JOM最新文献

The magnetic properties of Fe−80Ni alloy are significantly influenced by its microstructure, making it the focus of research. In this study, we investigated the pinning effect of inclusions on austenite grain growth in Fe−80Ni using high-temperature confocal laser scanning microscopy (HT-CLSM) and explored the impact of Ce treatment on the pinning process and magnetic properties of Fe−80Ni alloy. The findings revealed that primary inclusions were transformed into Ce-containing inclusions with Ce treatment. Moreover, the Ce treatment resulted in a certain reduction in the number of inclusions. Simultaneously, there was an enhancement in the level of inclusions after deformation and annealing with Ce treatment. The HT-CLSM results highlighted that these inclusions impede grain boundary migration, facilitating the formation of finer grains due to the pinning effect during the annealing process. Furthermore, a reduced number of inclusions led to a larger average grain size after annealing, from 152.3 μm to 170.2 μm, consequently improving the magnetic properties of the alloy by 10-20%. To assess the deformability of different inclusions, we calculated the Young's modulus, yielding values of 141.5 GPa for CeO₂ and 82.4 GPa for 6SiO₂·Al₂O₃, respectively. Additionally, we elucidated the evolution of inclusion pinning during annealing based on TEM results.

Rotary hearth furnaces and rotary kilns are the mainstream methods for large-scale treatment of electric furnace dust (EAFD) in steel companies, but they require a large amount of energy and have low product quality. The roasting conversion–separation technology uses calcium oxide to promote the conversion of zinc–iron spinel in EAFD into zinc oxide and dicalcium ferrite, but adding calcium oxide additionally increases production costs. Converter sludge (OGS) is rich in iron oxides and valuable components such as CaO, CaCO₃, ZnFe₂O₄, etc. The free calcium oxide and calcium carbonate can be used as substitutes for pure calcium oxide. This paper designed a multi-solid waste collaborative reduction roasting process to realize the recovery of zinc and iron elements from OGS and EAFD and explore the feasibility of industrial treatment in rotary hearth furnace. The results show that harmful OGS can be used as the calcium agent in the roasting process. The calcium carbonate in OGS not only improves the conversion of iron oxide into metallic iron, but the decomposed CaO can promote the conversion of zinc–iron spinel in OGS and improve the dezincification effect. Better conditions are: 60% OGS, n_C/n_O = 1.2, roasting temperature 1150°C, roasting for 25 min; zinc content in the reduction product is 0.21%, and metallization rate is 78.53%, which can be used as a high-quality substitute or coolant for scrap steel raw materials in the steelmaking process. This process can realize green and comprehensive utilization of EAFD and OGS and is expected to achieve industrialization.

During the directional solidification (DS) of superalloys, the active alloy elements react with the ceramic mold, deteriorating the surface quality and affecting the dimensional accuracy of the alloys. It is important to investigate the interfacial reactions between the alloy melt and ceramic mold and to investigate the effect of the interfacial reactions on the structures of the alloy. Superalloy DZ40M was prepared by DS technology, the microstructures and element distributions of the alloy and the alloy-ceramic interface were observed by a scanning electron microscope (SEM) equipped with an energy dispersive spectrometer (EDS), and the interfacial reactions were analyzed from a thermodynamic perspective. Carbides are important strengthening phases in the alloy. Interfacial reactions between the carbides and the ceramic mold were further investigated. The results show that the alloy structure mainly contains Co (Cr/Ni/Zr/Al/W/Ti) solid solution columnar crystals (Co_ss), nearly continuously distributed Cr-enriched M₇C₃-type carbides as well as Ti/Zr/W-enriched MC-type carbides skeletal precipitates. The reactions between the Co_ss and the ceramic mold were mild, with a reaction layer of about 20–40 μm thickness, while the reaction between the grain boundary precipitates and the ceramic mold was severe because of a high content of Cr in the M₇C₃-type carbides and the presence of active elements Ti and Zr in the MC-type carbides, with a reaction layer of about 50 μm thickness. In addition, almost no obvious penetration of the mold refractory was observed in the interior of the alloy, showing that the ceramic mold has a relatively stable performance in investment casting of superalloy DZ40M.

This study explores the effects of varied pulsed magnetic field strengths (0 mT, 16 mT, and 80 mT) on the microstructure and mechanical properties of A356 aluminum alloy. Advanced characterization techniques including an electron universal stretching machine, metallographic microscope (OM), scanning electron microscopy (SEM), electron backscatter diffraction (EBSD), and transmission electron microscopy (TEM), were employed. Key findings demonstrate a progressive enhancement in the alloy’s mechanical strength correlating with increased magnetic field intensities, achieving peak properties at 80 mT. This intensity level resulted in significant increases in tensile strength (27.35%), yield strength (19.05%), and elongation (9.23%) compared to the baseline (0 mT). SEM analyses reveal a marked improvement in both the quantity and size of eutectic Si under magnetic influence. EBSD outcomes show a notable shift in grain orientation disorder, with a clear preference emerging at the (111) crystal plane post 80 mT treatment. TEM examinations further confirm an uptick in Si particle numbers and Mg2Si phase precipitation at this intensity, indicating profound microstructural transformations induced by the magnetic field.

