and Cu-Na-Cl systems. Moreover, our theoretical predictions were validated through a chemical and mineralogical analysis of the precipitates that formed in the solution. Full article

This paper aims to investigate the response and local buckling of locally sharp-notched C2700 brass circular tubes (LSN C2700 brass circular tubes) under cyclic bending loads. The study considers four different notch orientations (0°, 30°, 60°, and 90°) and five distinct notch depths (0.2, 0.4, 0.6, 0.8, and 1.0 mm). The results reveal that notch orientation and depth exert minimal impact on the moment–curvature relationship, leading to the formation of stable loops. The ovalization–curvature graphs demonstrate a trend of symmetry, serration, and growth with an increasing number of bending cycles. Additionally, larger notch orientations or smaller notch depths result in reduced ovalization. Furthermore, the double logarithmic coordinates of controlled curvature–number of cycles necessary to induce local buckling reveal five non-parallel lines representing different notch depths when the notch orientation is fixed. Finally, by adopting the formulas for smooth tubes and for locally sharp-notched 304 stainless steel circular tubes (LSN SS304 circular tubes), this study adjusts the related material parameters accordingly. These modifications effectively describe the controlled curvature–number of cycles necessary to induce local buckling for LSN C2700 brass circular tubes with different notch orientations and depths under cyclic bending, demonstrating reasonable agreement with the experimental results. Full article

The present study aims to evaluate the effect of up to 3 wt.% Nd on pure Zn in terms of physical properties and in vitro analysis. The use of Nd as an alloying element is due to its relatively adequate biocompatibility and its potential capability to reinforce metals with a hexagonal close-packed (HCP) crystal structure, such as Mg and Zn. The microstructural assessment was executed using X-ray diffraction analysis, along with optical and scanning electron microscopy. The mechanical properties were evaluated by hardness and tensile strength testing. The corrosion performance in simulated physiological environments was examined by means of immersion tests, potentiodynamic polarization, and impedance spectroscopy using phosphate-buffered saline (PBS) solution. Cytotoxicity assessment was carried out by indirect cell viability analysis according to the ISO 10993-5/12 standard using Mus musculus 4T1 cells, which are known to be very sensitive to toxic environments. The obtained results clearly highlighted the reinforcing effect of Nd in Zn-base alloys, mainly due to the formation of a secondary phase: NdZn_5. This strengthening effect was acquired without impairing the inherent ductility and corrosion performance of the tested alloys. The cytotoxicity assessment indicated that the addition of Nd has a strong favorable effect on cell viability, which stimulates the inherent anti-inflammatory characteristics of Zn. Full article

Oxide inclusions in Ni-based superalloys play a crucial role in determining their mechanical properties, oxidation resistance, and corrosion resistance at high temperatures. In this paper, the source and formation mechanism of different types of oxide inclusions in a high-aluminum Ni-based superalloy were systematically studied. An automatic field emission scanning electron microscope equipped with an energy dispersive spectrometer and a self-designed superalloy inclusion analysis standard was utilized to quantitatively reveal the oxide inclusion characteristics of the high-aluminum Ni-based superalloy prepared via vacuum induction melting (VIM) and vacuum induction remelting (VIR) processes. The experimental results indicate that the typical oxide inclusions in the Ni-based superalloy before the VIR process are irregular MgO·Al₂O₃ inclusions with sizes of less than 2 μm. After the VIR process, the typical oxide inclusions in the Ni-based superalloy are also MgO·Al₂O₃ inclusions. However, these oxide inclusions can be classified into three categories: (i) endogenous irregular MgO·Al₂O₃ inclusions, less than 4.3 μm in size, inherited from the master alloy; (ii) several hundred-micron film-like MgO·Al₂O₃ inclusions generated as interface reaction products between the MgO crucible and melts; and (iii) millimeter-scale MgO·Al₂O₃ inclusions and several tens of microns of MgO inclusions from the exfoliation of the MgO crucible matrix. Full article

Hook defects are common in FSW butt–lap joints, resulting in a significant safety hazard for the parts that suffer cyclic load. In this study, a numerical simulation based on the Euler–Lagrange coupling method was conducted to investigate the formation process of hook defect during FSW of AA6005-T6 aluminum alloy. The simulation results were validated with experimental data, showing good agreement. The formation of the hook defect is caused by the threads on the probe promoting material flow in the thickness direction. In order to further study the effect of probe morphology on hook defects, three kinds of probe models with different morphology were established and numerically simulated by the CEL method. The simulation results show that all three kinds of probes can reduce the size of the hook. The welds obtained using the left–left probe (LLP) and the three-plane probe (TPP) both exhibit void defects, while the welds obtained by a right–left probe (RLP) have no internal void defects. The experimental results show the same characteristics as the simulation results, and the size of the hook defect is reduced to 58 μm. Full article

