Search Results (171)

This study investigates the thermal response and surface modification of low-carbon manganese-alloyed 20GL steel during electrolytic plasma hardening. The objective was to evaluate the feasibility of surface hardening 20GL steel—traditionally considered difficult to quench—by combining high-rate surface heating with rapid cooling in an electrolyte medium. To achieve this, a transient two-dimensional heat conduction model was developed to simulate temperature evolution in the steel sample under three voltage regimes. The model accounted for dynamic thermal properties and non-linear boundary conditions, focusing on temperature gradients across the thickness. Experimental temperature measurements were obtained using a K-type thermocouple embedded at a depth of 2 mm, with corrections for sensor inertia based on exponential response behavior. A comparison between simulation and experiment was conducted, focusing on peak temperatures, heating and cooling rates, and the effective thermal penetration depth. Microhardness profiling and metallographic examination confirmed surface strengthening and structural refinement, which intensified with increasing voltage. Importantly, the study identified a critical cooling rate threshold of approximately 50 °C/s required to initiate martensitic transformation in 20GL steel. These findings provide a foundation for future optimization of quenching strategies for low-carbon steels by offering insight into the interplay between thermal fluxes, surface kinetics, and process parameters. Full article

This study investigates the mechanical behavior and deformation mechanisms of Fe-30Mn-0.05C (30Mn0.05C) and Fe-34Mn-0.7C (34Mn0.7C) steels at room temperature (RT) and liquid nitrogen temperature (LNT). The 30Mn0.05C sample exhibited a significant enhancement in both strength and ductility at LNT, achieving a total elongation of 85%. In contrast, the 34Mn0.7C sample demonstrated superior ductility (90%) at RT, with a marginal reduction in plasticity but a remarkable increase in strength (>1100 MPa) at LNT. Compared to the 30Mn0.05C, the 34Mn0.7C, characterized by higher carbon content, displayed more pronounced dynamic strain aging (DSA) effects. Additionally, a greater density of deformation twins was activated at LNT, revealing a strong correlation between deformation twinning and DSA effects. This interplay accounts for the simultaneous strength improvement and ductility reduction observed in the 34Mn0.7C at LNT. Furthermore, the 34Mn0.7C sample exhibited a significantly refined grain structure after rolling, contributing to a substantial strength increase (approaching 1500 MPa) at the expense of ductility. This trade-off can be attributed to the pre-introduction of a higher density of dislocations and deformation twins during rolling, which facilitated strengthening but limited further plastic deformation. Full article

The Charpy impact toughness of single-phase austenitic Fe-32Mn-0.6C steel was systematically investigated across a wide temperature spectrum from 25 °C to −196 °C using Charpy V-notch impact tests. The material exhibited a remarkable temperature dependence of impact energy, decreasing dramatically from 120 J at ambient temperature (25 °C) to 13 J under cryogenic conditions (−196 °C). Notably, a steep transition in impact energy occurred within the critical temperature window of −100 °C to −150 °C. Microstructural analysis revealed that synergistic effects of high strain rates and low temperatures significantly restrict dislocation slip and multiplication mechanisms, while also suppressing deformation twinning activation. This restricted plasticity accommodation mechanism fundamentally differs from the deformation characteristics reported in conventional low-carbon high-manganese steels and other face-centered cubic (FCC) alloy systems. Full article

Solutions and new processes are continually being developed to produce components demonstrating high strength and elongation. This paper focuses on medium manganese steel with a composition of 0.2% carbon, 3% manganese, and 2.15% aluminium (by weight percent). The mechanical properties of the steel and the effect of aluminium and manganese on the microstructure are investigated. The steel sheets are shaped into omega profiles using a press tool, followed by the intercritical annealing of the samples to enhance their ductility. Before the experiment, the anticipated values were a tensile strength (UTS) of approximately 1100 MPa and elongation within 30–35%. A key objective was to achieve a microstructure that incorporates residual austenite. The experimental parameters were carefully derived from an extensive exploration to identify potential weaknesses in the experiment. The main parameters selected were the intercritical annealing (IA) temperature and IA dwell time. The results revealed that the highest recorded UTS was 1262 ± 6 MPa, while the maximum elongation achieved was 16 ± 1%. Full article