This study investigated two lightweight Cr_xV_0.5Nb_0.5ZrTi (x = 0.1 and 0.3) refractory high-entropy alloys to understand the relationship between phase composition, microstructure, and mechanical properties. The addition of Cr resulted in a transition from a single-phase BCC structure of the base alloy V_0.5Nb_0.5ZrTi to a multiphase structure comprising BCC and Cr-rich Laves phases in the Cr_xV_0.5Nb_0.5ZrTi alloys. The microstructure exhibited a typical dendritic pattern, consisting of BCC dendrites and Cr-rich Laves interdendrites. The area fraction of the Cr-rich Laves phase increased from 5% to 28% with the increase in Cr content. This increase led to elevated yield strength values, rising from 1100 ± 20 MPa to 1330 ± 30 MPa. The primary mechanisms contributing to the mechanical properties were solid-solution strengthening from the BCC phase and the formation of a small amount of hard Laves phase. These mechanisms, combined with the low density of the alloys, resulted in an excellent combination of specific yield strength and plasticity in the Cr_0.1V_0.5Nb_0.5ZrTi alloy. Specifically, it exhibited a specific yield strength of 180 MPa cm³/g and over 40% plastic strain without fracture. Overall, the study provides insights into the design and development of lightweight refractory high-entropy alloys with desirable mechanical properties for various engineering applications.

Current strategies for autologous chondrocyte implantation explore the use of gel systems that have structural similarity to an extracellular matrix of cartilage tissue and can act as chondrocyte carriers. However, the major requirement is to address the challenge of maintaining the phenotype and bio-functionality of chondrocytes which often undergo dedifferentiation on expansion, and the appropriate mechanical properties of the matrix that can influence cell attachment and growth. Injectable gel systems are developed in this study by blending different ratios of methacrylated chitosan and polyethylene glycol diacrylate, and photocross-linking the system to attain a stable gel. We hypothesize a multiscale approach of evaluating various parameters like the physical and structural properties of the gel, its wettability and surface free energy and mechano-rheological properties along with the biological characterization (viability assay, collagen, and glycosaminoglycan estimation by immunostaining, biochemical analysis, and RT-PCR assay) of the gel in ascertaining its ideal matrix system. The study provides a correlation between the different parameters to arrive at the most optimum characteristic of an ideal gel system which is dependent not only on the elastic modulus and surface free energy properties of the matrix but also on the composition of the matrix and the phenotype and functionality of the encapsulated chondrocytes.

Zirconia dental ceramics have evolved from uniform blocks of 3 mol.% yttria (3Y) to strength- and color-graded blocks containing 3 mol.% and 5 mol.% components. Relatively little is known about the graded materials’ compositions and microstructures. Concerns have been raised about aging and degradation. This study investigated the microstructure, elemental composition, and phase content of different zones of strength- and color-graded zirconia blocks using scanning electron microscopy, x-ray fluorescence, and x-ray diffraction. Specimens were made from green-state blocks using CAD/CAM machining and sintering. Two strength- and color-graded zirconia materials had different grain sizes, elemental compositions, and phase contents between their top and bottom zones, these data being internally consistent as well as being broadly consistent with prior compositional physical property data. A color-graded zirconia material did not exhibit substantial differences between its top and bottom zones, consistent with expectations and previously published data. Modeling phase content for complex yttria-doped zirconia crystal systems with multiple heterogeneous crystal lattices from XRD data was inherently difficult, which may account for the ranges among previously published data; authors should describe detailed methodologies. Detailed compositional data at the scale of the microstructure is needed to relate composition to phase content, physical behavior, including crack evolution.

The primary clinical indicator of fracture risk among the elderly is low bone mass, yet it accounts for less than half of fractures in individuals over 50 years. Age is recognized to influence bone quality, affecting bone structure and properties. Previous research indicates that age diminishes tissue plasticity and toughness conferred by collagen, suggesting that age-related changes in the collagen environment may contribute to bone fragility. This study explores the relationship between age-related collagen impairment, specifically the accumulation of non-enzymatic collagen cross-linking and molecular collagen denaturation, and bone toughness in middle-aged and older patients (postmenopausal 50–70 years old and senile osteoporosis age > 70 years old). Additionally, it examines the influence of blood glucose and HbA1c levels, as well as body mass index (BMI), on these factors. Despite not finding any differences in fracture toughness between groups, we found a significant correlation between hemoglobin A1c and collagen integrity (collagen denaturation and non-enzymatic cross-linking).