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Expansive soil exhibits significant swellings and shrinkages, which may result in severe damage or the collapse of structures built upon it. Calcium-based admixtures, such as lime, are commonly used to improve this problematic soil. However, traditional chemical additions can increase significant environmental stress. This paper proposes a sustainable solution, namely, the use of lignin fiber (LF) from the paper industry to partially replace lime as an amendment for expansive soils. Both the macroscopic and microscopic characteristics of the lignin fiber-treated expansive soil are extensively studied. The results show that the mechanical properties of expansive soil are improved by using lignin fiber alone. Under the condition of an optimal dosage of 8%, the compressive strength of lignin fiber-modified soil can reach 193 kPa, the shear strength is increased by 40% compared with the untreated soil, and the water conductivity is also improved with the increase in dosage. In addition, compared with 2% lime-modified soil, the compressive strength of 8% lignin fiber- and 2% lime composite-treated expansive soil increased by 50%, the cohesion increased by 12%, and the water conductivity decreased significantly. The microstructure analysis shows that at an 8% lignin fiber content, lignin fibers interweave into a network in the soil, which effectively enhances the strength and stability of the improved soil. Simultaneously, the fibers can form bridges across the adjacent micropores, leading to the merging of pores and transforming fine, dispersed micropores into larger, connected macropores. Lime promotes the flocculation of soil particles, forming larger aggregates and thus resulting in larger pores. The addition of fibers exerts an inhibitory effect on the flocculation reaction in the composite-improved soil. In conclusion, lignin fibers are an effective addition used to partially replace calcium admixture for the treatment of expansive soil, which provides a sustainable and environmentally friendly treatment scheme for reducing industrial waste. [ABSTRACT FROM AUTHOR]

Multi-walled carbon nanotubes (MWCNTs) are a high-quality interlamination reinforcement material, but the high viscosity of polyetheretherketone (PEEK) prevents good fusion between MWCNTs and PEEK. This study proposes a method to achieve the complete integration of MWCNTs and PEEK through the preparation of a composite film using the vacuum suction filtration (VSF) method and optimizes the process parameters. An orthogonal experiment with three factors (filter paper pore size, ultrasonic dispersion time, and PEEK content) at three levels is designed, and mechanical performance testing and microscopic morphology observation are conducted. The influence of the three factors of filter paper pore size, ultrasonic time, and PEEK content on the elastic modulus and tensile strength of the film is investigated. The results are a filter paper pore size of 0.45 μm, ultrasonic time of 8.3 h, and PEEK content of 336.524 mg. The mechanical performance obtained under the optimal process parameters are an elastic modulus of 2437.5723 MPa and a tensile strength of 46.5196 MPa. This optimal process increases the elastic modulus by 12.3152% while maintaining a high tensile strength. [ABSTRACT FROM AUTHOR]

This study evaluates the potential use of discarded plasterboard paper as fibers from buildings to reinforce concrete. Various concentrations of wastepaper fibers (0.5%, 1%, 1.5%, 2%, and 2.5% by weight of the binder) were investigated in this research. To mitigate the water absorption effect of the paper fibers, metakaolin was employed as a partial cement replacement. The results demonstrate that the inclusion of the wastepaper fiber enhances the mechanical and durability performance of the concrete. The optimal fiber proportion was identified as 1%, leading to a 29% increase in the compressive strength, a 38% increase in the splitting tensile strength, a 12% decrease in the water absorption, and a 23% decrease in the drying shrinkage with respect to the concrete containing 20% metakaolin. However, exceeding this optimal fiber content results in decreased mechanical and durability properties due to the fiber agglomeration and non-uniform fiber distribution within the concrete matrix. Based on the microstructural analysis, the improved performance of the concrete is ascribed to decreased porosity, more refined pore structure, and reduced propagation of microcracks within the concrete matrix in the presence of wastepaper fiber. According to the results, concrete containing 20% metakaolin and 1% wastepaper fiber exhibits durability and mechanical properties comparable to those of the traditional concrete. This finding highlights the significant promise of reducing dependency on conventional cement and incorporating suitable recycled materials, such as discarded plasterboard, and secondary by-products like metakaolin. Such a strategy encourages the preservation of resources, reduction in carbon dioxide emissions, and a decrease in the ecological footprint resulting from concrete production. [ABSTRACT FROM AUTHOR]

The use of geopolymer as a cementitious material for geopolymer concrete (GPC) is beneficial for the sustainable development and green transformation of the construction industry. Geopolymer concrete has many advantages, such as high strength, heat and corrosion resistance, low hydration heat, and carbon emissions. This paper adopted the water–binder ratio, alkaline activator modulus, and slag replacement as the influencing factors, and used the 28-day compressive strength and flexural strength of geopolymer concrete as the response values to seek a reasonable mix design. In addition, through microstructure analysis, the mechanism of geopolymer on concrete was studied. The results indicated that as the water–binder ratio increased, the compressive strength first increased and then decreased, while the flexural strength continuously decreased. As the amount of slag replacement increased, the compressive strength and flexural strength would also increase. The effect of alkaline activator modulus on compressive strength and flexural strength was not significant. Through response surface methodology (RSM) analysis, the optimal design of geopolymer concrete was determined to have a water–cement ratio of 3.50, a modulus of 1.54 for alkaline activator solution, and a slag substitution rate of 47%. The microstructure analysis showed that the water–binder ratio and slag replacement improved the pore structure and density of concrete, thereby enhancing the macroscopic mechanical properties of concrete. This paper can provide a theoretical basis for the application of geopolymer concrete in engineering. [ABSTRACT FROM AUTHOR]

This paper mainly explores the feasibility of using desert sand (DS) and recycled aggregate in cement-stabilized bases. Recycled coarse aggregate (RCA) and DS serve as the substitutes of natural coarse and fine aggregates, respectively, in cement-stabilized bases. A four-factor and four-level orthogonal test is designed to analyze the unconfined compressive strength, splitting tensile strength, and compressive resilient modulus. Furthermore, this paper investigates the effects of cement content, fly ash (FA) replacement rate, RCA replacement rate, and DS replacement rate on the road performance of cement-stabilized bases composed of RCA and DS. The test results reveal that the performance of cement-stabilized bases with partial RCA instead of natural coarse aggregate (NCA) and partial DS instead of natural fine aggregate satisfies the road use. The correlation and microscopic analyses of the test results imply the feasibility of applying DS and recycled aggregate to cement-stabilized bases. This paper calculates and evaluates the life cycle of carbon emissions of desert sand and recycled coarse aggregate cement-stabilized macadam (DRCSM) and finds that both DS and RCA can reduce the carbon emissions of CSM, which has a positive effect on improving the environment and solving the climate crisis. It is hoped that this paper can offer a solid theoretical foundation for promoting the application of DS and recycled aggregate in road engineering. [ABSTRACT FROM AUTHOR]

Before artificial ageing, extruded aluminium profiles are subjected to stretching with a small cold deformation in the range of 0.5–2%. This deformation improves the geometrical stability of the extruded product and causes changes in the microstructure of the profile, which leads to the strain hardening of the material after artificial ageing. The work has resulted in the creation of the prototype of an original device, which is unique in the world, for the dynamic stretching of the extruded profiles after quenching. The semi-industrial unit is equipped with a hydraulic system for stretching and a pneumatic system for cold dynamic deformation. The aim of this research paper is to produce advantageous microstructural changes and increase the strength properties of the extruded material. The solution of the dynamic stretching of the profiles after extrusion is a great challenge and an innovation not yet practised. The paper presents the results of microstructural and mechanical investigations carried out on extruded AlMgSi(Cu) alloys quenched on the run-out table of the press, dynamically stretched under different conditions, and artificially aged for T5 temper. Different stretching conditions were applied: a static deformation of 0.5% at a speed of 0.02 m/s, and dynamic deformation of 0.25%, 0.5%, 1%, and 1.5% at speeds of 0.05 and 2 m/s. After the thermomechanical treatment of the profiles, microstructural observations were carried out using an optical microscope (OM) and a scanning electron microscope (SEM). A tensile test was also carried out on the specimens stretched under different conditions. In all the cases, the dynamically stretched profiles showed higher strength properties, especially those deformed at a higher speed of 2 m/s, where the increase in UTS was observed in the range of 7–18% compared to the classical (static) stretching. The microstructure of the dynamically stretched profiles is more homogeneous with a high proportion of fine dispersoids. [ABSTRACT FROM AUTHOR]

