Molten steel cleanliness is critical for the performance and service life of H13 steel. CeO2 with a range of 0-20 wt% was added into refining slag to improve the cleanliness of H13 steel in this study. The effects of the amount of added CeO2 on the oxygen and sulfur contents and inclusion characteristics of molten steel were systematically investigated through high-temperature experiments, Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), and thermodynamic calculations. The optimum result was obtained at 5 wt.% CeO2, where the oxygen and sulfur contents decreased to 35 and 45 ppm, respectively, and the average inclusion size was reduced to 2.53 mu m. The steel-slag reaction mechanism was analyzed in terms of slag melting behavior, polymerization properties, component activities, crucible corrosion, and the existential form of rare earth. The results indicate that the effect of CeO2 on H13 steel cleanliness is mainly governed by polymerization properties of the refining slag, steel-slag reaction thermodynamics, and the transformation of CeO2 into Ce2O3. Below 5 wt.% CeO2, improved polymerization properties and thermodynamic conditions enhance steel cleanliness. At 5-10 wt.%, partial conversion of CeO2 to Ce2O3 weakens deoxidation and desulfurization. Above 10 wt.%, deterioration of polymerization properties and continuous Ce2O3 formation reduce steel cleanliness.

Mullite refractories are widely used in the production of alloy structural steels and affect the cleanliness of molten steel. In this study, the interaction between mullite and 20CrMoA alloy structural steel refined by slags with different compositions was analyzed systematically based on high-temperature experiments and thermodynamic calculations by FactSage. After the interface reaction, the contents of Al, Mn and Ca increased and that of Si decreased on the surface of mullite refractory, the change of corresponding elemental contents in steel and inclusions exhibited the opposite trend, indicating an erosion reaction between steel and mullite. The compositional changes in steel and inclusions were more pronounced during the process of low-basicity slag refined steel melt with mullite, with a large amount of granular SiO2 were observed. There was little change in the size of inclusions in the steel refined by high basicity slag after reacted with mullite, while that in the steel refined by low basicity slag increased from 1.79 mu m to 6.34 mu m. It indicated that the erosion reaction between steel refined by low basicity slag and mullite was more severe. Thermodynamic calculation also indicated that mass transfer occurred between melt and mullite refractory, and the change of elements were larger in the steel refined by the low-basicity slag which was in good agreement with the experimental results.

Additive manufacturing (AM) offers unique capabilities for producing high-performance alloys with refined microstructures. Here, 316 L stainless steels fabricated by AM and conventional vacuum arc melting (VAM) were systematically compared in terms of microstructure, defects, and mechanical response. The AM steel exhibited a 49% increase in hardness and a 29% improvement in ultimate tensile strength relative to the VAM steel, while its defect volume fraction was reduced to one-third. Both processing routes generated Si-Mn-O inclusions; however, the AM material uniquely contained a high density of nanoscale second-phase particles that contributed to strengthening. Thermodynamic modeling (FactSage) and molten pool simulations (ProCAST) revealed the role of rapid solidification and thermal gradients in promoting nanoscale precipitation and defect mitigation in AM. These findings demonstrate that AM not only tailors defect characteristics but also enables microstructural refinement, thereby offering a pathway to superior mechanical performance compared with conventional melting techniques.

Civil structures in the deep lithosphere are frequently exposed to thermal environments resulting from geothermal gradients and dynamic disturbances caused by blasting, rockbursts, and earthquakes during construction and operation. In this paper, a novel thermo-viscoplastic damage model is proposed within the consistency framework to capture the rate- and temperature-dependent behavior of rock-like materials. By rationally designing the free energy and dissipation potential functions, all the constitutive formulations relating the coupled thermo-elasto-viscoplastic-damage processes can be derived following the thermodynamic principle. The main innovation of our study lies primarily in deriving a fully coupled Lagrange multiplier satisfying the classical form of rate-independent plasticity while still retaining the rate-dependent characteristics, thus enabling a consistent solution for the viscoplastic strain, temperature, and damage variables. To better improve the usability of our model, a hierarchical procedure is formulated for identifying all model parameters based on conventional laboratory experiments. By reproducing a series of uniaxial/triaxial compression, SHPB tests, and large-scale impact tests across a broad range of pressures, strain rates, and temperatures, the proposed consistency thermo-viscoplastic damage model is proven able to characterize realistically the coupled dynamic and thermal responses, as well as corresponding failure patterns of rock-like materials. Our calculations show that greater thermal damage intensifies the strain rate sensitivity of dynamic rock strength. Moreover, we have newly discovered the competitive relations among different dissipation processes during inelastic material deformation, highlighting the potential application of our model in predicting the temperature evolution in geological fault zones associated with distributed rock fracturing and pulverization.