The structural design of steel–titanium composite plates significantly affects their corrosion resistance. To investigate the impact of defects of different shapes and sizes on the corrosion behavior of steel–titanium composite plates, this study designed six types of defects and conducted a series of characterization tests. The results showed that due to the galvanic interaction between carbon steel and titanium alloy, small defects initially accelerate corrosion, resulting in 50% to 200% more corrosion weight loss compared to large defects. However, in the later stages of immersion, the corrosion rate of small defects decreased by up to 35%, which was attributed to the accumulation of protective corrosion products. Additionally, there is an inverse relationship between the corrosion rate and the thickness ratio of the composite plate. The reduction in the area of Q345B also results in additional corrosion loss of up to 32%. Full article

In this work, two types of nanoporous alumina membranes were prepared and tested. Structural features of the samples obtained by using different acids were investigated by scanning electron microscopy (SEM). And further SEM-images were analyzed by different types of fractal dimension estimation methods. The transmission and scattering of accelerated He⁺ ions were studied in experiments on the ion irradiation of dielectric channels based on porous alumina. An ion accelerator was used as a source of the He⁺ beam with an energy of 1.7 MeV. Ion scattering was studied by Rutherford backscattering spectrometry. Helium transition through nanoporous alumina at various angles between the normal to the sample and the beam direction were observed. It is shown that the porous structure of anodic aluminum oxide is excellent as a dielectric matrix of nanocapillaries. Owing to the small angle scattering, it allows for the transportation of the accelerated charged particles through the dielectric capillaries, and, as a result, the localization of high energy ion irradiation effects. Additionally, according to the transmission of UV–V is spectra, the energy gaps of samples obtained were calculated. Full article

Flat-rolled steel sheets are one of the major products of the metal industry. Strip steel’s production quality is crucial for the economic and safety aspects of humanity. Addressing the challenges of identifying the surface defects of strip steel in real production environments and low detection efficiency, this study presents an approach for strip defect detection based on YOLOv5s, termed SDD-YOLO. Initially, this study designs the Convolution-GhostNet Hybrid module (CGH) and Multi-Convolution Feature Fusion block (MCFF), effectively reducing computational complexity and enhancing feature extraction efficiency. Subsequently, CARAFE is employed to replace bilinear interpolation upsampling to improve image feature utilization; finally, the Bidirectional Feature Pyramid Network (BiFPN) is introduced to enhance the model’s adaptability to targets of different scales. Experimental results demonstrate that, compared to the baseline YOLOv5s, this method achieves a 6.3% increase in mAP₅₀, reaching 76.1% on the Northeastern University Surface Defect Database for Detection (NEU-DET), with parameters and FLOPs of only 3.4MB and 6.4G, respectively, and FPS reaching 121, effectively identifying six types of defects such as Crazing and Inclusion. Furthermore, under the conditions of strong exposure, insufficient brightness, and the addition of Gaussian noise, the model’s mAP₅₀ still exceeds 70%, demonstrating the model’s strong robustness. In conclusion, the proposed SDD-YOLO in this study features high accuracy, efficiency, and lightweight characteristics, making it applicable in actual production to enhance strip steel production quality and efficiency. Full article

This paper considers the impact of copper mining-influenced water and metallurgical wastewater on the surface water in the Bor area, Serbia. Sampling, realized through the four campaigns (2020–2021), confirmed that both types of water, discharged without appropriate treatment in the Bor River, had a signific impact on the concentration of metal ions, pH and electrical conductivity on the watercourse in the Bor area. The highest concentrations of the following metal ions, Cu-271 mg/L, As-25991 μg/L, Ni-13856 μg/L, Cd-2627 μg/L, and Pb-2855 μg/L, were registered in the metallurgical wastewater samples. After changes occurred in the copper production process by stopping the discharge of untreated wastewater into the Bor River, the concentrations of monitored elements were drastically decreased. In the period 2022–2024, the concentration values for Cu, As and Pb ions were below the maximum allowable value, and the concentration values of Ni and Cd ions were also decreased. The values for pH and electrical conductivity were in the maximum allowable range. The return of wastewater to the copper production process would lead to both a reduction in the primary water consumption and reduction in the negative impact on the environment. Full article