This paper presents the influence of adding rinsed ilmenite mud waste (R-MUD) on the microstructure of Portland cement composites, compared to similar composites containing fly ash (FA). The aim of the study is the assessment of the pozzolanic activity of ilmenite mud waste by its impact on the microstructure of the cement matrix in comparison to the undoubted pozzolanic activity of fly ash. The presented test results include pore size distribution, phase composition, pozzolanic activity using thermal analysis, R3 bound water test, and microstructural analysis using scanning electron microscopy (SEM). Tests were performed on mortars cured for up to 360 days. The results presented in this paper have shown that R-MUD has a pozzolanic activity level similar to FA or better, which influences pore size distribution in the composite and its microstructure. During the curing process, the microstructure of composites containing R-MUD became more compact and sealed than those with FA, which might also increase their durability. The results of the R3 tests have proven the pozzolanic activity of R-MUD but its level was lower than FA. R-MUD might be a useful substitute for fly ash, especially given the lack of good-quality fly ash on the market. [ABSTRACT FROM AUTHOR]

Conventional book casting of Sm2TM17-type alloys (where TM = Co, Fe, Cu, Zr) leads to a coarse, highly segregated microstructure, predominantly due to the slow, variable cooling rate from the mould surface towards the centre of the ingot. These cast alloys require a long homogenisation treatment to remove this segregation and develop a super-saturated, metastable SmTM7-type hexagonal phase. This SmTM7 phase is a vital precursor phase required during magnet production to develop the complex cellular structure responsible for high magnetic properties. In this work, strip casting was employed to facilitate rapid solidification to develop thin flakes (<0.5 mm thick) with a columnar grain structure. Rapid cooling has the potential to produce a homogenous microstructure consisting predominantly of the metastable SmTM7 phase. This could remove or significantly reduce the need for the energy-intensive homogenisation treatment usually required in conventional magnet manufacture. This paper investigates the effect of wheel speed (and hence cooling rate) on flake thickness, microstructure, and phase balance of the cast alloys. It was shown that for wheel speeds between 1.1 and 3.0 m/s, the microstructure showed large variation; however, in all cases, evidence of the columnar SmTM7 phase was presented. The adhesion between the melt and the wheel was deemed to be critical for the nucleation and subsequent columnar growth of SmTM7 grains, where the wheel speed controlled both the flow of the alloy onto the wheel and the thickness of the resultant flake. It was determined that in order to achieve a homogenous columnar SmTM7 structure, the maximum flake thickness should be limited to 270 μm to avoid the formation of equiaxed Sm2TM17 grains through insufficient cooling. [ABSTRACT FROM AUTHOR]

A polarized light microscope (PLM) was utilized to examine the optical textures of mesophase pitch (MP) and MP-derived fibers, which aimed to reveal the arrangement and orientation characteristics of pitch molecules and to clarify the evolution and transformation mechanism of carbonaceous microcrystalline from pitch fibers to graphitized fibers. The results found that there were distinct optical textures in MP, where one side exhibited a transition from a flattening plane to a mountain-like undulating plane. This transition corresponded to the arrangement of pitch molecules, resembling stacked lamellar structures reminiscent of curved paper. Meanwhile, the optical textures of fibers revealed that the blue substance was wrapped around the red grain-like domains in the longitudinal section and confirmed that the red part belonged to the pyridine insoluble fraction of MP and the blue part belonged to its pyridine-soluble fraction. After graphitization, the red part was transformed into graphite sheets and the blue part was transformed into an amorphous carbon layer which was wrapped around the graphite sheets, forming a carbonaceous microcrystalline package-like bag. Therefore, this study provided a comprehensive interpretation of the structural evolution mechanism of MP and MP-derived fibers based on their macro-optical textures and micro-nanostructures. [ABSTRACT FROM AUTHOR]

The cellular automata (CA) method has played an important role in the research and development of metallic materials. CA can interpret the microstructure changes of materials and obtain more abundant, accurate and intuitive information of microstructure evolution than conventional methods. CA can visually represent the process of grain formation, growth, development and change to us in a graphical way, which can assist us in analysis, thinking and solving problems. In the last five years, the application of CA in materials research has been rapidly developed, and CA has begun to occupy an increasingly important position in the simulation research of metallic materials. After introducing the advantages and limitations of CA compared to other widely used simulation methods, the purpose of this paper is to review the recent application progress on the microstructure simulation of metallic materials using CA, such as solidification, recrystallization, phase transformation and carbide precipitation occurring during forming and heat treatment. Specifically, recent research advances on microstructure simulation by CA in the fields of additive manufacturing, welding, asymmetrical rolling, corrosion prevention, etc., are also elaborated in this paper. Furthermore, this paper points out the future work direction of CA simulation in the research of metallic materials, especially in the simulation of the crystal structure, the prediction of mechanical properties, CA simulation software and rule systems, etc. These are expected to attract wide attention of researchers in the field of metallic materials and promote the development of CA in materials research. [ABSTRACT FROM AUTHOR]

This research paper focuses on the fabrication of a microstructure based on a natural structure pattern of hydrophobic properties using micro-milling technology, followed by an investigation of the dimensional accuracy, roughness, and replication of the fabricated microstructure. Design, modeling (CAD system), fabrication, and replication are the steps of this process. Knowledge of biomimetics was used to select the microstructure. The main research aim of the experiments is to verify and extend the applicability of conventional CNC manufacturing technologies to obtain a functional surface structure. The micro-milling was carried out on a conventional DMG MORI CNC machine, a CMX 600 V three-axis horizontal milling center, using an external high-frequency electric spindle clamped to the machine. The machined material was aluminum alloy EN AW 7075. The tool was a 0.1 mm diameter double-edged ball mill made of sintered carbide and coated with TiSiN. The cutting conditions were determined according to the tool manufacturer's recommendations. To compare the achieved accuracies, the same microstructure was fabricated using PLA technology. For subsequent replication of the sample, the negative of the selected microstructure was created and machined. Subsequently, a positive microstructure was created using the silicone impression material by the replication process. This paper and the experiments performed extend the technical knowledge in the field of manufacturing surface functional structures and confirm the possibility of manufacturing the designed structures using chip and laser machining technology, with achieved discontinuities in the range of 3 to 50 μm. They also highlight the issues of replication of such structures with respect to critical manufacturing locations (geometrical parameters of the structures affecting the functional properties of the structure, venting, replica defects, etc.). [ABSTRACT FROM AUTHOR]

