Journal of Materials Engineering and Performance最新文献

The performance study of the fabricated stirrer was based on tensile, fatigue, flexural, and corrosion tests. The tensile specimen fractured at the base metal showed a higher value of ultimate tensile stress (≈ 12%) and extension (≈ twice) as compared to that of the specimen fractured at the weld zone (WZ) which was due to the difference in the fracture modes with the former being more plastic and the latter being restrained by precipitate decohesion–fragmentation phenomena. No fracture was visible for the specimens subjected to 10⁵ fatigue cycles, and the force–displacement behavior was observed to follow a closed-loop hysteresis curve. Implementation of the numerical method showed a logarithmic increase in the maximum deflection at the midspan, where the angular variable factor plays an important role in controlling the flexural deformation. The slower cooling rate of the WZ (= 44.97 °C/s) during solidification led to the Mo segregation and caused corrosion at the nanoscale level due to the formation of localized concentration cells. The introduction of ‘weld shield glass–camera’ assembly and ‘neutral density filter–infrared pyrometer’ combination helped in capturing the five stages of free-mode droplet transfer and the weld pool thermal cycle, respectively.

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In this study, the coefficient of thermal expansion (CTE), crystallization behavior, refractive index, and in-line transmittance of La₂O₃-Y₂O₃-Al₂O₃-B₂O₃-SiO₂ glasses with different TiO₂ contents were studied. With the increased in TiO₂ content, the CTE value could be adjusted in the range of 6.0 × 10⁻⁶/°C-6.5 × 10⁻⁶/°C. And the refractive index gradually increased from 1.6935 to 1.8010 due to the high refractive factor of TiO₂. Glass has an excellent in-line transmittance of more than 79%. This provides good conditions for brazing transparent ceramics to obtain joints with excellent in-line transmittance and high strength. Additionally, the increase in TiO₂ content decreased the crystallization characteristic temperature of the glasses. After crystallization treatment, the type of crystals changed and the crystal content gradually increased.

Recycled glass grit was applied to the blast-cleaning of AA6082 aluminum alloys. Effects on morphology, chemistry and corrosion of the substrates were studied and compared with garnet blast-cleaning. The substrates were inspected by means of scanning electron microscopy, energy-dispersive x-ray spectroscopy, x-ray diffraction and scanning confocal microscopy. Electrochemical impedance spectroscopy and cyclic corrosion tests in artificial seawater were applied. Glass grit generated irregular isotropic surface morphologies and promoted the embedment of glass debris into the substrate. The surfaces met the profile roughness requirements for offshore applications. The corrosion performance of glass grit blast-cleaned AA6082 was excellent in cyclic testing using artificial seawater. Specific energy consumptions and CO₂ footprints for all process steps were calculated and compared with garnet blast-cleaning. Influence classes were estimated for all working steps. Compressed-air-based working steps contributed critically to specific energy consumption and to CO₂ footprint.

This study provides new insights into the passivation behavior and growth mechanism of nickel-based alloy in a simulated deep-sea environment, with a focus on the effects of applied potentials and solution pH. To comprehensively elucidate the influence mechanisms of the experimental variables on the passive film formed on the nickel-based alloy surface, in situ electrochemical tests, x-ray photoelectron spectroscopy, and transmission electron microscopy were employed. The results obtained from these analyses demonstrate that the passive film exhibits characteristics of an n-type semiconductor and possesses an amorphous structure, where the film thickness decreases with increasing potential, leading to enhanced ionic transport through the film. A novel finding is that the increase in potential not only raises the CrO₃/Cr₂O₃ ratio but also significantly increases the oxygen vacancy diffusion rate, which accelerates the cation transport and reduces the corrosion resistance. Furthermore, the oxygen vacancies increase with pH due to enhanced hydroxyl ion adsorption, while the Cr₂O₃ content decreases, resulting in a less protective passive film.

The change in moisture content (MC) will lead to a change in the mechanical properties of molded fiber products (MFP). Therefore, for predicting the mechanical properties of MFP, it is necessary to construct a mechanical constitutive model with the MC term. In this study, quasi-static uniaxial tensile tests of sugarcane bagasse-molded fiber products (SBMFP) were conducted at different MCs (0 ~ 17%), and the stress-strain curves were obtained. The maximum failure strength of SBMFP was achieved at 6% MC. The phenomenon of MFP, the fiber moisture swelling-induced damage, was observed by SEM of the mesoscopic fiber structure of SBMFP. To accurately predict the SBMFP’s mechanical properties at different MCs, based on the test results, a plastic constitutive model containing the MC term of SBMFP was constructed using the Geometric Linear Mapping method. Based on the constitutive model, the tensile process was simulated in Abaqus. The maximum error between the simulation results and the test data was 5.91%. The influence mechanism and the new constitutive model were validated by wheat straw-molded fiber products (WSMFP) and waste paper-molded fiber products (WPMFP). This study provides theoretical support for predicting the mechanical properties of fiber products.

