Materials and Technology

STUDY ON THE EFFECT OF THERMAL-OXYGEN AGING ON THE ADHESION PROPERTIES OF WASTE RUBBER POWDER MODIFIED ASPHALT AGGREGATE BASED ON SURFACE FREE ENERGY THEORY

2025-12-17T06:33:11+01:00

Waste rubber powder modified asphalt (WRMA) has attracted considerable attention due to its environmental friendliness and excellent road performance. However, WRMA is susceptible to thermal-oxygen aging during long-term service, which causes changes in the adhesion between asphalt and aggregates. It can lead to water damage and other defects in an asphalt mixture. The present study was conducted to elucidate the mechanism, with which thermal-oxygen aging affects the adhesion properties of WRMA-aggregate systems, comprising aggregates of limestone and diabase. A thin film oven and a pressure aging vessel (PAV) were utilized in the simulation of various aging conditions of WRMA to systematically evaluate the adhesion energy, peeling energy, and the pull-off tension strength (POTS) in dry conditions of a WRMA-aggregate system, based on the surface free energy (SFE) theory, combined with pull-off tests and WRMA rheological properties. The results indicate that thermal-oxygen aging increases the surface free energy and adhesion energy of WRMA in dry conditions but decreases the peeling energy in wet conditions; thermal-oxygen aging weakens the water damage resistance of WRMA. In addition, the adhesion energy ratio (ER) of acidic diabase is lower than that of alkaline limestone, indicating that it is more susceptible to the influence of moisture. The pull-off tests showed that in dry conditions, a pull-off failure occurred within WRMA, while thermal-oxygen aging increased the complex viscosity and cohesion energy of WRMA, enhancing its resistance to failure and improving adhesion to aggregates in dry conditions. A strong positive correlation was observed between the complex viscosity, cohesion energy, and POTS of WRMA. The V&C index proposed in this paper exhibits a high linear correlation with tensile strength, indicating that the V&C index can effectively predict the adhesion performance of WRMA-aggregate systems in dry conditions. This study provides a theoretical basis for optimizing the anti-aging design of WRMA pavement and evaluating the water stability of asphalt mixtures.

APPLICATION OF GROUND GRANULATED BLAST-FURNACE SLAG IN WASTE ROCK-TAILINGS CEMENTED BACKFILL OF A COPPER MINE

2025-12-17T06:33:13+01:00

This research investigates the feasibility of utilizing ground granulated blast-furnace slag (GGBS), crushed stone and copper tailings (CTs) for cemented paste backfill. Experiments were conducted with waste rock and CTs as aggregates, in a ratio of 6:4, along with various combinations of GGBS and cement as binders. The influence of the GGBS proportion on the consolidation of backfill was also explored. The unconfined compressive strength (UCS), the tensile strength (TS) and the ASTMC1202 of electric flux were all tested and used in the analysis of backfill characteristics. The results show that (i) under standard curing conditions, after 28 days of cement hardening, ground granulated blast-furnace slag (GGBS) continues to hydrate, exhibiting a strength effect that results in a strength increase range of 14–38 %; (ii) the addition of mineral powder to concrete can reduce the hydration heat of the paste; (iii) for the same curing time, the migration charge of the concrete test block decreases with the increase in the GGBS content, while for the same GGBS content, the migration charge of the test block decreases with the increase in the curing time; (iv) as the GGBS’s activating effect gradually develops, the interfacial forces and diffusion process at the adjacent boundaries become active, and the hydration reaction rate increases, improving the later strength of the fill material. Based on these results, it was concluded that GGBS can be utilized as a binder when a gravel-tailings aggregate mixture is used as the backfill material.

ABSORBED ENERGY MODELING OF HYPOEUTECTOID STEELS USING LINEAR REGRESSION AND GENETIC PROGRAMMING TAKING INTO ACCOUNT CONTINUOUS CASTING PARAMETERS

2025-12-17T06:33:15+01:00

Štore Steel Ltd. is one of the major flat spring steel producers in Europe, producing several hundred steel grades with different chemical compositions. (180 × 180) mm billets are cast using a continuous casting machine with a 9-m radius. The macrostructure of the billets influence the mechanical properties of rolled material. For impact testing, standard test pieces are obtained from the rolled material at a defined location and orientation. Accordingly, the reduction ratio is also essential. Based on 2243 V-notch test pieces obtained from rolled materials produced in several batches between January 2019 and May 2024, models for predicting the absorbed energy of the rolled material at temperatures ranging from –60 °C to 20 °C were developed using linear regression and genetic programming. The models incorporated parameters such as chemical composition (contents of C, Si, Mn, S, Cr, Mo, Ni, Al, and V), casting conditions (average casting temperature, mold water flow, average difference between input and output mold cooling water temperature, average cooling water flow and pressure in three zones of secondary cooling), as well as the width and thickness of the rolled bars and test temperature. The genetic programming model outperformed the linear regression model.