To mitigate the harmful effects of Al2O3 inclusions in steel, it is necessary to conduct comprehensive research on the mechanisms and kinetic laws of Al2O3 inclusion modification by Ce. Combined with laboratory experiments, first-principles calculations, and molecular dynamics simulations, the kinetic model of Ce modification for Al2O3 inclusions was established. Based on first-principles calculations, differential charge analysis, density of states analysis, and adsorption energy analysis were performed on the transformation process from Al2O3 to CeAlO3 at the atomic scale, and the microscopic transformation mechanism of inclusions at the atomic scale was obtained. Molecular dynamics simulations and the solution of mean square displacement function show that the diffusion coefficient for Ce atoms was 2.169 × 10−4 cm2/s, which agreed well with experimental results. In this model, the rate-determining step is the diffusion of Ce atoms across Ce–Al–O inclusions. The relationship between the conversion rate, refining time, and initial radius was discussed. A refining time of 60 s can completely transform Al2O3 inclusions less than 2.56 μm into CeAlO3 inclusions, while refining time of 1200 s is sufficient to modify inclusions size below 11.47 μm.

It is challenging to assess the mechanism responsible for the nucleation of inclusions in metals at high temperatures.The present work therefore systematically investigates the nucleation of cerium oxide inclusions according to classical nucleation theory and a two-step nucleation mechanism.The nucleation rates and nucleation radii of these inclusions are obtained,and the results demonstrate a considerable difference between theoretical and experimental values.On the basis of a two-step nucleation mecha-nism,(CeO2)n and(Ce2O3)n(n=1-6)clusters were constructed and the thermodynamic properties of both these clusters and of cerium oxide nanoparticles were analyzed.In addition,the entropies and heat capacity changes of cerium oxides were determined using first principles calculations and are found to be consistent with literature data.The present data indicate that the cerium oxide inclusion nucleation pathway can be summarized as[Ce]+[O]→(CeO2)n/(Ce2O3)n →(Ce2O3)n →(Ce2O3)2 → core(Ce2O3 crystal)-shell((Ce2O3)2 cluster)nanoparticles →(Ce2O3)bulk.

This research added rare Earth elements Ce to the P110-grade oil casing steel to reveal their influence on the inclusions and tensile properties. The content of cerium in the steel varied from 0 to 452 ppm. Based on the classical thermodynamic calculation, the predominance diagram of Re-containing inclusions in P110-grade steel was obtained. The evolution route of the inclusions composition with the increasing cerium content in the steel was xCaO⋅yAl2O3 → Al2O3–CeAlO3 → Ce2O3–CeAlO3 → Ce2O3–Ce2O2S → Ce2O2S, which agreed well with the thermodynamic analysis. As the cerium content at 235 ppm, the size of Ce containing inclusions has a minimal size at 2.82 μm. Suitable Ce content can modify the big-size xCaO⋅yAl2O3 inclusions into small-size Re-containing inclusions. The results demonstrate that the tensile performance of this steel can be improved as the cerium content increases from 0 to 235 ppm. However, once the cerium content exceeds 235 ppm, further increases in cerium content led to a decline in performance. The experimental results shows that the presence of large-sized Ce2O2S inclusions and the change of microstructure, will lead to the decrease in tensile performance.

Nozzle clogging frequently occurs in steel containing rare earth (RE) due to the aggregation of RE inclusions, which seriously interferes with the application of RE in steel. To provide insights into nozzle clogging, the agglomeration behavior of inclusions in RE-containing steel was investigated by laboratory experiments and theoretical calculations. High-temperature confocal laser scanning microscopy (HT-CLSM) was applied to observe the behavior of inclusions at molten steel surfaces and their interactive forces. Kralchevsky-Paunov (K-P) model was used to predict the capillary force acting on different inclusions. The results show that the interactive forces that acted on inclusions were investigated as a function of inclusion size, inter-distance, and inclusion composition. It is found that the capillary force acting on the inclusions decreases in the order of Ce2O3 > CeAlO3 > Al2O3. This study verified the applicability of the K-P model in RE-containing steel, which can provide theoretical support to help solve the nozzle clogging problem during rare earth steel production. (c) 2022 Chinese Society of Rare Earths. Published by Elsevier B.V. All rights reserved.

