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The microstructure of high-strength martensitic steel specifically made for additive manufacturing was modified via in situ plasma arc remelting (PAR) to improve its surface properties. The results reveal that the microstructure is characterized by the intragranular martensite and intergranular eutectic structure of high-strength martensitic steel. The intragranular worm-like δ-ferrite embedding in the martensite matrix was clearly observed after PAR. Compared with the as-deposited part, the tensile strength of the PAR part reached 1753 MPa, and the ductility increased to 2.3%. The strength and elongation had increased by 20% and 229%, respectively. After in situ PAR, the wear loss decreased to 80% of the tailored high-strength martensitic steel, and the corrosion current density decreased to 17%. Both the as-deposited part and the PAR part exhibited significant intergranular corrosion morphological characteristics.

The alloy in the final stage of solidification is in the semi-solid region, composed of solid grains and liquid film. This article focuses on the effect of liquid film on hot tearing in the final stage of solidification. It investigates the mechanism of the effect of liquid film on the initiation of hot tearing. The mechanical behavior of Al-27%Si hypereutectic Al-Si alloy in high-temperature stress–strain testing was studied. The results showed that the overall content of the liquid film during the solidification process affects the mechanical properties of the alloy; the alloy exhibited viscoelasticity in a high solid fraction state and viscoplasticity in a low solid fraction state. At the same time, a Si-liquid film-Si structure was constructed to simulate the intergranular liquid film structure of hypereutectic Al-Si alloy in the final stage of solidification. The stress variation characteristics of the intergranular liquid film showed that the smaller the liquid film thickness, the stronger the interaction force between Si wafers, which is not conducive to improving the liquid film fluidity. In addition, the fracture morphology of the tensile fracture was observed, and it was found that under the condition of thick liquid film, the flowability of the residual liquid phase was better, making it easier to feed for hot tearing. Finally, CFD simulation technology was used to study the mechanism of the effect of a single factor of liquid film characteristics on hot tearing. The results showed that the thicker the liquid film, the greater its ability to feed and heal the formed hot tearing, thus effectively reducing the alloy's tendency toward hot tearing.

Pore fluid chemistry can obviously influence the deformation and strength of expansive soil. To investigate the change rules and the underlying mechanisms, free swelling rate and direct shear experiments are conducted on expansive soils immersed with different concentrations of NaCl and CaCl 2 solutions. The free swelling rate of the expansive soil, with increasing solution concentration, first rapidly decreases and then continues to gently decrease. Moreover, the NaCl solution has a greater effect on the free swelling rate of the expansive soil than the CaCl 2 solution. The soil shear strength and cohesion decrease with increasing solution concentration; nevertheless, the effect of solution concentration on the internal friction angle is less significant. The test result analysis indicate that the expansive soil surface carries a fixed negative charge, forming an electric double layer on the particle surfaces. With increasing salt solution concentration, the double layer thickness decreases, resulting in reduced particle repulsion and increased intergranular stress. Consequently, soil particle settlement occurs, which reduces the free swelling rate. Specifically, twice as much Cl − is dissociated from CaCl 2 as NaCl for salt solutions with the same molar concentration, resulting in greater intergranular stress and smaller free swelling rate. Theoretically, the shear strength should increase with the salt solution concentration, due to the increase of intergranular stress. However, the scanning electron microscope experiments and the mercury intrusion porosimetry experiments show that the expansive soil microstructure changes based on the salt solution concentration, contributing to the reduction of the shear strength. The above two factors have opposite effects on the shear strength. For the Ningming expansive soil considered herein, the shear strength decreases with increasing concentration, as the impact of structure surpasses that of intergranular stress.