This paper employed squeeze-casting (SC) technology to develop a novel Al-7Si-1.5Cu-1.2Ni-0.4Mg-0.3Mn-0.15Ti heat-resistant alloy, addressing the issue of low room/high temperature elongation in traditional gravity casting (GC). Initially, the effects of SC and GC processes on the microstructure and properties of the alloy were investigated, followed by an examination of the evolution of the microstructure and properties of the SC samples over thermal exposure time. The results indicate that the SC process significantly improves the alloy's microstructure. Compared to the GC alloy, the secondary dendrite arm spacing of the as-cast SC alloy is refined from 50.5 μm to 18.5 μm. Meanwhile, the size and roundness of the eutectic Si phase in the T6-treated SC alloy are optimized from 11.7 μm and 0.75 μm to 9.5 μm and 0.85 μm, respectively, and casting defects such as porosity are reduced. Consequently, the ultimate tensile strengths (UTSs) at room temperature and at 250 °C of the SC alloy are 5% and 4.9% higher than that of GC alloy, respectively, and its elongation at both temperatures shows significant improvement. After thermal exposure at 250 °C for 120 h, the morphology of the residual second phase at the grain boundaries in the SC alloy becomes more rounded, but the eutectic Si and nano-precipitates undergo significant coarsening, resulting in a 49% decrease in UTS. [ABSTRACT FROM AUTHOR]

Magnesium sulphoaluminate (MSA) cement has good bonding properties and is suitable as an inorganic adhesive for repairing materials in civil engineering. However, there are still some problems with its use, such as its insufficient 1 day (d) strength and poor volumetric stability. This paper aims to investigate the influences of metakaolin (MK) on the physical and mechanical properties of magnesium sulphoaluminate (MSA) cement. The hydration products and microstructures of typical MSA cement samples were also analysed using X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDS). The results showed that the addition of metakaolin reduces the fluidity and shortens the setting time of the MSA cement. The initial setting time and final setting time shortened maximally by 15–27 min and 25–48 min, respectively, with the addition of 10–30% metakaolin. Moreover, the compressive strength and flexural strength of the MSA cement improved significantly with the addition of 10–30% metakaolin at a curing age of 1 d. Compared with the compressive and flexural strengths of the control sample at 1 d, the compressive strengths of the modified samples showed obvious increases of 98%, 101%, and 109%, and the flexural strengths increased by 39%, 31%, and 26%, respectively, although they decreased slightly when the curing ages were 7 d, 14 d, and 28 d. The addition of 10% metakaolin improved the water resistance of the MSA cement immersed in water for 7 d and resulted in even higher water resistance at 28 d. The addition of 10–30% metakaolin improved the volumetric stability of the MSA cement with increasing dosages before 28 d of ageing. XRD and SEM-EDS analyses showed that the metakaolin accelerated the early hydration reaction and optimised the phase composition of the MSA cement. The results indicate that the addition of 10–20% metakaolin improved the strength after 1 d of ageing, water resistance, and volumetric stability of the MSA cement, providing theoretical support for the application of MAS cement as an inorganic bonding agent for repairing materials. [ABSTRACT FROM AUTHOR]

This paper presents selected results of theoretical and experimental research into the manufacture of axisymmetric bimetallic components using three-tool skew rolling technology. In the tests, it was assumed that the outer layer would be a material intended for heat treatment. However, low-carbon steel was used for the core. Experimental investigations were carried out in an innovative CNC skew rolling mill. Tests were carried out at different technological parameters of the process. In addition, the geometric parameters of the billet and the way it was heated were analyzed in relation to the quality of the resulting weld between the two materials. The quality of the weld was assessed based on metallographic observation and on strength tests (shear method). On the other hand, theoretical studies were based on numerical modeling (FEM). The numerical analysis made it possible to determine the distribution of temperature, deformation and stress in the rolling bimetallic component. The results obtained indicated that it is possible to produce bimetallic materials from the proposed steel grades. In addition, a significant effect of the method of heating the billet in the chamber furnace on the microstructure in the joining zone and the shear strength was found. There was an increase in Rc strength of about 35% when using oxidation protection. The results indicated better strength when the billet is rolling with a smaller outer layer thickness (about 50 MPa). This was confirmed by the results obtained from the FEM analysis, which indicated higher values of plastic strain and the occurrence of higher compressive stresses in the near-surface zones of the rolled bimetallic forging, both of which facilitate the welding process. From the temperature distribution (in the range of (600–1200) °C) obtained during the rolling of the bimetal forging, it can be seen that contact with cold tools does not affect the temperature in the welding zone. [ABSTRACT FROM AUTHOR]

In order to prepare coating with good friction and wear resistance at elevated temperature on the surface of hot-working tool steel, by using a CO2 laser, FeCrNiTiZr high-entropy alloy coating with different laser scanning speeds (360, 480 and 600 mm/min, respectively) was successfully fabricated by using laser cladding technology on the surface of H13 steel in this paper. Phase constitutions, microhardness, microstructure, and wear characteristics of FeCrNiTiZr coatings under different laser scanning speeds were analyzed. It was determined that 480 mm/min was the optimal laser scanning speed. The results showed that the coating at the scanning speed of 480 mm/min consists of a BCC phase with significant lattice distortion and high dislocation density; the crystal structure is cellular crystal and dendrite crystal. The coating demonstrates the highest microhardness (842 HV0.2), which is 4.2 times that of the substrate (200 HV0.2). Its average friction coefficients at room temperature and 823 K are approximately one-seventh and one-third of the substrate's, respectively, and its wear volume is reduced by about 98% and 81% under these conditions. Compared to the substrate, the coating underwent slight abrasive wear, adhesive wear, and oxidative wear at both room temperature and 823 K. In contrast, the substrate underwent severe abrasive wear, adhesive wear, oxidative wear, and even fatigue wear. [ABSTRACT FROM AUTHOR]

Arc spraying is one of the most effective and cost-efficient thermal spraying technologies for creating high-quality protective coatings. This paper examines the influence of arc spraying process parameters on the properties of steel coatings. The parameters varied in this study included gas pressure, wire feed rate, and the distance from the spray gun to the substrate (standoff distance). Experimental evaluations focused on surface roughness, thickness, porosity, structure, and hardness of the coatings. The techniques used for these evaluations included profilometry for roughness measurement, scanning electron microscopy (SEM) for structural analysis, Vickers hardness testing, and optical microscopy. The results demonstrate a significant influence of arc spraying parameters on the characteristics of the resulting coatings. The analysis revealed that the coatings produced under different modes exhibit a layered structure and vary in thickness. A detailed examination of the coating structure identified defects such as unmelted particles, voids, and delamination in the interface zone. The study of coating thickness and porosity showed that increasing the wire feed rate and decreasing the standoff distance leads to the formation of thicker and denser coatings. Specifically, increasing the wire feed rate from 2 to 12 cm/s resulted in a decrease in porosity from 12.59% to 4.33% and an increase in coating thickness to 699 μm. The surface analysis highlighted the importance of a comprehensive approach to selecting the optimal roughness. While increasing the wire feed rate up to 12 cm/s can increase the Ra roughness parameter, gas pressure also significantly influences this parameter, reducing roughness from Ra = 18.63 μm at 6 MPa to Ra = 15.95 μm at 8 MPa. Additionally, it was found that varying the arc spraying parameters affects the hardness of the coatings, with all modes resulting in hardness values higher than that of the substrate. Therefore, optimizing these parameters enables the achievement of the best combination of mechanical and structural properties in the coatings. These findings can be valuable for further improvement of arc spraying technologies and the expansion of their application across various industries. [ABSTRACT FROM AUTHOR]

This paper presents and demonstrates the development of a new lightweight coating for aluminum alloy from a novel multicomponent alloy based on the AlSiMgCu system. The coating was applied using a newly designed approach that combined high velocity oxy-fuel (HVOF) and plasma spraying processes. This hybrid technique enables the deposition of coatings with enhanced performance characteristics. The optical microscopy (OM) and scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM + EDS) revealed a strong adhesion and compaction between the multicomponent coating and the A6061 substrate. The new coating improved hardness by 50% and increased electrical conductivity by approximately 3.3 times compared to the as-cast alloy. Corrosion tests showed a lower corrosion rate, comparable to thermally treated A6061 alloy. Tribological tests indicated over 20% reduction in friction and over 50% reduction in wear rate. This suggests that multicomponent aluminum coatings could improve automotive and parts in contact with hydrogen by enhancing hydrogen fragilization resistance, corrosion resistance, electrical conductivity, and wear properties, with further optimization of thermal spraying potentially boosting performance even further. [ABSTRACT FROM AUTHOR]