Ultra-low-carbon, high-strength steels have gained significant attention due to their exceptional mechanical properties. To enhance the performance of the steel, understanding the precipitation behavior of strengthening precipitates is crucial. In this study, the precipitation behavior of ultra-low-carbon high-strength steel strengthened by nanoscale copper (Cu)-rich precipitates (CRPs) and carbonitride (CN) atomic clusters was characterized using atom-probe tomography after tempering at 400, 450, 600, and 650 °C for 2 h. The results revealed that the nanoscale copper CRPs and the CN atomic clusters were the main strengthening precipitates. The CRPs, enriched only in Cu, were observed at 400 °C. Segregation of nickel (Ni) and manganese (Mn) to the CRPs occurred at 450 °C, and the number densities of CRPs achieved the maximum value, leading to the highest strengthening effects. The size of the CRPs increased with increasing temperature; however, the size of the clusters of the carbide-forming atoms remained at almost ~1.6 nm. At 650 °C, the concentration of Cu, Ni, and Mn atoms in the CRPs was about 85.4, 4.5, and 4 at.%, respectively; however, that of Fe decreased significantly. In the lath boundaries, the size of 10% C and 0.4% C iso-surfaces was relatively larger than that in the matrix. In a reverted austenite region at 600 °C, the concentration of Ni in the reverted austenite, CRPs, and matrix was about 15, 2.5, and 2.5 at.%, respectively. Full article

This study examines the deformation behaviour and fracture mechanisms of bimetal composites (BCs) composed of high-carbon medium-manganese steel (Mn8) and low-carbon steel (SS400), fabricated through hot roll bonding. The research highlights the effect of varying thickness ratios on the mechanical properties of Mn8/SS400 BCs. The microstructure and interfacial characteristics were analysed using scanning electron microscopy (SEM), revealing a well-bonded and defect-free interface with distinct elemental distributions. Tensile and bending tests were conducted to evaluate the composites’ mechanical performance, highlighting the synergistic effects of Mn8’s high strain hardening capacity and SS400’s ductility. Mathematical models, including the rule of mixtures (ROM) and the long-wavelength approach (LWA), were employed to predict the tensile strength and plastic instability strain (PIS), with experimental results showing deviations due to interfacial strengthening mechanisms and dislocation pile-ups. The findings provide insights into the interplay between layer thickness ratios, interfacial properties, and strain hardening, offering valuable guidance for optimising the design and industrial-scale production of Mn8/SS400 BCs. Full article

The potential of an optimization process with respect to reduced mass can be used to the full extent by utilizing a high-strength material as it is, among others, strength-dependent. For the additive manufacturing process, Powder Bed Fusion of Metals using a Laser Beam (PBF-LB/M), 316L is commonly used. PBF-LB/M/316L has its benefits, like good material properties, such as availability, corrosion resistance, strength, and ductility. Nevertheless, a higher-strength material is required to fully take advantage of the optimization process and achieve a greater reduction in the mass of manufactured parts. The high-strength austenitic stainless steel investigated in this study is Printdur^® HSA. Its main alloying elements are manganese, chromium, molybdenum, carbon, and nitrogen. The steel obtains its high strength properties from the alloyed carbon and nitrogen via solid solution hardening and improving the austenite stability. Therefore, it is defined as (C+N) steel. The datasheet of the powder manufacturer describes a yield strength (R_p0.2; 0.2% offset proof stress) of 915 MPa, an ultimate tensile strength of 1120 MPa, and an elongation at fracture of 30%. These are clear benefits in comparison to PBF-LB/M/316L. Since there are no further investigations made on Printdur^® HSA, a thorough investigation of material behavior, fatigue life, and microstructure is needed. Full article