The effects of electro-pulse on microstructure and mechanical properties of Al-Cu-Mn-Zr-V alloy were investigated, and the ageing mechanism was analyzed. As the current density increases, the size and quantity of precipitates gradually transit from continuous aggregation to dispersion at grain boundaries, and the mechanical properties are improved. When the current density is 15 A·mm⁻², the precipitates are smallest and the mechanical properties are best. The tensile strength is 443.5 MPa and the elongation is 8.1%, which are 51.7% and 42.1% higher than those of conventional ageing treatment, respectively. Once the current density exceeds 15 A·mm⁻², the precipitates will increase again and gather at grain boundaries, and the mechanical properties also decrease. An additional electrical free energy arising from an electro-pulse provides thermodynamic and kinetic conditions for the ageing precipitation of second phases. The electro-pulse can enhance the ageing diffusion coefficient, being improved by 34 times for 15 A·mm⁻². The electro-pulse improves the nucleation rate and decreases the critical nucleation radii of second phases. However, it also accelerates the grain growth, making the second phases become coarse. An electro-pulse with a current density of 15 A·mm⁻² can rapidly nucleate the second phase at 463 K while the precipitates are relatively small after growth. Full article

The influence of elevated temperatures and strain rate on the mechanical and structural properties of steel 42CrMo4 were analysed experimentally in this paper. The experiments were based on uniaxial tension and compression tests at high temperatures between 700 °C and 1100 °C and strain rates in the range 0.0018–0.1 s⁻¹. The influence of temperature and strain rate on yield stress, strain to fracture, hardness, structural changes, and fracture characteristics were analysed. The non-uniformity of deformations obtained at different values of the strain rate and temperature were also analysed. Analysis by scanning electron microscopy showed the ductile behaviour of the material. The degree of damage in the material caused by the presence of cavities increased with increasing deformation temperature. For all the presented deformation conditions, the formation of the fracture through the ductile fracture mechanism resulted from localized necking and the coalescence of microvoids. By increasing the deformation temperature and reducing the strain rate, the fracture behaviour of 42CrMo4 steel can be improved. Full article

The alloy element Nb plays an important role in improving the performance of zirconium alloys in nuclear reactors. The effect mechanism of Nb doping on mechanical and thermodynamic properties was investigated using experimental and theoretical methods. The results of this study showed us that Nb doping refines grains and enhances hardness. The hardness increases from 2.67 GPa of pure Zr to 2.99 GPa of Zr1.5Nb. Depending on the first-principles calculations, the hardness decreases with the increase in the Nb concentration in the Zr matrix, namely from 2.45 Gpa of pure Zr to 1.78 GPa of Zr1.5Nb. If the first-principles calculations indicate that the hardness decreases with the increase in the Nb concentration in the Zr matrix, grain refinement or defects could play a major role in the increase in hardness. Furthermore, regarding the effect of Nb doping on thermal expansion coefficients, the increase in Nb content causes the thermal expansion coefficients to decrease, which might stem from the strong binding energy between Nb and Zr atoms. The thermal conductivities of three samples show similar changing trends, indicating that thermal conductivity begins to decrease at room temperature and reaches a minimum value of around 400 °C. The thermal conductivity of pure zirconium samples is consistently higher, is more obvious than that of Nb-doped samples in the test range, and decreases with an increase in the doping concentration. The possible reasons for this might stem from the distortion of the Zr matrix due to Nb substitution doping and grain refinement, both of which cause phonon propagation scattering and thus hinder the propagation of phonons. The results obtained herein may be useful for the development of advanced nuclear fuels and waste forms that utilize zirconium in applications beyond their current usage. Full article

In this paper, Cr (8 μm)/Ta (3 μm) bilayer coatings deposited on a Zr-1Nb alloy substrate were investigated and compared with a Cr-coated alloy under high-temperature steam oxidation at 1200–1400 °C. The bilayer coatings with α- and β-Ta interlayers were obtained by magnetron sputtering. The Cr/Ta-coated samples were studied using scanning electron microscopy (SEM), X-ray diffraction (XRD), and optical microscopy (OM). The coating with an α-Ta interlayer can suppress the interdiffusion of chromium and zirconium more effectively up to 1330 °C in comparison with the coating having a β-Ta interlayer. The weight gain of the α-Ta-coated samples after oxidation at 1200 °C for 2000 s was 5–6 times lower than that of the Cr-coated Zr alloy samples. Oxidation at 1400 °C for 120 s showed no significant difference in the weight gain of the Cr- and Cr/Ta-coated Zr-1Nb alloy samples. It was shown that the effect of suppression of Zr-Cr interdiffusion by the barrier coating (α- and β-Ta) is only short-term. Full article