EFFECT OF SULPHUR ON WETTABILITY OF LIQUID FE-0.45%C WITH ALUMINA

2025-12-17T06:33:16+01:00

Non-metallic inclusions, particularly alumina (Al₂O₃), pose significant challenges in steelmaking. Their behaviour in molten steel is largely governed by wettability. This study investigates the effect of sulphur, a surface-active element, on the wettability between liquid Fe-0.45%C and alumina substrates, to improve the understanding of alumina non-metallic inclusion formation in medium carbon steel. Experiments were conducted using the sessile drop method in a high-temperature melting microscope. Three Fe-0.45%C samples with varying sulphur contents (0.0020, 0.0120, and 0.0340 w/%) were placed on polished single-crystal alumina substrates and heated to 1600 °C in a purified argon atmosphere. Results show that increasing sulphur content in the Fe-0.45%C melt decreases the contact angle with alumina substrates from 106.5° (0.0020 w/% S) to 102.0° (0.0340 w/% S). Furthermore, sulphur addition increases the influence of temperature leading to a clearer trend of decreasing contact angle values as temperature rises. This implies an increased risk of solid alumina non-metallic inclusion formation if the sulphur content is elevated.

INFLUENCE OF CURING STRESS ON THE PULL-OUT BEHAVIOR OF A SINGLE GEOGRID RIB PLACED IN CEMENT-STABILIZED DREDGED SLURRY

2025-12-17T06:33:18+01:00

Cement-stabilized dredged slurry, despite its enhanced compressive strength, lacks tensile strength, particularly with low cement contents. Geogrid reinforcement is usually used in high-fill projects to improve the soil tensile and shear strengths, but research on their interface characteristics under curing stresses is limited. A prior understanding of the frictional properties at the interface is crucial for assessing the impact of curing stress on the interface property of geogrid-reinforced cement-stabilized slurry, given the geogrid mesh’s intricate interlocking. The study included pull-out tests on cement-stabilized dredged slurry reinforced with a single geogrid rib, after removing the mesh openings. The results showed that regardless of whether the curing stress was applied, the pull-out curves showed that the pull-out force increased rapidly in the initial stage and then gradually decreased after reaching the peak force. Specimens that had undergone curing stress exhibited consistently higher peak pull-out forces compared to those that had not. The interfacial shear strength increased with the normal stress, with reduced moisture content and increased cement dosage correlating with elevated shear strength. Higher moisture content significantly reduced interfacial cohesion, with a slight increase in the friction angle. Conversely, increased cement content significantly raised both interfacial cohesion and friction angle. Curing stress primarily affected the interfacial cohesion, with a relatively minor impact on the friction angle.

EFFECTS OF A LaNaY CATALYST ON THE PYROLYSIS PRODUCT DUSTRIBUTION AND REACTION MECHANISM OF OIL-PRONE COAL

2025-12-17T06:33:20+01:00

Currently, traditional coal pyrolysis processes suffer from low tar yield and poor tar quality, which seriously hinder the development and industrial application of coal pyrolysis technology. To address these challenges, this study innovatively prepares a LaNaY catalyst using ion exchange method and systematically investigates its effect on product distribution during the pyrolysis of oil-prone coal. It designs experiments to optimize the La loading, pyrolysis temperature, and catalyst coal contact method, and investigates the effect of the H₂ atmosphere. The results showed that when the La loading amount was 1.5 w/%, the La:Na molar ratio was 1:1, and the catalyst was fully in contact with coal using the in-situ loading method, the tar yield reached a maximum value of 18.6 % at 600 °C under the H₂ atmosphere. At 700 °C, under the same conditions, the H₂/CO molar ratio in the gas product reached 2.5. Compared with traditional NaY molecular sieve catalysts, the introduced La element significantly enhanced the catalytic performance of the LaNaY catalyst. It not only effectively improved the tar yield, but also promoted the generation of light aromatic hydrocarbons by inhibiting heavy polycyclic aromatic hydrocarbons (PAHs), thereby increasing the H/C atomic ratio of tar from 1.2 to 1.5, significantly improving the tar quality. Crucially, the catalyst exhibited high stability over multiple cycles and excellent regenerability, underscoring its potential for industrial application. This study provides an effective solution for an efficient and high-value conversion of oil-prone coal, providing a significant technical foundation for the future optimization of the catalytic pyrolysis technology.