17–7 PH stainless steel is a highly versatile material with a multitude of applications in a diverse range of fields, including aerospace, chemistry and petrochemistry, and medicine. The material's exceptional mechanical properties and corrosion resistance render it the optimal selection for numerous components and instruments. Nevertheless, the surface properties of 17–7 PH stainless steel are inadequate for applications requiring high hardness and wear resistance in certain extreme environments. Due to its excellent mechanical properties and corrosion resistance, it can be utilized in the manufacturing of pharmaceutical equipment components. However, certain specialized environments still require surface nitriding treatment. Considering the complex heat treatment process required for this material, this paper reports a detailed study of the surface performance changes of 17–7 PH steel before and after ion nitriding following aging heat treatment. The study employs rolled 17–7 PH stainless steel as the subject material. The impact of heat treatment on plasma nitriding of stainless steel is investigated by comparing and analyzing the influence of martensite content and dislocation density within the martensite of the material prior to and following heat treatment on the hardness, thickness, and corrosion resistance of the nitrided layer on the surface of the steel after nitriding. The results demonstrate that 17–7 PH stainless steel, which does not undergo heat treatment, exhibits a high internal dislocation density, a high nitriding efficiency, and consequently, a high surface hardness. Following the application of a heat treatment, there is an increase in the martensite content of 17–7 PH stainless steel, a decrease in the dislocation content, and an increase in the matrix hardness. [ABSTRACT FROM AUTHOR]

This paper introduces an innovative approach that enables the automated and precise prediction of steel's chemical composition based on the desired Jominy curve. The microstructure, and in fact the presence of martensite, is decisive for the hardness of the steel, so the study considered the occurrence of this phase at particular distances from the quenched end of the Jominy sample. Steels for quenching and tempering and case hardening were investigated. With the representative collected dataset of hardness values from the quenched end of the Jominy specimen, microstructure and chemical composition of steels, the complex regression model was made using supervised artificial neural networks. The balance between cost and required hardenability can be achieved through optimizing the chemical composition of steel. This model of designing steel with required hardenability can be of great benefit in the mechanical engineering and manufacturing industry. The model is verified experimentally. [ABSTRACT FROM AUTHOR]

Reliable microstructure characterization is essential for establishing process–microstructure–property links and effective quality control. Traditional manual microstructure analysis often struggles with objectivity, reproducibility, and scalability, particularly in complex materials. Machine learning methods offer a promising alternative but are hindered by the challenge of assigning an accurate and consistent ground truth, especially for complex microstructures. This paper introduces a methodology that uses correlative microscopy—combining light optical microscopy, scanning electron microscopy, and electron backscatter diffraction (EBSD)—to create objective, reproducible pixel-by-pixel annotations for ML training. In a semi-automated manner, EBSD-based annotations are employed to generate an objective ground truth mask for training a semantic segmentation model for quantifying simple light optical micrographs. The training masks are directly derived from raw EBSD data using modern deep learning methods. By using EBSD-based annotations, which incorporate crystallographic and misorientation data, the correctness and objectivity of the training mask creation can be assured. The final approach is capable of reproducibly and objectively differentiating bainite and martensite in optical micrographs of complex quenched steels. Through the reduction in the microstructural evaluation to light optical micrographs as the simplest and most widely used method, this way of quantifying microstructures is characterized by high efficiency as well as good scalability. [ABSTRACT FROM AUTHOR]

In this paper, the nucleation and growth of austenite are controlled through a two-step annealing process to achieve multi-scale distribution and content increase of retained austenite in low manganese series medium-Mn steel. Combining SEM, EBSD, AES, and other experimental equipment, the evolution rules of the microstructure, properties, and element distribution behavior of the test steel during the annealing process are studied. Compared with one-step annealing, the two-step annealing significantly broadens the size distribution range of retained austenite. In the first step, after annealing at a higher intercritical temperature (760 °C), the ferrite and the M/A island are obtained, completing the initial partition of Mn and the refinement of microstructures. During the second step of annealing (720 °C), the primary Mn-rich martensite region provides higher nucleation driving force and finer dispersed nucleation sites, promoting the nucleation and growth of reverse transformation austenite. At the same time, the metastable-retained austenite formed after the first step of annealing continues to grow through interface movement. Furthermore, a high proportion (23.4%) of retained austenite with multi-scale distribution is formed in the final microstructure, and the product of strength and elongation increased from 21.8 GPa·% by the one-step annealing process to 30.1 GPa·%. [ABSTRACT FROM AUTHOR]

The continuous retained-mandrel rolling process is a promising method for titanium tube production with high efficiency and a short process. The importance of mandrel as a deformation tool supporting the inner wall is crucial. This paper thoroughly examines the influence of mandrel velocity on the deformation characteristics at the groove vertex using three approaches: numerical simulation, shear-deformation observation experiments, and microstructure analysis. The following conclusions are drawn: Decreasing the mandrel velocity enhances the penetration of shear deformation into the inner wall of the titanium tube, improves thickness uniformity, and shifts the deformation mechanism near the inner wall from twinning to dislocation slip. As a result, the volume fraction of recrystallization increases from 18.4% to 42.3%. However, the mean shear strain increases first and then decreases to a certain value as the mandrel speed decreases, which is attributed to the combined influence of the cross-shear zone and the rolling force. [ABSTRACT FROM AUTHOR]

Laser powder bed fusion (LPBF) presents both opportunities and challenges with regard to the customisation of NiTi alloy properties. This paper presents a systematic study of the influence of process parameters on the superelasticity of LPBF Ni-rich Ni51.3Ti48.7 shape memory alloy. The findings demonstrate that NiTi alloys produced through disparate process parameters exhibit disparate phase transformation behaviours and microstructures, which in turn result in varying degrees of superelasticity. At an energy density of 166.7 to 233.3 J/mm3, LPBFed Ni-rich Ni51.3Ti48.7 is predominantly in the martensite phase at room temperature due to the high phase transition temperature caused by a large amount of Ni evaporation loss, and exhibits almost no superelasticity. At an energy density of 66.7 to 116.7 J/mm3, LPBFed Ni-rich Ni51.3Ti48.7 has less Ni evaporation loss and lower phase transition temperature. It is primarily austenite phase at room temperature, and contains nano-precipitated phases internally, thereby exhibiting excellent superelasticity. The recovery rate is in excess of 5.5% at the initial compression (up to 5.7%) and in excess of 5.0% following ten cycles (up to 5.3%). Furthermore, the lower the energy density, the smaller the stress–strain hysteresis of LPBFed Ni-rich Ni51.3Ti48.7, with a variation range of 1.8–3.9 mJ/mm3. [ABSTRACT FROM AUTHOR]