Friction stir processing (FSP), a severe plastic deformation process, was applied on commercially pure Ti to obtain an improved microstructure. The process yielded a refined microstructure and higher mechanical properties at room temperature (RT). Yet the microstructure was found to contain bright bands demonstrating high hardness values of about 500 HV. High-resolution scanning electron microscopy (HRSEM) as well as electron backscattering diffraction (EBSD) analysis indicated that these bands were composed of extra-fine equiaxed α-Ti grains with an average radius of 1–2 microns. In addition, a retained β phase was detected at the boundaries of these α-Ti grains, together with a small quantity of separate β grains. The results of a fractography study conducted on broken tensile specimens showed that the material that underwent FSP was free of defects and that the fracture started at these bands. It is proposed that these bright bands are due to excessive deformation occurring during the processing stage, leading to an accelerated dynamic recrystallization (DRX) process. In turn, these heavy deformation regions act as a strengthening constituent, making the material superior to the parent material as far as its mechanical RT properties are concerned. Consequently, this means that the FSP of CP-Ti has the potential to serve as an industrial means of improving the mechanical properties of the material. Full article

In the present study, microstructure and cyclic tensile tests were used to measure the superelastic responses of Fe_40.95Ni₂₈Co₁₇Al_11.5Ta_2.5B_0.05 (at.%) shape memory alloys after 97% cold rolling. Cold-rolled samples underwent annealing heat treatment (1250 °C/1 h) followed by quenching in water or aging heat treatment (700 °C/6 h and 700 °C/12 h) followed by quenching in water. The microstructure results showed that the average grain size increased from 210 μm to 1570 μm as annealing times increased from 0.5 h to 1 h. X-ray diffraction (XRD) spectra for FeNiCoAlTaB (NCATB) showed that in cold-rolled alloys after solution, the strong peak was in the face-centered cubic (γ, FCC) <111> structure. In aged samples, a new peak (γ’, FCC) emerged, the intensity of which increased as aging times rose from 6 to 12 h. Transmission electron microscope (TEM) images showed that the average precipitate size was around 10 nm in 700 °C/6 h specimens and 18 nm in 700 °C/12 h specimens. The precipitate was enriched in Ni, Al, and Ta elements and exhibited an L1₂ crystal structure. Tensile samples aged at 700 °C for 6 and 12 h exhibited recoverable strains of 1% and 2.6%, respectively, at room temperature. Digital image correlation (DIC) results for the sample aged at 700 °C for 12 h showed that two martensite variants were activated during the superelastic test. Such variants can form corresponding variant pairs (CVPs), which promote tensile deformation. The tensile sample exhibited a gradual cyclic degradation, and a large irrecoverable strain was observed after the test. This irrecoverable strain was the result of residual martensite, which was pinned by dislocations. Full article

The plastic deformation behavior and mechanisms of Co-Cr-Ni-Mo alloy were investigated. The wires were subjected to different reductions using a multi-pass drawing approach and the resulting microstructures were characterized by EBSD and TEM. It was found that the alloy cold-drawn from surface to center exhibited non-uniform radial strain, with decreasing strain from surface to center. As the strain increased, the transverse texture of the alloy evolved from the initial bimodal texture consisting of strong {100}<110> and weak {110}<001> components to bimodal texture with {110}<233> and {112}<111> components, with significant twinning and mirror orientation between twin and matrix. The longitudinal texture evolution of the alloy mainly occurred on the α-fiber line, and ultimately did not form a significant texture due to grain elongation and crystal rotation. The plastic deformation mechanism of the Co-Cr-Ni-Mo alloy was dominated by dislocation slip at lower strain levels, which gradually transitioned to a combination of dislocation slip and twinning at higher strain levels. The deformation twins were typically distributed in high-density dislocation regions, and the twin boundaries transformed into high-angle sub-grain boundaries, hindering the extension of dislocation slip and deformation twin. With the increase in strain, work hardening results in a significant increase in strength and microhardness. Full article