IN-SITU TEM STUDIES ON PLASTIC DEFORMATION MECHANISMS IN SLM AUSTENITIC STAINLESS STEEL

2025-12-17T06:33:22+01:00

This paper reviews the research on the plastic deformation mechanisms of selective laser melting (SLM) austenitic stainless steel using in-situ transmission electron microscopy (TEM). The SLM technology, which manufactures 3D metal components with ultra-fast cooling rates, demonstrates unique plastic deformation mechanisms, including coordinated effects of dislocation slip, twinning, and phase transformation. In-situ TEM tensile experiments visually reveal these dynamic processes: dislocation cell walls replacing grain boundaries as the primary dislocation sources, “slip-step” characteristics of dislocations at cell walls, and the layer-by-layer growth mechanism of nano-twins. These processes significantly enhance the material’s strength-plasticity synergy. At low temperatures, deformation-induced martensitic transformation (DIMT) occurs via the γ→ε→α' path. Phase nucleation is closely related to dislocation accumulation and the intersection of ε-plates, with in-situ TEM capturing the dynamic process of phase transformation in real-time. This research indicates that stacking fault energy (SFE) is a key factor influencing phase transformation. The unique delayed DIMT phenomenon in SLM austenitic stainless steel is attributed to the high dislocation density, which hinders the movement of partial dislocations, significantly enhancing the material’s ductility. The in-situ TEM technique provides key evidence for revealing the plastic deformation mechanisms of advanced metals and offers guidance for high-performance material design.

NUMERICAL SIMULATION AND EXPERIMENTAL VERIFICATION OF HEAT TREATMENT OF A SADDLE HOLLOW TUBE

2025-12-17T06:33:24+01:00

To study the microstructure evolution of 42CrMo steel saddle-shaped hollow tubes during heat treatment, this study integrates numerical simulation with experimental validation, establishing a thermophysical database developed in JMatPro software and coupled with a DEFORM-based 3D finite element model for multiphysics-coupled quenching-tempering simulations. Four monitoring nodes (P1–P4) recorded temperature field variations and microstructure evolution. The results show that the simulated microstructure evolution agrees with the predictive law of continuous cooling phase transition. After quenching, a metallographic structure mainly composed of martensite is formed, and it transforms into tempered sorbite during tempering. Eventually, a typical tempered sorbite-ferrite dual-phase structure is formed, and there is no obvious tendency of tempering brittleness. The actual experiment is basically consistent with the simulation results. The geometric parameters (wall thickness, radius of curvature) had a relatively small influence on the uniformity of microstructure transformation, confirming the effectiveness of the heat-treatment parameters.

ANISOTROPIC MICROSTRUCTURAL EVOLUTION OF (001), (110) AND (111) PLANES IN SRR99 SINGLE-CRYSTAL SUPERALLOY

2025-12-17T06:33:26+01:00

We investigate plane-dependent microstructures in an SRR99 single-crystal superalloy in the as-cast condition. Using optical and scanning electron microscopy, we examine sections parallel to the (001), (110), and (111) planes. Dendrite traces display "+" symmetry on (001), asymmetric "+" symmetry on (110), and an "×" pattern on (111). The γ' precipitates appear as irregular cube-like, triangular-prism-like, and triangular-pyramid-like shapes on (001), (110), and (111), respectively, whereas eutectic pools and carbides show no marked plane-dependent differences under the present conditions. These plane-specific observations provide a concise basis – limited to the as-cast state – for discussing anisotropic microstructural features that may be relevant to hot-cracking susceptibility and for clarifying how sectioning orientation influences apparent morphology in single-crystal superalloys.

SYNERGISTIC EFFECTS OF MARBLE POWDER ON MECHANICAL PROPERTIES IN 3D PRINTED PLA/PCL HYBRID COMPOSITES

2025-12-17T06:33:27+01:00

Rising concerns about environmental pollution and the depletion of fossil-based resources have increased the demand for biodegradable alternatives to traditional petroleum-based plastics, particularly in industries such as automotive manufacturing. In this study, biodegradable composites made from polylactic acid (PLA) and polycaprolactone (PCL), reinforced with marble powder (MP) as the filler, were developed and thoroughly evaluated. Composite samples were fabricated using 3D printing to ensure precision and consistency. The structural and mechanical properties of the PLA/PCL/MP composites were examined using X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM). XRD results indicated that the addition of marble powder enhanced the crystallinity of the composites, while FTIR analysis showed chemical interactions between the polymers and the filler, suggesting improved compatibility. SEM images revealed better interfacial bonding and a uniform phase distribution, which contributed to enhanced mechanical performance. Compared to pure PLA/PCL blends, the composites reinforced with marble powder demonstrated significant improvements in tensile strength, flexural strength, impact resistance, and overall density. These results highlight marble powder’s dual role as an economical filler and an effective reinforcement. Overall, the findings suggest that PLA/PCL/MP composites are lightweight, durable, and sustainable, making them highly promising for automotive applications as they support the broader move toward eco-friendly, high-performance materials in engineering.

