Journal of Materials Engineering and Performance最新文献

Spray polyurea elastomer (SPUA) modifiers are finding increasingly widespread application in road engineering, particularly due to their significant importance in enhancing pavement performance in terms of high-temperature rutting resistance and fatigue resistance. To gain an in-depth understanding of the physicochemical properties of SPUA powder as a modifier, especially the damage mechanisms of its key functional spherical microstructures during the fine grinding process, this study prepared SPUA powder materials with different particle sizes and developed a novel quantitative method to assess the extent of their typical microstructural damage. Multiscale characterization combining x-ray diffraction, Fourier transform infrared spectroscopy, and thermal analysis (DSC/TGA) confirmed the material’s amorphous structure, intact functional groups, and thermal stability. Laser particle size analysis with scanning electron microscopy revealed surface-located spherical microstructures (50-200 μm). A ResNet18 convolutional neural network was developed to quantify structural damage in SEM micrographs through automated feature recognition. Results showed that progressive particle size reduction from 0.3 to 0.075 mm induced exponential microstructure degradation, with pore damage rates increasing from 21-37 to 61-72% (p < 0.01). The machine learning framework established quantitative correlations between grinding intensity and functional structure preservation, demonstrating 92.7% prediction accuracy in independent validation. This study not only clarified the quantitative dependence of the damage extent to typical SPUA microstructures on particle size reduction induced by fine grinding, but also proposed a novel SEM image analysis method based on machine learning. This approach provides an efficient and objective new pathway for quantitatively assessing the impact of the grinding process on the functional structures of SPUA modifiers.

In situ duplex TiC-Al₃Ti reinforcements synergistically strengthened aluminum matrix composites exhibit superior mechanical properties; however, the probable formation of the Al₄C₃ impurity in the Al matrix greatly restricted their practical applications. Herein, the present study focuses on the Ti₃AlC₂-2024Al composite material, thoroughly investigating the reaction mechanism and phase evolution process of the composite. Meanwhile, the dry sliding friction and wear behavior of this composite material are systematically explored. The results show that at 780 °C, partial Ti₃AlC₂ decomposes and reacts with 2024Al, facilitating the formation of blocky Al₃Ti and ultrafine Al₄C₃ in the 2024Al matrix. Fortunately, with the rising temperature from 780 to 950 °C, Al₄C₃ would stepwise react with Al₃Ti to form TiC and Al, and the complete elimination of Al₄C₃ occurred at 950 °C. The sliding wear behavior of the resulting composite at 150 °C indicates that in situ Al₃Ti and TiC significantly enhance the thermal stability and load-bearing capacity of the 2024Al matrix. The synergistic effect of the duplex reinforcements effectively reduces the wear rate from 7.2 × 10^-4mm³/mN to 4 × 10^-4mm³/mN, and the related wear mechanism of TiC-Al₃Ti/2024Al composites are determined to be adhesive wear and abrasive wear, respectively.

In this paper, the convention current mode and pulse current mode of metal inert gas (MIG) were used to repair the TC4 titanium alloy with the different size of cracks. The forming quality of the repaired zone was detected by the RF 100EGB x-ray flaw. The microstructure, grain size, and orientation deviation were observed by OM, SEM, and EBSD. Microhardness and tensile test were carried out by the HVS-1000 Vickers microhardness tester and WDW-100 microcomputer controlled universal testing machine. In order to analyze the fracture mechanism, the fracture morphology was observed by SEM. The results showed that under the action of periodically varying forces, the size of the α' martensite of the P-MIG repaired specimens were smaller than that of the C-MIG repaired specimens. When the notch width was 2 mm, the average grain size of α' martensite of the C-MIG repaired specimens and the P-MIG repaired specimens were approximately 10.2 and 6.1 μm, respectively. The maximum texture strength and the large angle grain boundaries proportion of the P-MIG repaired specimens were lower than that of the C-MIG repaired specimens. In terms of mechanical properties, the P-MIG repaired specimens achieved higher Vickers microhardness and tensile strength values relative to the C-MIG repaired ones. A large number of cleavage steps, river patterns, and dimples were observed on the whole tensile fracture of both the C-MIG repaired specimens and P-MIG repaired specimens, which belongs to ductile and brittle mixed fracture mode.

The influence mechanism of laser power on corrosion resistance of laser-arc hybrid welded joints of Ti-containing weathering steel was studied. The results show that, except for the samples at the laser power of 1500W, the amount of corrosion of the specimen increases with the laser power, that is, the corrosion resistance decreases with the increase of the laser power. According to the macroscopic corrosion morphology, the thickness of the rust layer on the sample surface increases with the increase of laser power. In addition, the corrosion degree of heat-affected zone (HAZ) and weld metal (WM) is more serious compared with the base metal (BM). After cleaning, the microstructure in the WM at the laser power of 2000W is seriously corroded, and more small corrosion pits occurs. However, the other samples are corroded lightly. When the laser power increases, the surfaces of samples are more seriously corroded, i.e., more pits can be found and the corresponding corrosion resistance decreases. The main form of corrosion in the BM and HAZ is intercrystalline corrosion, while it transforms into intercrystalline corrosion and point corrosion in the WM. During the corrosion process, titanium element can form stable oxides, resulting in the change in the corrosion form and corrosion resistance of weathering steel welded joints. The results provide the experimental basis for the corrosion properties of Ti-containing weathering steel.

