In this work the effects of long-term ageing of 9Cr-1Mo (T91) heat-resistant steel on its dynamic hydrogen embrittlement resistance in impact loading conditions were investigated. Altogether three heat-treated material states were studied, namely the initial normalized and tempered (N&T) state, i.e., 1050 degrees C/0.5 h + 750 degrees C/1 h and two long-term aged states, i.e., 600 degrees C/5000 hand 650 degrees C/5000 h. Charpy V-notch (CVN) impact bending tests were performed at room temperature for all the heat-treated material states in conditions either without or with electrochemical hydrogen charging. A brittle fracture resistance of the investigated material in individual material conditions was evaluated by the determination of Embrittlement Index (EI) values in terms of relative changes in CVN impact toughness with respect to variously selected initial and final material conditions. This approach enabled to differentiate the effects of long-term ageing, hydrogen charging, and their mutual superposition on the resulting brittle fracture resistance. The obtained results indicated excellent brittle fracture resistance of studied T91 steel in both the aged and hydrogen-charged material states at impact loading conditions.
The fatigue performance of 2024-T3 aluminum alloy is of critical importance in aerospace applications, yet the combined effects of stress ratio and geometry remain insufficiently explored. The objective of this study is to numerically investigate how different stress ratios (R = -0.2, 0.1, 0.4) and specimen geometries influence fatigue life, damage, and safety factor under varying tensile stresses (483, 241.5, and 120.75 MPa). Three specimen configurations-open-hole, transverse, and shear-were modeled and simulated using ANSYS Workbench, with input data obtained from literature-based mechanical properties and S-N curves. Results demonstrate that increasing tensile stress markedly reduces fatigue life and safety factor, whereas stress ratio exerts a non-linear influence, with intermediate values yielding the most detrimental effect. The findings reveal the interaction between stress ratio and geometry, providing new insights for fatigue life prediction and structural design of 2024-T3 aluminum alloy.
This study investigates the combined effect of temperature and notch depth on the Charpy impact toughness of API 5L X70 pipeline steel using an experimental approach coupled with statistical modeling. A 22factorial design of experiments was implemented to evaluate the influence of two factors: temperature (T), coded as X1, and notch depth (Nd), coded as X2. Charpy V-notch impact tests were performed according to the experimental matrix defined by the design of experiments, and the absorbed fracture energy (U) was measured for each condition. The results indicate that the notch depth has a more significant influence on the absorbed energy than temperature within the studied range. Furthermore, the fracture energy increases within creasing temperature, confirming the typical ductile-to-brittle transition behavior of HSLA steels. Response surface methodology was applied to model the variation of absorbed energy as a function of the studied parameters. A first-order interaction model was developed to correlate the experimental parameters (T, Nd) with the fracture energy (U) and to predict its values within the investigated domain. The obtained results contribute to a better assessment of the structural integrity of pipelines under different operating conditions.
The aim of the study is to investigate the effects on impact toughness properties of powder metallurgy (P/M) steels depending on different nickel ratios. For this purpose, ferrous P/M alloy samples containing 1.2 wt.% carbon and different nickel contents (0.5-5 wt.%) were compacted under 700 MPa pressure and sintered at 1200 degrees C under 5 & times; 10-2 Pa vacuum atmosphere. Following sintering, the densification rate and macrohardness (HV2) measurements of the samples were carried out. Fracture morphologies of the samples having different nickel content following impact toughness tests at various temperature (-40 to 40 degrees C) were imaged by scanning electron microscopy (SEM). Metallurgical characterizations of the samples with different nickel content were analyzed SEM and X-ray diffractometer (XRD). It was understood that pearlitic transformation was suppressed with the formation of nickel-rich austenitic areas in the microstructure of nickel-doped P/M steels. The hardness and impact toughness values of PM steel samples with 5 % nickel addition were increased by approximately 121 and 247 %, respectively, compared to samples without nickel addition, at all test temperatures.