The high-quality TiO 2 insulating layer on the commercial gas-atomized FeSiAl powder surface was efficiently prepared within a total time of 1 h at room temperature via a one-pot sol–gel method based on a developed industry-oriented coating equipment. The core-shell structure for the chemically coated FeSiAl powders was detected by the joint tools of SEM, EDS, and FTIR. Combined with the establishment of loss separation fitting model, the regulation mechanism analysis on soft magnetic properties was carried out for the FeSiAl powder cores insulated with different TiO 2 coating amounts. It is found that the interface-pinning effect, which is closely related to the core’s density, is an important factor affecting the magnetic properties of powder cores. With the elevating TiO 2 coating amount, the hysteresis loss, the excess loss, and DC-bias property of the core specimen exhibit the same increasing tendency, while the real part of complex permeability at 100 kHz gradually decreases owing to the increase of non-magnetic gap between the particles in the core, which can impede the domain-wall motion during magnetization. Correspondingly, the eddy current loss persistently decreases and contributes only 18.7% ~ 21.6% of total core loss when the precursor concentration is over 0.08 ml/g due to the formation of the intergranular insulated structure blocking the inter-particle eddy current flows in the composites. These results offer insights into subtly regulating magnetic properties when the adjusting process parameters for the soft magnetic composites are used in high-power and high-frequency applications.

This study examines the design and numerical analysis of induction hardened of Inconel 718 superalloys on the tensile properties. The two tensile specimens (IHT1 & IHT2)’s outside surfaces are heated to temperatures of 850 and 1000 °C. The heated samples are then quenched in oil. The samples are evaluated utilizing a 250kN capacity servo hydraulic universal test at ambient temperature and an enhanced temperature of 800 °C. At both room temperature and a raised temperature of 800 °C, the metrics yield strength (YS), ultimate tensile strength (UTS), and elongation of induction hardened sample have risen. Induction-hardened materials have better mechanical characteristics than non-induction-hardened samples, according to numerical results from ANSYS Workbench that are corroborated with experimental data. The results of the tensile test’s cracked surfaces under a scanning electron microscope (SEM) show that the presence of shallow dimple structure at 800 °C caused transgranular cleavage and intergranular dimple rupture as the modes of failure.

The distribution of second phase particles in the microstructure of composite ceramics affects the mechanical properties, and the intragranular structures often result in better properties compared to the intergranular structures. However, it is difficult to obtain composite ceramics with intragranular structure by conventional route. To produce composite ceramics with an intragranular structure in a simpler route. In this work, starting powders with different phase compositions were obtained by the co-precipitation method, and zirconia toughened alumina (ZTA) composite ceramics were prepared with these starting powders by spark plasma sintering (SPS). The results show that it is easier to fabricate ZTA composite ceramics with an intragranular structure by using composite powders containing amorphous or transition phase Al2O3 as starting materials. The phase composition of the powder prepared by the co-precipitation method after calcination at 1100 °C is θ-Al2O3 and t-ZrO2, and the average grain size after sintering at 1500 °C is 1.04 ± 0.28 µm, and the maximum Vickers hardness and fracture toughness of the specimens reach 19.37 ± 0.43 GPa and 6.18 ± 0.06 MPa·m1/2, respectively. The ZrO2 particles were the core of crystallization and grow together with the Al2O3 matrix, forming the intragranular structure of ZTA ceramics. This work may provide a new idea for preparing composite ceramics with intragranular structure.

There has long been a certain enterprise that leads the line products of lead and zinc, which is facing inequality problems that seriously affect economic benefits. This study uses a confocal microscope, scanning electron microscope, electron probe, and chemical constant volume method to study the causes of the problem and the mechanism of the main influence factors. The results show that the surface roughness of hot rolled acid-washed substrate and the distribution of carbide in steel are the main factors that cause the zinc flower inhomogeneity. The increase of the nucleation point in the cooling process of the zinc pans with the roughness of the base plate. When the distribution of carbides along the ferrite grain boundary in steel occurs, the formation of Fe2Al5 is restricted. This results in a thinner inhibition layer on the substrate surface, leading to less consumption of aluminum. Consequently, the zinc layer nearby retains more aluminum content. Steel and carbide precipitation occurs in the intercrystalline structure, which inhibits the increase in the thickness of the strip’s surface layer. This leads to a higher consumption of aluminum, resulting in a lower zinc layer with reduced aluminum content. As a consequence, the liquid zinc forms droplets, allowing lead (Pb) and antimony (Sb) in the liquid zinc enough time for dendritic segregation to take place. This process increases dendrite growth and results in the formation of larger zinc grains.