Due to the scarcity of high-grade minerals on the Earth’s surface and the ever-increasing demand for critical metals required in the production of clean energy, the search for alternative sources has become essential. Ferromanganese crusts, a mineral resource located in the depths of the ocean, contain high concentrations of valuable metals, particularly cobalt (Co) and manganese (Mn). A leaching process using sulfuric acid, with the addition of steel scrap, has been proposed for processing this resource. The study investigated the extraction of manganese (Mn) and cobalt (Co) under acidic conditions at 25 °C, employing a factorial experimental analysis. Statistical models were adjusted using response surface methodology to evaluate the effects of time and the ferromanganese crust/Fe(res) (iron residue) ratio as predictive variables. The results demonstrated that the extraction of Mn and Co could be effectively modeled through multiple regression, with strong goodness-of-fit indicators. Optimal extraction was achieved at extended durations (30 min) and lower ferromanganese crust/Fe(res) ratios (1/3) for the sampled values. Gradient analysis revealed that extraction efficiency was directly proportional to time and inversely proportional to the ferromanganese crust/Fe(res) ratio, except in the case of Co extraction at higher durations and lower ratio levels. Additionally, no precipitation of Mn or Co species was observed in the analyzed residues. Full article

The morphology and microstructure of pearlite formed in 100Mn13 high-carbon high-manganese steel aged, respectively, at 525 °C and 650 °C after 1050 °C water toughening treatment were observed and analyzed by a scanning electron microscope (SEM) and transmission electron microscope (TEM). The results show that some pearlite colonies are chrysanthemum-like and are composed of M₇C₃ lamellae and ferrite lamellae, maintaining an orientation relationship (OR) of ($\overline{3}$$3$$12$)_M7C3‖($0 \overline{2} 4$)_α, [$4 0 1$]_M7C3‖[$5 2 1$]_α. Moreover, the lamellae in pearlite colonies with chrysanthemum-like morphology are distributed in an emanative way, where there are protrusions and branches at the growth frontier. A growth physical model describing the growth process of chrysanthemum-like pearlite is proposed. Full article

The abrasive wear performance of TiC particle-reinforced high-manganese steel matrix composites with a spherical hierarchical structure under moderate impact energy was investigated. In the composites, TiC particles (10 μm in diameter) were concentrated within discrete spherical composite regions with diameters of about 100 μm. Impact abrasive wear tests were conducted to evaluate the wear performance of the composites with different volume fractions (30%, 40%, and 50%) of TiC particles compared with the matrix and a uniformly distributed TiC particle composite. The applied impact energy was 3 J. The results show that the hierarchical composite with 40% TiC particles exhibits the best wear resistance, with the wear rate reduced by 43.5% and 75.4% compared to the matrix steel and the uniformly distributed composite, respectively. The primary wear mechanism of the hierarchical composite is abrasive cutting. The design of the hierarchical configuration significantly enhances the material’s toughness, reducing fatigue spalling in the composite region during wear, thereby improving its wear resistance. Full article

The toughness of steel is a critical material property that represents the ability to absorb energy at fracture, particularly in ultra-high-strength steels. The optimal balance between high strength and ductility depends on the complexity of the microstructure formed during heat treatment, which influences the toughness of the steel. In this study, a numerical modeling approach was used to investigate the Charpy impact behavior of medium manganese Q&P (quenching and partitioning) steel with a focus on toughness and stress distribution. ANSYS Explicit Dynamics was used for numerical modeling to simulate stress distribution and energy absorption in Charpy specimens. The Johnson–Cook model approach was used to describe the material behavior for such dynamic conditions. The results showed that ductility and toughness decreased with increasing partitioning time from 300 s to 900 s. The simulation results also showed that the stress distribution was more pronounced near the notch radius. The absorbed energy of the samples increased slightly as the notch radius increased from 0.1 mm to 0.25 mm, and it significantly increased as the plate thickness increased from 7 mm to 12 mm. Full article