The purpose of this article is the fatigue crack growth rate and stress-strain characteristic of a nickel superalloys ZhS6K. The da/dN(K) data from near-threshold to Paris regime and the stress-strain curve were obtained using a new methodology designed for bending small specimens using material extracted directly from the blade. The Hartmann-Schijve formula was fitted to describe the fatigue crack growth rate data. Failure mechanism was related to the crack propagation rate by help of fractographic analysis. A comparative analysis of the investigated material with the related alloy Inconel 718 was also performed. The tensile and compression stress-strain behavior, fatigue crack growth rate, and fracture toughness of the ZhS6K nickel superalloy were determined from a single turbine blade, with failure mechanisms examined using scanning electron microscopy. Compared to Inconel 718, ZhS6K offers higher resistance to fatigue crack growth but has significantly lower fracture toughness and stress-strain properties. The obtained results fill a gap in materials data necessary for the durability and damage tolerance assessment of turbine blades made of ZhS6K alloy. Although the primary focus is on the fracture behavior of the newly characterized material ZhS6K, the findings contribute to a broader understanding of the fracture mechanics within the entire class of structurally similar materials.
Super alloys are high-performing alloys used in gas turbine components that are exposed to high temperatures and pressures. When alloys are exposed to temperatures beyond the operating limit of turbines, the material fails. To avoid such a failure, a thermal barrier coating is provided on the substrate. In this work, a single-layer coating of CeO2 doped with YSZ in the proportion of 1 : 3 percentage is applied on Inconel X750 using the air plasma spray technique. Additionally, a double-layer coating of CSZ as the first layer and, Al2O3-TiO2 as the second layer in the proportion of 3: 2, is applied on another Inconel sample by the same process. The presence of bond coat and ceramic top coat on the substrate are confirmed by the SEM images. It is perceived from the investigations that, the porosity of the single CSZ layer is more compared to that of the double-layer (CSZ-Al2O3-TiO2) coating. The XRD analysis of the CSZ sample shows the phase transformation of monoclinic to tetragonal ZrO2 and that of double-layer coating (CSZ-Al2O3-TiO2) shows the transformation of alumina. Raman spectroscopy is done to ascertain the states of various oxides present in the coatings. The double-layer coating exhibits more hardness when compared to the single-layer coating. The hot corrosion test is carried out for 50 hours for both single and double-layer coating in the medium of the mixture containing 25% NaCl and 75% Na2SO4 solution. The change in mass per unit area of the CSZ single layer coated sample is more compared to that of CSZ-Al2O3-TiO2 double layer coating.
This study focuses on the wear behaviour of Ti-Cu-based friction composites during tribological testing at 350 degrees C under a load of 5 N and a sliding distance of 500 m. Composites were fabricated using a planetary ball mill and Spark Plasma Sintering (SPS). A mixture based on Ti and Cu is supplemented with waste-metal components (stainless steel, CuZn, and MgAl), reinforced with Al2O3 and graphene, and also serves as a lubricant. The Coefficient of Friction (COF) was determined using a ball-on-disc technique with a 100Cr6 ball as the counterbody. Microstructure and mechanical properties were determined using a Scanning Electron Microscope (SEM), Energy-Dispersive X-ray Spectroscopy (EDS), and confo cal microscopy. SEM/EDS and 3D confo cal profilometry reveal that the CuZn-containing composite (TC3) forms the smoothest and most continuous Cu/Zn-oxide-carbon glaze-like film, which minimizes abrasive wear and results in the mildest polishing of the counterbody. It combines the highest but most stable COF (similar to 0.75) with a similar to 25 % lower ball penetration depth than TC2 with MgAl.
To overcome the restriction that the solid-state recycled processes can only be performed for the single brand of aluminium alloy chips, the feasibility of solid-state recycling of ADC12 and 6005A aluminium chips at varying ratios was investigated. The chips were first mixed by ball milling and then hot compacted before hot extrusion. The results revealed that ball milling can effectively mix and refine the chips, the chips gradually refined as the milling speed increased, in contrast, the milling time and the ratio of mixed chips had little effect on the morphology and average size of the chips. Microscopic examination showed that the recycled alloy with a mixing ratio of 9:1 between ADC12 and 6005A alloy achieved the best bonding quality, with the oxide layer and Fe-rich phases crushed and dispersed in the Al matrix, which improved the strength of the recycled alloy through the dispersion strengthening mechanism. The tensile test results also showed that the recycled alloy with the ratio of 9: 1 between ADC12 and 6005A alloy has prominent mechanical properties, with the ultimate tensile strength, yield strength, and elongation of 271 and 151 MPa, and 12 % respectively. The investigation in this work provides a novel and effective method for the recycling of aluminium alloy chips and contributes to the sustainable resource utilization of the aluminium industry.