This paper investigates the failure mechanism of the rear drive shaft in a modified pickup truck which had operated for about 3000 km. The investigation included macroscopic and microscopic evaluation to document the morphologies of the fracture surface, measurement of the material composition, metallographic preparation and examination, mechanical testing, and finite element modelling and calculations. The results obtained suggest that rotation-bending fatigue was the primary cause of the drive shaft failure. The crack initiation is located in the root of the machined threads on the drive shaft surface and expanded along the side of the machining line surface. The main cause of fatigue cracks is attributable to a high stress concentration owing to a large unilateral bending impact under overload. Meanwhile, the bidirectional torsional force also produces a higher stress concentration and thus accelerates the fatigue crack to expand radially along the surface. Furthermore, the hardness of the central section of the drive shaft was marginally below standard. This deficiency results in harm to the bearings and other mechanical components, as well as expediting the enlargement of cracks. Finite element analysis revealed significant contact stress between the bearing and drive shaft, with stress levels exceeding the fatigue limit stress of the parent material. This highlights the need for reevaluation of the heat treatment process and vehicle loading quality to enhance the drive shaft’s longevity. Full article

Fatigue limit assessment methodologies based on the thermography technique are comprehensively studied in this work. Three fundamental indicators pertaining to temperature increase, intrinsic energy dissipation, and thermodynamic entropy are discussed in sequence. The main train of thought of thermo-based research is outlined. The main objective of this paper is, on the one hand, to describe some works that have been accomplished in this field and, on the other hand, to present further potential for future studies involving fatigue behaviors and thermography approaches. Full article

The effects of different molten salts on the corrosion resistance of laser powder bed fusion (L-PBF) 316L stainless steel was evaluated at 650 and 700 °C. The samples were characterized via XRD and SEM/EDX after high-temperature corrosion tests to evaluate the corrosion damage to the L-PBF 316L stainless steel caused by the molten salts. The presence of the salts accelerated the corrosion process, the chloride-based salts being the most aggressive ones, followed by the carbonate-based and the nitrate/nitrite-based salts, respectively. The L-PBF 316L did not react strongly with the nitrate/nitrite-based salts, but some corrosion products not found in the samples tested in the absence of salts, such as NaFeO₂, were formed. LiFeO₂ and LiCrO₂ were identified as the main corrosion products in the samples exposed to the carbonate-based molten salts, due to the high activity of Li ions. Their growth produced the depletion of Fe and Cr elements and the formation of vacancies that acted as diffusion paths on the surface of the steel. In the samples exposed to chloride-based molten salts, the attacked area was much deeper, and the corrosion process followed an active oxidation mechanism in which a chlorine cycle is assumed to have been involved. Full article

The maximum thickness for ferritic steel specimens’ residual stress measurements using neutron diffraction is known to be about 80 mm. This paper proposes a new neutron diffraction configuration of residual stress measurements for cases that are over 80 mm thick. The configuration utilizes a neutron beam with a wavelength of 1.55 Å diffracted from the (220) plane with a diffraction angle (2θ) of 99.4°. The reason for the deep penetration capability is attributed to the chosen wavelength having enough intensities due to the low cross-section near the Bragg edge and the reduced beam path length (~16 mm) reflected by the large diffraction angle. Neutron diffraction experiments with this configuration can decrease strain errors up to ±150 με, corresponding to a stress of about ±30 MPa. Full article

This work explores the advantages and disadvantages of a methodology using high-energy X-ray diffraction to determine residual stresses in multilayer structures produced by atmospheric plasma spraying. These structures comprise a titanium alloy substrate (Ti64), a bonding layer (Ni-Al), and an abrasive coating (Al${}_2$O${}_3$). This study focuses on analyzing the residual stress gradients within these layers. The presented method is used to determine stresses across the entire thickness of multilayer structures. Experiments were carried out using a high-energy rectangular beam, operating in transmission mode, on the cross-section of the sample. The results indicate variable stresses throughout the depth of the sample, particularly near the layer interfaces. The semi-automatic methodology presented here enables us to follow stress evolution within the different layers, providing indications of the load transfer between them and at their interfaces. The sin${}^2\psi$ method was used to analyze the diffraction data and to determine the stresses in each phase along the sample depth. However, interpreting results near the interfaces is complex due to the geometric and chemical effects. We present a discussion of the main advantages and disadvantages of the methodology for this kind of industrial sample. Full article