Alkali-activated slag cementitious (AASC) foamed concrete (FC) has presented challenges such as rapid setting time and poor working performance. The use of sodium citrate (Na3Cit) as a retarding agent can improve the workability and microstructure of AASC foamed concrete. The effects of the dosage, modulus of water glass (WG, the main component is Na2O·nSiO2), and retarding agent on the properties and structure of FC were studied in this paper. The results indicated that using a water binder ratio of 0.4, WG with a modulus of 1.2, and an additional amount of 15% and 0.5% of Na3Cit, the prepared FC had a flowability of 190 mm. Its initial and final setting times were 3.7 h and 35.3 h. Its 7 d and 28 d compressive strengths reached 1.1 MPa and 1.5 MPa, respectively. After hardening, the pore walls were dense and consistent in size, with few larger pores and nearly spherical shapes. The addition of Na3Cit resulted in the formation of calcium citrate, which adsorbed onto the slag surface. This hindered the initial dissolution of the slag, reduced the number of hydration products produced, and decreased the early strength. With increasing curing time, the slag in the FC mixture dissolved further. This led to the decomposition of a portion of calcium citrate and the release of Ca2+. The Ca2+ reacted with [Si(OH)4]4− and [Al(OH)4]−, creating more C-(A)-S-H gel. This gel filled the voids in the FC and repaired any defects on the pore walls. Ultimately, this process increased the compressive strength of the FC in the later stages. [ABSTRACT FROM AUTHOR]

Over the past few decades, remarkable breakthroughs and progress have been achieved in ultrafast laser processing technology. Notably, the remarkable high-aspect-ratio processing capabilities of ultrafast lasers have garnered significant attention to meet the stringent performance and structural requirements of materials in specific applications. Consequently, high-aspect-ratio microstructure processing relying on nonlinear effects constitutes an indispensable aspect of this field. In the paper, we review the new features and physical mechanisms underlying ultrafast laser processing technology. It delves into the principles and research achievements of ultrafast laser-based high-aspect-ratio microstructure processing, with a particular emphasis on two pivotal technologies: filamentation processing and Bessel-like beam processing. Furthermore, the current challenges and future prospects for achieving both high precision and high aspect ratios simultaneously are discussed, aiming to provide insights and directions for the further advancement of high-aspect-ratio processing. [ABSTRACT FROM AUTHOR]

This paper presents the experimental results of a study evaluating the mechanical and fatigue performance of welded Fe-Mn-Si SMA. For the experimental study, welded and welded-and-heat-treated Fe-Mn-Si SMA specimens were fabricated, and fatigue tests were performed at various stress amplitudes. In addition, direct tensile tests and recovery stress tests were also performed to evaluate the material properties of Fe-Mn-Si SMAs. The elastic modulus, yield strength, and tensile strength of the welded specimens were reduced by 35.4%, 12.1%, and 8.6%, respectively, compared to the values of the non-welded specimens. On the other hand, the elastic modulus, yield strength, and tensile strength of the welded-and-heat-treated Fe-Mn-Si SMA specimens were increased by 18.6%, 4.9%, and 1.3%, respectively, compared to the values of the welded specimens. Both welded and welded-and-heat-treated Fe-Mn-Si SMAs failed at lower cycles than the conventional Fe-Mn-Si SMAs at the same stress amplitude. High-cycle fatigue failure, characterized by cycles exceeding 104, typically occurs at relatively low stress levels within the elastic region, whereas low-cycle fatigue failure, generally occurring within cycles below 104, involves high stress levels that encompass both elastic and plastic deformation. Regardless of the welding condition, the stress amplitude at which Fe-Mn-Si SMA transitions from high-cycle to low-cycle failure exceeded the yield strength. [ABSTRACT FROM AUTHOR]

With the rapid advancement of 3D-printing technology, additive manufacturing using FDM extrusion has emerged as a prominent method in manufacturing. However, it encounters certain limitations, notably in surface quality and dimensional accuracy. Addressing issues related to stability and surface roughness necessitates the integration of 3D-printing technology with traditional machining, a strategy known as the hybrid technique. This paper presents a study of the surface geometric parameters and microstructure of plastic parts produced by FDM. Sleeve-shaped samples were 3D-printed from polyethylene terephthalate glycol material using variable layer heights of 0.1 mm and 0.2 mm and then subjected to the turning process with PVD-coated DCMT11T304 turning inserts using variable cutting parameters. The cutting depth was constant at 0.82 mm. Surface roughness values were correlated with the cutting tool feed rate and the printing layer height applied. The selected specimen's microstructure was studied with a Zeiss EVO MA 15 scanning electron microscope. The roundness was measured with a Keyence VR-6200 3D optical profilometer. The research results confirmed that the additional application of turning, combined with a reduction in the feed rate (0.0506 mm/rev) and the height of the printed layer (0.1 mm), reduced the surface roughness of the sleeve (Ra = 1.94 μm) and increased its geometric accuracy. [ABSTRACT FROM AUTHOR]

Due to its exceptional mechanical and chemical properties at high temperatures, Inconel 718 is extensively utilized in industries such as aerospace, aviation, and marine. Investigating the flow behavior of Inconel 718 under high strain rates and high temperatures is vital for comprehending the dynamic characteristics of the material in manufacturing processes. This paper introduces a physics-based constitutive model that accounts for dislocation motion and its density evolution, capable of simulating the plastic behavior of Inconel 718 during large strain deformations caused by machining processes. Utilizing a microstructure-based flow stress model, the machinability of Inconel 718 in terms of cutting forces and temperatures is quantitatively predicted and compared with results from orthogonal cutting experiments. The model's predictive precision, with a margin of error between 5 and 8%, ensures reliable consistency and enhances our comprehension of the high-speed machining dynamics of Inconel 718 components. [ABSTRACT FROM AUTHOR]

This paper investigates the tensile properties and microstructures of Cu/Al clad sheets with an SUS304 interlayer after cryorolling and subsequent annealing and compares them with hot-rolled samples. The experimental results show that the inhibition of dynamic recovery by cryorolling enables the Cu/Al clad sheets to achieve a tensile strength of 302 MPa. After annealing, the tensile strength sharply drops to 159 MPa, while the elongation recovers to 29.0%. Compared with hot-rolled samples, the tensile strength of cryorolled samples is increased by 13.1% due to the effect of fine-grain strengthening. During the annealing process, the cryorolled samples exhibit improved elongation under a comparable strength with the hot-rolled samples, profiting from the higher degree of recrystallization and a higher proportion of annealing twins. The tensile properties of Cu/Al clad sheet with an SUS304 interlayer are strengthened by cryorolling and subsequent annealing, providing a new method for the fabrication of high-performance Cu/Al clad sheets. [ABSTRACT FROM AUTHOR]

The welding of TC4 titanium alloy sheets with a thickness of 1 mm was successfully accomplished by a swinging laser. The microstructure and mechanical properties of the welding seam under different swing amplitudes were studied. In this paper, the microstructure, phase composition, mechanical properties, and fracture morphology of the weld with swing frequency of 50 Hz and different swing amplitudes (0.2 mm, 1 mm, 2 mm, and 3 mm) were tested and analyzed. The results show that basket-weave microstructures are present in the fusion zone of welds under different oscillation amplitudes, but the morphology of martensite within the basket-weave differs. The weld microstructure is mainly composed of acicular α′ martensite, initial α phase, secondary α phase, and residual β phase. The hardness of the weld is higher than that of the base metal, and the overall hardness decreases from the weld center to the base metal. When the oscillation amplitude A = 1 mm, the weld microstructure has the smallest average grain size, the highest microhardness (388.86 HV), the largest tensile strength (1115.4 MPa), and quasi-cleavage fracture occurs. At an oscillation amplitude of A = 2 mm, the tensile specimen achieves the maximum elongation of 14%, with ductile fracture as the dominant mechanism. [ABSTRACT FROM AUTHOR]