The development of low-temperature, lead-free solders with balanced mechanical reliability, functional properties, and soldering performance remains a key challenge in electronic packaging. This study systematically investigates the mechanical, electrical, thermal, microstructural, and soldering behavior of pure Sn, a hypoeutectic Sn88Bi12 alloy, and two Sn88Bi12-based composites reinforced with Cu and graphite particles. The addition of 12 wt.% Bi to pure Sn resulted in pronounced grain refinement and substantial increases in microhardness and tensile strength, while further improvements were achieved through particulate reinforcement. These strengthening effects were accompanied by moderate reductions in electrical conductivity and thermal transport properties due to enhanced electron and phonon scattering. Differential scanning calorimetry showed that Bi addition effectively lowers the melting temperature of Sn, whereas Cu and graphite reinforcements broaden the melting interval without increasing the melting temperature. Soldering tests on Cu substrates revealed improved wettability of Sn88Bi12 compared to pure Sn, characterized by a lower contact angle, enhanced spreading, and reduced intermetallic compound (IMC) thickness. Although particle reinforcement slightly reduced spreading behavior, both Cu and graphite effectively suppressed IMC growth, with graphite providing the strongest inhibition.
To address the insufficient strength-toughness, wear resistance, and corrosion resistance of AlCoCrNiMox high-entropy alloys, graphene (Gr)-reinforced AlCoCrNiMox(x = 0.1, 0.2, 0.3, 0.4) high-entropy alloy composites were fabricated by vacuum arc melting. The regulatory mechanisms of Mo content and graphene on the phase composition, microstructure, and comprehensive properties of the alloys were systematically revealed primarily via qualitative analysis, without quantitative separation of individual strengthening contributions. The phase structure, morphology, and elemental distribution were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDS). Microhardness, dry sliding wear behavior, and electrochemical corrosion performance in 3.5 wt.% NaCl solution were tested. The results show that the as-cast microstructure of the composite consists of an FCC phase, a B2 ordered phase, and a minor sigma phase. With increasing Mo content from 0.1 to 0.4, the fraction of the FCC phase gradually decreases, while those of the B2 and sigma phases continuously increase; the grains transform from coarse equiaxed grains to fine columnar grains. Graphene is inferred to be uniformly distributed at grain boundaries and phase boundaries, which is proposed to significantly refine grains, suppress elemental segregation, and forms a sound interfacial bond with the matrix. Mechanical and corrosion tests indicate that the hardness and wear resistance of the alloy increase continuously with increasing Mo content. The composite exhibits optimal comprehensive performance at x = 0.4 with 0.5 wt.% graphene addition: a microhardness of 625 HV, a wear rate as low as 2.75 & times; 10-6 mm3 N-1 m-1, and a corrosion current density of 3.82 & times; 10-6 A cm-2. The synergistic improvement in comprehensive properties is attributed to the combined effects of solid-solution strengthening by Mo, second-phase strengthening by B2 and sigma phases, as well as grain refinement, dispersion strengthening, self-lubrication, and physical barrier effects of graphene. This study focuses on qualitative discussion of the synergistic mechanisms, and the individual contribution of each mechanism is not quantified separately. This study provides experimental evidence and theoretical support for the compositional design and engineering applications of high-performance high-entropy alloy composites.