THERMAL DEGRADATION OF CEMENTED-CARBIDE CUTTING INSERTS AND INFLUENCE OF DRY CUTTING ON REPEN LIMESTONE

2025-12-17T06:33:29+01:00

This paper presents the results of a thermographic analysis of Fantini Sandvik H6T cutting inserts during the dry cutting of dimension stone – Repen limestone – using a Fantini 70-RA-BU bank chainsaw machine in the underground rooms of the Debela Griža quarry, Slovenia. It is known from literature that the temperature reached at the contact between a cutting insert and stone is also an important factor affecting the service life and cutting performance when cutting dimension stone. Furthermore, the critical temperature for thermal damage during granite cutting was identified as 100–200 °C, while for cutting sandstone or limestone, it was 100 °C. Specimens of the used H6T cutting inserts were subjected to a detailed metallographic investigation to evaluate the changes in the surface structure and hardness. Additionally, possible reasons for the wear of cutting inserts due to the contact temperature and surface tension were discussed.

PERFORMANCE EVALUATION AND MICROSTRUCTURAL ASSESSMENT OF ECO-FRIENDLY CONCRETE WITH MICRONIZED BIOMASS SILICA AND STEATITE POWDER

2025-12-17T06:33:30+01:00

Cement is the most widely used binder in concrete around the globe. Natural assets are utilised as raw materials to make the essential components used in the production of concrete. This process requires an enormous quantity of energy and emits greenhouse gases, especially carbon dioxide (CO₂), which contribute to global warming and have an adverse effect on the environment. These hazardous emissions produced by the cement industry can be minimized by employing alternate approaches, such as partially replacing cement with supplementary cementitious materials (SCMs). Many research investigations examined the effectiveness and performance of pozzolanic substances as an alternative to cement. In the present study, cement is partly replaced with different SCMs, such as micronized biomass silica (MBS) and steatite powder (SP). Various proportions of MBS – (3, 6, 9 and 12) % – were used. Furthermore, a consistent SP content of 5–10 % was utilised. Fresh, mechanical and microstructural features of concrete were studied after the inclusion of SP and MBS. The incorporation of 6 % MBS and 5 % SP generated an excellent compressive strength of 41 MPa, which was 17 % higher than that of ordinary concrete. Similarly, the split tensile and flexural strengths were 3.66 MPa and 4.5 MPa, respectively. It was observed that introducing these elements to cement enhanced its mechanical and microstructural properties. Thus, the optimal combination determined included 5 % SP and 6 % MBS. According to the scanning electron microscopy (SEM) study, the structure of the concrete matrix was improved by sealing the micropores and interfacial transition zone (ITZ) with the calcium silicate hydrate (CSH) and magnesium silicate hydrate (MSH) gels, resulting in a denser microstructure. These components demonstrated their ability to substitute cement without impairing the performance of concrete. Overall, MBS and SP are excellent supplementary cementitious materials. Thus, the results of this research have practical significance for potential application of these components in the production of sustainable concrete.

ACCURATE MEASUREMENT OF COATING THICKNESS ON FULLY-FINISHED NON-ORIENTED ELECTRICAL STEELS USING FIB-SEM

2025-12-17T06:33:32+01:00

In this study we investigated the potential of using FIB-SEM microscopy to measure the thickness of coated layers on fully-finished, non-oriented electrical steel of NO grades. When using FIB-SEM with gallium ions (Ga⁺) to prepare cross-sections of layers with a thickness of a few micrometers (µm), precise ablation of the material with good spatial resolution is essential. Ga⁺ generated at an accelerating voltage of 30 kV enable the effective localized removal of material. The sample can be protected with a thin layer of platinum (Pt) deposited by Ga⁺ to prevent damage to the top layer during the initial ablation process and to achieve a smoother final cut. The result of this procedure is a clean and sharp cross-section suitable for high-resolution SEM imaging. The presented microscopic method for measuring the thickness of the coatings on fully-finished, non-oriented, electrical steel samples using FIB-SEM has proven to be repeatable, robust, specific, and has an appropriate detection limit for the thickness range of typical coated layers in non-oriented electrical steel sheet.