As the pace of human development in the ocean accelerates, the demand for corrosion-resistant building materials in marine engineering projects is constantly increasing. The development of high-performance corrosion-resistant materials and their mechanism research has gradually become the latest hotspot in the field of metal materials. Through cyclic dry–wet testing, electrochemical techniques, morphological characterization, and compositional analysis, this study simulated the impact of varying manganese content on weathering steel corrosion resistance in chloride environments. The results indicated that, compared to low-manganese weathering steel, the average rust layer thickness of high-manganese weathering steel increased by 22.5%. Additionally, manganese was found in the rust as MnO/MnO₂, acting as a catalyst to promote electron transfer, which led to a decrease in the α/γ* ratio in the high-manganese weathering steel, thereby accelerating the corrosion reaction. Full article

The effects of different pre-strain levels on the dislocation density, twinning behavior, resultant tensile properties, and cryogenic impact toughness of a high-manganese austenitic steel for low-temperature service were investigated. The results indicate that the dislocation density and volume fraction of twins are sharply increased when the pre-strain exceeds 15%, leading to an increase in yield strength and a decrease in impact toughness. At a 5% pre-strain level, few mechanical twins are observed while the dislocation density increases, resulting in enhanced yield strength whilst maintaining the toughness. The dislocation and grain refinement strengthening effects dominate the yield strength at various pre-strain levels. The initial mechanical twins and increased dislocations induced by pre-straining adversely affect the impact toughness. These findings validate the potential of controlling the mechanical twins and dislocations via pre-strain treatment as an effective approach to tailoring the mechanical properties of high-manganese austenitic steel. Full article

Among the materials used for components subjected to abrasive wear, chromium cast iron, hardfaced layers, martensitic steels and Hadfield steel should be singled out. Each of these types of materials exhibits a different morphology of structure and strength properties. Hadfield steel, characterized by an austenitic microstructure, shows the ability to strengthen the subsurface layers by cold work, while maintaining a ductile core. Hardox steels belong to the group of low-alloy martensitic boron steels. However, it should be noted that increasing hardness does not always translate into low wear values due to a change in the nature of wear. In view of the above, the authors decided to subject selected Hardox steels and Hadfield cast steels in the post-operational condition to abrasive wear tests in the presence of loose abrasive. The study showed that Hardox Extreme steel exhibits the highest resistance to abrasive wear (value of the coefficient k_b is equal to 1.39). In the case of Hadfield steel, the recorded values are slightly lower (k_b = 1.32 and 1.33), while the above ratios remain higher compared to Hardox 600 and Hardox 500 steels. The main wear mechanism of high-manganese steels is microploughing, plastic deformation and breakouts of larger fragments of material. In the case of Hardox 450 and Hardox 500 steels, the predominant wear mechanisms are microploughing and breaking out of material fragments. As the hardness of the steel increases, the proportion of wear by microcutting and scratching predominates. Full article

The research presented in this paper is part of a larger project concerning high-manganese alloys with different chemical compositions (mainly in manganese content from 21 to 31 wt.%). The presented examination results concern the analysis of the microstructure and textures in high-manganese X85MnAl29-9 steel, an age-hardenable steel, during aging at 550 °C for various times. X85MnAl29-9 steel was first hot rolled and subsequently cold rolled up to a 30% reduction. The samples were aged after deformation at 550 °C for various times in an argon atmosphere and cooled in air. The studies include X-ray phase analysis, texture measurement and observation of the microstructure by light microscopy, transmission electron microscopy (TEM) and scanning electron microscopy (SEM), as well as microhardness measurement. Research using scanning and transmission electron microscopy identified carbides in the analyzed samples. The results indicate that, when aging takes place, precipitation of κ′-carbide in an austenitic matrix and carbide κ at grain boundaries occurs. The appearance of satellites on diffraction patterns suggests that (Fe, Mn)₃AlC nano-carbides are formed within the austenite matrix by a spinodal decomposition mechanism after the alloy is subjected to long-term aging, which is a key element for structure analysis in the design of safety systems. The use of shorter aging times (up to 24 h) leads to an increase in hardness caused by the precipitation of small κ′-carbide particles in the matrix. However, long aging times (100 h) lead to an increase in the precipitation of the carbide phase (κ and κ′), i.e., the steel becomes overage, which results in a decrease in hardness. Full article