Ti36Ni49-xZr15Tax(x = 5, 10, 15 at.%) alloys were prepared using a lab-scale arc-melting furnace and homogenized at 1173 K under an argon atmosphere for 2 hours, followed by furnace cooling. The buttons were sliced into 1-2 mm-thick sheets using wire cutting. These sheets were solution-treated under an argon atmosphere, followed by aging and annealing. The results revealed an increase in hardness with Ta addition, due to solid-solution strengthening. With aging and annealing, the hardness decreased due to the softening effect of Ta diffusing from the matrix to form beta phase (beta), whose peaks were observed in XRD for the quaternary samples, as well as the development of B2 peaks for the 10 Ta and 15 Ta samples in the diffractogram. Microstructure analysis showed grain refinement with 5 Ta addition. At higher Ta content of 10 and 15 at.%, the martensite structure coarsened due to decreased grain boundary mobility.
This study aims to investigate the structure and chemical composition of zinc-aluminum coatings with a grain defect. Defects and irregularities, such as localized thickening and adhered "grains," were noticed in the coating obtained from the Zn + 7 wt.% Al melts at 480 degrees C. As a solution, it was observed that the galvanizing temperature range of 410-460 degrees C maintains a thickness of 8-13 mu m. At 480 degrees C, the coating thickness increases to 35-40 microns, and local defects in the form of grains measuring 110-120 microns appear. By analyzing the binary systems Al-Fe, Fe-Zn, and Zn-Al, and the ternary system Zn-Al-Fe, conclusions were drawn about the phase composition of the defect and the possible reasons for its occurrence. Finally, the steps to rectify this issue have been outlined.
The stabilizing device is a component of the automatic surveying robot. To address wear and tear on the friction plates during use, graphene (Gr)/high-entropy alloy coatings were applied to the aluminum alloy friction plates using laser cladding technology. A systematic study was conducted on the alloy using scanning electron microscopy/EDS, a hardness tester, a friction and wear tester, etc. The experimental results show that the coating bonds well to the substrate. The Gr/CoCrFeNiNbx coating is mainly composed of equiaxed crystals, with Gr playing a strengthening role and Nb element playing a fine grain strengthening role. The coating has excellent mechanical properties, with a microhardness between 462-487 HV and an average friction coefficient between 0.46-0.54. Through practice, laser cladding a Gr/CoCrFeNiNbx coating on the surface of the stable device of the automatic surveying robot ensures its normal operation and extends its service life.
This study evaluated the microstructure, martensite morphology, and mechanical properties of API X60 dual-phase pipeline steel, aiming to understand the relationship between microstructure and mechanical properties. Following annealing at various intercritical temperatures (740, 760, 780, and 810 degrees C), X60 dual-phase steel with varying martensite volume fractions was produced. To create distinct martensite morphologies, three treatments were developed. Due to the Intermediate Quenching (IQ) treatment, fine and fibrous martensite morphology was formed, which was evenly distributed throughout the ferrite matrix. The Direct Quenching (DQ) treatment showed dispersed martensite islands within a ferritic matrix. However, the martensite and ferrite morphologies produced by the Step Quenching (SQ) treatment were blocky and banded. Results revealed that increasing the amount of martensite improves both yield strength and ultimate tensile strength while decreasing ductility. This result indicated that adjusting heat treatment parameters can optimize X60 (DP) steel for strength-critical applications. According to the results of the experiment, API X60 (DP) steel with a finely distributed microstructure has higher tensile strength than steel with other microstructures.
The effects of annealing temperature on the microstructure and texture of the Zr-Snanalysis, and texture analysis. The results show that as the annealing temperature following beta-quenching increases, the grain size in the metallographic structure of the Zr-Sn-Nb-Fe-V sheet gradually increases, and the average size and size distribution range of the SPPs gradually increase. The Zr-Sn-Nb-Fe-V sheets at various annealing temperatures all have {0001} basal texture, and the texture strength of the sheets at different annealing temperatures varies significantly.
This paper investigates the effects of intercritical annealing time on the mechanical properties, microstructure, and element distribution of Fe-0.21C-10Mn-4.8Al-0.5Cu-0.4Cr-0.2Ti medium manganese steel by setting different intercritical annealing times in the critical zone. The mechanisms underlying the observed phenomena were analyzed using characterization tron microscopy (SEM), and electron backscatter diffraction (EBSD). The results show that the material exhibits a tensile strength of 1250 MPa, an elongation of 45 %, and a strengthductility product as high as 56.3 GPa%. The optimal microstructure is a complex phase structure composed primarily of austenite with multiple morphologies, delta-ferrite, and martensite. With the prolongation of annealing time, the morphology of retained austenite gradually transforms from fine lath-shaped to larger block-shaped austenite. The thermodynamic and mechanical stability of retained austenite in the AT40 sample is significantly improved, thereby enhancing the mechanical properties of the sample.