In this paper, the microstructure of an alloy was regulated by means of strengthening solution aging, and microstructure observation and composition analysis were carried out by means of an optical microscope and X-ray diffractometer. Combined with the Vickers hardness tester, electronic universal testing machine and high-temperature persistent creep testing machine, the mechanical properties and high-temperature properties of the alloy were tested, and the strengthening mechanism of the alloy was explored. The results showed that the dendritic morphology and structure of the alloy decreased with an increase in temperature during the solution process, and the γ′ phase morphology also changed with the solution temperature: oval → cross → cubic. The γ′ phase after solid solution at 1295 °C was closest to the cubic form. Therefore, it is believed that the 1295 °C solution treatment had the best effect. In the aging process, the uniform cubic degree of γ′ phase distribution was the highest at 1090 °C. On the basis of fixed aging temperature (1090 °C), it was found that the volume fraction of the γ′ phase increased significantly after 8 h. The γ′ phase, which was closest to the cubic form, had the largest proportion of precipitation, and the volume fraction increased to 70.3%. The minimum carbide volume was 1.0%. The hardness of the alloy reached 435.8 HV; the yield strength increased to 280.1 MPa; and the durability of the alloy under the conditions of 1000 °C/230 MPa and 870 °C/655 MPa was 99.7 h and 42.7 h, respectively, which achieved the purpose of alloy design. [ABSTRACT FROM AUTHOR]

To further enhance the performance of the fast tool servo (FTS) system in terms of stroke, load capacity, and application area, this paper proposes a novel fast tool servo device driven by a voice coil motor (VCM), based on a three-segment uniform corrugated flexure (CF) guiding mechanism, with a large stroke, high accuracy, and high dynamics. To describe the unified static characteristics of such device, the compliance matrix method is applied to establish its model, where the influence of CF beam structural parameters on the FTS device is investigated in detail. Furthermore, resolution and positioning accuracy tests are conducted to validate the features of the system. The testing results indicate that the maximum stroke of the FTS device is up to 3.5 mm and the positioning resolution values are 3.6 μm and 2.4 μm for positive and negative stroke, respectively, which further verifies the device's effectiveness and promising application prospect in ultra-precision microstructure machining. [ABSTRACT FROM AUTHOR]

This paper investigates the preparation and properties of high-strength artificial blocks made from dredged silt with a clay content of 52.0%. A comparative analysis of the mechanical properties of dredged silt blocks produced using semi-dry pressing and vibration molding methods was conducted. The study examined the effects of using fly ash (FA) and ground granulated blast-furnace slag (GGBS) as substitutes for cement on the compressive strength, splitting tensile strength, and dry shrinkage of the blocks. Additionally, the microstructure of the dredged silt blocks was analyzed using scanning electron microscopy (SEM), mercury intrusion porosimetry (MIP), and thermogravimetric analysis. The results show that specimens prepared using the pressing method exhibit better mechanical performance with compressive and splitting tensile strength reaching 64.8 MPa and 5.6 MPa at 28 d, respectively, which increased by 111.07% and 143.48% compared to specimens prepared through vibration molding. The addition of FA and GGBS reduces the early strength of the block to a certain extent but without a significant adverse effect on later strength. GGBS demonstrates faster hydration and a better filling effect. The addition of GGBS or FA refines the pore structure and reduces the diameter of pores in the paste, which is beneficial for improving the dry shrinkage performance of the block. At 120 d, the dry shrinkage of blocks containing 50% FA and GGBS shows a reduction of 29.7% and 27.1%, respectively, compared to blocks made with cement. The properties of the silt blocks can be notably enhanced through mechanical force, particle gradation, and hydration action. The preparation of artificial blocks such as road bricks and ballast blocks using dredged soil as the main raw material has been applied in projects such as the Yangtze River waterway regulation in China and Skikda Port in Algeria. [ABSTRACT FROM AUTHOR]

Fused filament fabrication (FFF) is a key extrusion-based additive manufacturing (AM) process for fabricating components from polymers and their composites. Functionally gradient materials (FGMs) exhibit spatially varying properties by modulating chemical compositions, microstructures, and design attributes, offering enhanced performance over homogeneous materials and conventional composites. These materials are pivotal in aerospace, automotive, and medical applications, where the optimization of weight, cost, and functional properties is critical. Conventional FGM manufacturing techniques are hindered by complexity, high costs, and limited precision. AM, particularly FFF, presents a promising alternative for FGM production, though its application is predominantly confined to research settings. This paper conducts an in-depth review of current FFF techniques for FGMs, evaluates the limitations of traditional methods, and discusses the challenges, opportunities, and future research trajectories in this emerging field. [ABSTRACT FROM AUTHOR]

In this paper, the laser beam oscillation welding (LBOW) was utilized to weld a 2 mm thick AA2060 aluminum-lithium (Al-Li) alloy plate. The weld pool behaviors under three scanning paths (pure laser, O-shaped, and ∞-shaped) were investigated. It was observed that the O-shaped scanning path resulted in the most stable welding process. In addition, the weld macroscopic formation, microstructure, and mechanical property between different paths were studied. The results showed that pure laser and ∞-shaped patterns produced welding defects such as spatters and collapse during the welding process, while the O-shaped pattern exhibited good macroscopic formation at varying laser powers. The O-shaped pattern promoted the finest grain in the weld center and reduced the heat input during the welding process. The equiaxed grain zone (EQZ) width of the O-shaped pattern is the smallest compared to the other two patterns at high laser power. In addition to this, the O-shaped pattern could effectively reduce the porosity in the weld. When an O-shaped scanning pattern was adopted at the ideal laser power parameter of 3000 W, the microhardness of the weld center increased by approximately 5.6% compared to pure laser mode. [ABSTRACT FROM AUTHOR]

In this study, based on the element powder metallurgy method, a new hybrid method is proposed, which firstly prepares TiAl-based deposit precursors by the cold spraying of mixed Ti and Al powders and then combines this with hot isostatic pressing to achieve the preparation of TiAl-based alloys. This paper explores the effects of deposition parameters on deposition efficiency and coating composition and investigates the evolution of the microstructure and properties of TiAl-based alloys by different hot isostatic pressing parameters. The results show that the prepared TiAl deposits are dense and free of microstructural defects; a high deposition efficiency (75%) and small deviation of coating composition (3 at %) are obtained under the spraying parameters of 5 MPa, 500 °C. The TiAl-based alloy with a dense microstructure can be prepared by controlling the parameters such as temperature, pressure, and heating rate of subsequent hot isostatic pressing. [ABSTRACT FROM AUTHOR]

The fabrication of a single-phase (Ni,Pt)Al coating, doped with zirconium, was achieved via a method that included the simultaneous electroplating of a Pt-Zr layer, followed by a process of gas-phase aluminizing. The Zr-doped (Ni,Pt)Al coating was then subjected to an evaluation of its isothermal oxidation resistance at a temperature of 1150 °C in static air compared with a conventional (Ni,Pt)Al coating. The findings indicated that the incorporation of zirconium into the (Ni,Pt)Al coating led to a marked escalation in the rate of oxidation and a worse-scale spallation resistance, which was totally opposite to the results obtained at 1100 °C. The harmful effect of Zr on the oxidation resistance of the coating is discussed in this paper. [ABSTRACT FROM AUTHOR]

The issue of interfacial shear damage has been a significant challenge in the field of geotechnical engineering, particularly in the context of diaphragm walls and surrounding soils. Polymer grouting is a more commonly used repair and reinforcement method but its application to interface repair and reinforcement in the field of geotechnical engineering is still relatively rare. Consequently, this paper presents a new polymer grouting material for use in grouting reinforcement at the interface between concrete and soils. The bonding characteristics and shear damage mode of the interface after grouting were investigated by the direct shear test, and the whole process of interface shear damage was investigated by digital image correlation (DIC) technology. Finally, the reinforcement mechanism was analyzed by microscopic analysis. The results demonstrate that the permeable polymer is capable of effectively filling the pores of soil particles and penetrating into the concrete-soil interface. Through a chemical reaction with water in the soil, the polymer cements the soil particles together, forming chemical adhesion at the interface and thereby achieving the desired reinforcement and repair effect. In the shear process, as the normal stress increased, the horizontal displacement and horizontal compressive strain at the distal end of the loading end decreased, while the maximum vertical displacement and maximum vertical strain of the cured soil also decreased. The results of scanning electron microscopy (SEM) demonstrated that the four groups of test polymers exhibited a reduction in soil porosity of 53.47%, 58.79%, 52.71%, and 54.12%, respectively. Additionally, the form of concrete-soil interfacial bonding was observed in the concrete-cohesive layer-cured soil mode. The findings of this study provide a foundation for further research on diaphragm wall repair and reinforcement. [ABSTRACT FROM AUTHOR]