Graphical Abstract

In this work, two kinds of NiCrAlY coating with different porosities were prepared on the surface of 310S stainless steel using supersonic plasma spraying technology. The long-term field exposure test in the SOFC system revealed that the supersonic plasma-sprayed NiCrAlY coating exhibited excellent oxidation resistance in the SOFC environment containing O₂ and water vapor. The well-prepared coatings showed only slight interfacial oxidation after 10,000 h, indicating their potential as candidate materials in the SOFC system. The oxidation resistance and anti-stripping performance of the NiCrAlY coating in the SOFC environment is significantly influenced by the porosity of the coating. Coatings with higher porosity tend to form clusters of Cr- and Al-rich oxides in the coating, which led to interfacial delamination at the coating/substrate interface.

This study investigates the tribological performance of DIN-16MnCr5 steel subjected to six different surface treatments—untreated, nitriding, carburizing, nitriding with post-oxidation, manganese phosphate coating, and the powder pack boriding process—under three loading conditions (5 N, 10 N, and 20 N) for the case of wear tests. Key tribological indicators, including specific wear rate, coefficient of friction, wear depth, and tribocorrosion synergy, were evaluated using a ball-on-flat setup in a saline environment. A statistical experimental design based on response surface methodology (RSM) with 3 replicated trials enabled robust modeling and optimization. ANOVA revealed that surface treatment and load significantly influence tribocorrosion responses (P < 0.005), contributing 71.3% to the variation in S, 61.3% in wear depth, and 52.0% in k. Among all treatments, boriding and phosphate with manganese coatings (PPBP and CMnP) exhibited the best performance, reducing k and S by up to 99.6% and 97%, respectively. On the other hand, the untreated material steel showed the most severe degradation (k = 900.5 mm³/Nm × 10⁻⁶; and S = 1.12). The developed second-order models highlighted nonlinear interactions and confirmed the strong synergy between mechanical wear and corrosion. These findings support the strategic selection of surface treatments for high-performance applications exposed to aggressive tribocorrosive environments.

The aim of this study is to investigate the low-cycle fatigue performance of weathering bridge steels after corrosion. This study investigates the low-cycle fatigue performance of smooth and rusted Q500qENH bridge steel under symmetric strain control conditions. The microstructure, fracture morphology, and crack propagation characteristics of high-strength steel under low-cycle fatigue loading were analyzed by means of electron backscatter diffraction (EBSD) and scanning electron microscopy (SEM). The results show that the corrosion pits in the rusted specimens lead to the generation of more crack sources. The stress concentration caused by the corrosion pits intensifies dislocation motion, thereby refining the grains around the cracks. In addition, the rusted specimens have a greater impact on plasticity, leading to a decline in their low-cycle fatigue performance.

To address the shortcomings of Fe/Cu bimetallic materials, including uneven surface microstructure, low surface hardness, and inadequate friction and wear performance, this study investigates the influence of varying Fe contents on the microstructure and mechanical properties of Fe/Cu bimetallic materials using solid–liquid composite casting technology. Experimental results indicate that with 1.5 wt.% Fe, the coarse dendritic structure of the α-Cu matrix is refined into equiaxed grains, and the Pb particle distribution becomes more uniform with the size of Pb particles reduced, which decreases the average grain size from 99.1 μm to 71.7 μm. This refinement, alongside the precipitation of Fe particles, markedly enhances interfacial shear strength and microhardness, with improvements of 12.35% and 28.63%, respectively. However, at 2.5 wt.% Fe, grain coarsening occurs, leading to reduced shear strength and hardness, likely attributed to the formation of coarse dendrites and uneven δ-phase segregation. Friction and wear performance also improves with 1.5 wt.% Fe, exhibiting lower coefficient of friction and wear rates, with reductions of 60% and 21% under oil-lubricated and dry friction conditions, respectively, compared to 0 wt.% Fe.

Grain boundary engineering (GBE) involves improving resistance to grain boundary failure in a material by increasing the proportion of low ∑ coincidence site lattice (CSL) grain boundaries in grain boundary character distributions (GBCDs). In this work, GBCDs in annealed austenitic stainless steel samples with and without Sn were analyzed by electron backscatter diffraction (EBSD). The results showed that the addition of elemental Sn improved the intergranular corrosion resistance of austenitic stainless steel 316L. Compared with austenitic stainless steel without Sn, the proportion of Σ3ⁿ special grain boundaries (SBs) in samples containing Sn was higher, the size of the large-sized grain clusters was larger, and the original high-angle grain boundaries (HAGBs) were more discontinuous. Therefore, the addition of elemental Sn promoted the recrystallization process during twin-induced GBE.

Low-nickel high-nitrogen austenitic stainless steel is susceptible to N loss during the welding process, which diminishes its tensile strength and compromises the reliability of the equipment. Although the use of rich-Cr stainless steel welding wire can ensure the corrosion resistance of the welded joint to a certain extent, it cannot guarantee the plasticity; and the use of rich-Mn welding wire for welding cannot guarantee the plasticity of the welded joint even if it can significantly improve the strength of the welded joint. In order to obtain a welded joint with coordinated optimization of strength, plasticity and corrosion resistance, and to ensure the safe service of the welded joint of low-nickel austenitic stainless steel, Ni-Cr-Mo alloy welding wire without N element was developed and designed as filler metal. Metal Active Gas welding (MAG) of low-nickel high-nitrogen austenitic stainless steel was carried out with different heat input and 8%N₂ + 92%Ar shielding gas. The results show that with the increase of heat input, the secondary dendrite spacing in the welded metal (WM) is 2.52 μm, 5.55 μm and 6.11 μm respectively, and the proportion of high-angle grain boundaries in the WM increases from 83.4 to 85.7%. Meanwhile, with the increase of heat input, the tensile strength and hardness of welded joints increase, and the corrosion potential of welded joints decreases slightly. When the welding heat input is controlled at 7.5 KJ/cm, the strength, plasticity and corrosion resistance of the welded joint can be in a coordinated and consistent manner, which provides technical support for the safe service of the welded joint.