In this investigation, the taguchi methodology was employed to examine the effects of fused deposition modeling parameters on printed polylactic acid (PLA) material. The fabricated samples were tested for the tensile and flexural strengrh using a universal testing machine. Finally, the signal-to-noise ratio and analysis of variance were applied to choose the best possible combinations of the parameters. The optimal results were obtained at optimal process parameters (angle was 0°, printing speed was 30 mm/sec, and layer height was 0.10 mm). At these optimal parameters, maximum tensile strength (44.56 MPa) and flexural strength (110.25 MPa) were achieved. In addition, a differential scanning calorimetry (DSC) test on the highest tensile strength sample was conducted to examine the thermal characteristics of polymer materials. The plot between temperature vs. heat flow shows reactions at a particular temperature. This indicates that a high-strength PLA sample absorbs a significant quantity of energy. In addition, a surface roughness test was also performed using Mitutoyo SJ-301 roughness tester on the lowest and highest tensile strength samples to examine the effect of printing parameters. The average surface roughness of lowest and highest tensile strength samples was 15.24 µm and 10.233 µm, respectively. Thus, the surface roughness study demonstrates that printing parameters (printing speed, layer height, etc.) play the major role in achieving the desired surface roughness.

Process parameters, such as wire feed rate, deposition travel speed and energy input per unit length, have a direct impact on controlling the dimensional consistency of the multi-layer components in the gas metal arc directed energy deposition (GMA-DED) process. The present investigation proposes a novel analytical methodology to estimate the build profile of single-track-multi-layer builds following mechanistic principles of energy balance and thermo-physical properties of the materials. The analytically estimated and the corresponding experimentally measured results for a range of process conditions considered in the present study have shown a fair agreement with a deviation of around 0.87%, 3.9% and 4% for build height, net build width and surface waviness, respectively. The present methodology can be employed to design the optimum process parameters for enhancing the reliability of GMA-DED components.

This research explores the optimization of mechanical properties of the Nylon-Glass Fiber composites manufactured by Selective Laser Sintering (SLS) under varying annealing conditions. Nylon 12, which is reinforced with glass fibers, was fabricated by SLS process, after which annealing at room temperature, 110, 130, and 150 °C was done. The effects of these thermal treatments had made changes on the composite’s mechanical properties like tensile, flexural, and impact properties which were then evaluated. Metallurgical tests such as Fourier transform infrared spectroscopy (FTIR) and field emission scanning electron microscopy (FE-SEM) were employed to understand the microstructural changes that had happened due to annealing and to identify the reasons for the property enhancements. Results revealed a significant improvement in mechanical performance, particularly at 150 °C, where the composites exhibited superior tensile, flexural, and impact strength due to its lesser structural defects, improved polymer chain alignment, and upgraded fiber-matrix bonding. However, further increases in temperature led to poor performance, bringing into view the critical importance of precise annealing parameters to get the best results. FTIR analysis confirmed the rearrangement of the polymer chains and reduced chemical degradation after annealing, while FE-SEM images showed improved inter-molecular bonding and a more homogeneous microstructure. These findings bring into a conclusion the potential of controlled annealing processes to significantly enhance the durability, strength, and resilience of SLS-printed composites, making them particularly suitable for demanding applications in the aerospace, automotive, and industrial manufacturing sectors. This study provides a comprehensive framework for tailoring composite properties through post-processing, thereby advancing the capabilities and industrial relevance of additive manufacturing technologies.

This resarch systematically investigated the alternating current (AC) interference corrosion of B30 alloy in simulated ocean environment. The results exhibit that the imposed AC apparently facilitates the dissolution of surface passive film, augments the level of internal flaws in the film, diminishes its protective effect, and reduces the anti-corrosion performance of the alloy. As AC density rises, the adsorption of H⁺/Cl⁻ at the flaws of passivation film is promoted, causing the film integrity and stability to decrease and deteriorating the local corrosion degree. The pits produced on the alloy result from the selective dissolution of the Cu element.

A₂B^′BO₆ (where A is the rare-earth metal, B is a transition metal, and B^′ is any metal) double perovskite-based oxides exhibit novel and interesting features such as exchange bias, multiferroic and magnetocaloric effect, which promote their candidature for magnetic cooling applications. The double exchange interaction (existing between B′-O-B) that influences the observed magnetocaloric effect for cooling applications becomes strengthened by the proper combination of electronic configuration and ionic radii of rare-earth and B^′ and B ions. In this contribution, the magnetocaloric effect of the A₂B′BO₆ system, a double perovskite, is modeled using random forest regression (RFR) and hybrid genetically optimized support vector regression (GSVR) algorithms, which employ crystal lattice parameters and ionic radii as predictors at various applied magnetic fields. Using assessment parameters such as correlation coefficient (CC), root mean square error (RMSE), and mean absolute error (MAE), the performances of the developed GSVR-ionic and RFR-ionic models with ionic radii descriptors are compared with those of the GSVR-latt and RFR-latt models, which employ crystal structural parameters as predictors. In the case of the RFR-based model, the values of assessment parameters computed for training samples of double perovskite magnetocaloric oxides using RFR-IONIC were 0.9873, 1.3750, and 1.1069 J/Kg K corresponding to CC, RMSE, and MAE, respectively. For the same assessment parameters using the RFR-latt model, 0.9096, 2.6041, and 1.7635 J/Kg K were, respectively, computed. The GSVR-ionic model outperforms the GSVR-latt, RFR-ionic, and RFR-latt models, achieving improvements of 8.18, 57.63, and 47.85%, respectively, as measured by the RMSE metric. Performance superiorities of 4.89, 60.13, and 40.95% were obtained using the MAE performance metric with double perovskite magnetocaloric oxide testing samples. The outstanding performance demonstrated by the models developed would strengthen the exploration of the magnetocaloric effect in the A₂B′BO₆ system of double perovskite for addressing energy crises in cooling applications.