Hexagonal close-packed (HCP) metals, particularly Zirconium (Zr), Titanium (Ti), and Magnesium (Mg) alloys, have attracted significant attention due to their unique properties and wide-ranging applications in the aerospace, biomedical, and energy industries. This review paper provides a comprehensive analysis of the microstructural and textural evolution in these HCP materials under various conditions, including rolling, extrusion, drawing, and annealing. The focus of the present work lies on the deformed microstructure and texture development in HCP metals, thus elucidating the fundamental mechanisms that govern their response to mechanical stress. The interaction between dislocation movements, twinning, and slip systems is discussed in detail, illustrating how these factors contribute to the anisotropic behavior characteristic of low-symmetry HCP structures. Unlike high-symmetry metals, deformation in Zr alloys depends on the activation of various slips and twin deformation modes, which are sensitive to crystallographic orientation and strain. Like Zr, Ti alloys present a more complex deformation behavior, heavily influenced by their crystallographic orientation. The most common deformation textures in Ti alloys include split-transverse direction (split-TD), split-rolling direction (split-RD), and normal direction (ND) symmetric basal fiber textures. These textures emerge due to the activation of multiple slip systems and twinning, which are dependent on external factors such as temperature, strain rate, and alloy composition. For Mg alloys, the poor formability and brittleness associated with the dominance of the basal slip system under ambient conditions is a critical material development challenge. The activation of non-basal slip systems introduces complexities in controlling texture and microstructure. However, their activation is crucial for optimizing mechanical properties such as strength and fatigue resistance. The tendency for twinning in Mg alloys further complicates their deformation behavior, leading to challenges in ensuring uniform mechanical performance. Modifying the alloy composition, grain size, and texture can additionally influence the activation of these deformation mechanisms. This review further explores the roles of dynamic recrystallization and grain growth in tailoring mechanical properties, with a particular focus on microstructure and texture evolution during annealing. Through this detailed review, we aim to present a thorough understanding of the microstructural and textural evolution in HCP materials, thereby guiding future research and industrial applications. [ABSTRACT FROM AUTHOR]

In this paper, the effects of laser heat input on the microstructures, tensile strength, and fatigue properties of Ti60 laser welded joints were investigated. The results show that with the increase in laser heat input, the macro morphology of the weld zone (WZ) changes from the Y-type to X-type. In the Y-type WZ, the porosity defects are almost eliminated. In contrast, there are a lot of porosity defects in the lower part of the X-type WZ. The microstructure of the base metal (BM) comprises equiaxed α phases, and β phases are mainly distributed at the boundaries of α phases. The heat-affected zone (HAZ) is comprised of α phases and acicular α′ phases, while the WZ mainly contains acicular α′ phases. With the increase in laser heat input, the quantity of the α phase gradually decreases and the acicular α′ phase gradually increases in the HAZ, and the size of the acicular α′ phase in the WZ gradually decreases. Due to the different microstructures, the hardness of BM is lower than the HAZ and WZ under different laser heat input conditions. In the tensile tests and low-cycle fatigue tests, the welded joints are fractured in BM. The porosity defects do not have decisive effects on the tensile and low-cycle fatigue properties of Ti60 laser welded joints. [ABSTRACT FROM AUTHOR]

This paper gives an overview of findings, connected with metallurgical activity, at the Pržanj archeological site near Ljubljana, Slovenia. More than 230 kg of slag and other remains connected with early medieval (from the 5th to the 12th century AD) metallurgical activities was found at the excavation site. The remains were grouped into four categories, i.e., furnace remains, ore, slag and a ferrous product, and analyzed in detail to obtain their chemical composition, microstructural characteristics, and mineral phase composition. The furnace wall remains, identified by their morphology and chemical composition, revealed an intensive iron processing activity at the site. The iron ore at the site was identified as goethite (FeO(OH)), a surprising find in Slovenia where limonite is typically used, and its presence suggests the potential exploitation of local bog iron ore, given the site's geological context. Abundant slag remains at the site, identified by their shape, molten microstructure, and mineral components like wuestite, fayalite, and hercynite, indicated sophisticated smelting practices, including the use of CaO-rich materials to lower the melting temperature, a technique likely preserved from antiquity. Findings of ferrous products at ancient metallurgical sites are rare due to their value, but the discovery of a corroded iron bloom conglomerate at this site, initially mistaken for furnace remains, highlights the challenges in identifying small, corroded ferrous fragments that are often misidentified as ore. The results indicate extensive metallurgical activity at the excavation site, marking it as the first documented early medieval iron smelting production site in Slovenia. [ABSTRACT FROM AUTHOR]

This document is a collection of research papers on advanced aerospace materials. The first section focuses on deformation processing of aerospace alloys, including the flow stress constitutive model and deformation mechanism of Nb521, the hot-deformation behavior of the 2219 aluminum alloy, and the texture formation of Cu-8%Al alloys. The second section explores materials suitable for extreme-environment applications, such as high-entropy ceramics and Cu40Nb30(TiB2)20C10 multi-principal element alloys. The third section discusses light-weighting advanced aerospace materials, including aero-nanomaterials, the mechanical performance of the β-Mg17Al12 interphase in magnesium-aluminum alloys, and the mechanical response and fracture of carbon-fiber-reinforced polymer matrix composites. The collection aims to provide readers with new developments in the field of advanced aerospace materials for further research. [Extracted from the article]

To overcome the problem of Cr2O3 and Al2O3 inclusions in CuCr50 alloy prepared by aluminothermic reduction method, in this paper, a novel methodology for strengthening metal–slag separation through in situ slagging is proposed. CuCr50 alloys were prepared by metallothermic reduction using Al and Al-Mg as reducing agents, and the physical properties of the slag, such as viscosity, density, and surface tension, were adjusted by controlling the proportion of CaO in the slagging agent in the raw material to achieve good separation of the slag–metal. The results show that with the ratio of CaO increased, CaO and MgO were coupled to make slag, which combined with Cr2O3 and Al2O3 to form CaCr2O4, MgCr2O4, and CaAl4O7 in the slag, thus reducing the content of impurities in the alloy. When RCaO/(CaO + Al2O3 + MgO) = 20%, the Cr content ranged from 46.61% to 47.09%, the inclusions accounted for 1.60%, the Cr particle size was refined to 20 µm, the number of Cr spherical crystals accounted for 9.88%, the conductivity reached 14.96 MS/m, and the hardness reached 100.23 HB. After heat treatment, the Cr phase was refined in the alloy, the conductivity increased from 14.96 MS/m to 18.27 MS/m, and the hardness increased from 100.23 HB to 103.1 HB. This method is expected to provide an effective method for the preparation of CuCr50 contact materials. [ABSTRACT FROM AUTHOR]