This study investigates the effects of heat treatments and hot isostatic pressing (HIP) on the microstructure and mechanical behavior of Ti-6Al-4V parts manufactured by electron-beam powder bed fusion. Solution treatment at 950 degrees C, followed by aging at 500-600 degrees C, did not alter porosity. Aging increased the alpha-phase ratio and compensated for the strength reduction induced by ST. All HIP cycles significantly reduced pore size and pore count, with the 800 degrees C/200 MPa cycle yielding the highest average relative density of 99.86 %, resulting in a maximum yield strength of 948 MPa and a maximum ultimate tensile strength of 1013 MPa. An 800 degrees C/200 MPa HIP cycle increased ductility while maintaining strength, owing to limited alpha-lath coarsening. Super-transus HIP at 1050 degrees C/100 MPa transformed columnar beta grains into equiaxed structures, causing significant alpha-lath coarsening, a loss of mechanical strength, and increased anisotropy. These findings emphasize the need to optimize post-processing to balance porosity elimination, microstructural refinement, and mechanical performance in Ti-6Al-4V components.
This study investigated the conditions for self-propagating high-temperature synthesis (SHS) of FeB. Hematite (Fe2O3) and magnetite (Fe3O4) powders were used as iron sources, and phases generated under varied aluminum stoichiometries were identified. The SHS reactions produced loose powder products. Significant levels of impurities were detected in both experimental sets along with the FeB compounds. XRD analysis of the SHS products revealed the presence of only Fe2B and MgO phases. Removal of Mg-based impurities was carried out through HCl leaching at different concentrations. The targeted FeB structure was obtained as intended in the experiments. Optimal conditions were identified as a reduction of the hematite-boron oxide mixture with 110 % stoichiometric Mg and subsequent leaching in 8 M HCl.
Titanium alloys are ideal materials for load-bearing components, and hot forming is the primary method for manufacturing these parts. In this work, the hot deformation behavior and microstructure of an anti-damage titanium alloy are studied, and a phenomenological constitutive model is established. The results show that hot deformation has little effect on the shape of the equiaxial alpha phase, and the alpha phase retains its equiaxial morphology. The size and fraction of the alpha phase vary with the hot-deformation parameters. The dynamic phase transformation, Ostwald ripening, and spheroidization occur simultaneously during hot deformation. An Arrhenius constitutive equation is established with a correlation coefficient of 0.9848, and the model can be utilized to predict the flow behavior of the studied titanium alloys at high-temperature deformation.
In this study, the influence of the dual-beam energy ratio on weld metal geometry, microstructural evolution, and mechanical performance was investigated for two duplex stainless steels: 2507 type super duplex, 2304 type lean duplex, and their combination. Butt joints in 5 mm thick sheets were produced using an IPG YLS-5000 fiber laser equipped with a twin-spot module, with a beam power ratio of 50: 50 and 65 : 35. Weld cross-sections were analyzed using optical and scanning electron microscopy, phase fractions were quantified by image analysis, and mechanical properties were assessed via Vickers hardness mapping and room-temperature tensile tests. A 65 : 35 split concentrated energy in the primary beam, narrowing the bead by up to 33 % and deepening penetration by up to 329 %, while accelerating cooling to refine ferrite dendrites, suppress coarse boundary austenite, and shift phase balance toward higher ferrite contents (up to +10 %). These microstructural changes moderated weld metal hardness, bringing 2507 type super duplex steel closer to base-metal levels, and promoted mixed-mode fracture with smaller, more uniform dimples in a combination of 2507 type super duplex and 2304 type lean duplex steels, exhibiting the highest toughness under primary beam dominance. The results demonstrate that precise control of beam power ratio enables tailored duplex weld microstructures and properties, offering a route to optimize joint performance in demanding applications.