In this paper, hybrid coatings based on ZnO dispersion in water soluble chitosan oligosaccharides (COS) as dispersion medium were prepared. The obtaining procedure of anti-corrosion hybrid zinc-based coatings containing COS coated ZnO particles in the metal matrix has been described. The available ZnO particles coated with COS were observed by TEM and thereafter added to the starting electrolyte for electrodeposition of hybrid zinc coatings on low-carbon steel substrates. The newly developed objects were collated with ordinary zinc coatings concerning the peculiarities of the morphology, topography and hydrophilicity of the surface (SEM and AFM analyses, water contact angle measurements), as well as corrosion behavior and electrochemical characteristics (cyclic voltammetry, potentiodynamic polarization curves, polarization resistance measurements). XRD and XPS methods were applied for studying of the crystallographic structure, as well as chemical and phase composition of the newly appeared corrosion products during the corrosion treatment in the test medium. Protective parameters of the coatings were evaluated in chloride environment of 5% NaCl solution. The results showed the effect of the concentration of the COS coated ZnO particles on the crystallographic structure and on the anticorrosion stability of the hybrid coatings. Full article

The deformation behavior of a high-strength Mg-Al-Sn-Zn alloy under loading reversals has been thoroughly examined through a combination of experimental measurements and crystal plasticity modeling. We focused on an age-treated alloy fortified by distributed Mg₂Sn particles and Mg₁₇Al₁₂ precipitates, which underwent two distinct loading cycles: tension-compression-tension (TCT) and compression-tension-compression (CTC), aligned with the extrusion direction (ED). The initial and deformed microstructures of the alloy were analyzed using the electron backscattering diffraction (EBSD) technique. Notably, the alloy displays tensile and compressive yield strengths (YS) of 215 MPa and 160 MPa, respectively, with pronounced anelastic behavior observed during unloading and reverse loading phases. Utilizing the elasto-viscoplastic self-consistent model incorporating a twinning–detwinning scheme (EVPSC-TDT), the cyclic stress–strain responses and resultant textures of the alloy were accurately captured. The predicted alternation between various slip and twinning modes during plastic deformation was used to interpret the observed behaviors. It was found that prismatic <a> slip plays an important role during the plastic deformation of the studied alloy, and its relative activity in tensile loading processes accounts for up to ~66% and ~67% in the TCT and CTC cases, respectively. Moreover, it was discerned that detwinning and twinning behaviors are predominantly governed by stresses within the parent grain, and they can concurrently manifest during the reverse tensile loading phase in the TCT case. After cyclic deformation, the area fractions of residual twins were determined to be 7.51% and 0.93% in the TCT and CTC cases, respectively, which is a result of the varied twinning–detwinning behavior of the alloy in different loading paths. Full article

Artificial bone porous titanium materials are widely used in orthopedic implants. However, the traditional constitutive model is often limited by the complexity and accuracy of the model, and it is difficult to accurately and efficiently describe the constitutive relationship of porous titanium materials. In this study, structured data were established based on experimental data from published papers, and goodness of fit (R²), mean absolute error (MAE) and mean absolute percentage error (MAPE) were used to evaluate the model. The prediction effect of random forest (RF), multi-layer perceptron (MLPR) and support vector machine (SVR) on the constitutive relationship of porous titanium materials was discussed. Through comprehensive comparison, it can be seen that the RF model with max_depth of 24 and n_estimators of 160 has the best performance in prediction, and the average absolute percentage error is less than 4.4%, which means it can accurately predict the temperature sensitivity and strain rate sensitivity of porous titanium materials. And its predictive ability is better than that of the traditional constitutive model, which provides a new idea and method for the constitutive modeling of porous titanium materials. Full article

Due to the phenomenon of deformation-induced phase transformation, the mechanical properties of TRIP steel, including the elastic modulus, undergo changes during the deformation process. This deviation from plastic theory in describing the deformation process is addressed in this study. Through tensile and cupping tests conducted at different rates, the relationship between inelastic deformation and forming time in TRIP steel is established. These tests demonstrate the presence of viscosity and the rheological behavior of solid metal materials during inelastic deformation. The experimental findings also highlight the significance of selecting an appropriate deformation rate for successful TRIP steel forming. Excessive deformation rates can result in the rapid transformation of residual austenite into martensite and increase the likelihood of material cracking. Building upon rheological theory, a constitutive equation is developed to describe the relationship between stress, strain, and strain rate for TRIP600 under creep test conditions. This constitutive model is then applied to simulate the cupping test, and by comparing the simulation results with actual test data, it is confirmed that the rheological constitutive model provides a more accurate representation of TRIP steel deformation. Furthermore, it can guide the improvement of the forming process to enhance the success rate of forming operations. Full article