The growing use of aluminum and its compounds has increased the volume of aluminum waste. To mitigate environmental impacts and cut down on manufacturing expenses, extensive investigations have recently been undertaken to recycle aluminum compounds. This paper outlines the outcomes of a study on fabricating standard EN AW-2007 alloy using industrial and secondary scrap through continuous casting. The resultant recycled bars were analyzed for their chemical makeup and examined for microstructural features in both the cast and T4 states, undergoing mechanical property evaluations. The study identified several phases in the cast form through LM, SEM + EDS, and XRD techniques: Al7Cu2Fe, θ-Al2Cu, β-Mg2Si, Q-Al4Cu2Mg8Si7, and α-Al15(FeMn)3 (SiCu)2, along with Pb particles. Most primary intermetallic precipitates such as θ-Al2Cu, β-Mg2Si, and Q-Al4Cu2Mg8Si7 dissolved into the α-Al solid solution during the solution heat treatment. In the subsequent natural aging process, the θ-Al2Cu phase predominantly emerged as a finely dispersed hardening phase. The peak hardness achieved in the EN AW-2007 alloy was 124.8 HB, following a solution heat treatment at 500 °C and aging at 25 °C for 80 h. The static tensile test assessed the mechanical and ductility properties of the EN AW-2007 alloy in both the cast and T4 heat-treated states. Superior strength parameters were achieved after solution heat treatment at 500 °C for 6 h, followed by water quenching and natural aging at 25 °C/9 h, with a tensile strength of 435.0 MPa, a yield strength of 240.5 MPa, and an appreciable elongation of 18.1% at break. The findings demonstrate the feasibility of producing defect-free EN AW-2007 alloy ingots with excellent mechanical properties from recycled scrap using the continuous casting technique. [ABSTRACT FROM AUTHOR]

In this paper, the effect of waste rock-wool dosage on the workability, mechanical strength, abrasion resistance, toughness and hydration products of PVA and steel fiber-reinforced mortars was investigated. The results showed that the fluidity of the mortar gradually decreased with the increase in the dosage of waste rock wool, with a maximum reduction of 10% at a dosage of 20%. The higher the dosage of waste rock wool, the greater the reduction in compressive strength. The effect of waste rock wool on strength reduction decreases with increasing age. When the dosage of waste rock wool was 10%, the 28 days of flexural and compressive strengths were reduced by 4.73% and 10.59%, respectively. As the dosage of waste rock wool increased, the flexural-to-compressive ratio increased, and at 20%, the maximum value of 28 days of flexural-to-compressive ratio was 0.210, which was increased by 28.05%. At a 5% dosage, the abraded volume was reduced from 500 mm3 to 376 mm3—a reduction of 24.8%. Waste rock wool only affects the hydration process and does not cause a change in the type of hydration products. It promotes the hydration of the cementitious material system at low dosages and exhibits an inhibitory effect at high dosages. [ABSTRACT FROM AUTHOR]

Metal products for the metallurgical and machinery industries must meet high requirements in terms of their performance, including reliability, accuracy, durability and fatigue strength. It is also important that materials commonly used to manufacture such products must meet specific requirements. Therefore, various techniques and technologies for modifying the surface layer are becoming more and more widely used. These include burnishing, which may be dynamic or static. This article studies the process of slide burnishing of surfaces of cylindrical objects. The burnishing was performed using a slide burnisher with a rigid diamond-tipped clamp on a general-purpose lathe. The tests were performed for corrosion-resistant steel X2CrNiMo17-12-2. The aim of the research was to determine the impact of changes in burnishing conditions and parameters—feed rate, burnisher depth and burnishing force at a constant burnishing speed—on the surface roughness and hardness. Additionally, the microstructure was assessed in the critical areas: the surface and the core. Another phenomenon observed was surface cracking, which would be destructive due to the occurrence of indentation. In the paper, it was stated that the microstructure, or rather the grains, in the area of the surface layer was oriented in the direction of deformation. It was also observed that in the area of the surface layer, no cracks or other flaws were revealed. Therefore, slide burnishing not only reduces the surface roughness but hardens the surface layer of the burnished material. [ABSTRACT FROM AUTHOR]

The sea cucumber is an essential nutrient source and a significant economic marine resource associated with successful aquaculture. However, sea cucumbers are highly susceptible to autolysis induced by endogenous protease after postmortem, and the phenomenon of body wall “melting” occurs, which seriously affects the food quality of products and the degree of acceptance by consumers. To satisfy the growing demand for fresh or processed sea cucumbers, we must clarify the autolysis mechanism of sea cucumbers and the methods to achieve autolysis regulation. In this paper, the factors leading to the quality deterioration and texture softening of sea cucumbers are reviewed, with emphasis on enzymatic characteristics, the autolysis mechanism, the effects of autolysis on the physicochemical properties of the body wall of the sea cucumber, and the development of potential natural protease inhibitors. We aim to provide some reference in future preservation and processing processes for sea cucumbers, promote new processing and preservation technologies, and advance the sea cucumber industry’s development. [ABSTRACT FROM AUTHOR]

This paper identifies and analyzes the microstructure of a carburized layer by using a deep convolutional neural network, selecting different carburizing processes to conduct surface treatment on 23CrNi3Mo steel, collecting many metallographic pictures of the carburized layer based on laser confocal microscopy, and building a microstructure dataset (MCLD) database for training and testing. Five algorithms—a full convolutional network (FCN), U-Net, DeepLabv3+, pyramid scene parsing network (PSPNet), and image cascade network (ICNet)—are used to segment the self-built microstructural dataset (MCLD). By comparing the five deep learning algorithms, a neural network model suitable for the MCLD database is identified and optimized. The research results achieve recognition, segmentation, and statistic verification of metallographic microstructure images through a deep convolutional neural network. This approach can replace the high cost and complicated process of experimental testing of retained austenite and martensite. This new method is provided to identify and calculate the content of residual austenite and martensite in the carburized layer of low-carbon steel, which lays a theoretical foundation for optimizing the carburizing process. [ABSTRACT FROM AUTHOR]

The traditional microstructure detecting methods such as metallography and electron backscatter diffraction are destructive to the sample and time-consuming and they cannot meet the needs of rapid online inspection. In this paper, a random forest regression microstructure characterization method based on a laser ultrasound technique is investigated for evaluating the microstructure of a titanium alloy (Ti-6Al-4V). Based on the high correlation between the longitudinal wave velocity of ultrasonic waves, the average grain size of the primary α phase, and the volume fraction of the transformed β matrix of the titanium alloy, and with the longitudinal wave velocity as the input feature and the average grain size of the primary α phase and the volume fraction of the transformed β matrix as the output features, prediction models for the average grain size of the primary α phase and the volume fraction of the transformed β matrix were developed based on a random forest regression. The results show that the mean values of the mean relative errors of the predicted mean grain size of the native α phase and the volume fraction of the transformed β matrix for the six samples in the two prediction models were 11.55% and 10.19%, respectively, and the RMSE and MAE obtained from both prediction models were relatively small, which indicates that the two established random forest regression models have a high prediction accuracy. [ABSTRACT FROM AUTHOR]

MCrAlY (M = Ni and/or Co) metallic coatings are essential for the protection of hot-end components against thermal and corrosion damage. Increasing the Al content is considered a feasible solution to improve the high-temperature performance of MCrAlY coatings. In this paper, the effects of high Al contents (12–20 wt.%) on the phase constituents and cast microstructures in MCrAlY alloys were studied by high-energy X-ray diffraction and electron microscopy techniques combined with phase equilibria calculations. High Al content improved the stability of β, σ, and α phases. Meanwhile, an evolution of the cast microstructure morphology from a dendrite structure to an equiaxed grain structure was observed. The thermal properties were analyzed, which were closely related to the phase constituents and solid-to-solid phase transitions at evaluated temperatures. This work is instructive for developing high-Al-content MCrAlY coatings for next-generation thermal barrier applications. [ABSTRACT FROM AUTHOR]