The work is devoted to the analysis of the nonlinear effects resulting from the influence of excess volumes of intergranular boundaries on the structure of segregations of impurity atoms in polycrystals. It is shown that the adsorption isotherm can describe the nonuniformities in the distribution of impurity atoms in the plane of an intergranular boundary. This suggests the existence of adsorption sites at the internal boundaries of polycrystals. It is proven that an excess volume of intergranular boundaries is the main parameter determining the magnitude of impurity segregations at the boundaries.

In this work, Inconel 625 alloy is explored regarding high-temperature tensile deformation and fracture behaviors at a strain rate of 0.005–0.01 s−1 under a deformation temperature ranging from 700–800 °C. The subsequent analysis focuses on the impact of deformation parameters on flow and fracture characteristics. The fractured surface reveals that ductile fracture is dominated by the nucleation, growth, and coalescence of microvoids as the primary failure mechanisms. The elevated deformation temperature and reduced strain rate stimulate the level of dynamically recrystallized (DRX) structures, resulting in intergranular fractures. The Arrhenius model and the particle swarm optimization-artificial neural network (PSO-ANN) model are developed to predict the hot tensile behavior of the superalloy. It indicates that the PSO-ANN model exhibits a correlation coefficient (R) as high as 0.9967, surpassing the corresponding coefficient of 0.9344 for the Arrhenius model. Furthermore, the relative absolute error of 9.13% (Arrhenius) and 1.85% (PSO-ANN model) are recorded. The developed PSO-ANN model accurately characterizes the flow features of the Inconel 625 superalloy with high precision and reliability.

The Chang 8 reservoir of the Maling Oilfield in the Ordos Basin, China is facing a series of challenges in hydrocarbon resource development, including rapidly decreasing production rates, declining dynamic fluid levels, and elevated water cuts in oil wells, along with heterogeneity in microscopic pore-throat structures and notable interstratal inconsistencies. To systematically address these issues, this study selected representative samples from the reservoir and conducted rigorous microscopic percolation experiments on them. A comprehensive evaluation of the heterogeneity in microscopic pore structures was conducted using an integrative methodological approach, involving physical property quantification, petrographic thin-section analysis, scanning electron microscopy, constant-rate mercury intrusion, and nuclear magnetic resonance techniques. The primary objective of this investigation is to elucidate the underlying formation mechanisms, states of occurrence, and spatial distributions of residual oil. Understanding of these issues will facilitate the establishment of empirical correlations between diverse microscopic pore structures and water-flooding efficiencies, and aid in the identification of key variables governing the distribution of residual oil. Analytical outcomes reveal substantial variations in seepage characteristics contingent upon the nature of microscopic seepage conduits. Specifically, the Chang 8 reservoir manifests four discernible categories of microscopic seepage pathways: solely intergranular pores, a confluence of dissolution and intergranular pores, exclusively dissolution pores, and micropores. A correlative decline in oil displacement efficiency is observed across these conduit types. Critical variables such as throat radius and its distribution patterns emerge as pivotal determinants influencing oil displacement efficiency, eclipsing the impact of conventional physical properties and mobile fluid saturation levels. Remarkably, samples characterized by a composite of dissolution and intergranular pores demonstrate superior displacement efficiency. Distinct types of pore structures correspond to noticeably different water-flooding oil pathways and oil displacement efficiencies. During the water-flooding process, fingering network displacement is dominant, and it exerts a significant control on oil displacement efficiency. Key factors affecting this efficiency include the injected water volume multiples and displacement pressure, values of which should be optimized during the actual water-flooding process.