Li4Ti5O12 is a lithium-ion battery cathode material with great potential for development because of its "zero-strain" characteristics, but its low lithium ion diffusion and conductivity rate lead to poor rate and cycling performance. NaN-LTO, a nanorod-like material with oxygen vacancies on the surface, was prepared by calci-nation after hydrothermal reaction using sodium molybdate as the sodium source and L-cysteine as the nitrogen source and structural guiding agen, while achieving co-doping of N and Na at the O and Li positions in situ respectively. The effects of N and Na co-doping on the crystal and electronic structures were revealed. The electrochemical test results show that rate and cycle performance of NaN-LTO are greatly improved, which can reach 126.0 mAh/g at 20C (1C = 175 mAh/g), 126.9 mAh/g after 1000 cycles with a capacity retention rate of 100.7% and the capacity retention rate is 74.0% after 3000 cycles. The co-doping strategy of Li-site and O-site provides a new modification idea to enhance the electrochemical performance of lithium titanate. Meanwhile, the preparation cost of lithium titanate can be reduced by the partial replacement of Li by inexpensive Na.

The comprehensive and accurate characterization of the characteristics of non-metallic inclusions in steel is conducive to the discovery and recognition of new inclusions and is also the prerequisite for the regulation of non-metallic inclusions and the improvement of steel quality. This paper uses scanning electron microscopy with energy spectrum (SEM-EDS), Raman spectrum, high-resolution transmission electron microscope(TEM) and micro-region X-ray diffraction (mu XRD), combined with the inclusion of electrolytic extraction technology and image analysis technology, the characterization of zirconium deoxidization non-metallic inclusions in steel shape, size, quantity, distribution, composition, crystal structure, characteristic parameters such as comparative analysis the advantages and disadvantages of four kinds of methods for characterizing the inclusions. The results show that the inclusion in zirconium deoxidized steel was mainly composed of Zr, O and a small amount of Al by SEM-EDS method. Based on the stoichiometric relationship between zirconium oxide and aluminum oxide, the inclusion was analyzed to be composed of 94% ZrO2 and 6% Al2O3. The inclusion size distribution in zirconium deoxidized steel is normal. The average inclusion size is 0. 62 mu m, and the number of inclusions is the largest in the range of 0. 7 similar to 0. 8 mu m. The three-dimensional morphology of non-metallic inclusions in steel can be observed using SEM combined with electrolysis. The EDS method can be used to qualitatively analyze the composition and distribution of elements in inclusions individually. The composition of inclusions with single valence can be quantitatively analyzed. However, for non-metallic inclusions with many valence states and unknown valence states, the EDS method alone cannot accurately analyze the phase and composition of inclusions. The presence of monoclinic zirconia in zirconium-deoxidized steel was detected by Raman spectroscopy combined with electrolysis extraction of inclusions. TEM diffraction pattern calibration and energy spectrum analysis of a single inclusion detected Zirconia with monoclinic phase. Two phases, including monoclinic and tetragonal zirconia, were detected by mu XRD combined with electrolytic extraction of inclusions, and the lattice parameters of zirconia inclusions were obtained. These three methods detected no aluminum-containing phase. Raman spectroscopy, TEM and mu XRD can be used to qualitatively analyze the phase and composition of inclusions after electrolytic extraction, but the three methods cannot accurately characterize the phase with low content. TEM and mu XRD can characterize the crystal structure and lattice parameters of the inclusion. TEM and SEM can only characterize individual inclusions one by one. mu XRD and Raman spectroscopy can characterize the phase of all the inclusions in the detected region, a statistically significant method to characterize inclusions. Therefore, the inclusion characteristics can be characterized comprehensively and accurately by SEM-EDS analysis combined with mu XRD analysis.

To study the effects of Al and Ti additions on the formation of inclusions in nickel-based superalloys, laboratory experiments were carried out at 1823 K. We observed mainly pure Al2O3 inclusions and some Al2O3-TixOy and Al2O3(-TixOy)-titanium nitride (TiN) composite inclusions in the nickel-based alloy with initial deoxidants of 0.3-0.7% Al and 0.7-1.2% Ti (wt%). The total Ti content in the inclusions increased slightly with an increasing amount of added Ti. Thermodynamic calculations were conducted to understand the formation mechanism of the inclusions and control the inclusions. The predominance diagram obtained for the Al-Ti-O inclusions in the nickel-based superalloy system was based on Factsage and classical thermodynamic calculations. The inclusions obtained from experiments were not completely consistent with the Factsage calculated results; however, they agreed well with the classical thermodynamic calculation. The calculated results indicated that the thermodynamic stable inclusion was Al2O3 in liquid K4169 alloy at 1823 K. The oxygen content should be controlled to < 10 ppm to avoid the formation of Al2O3 inclusions in the superalloy. Thermodynamic results indicated the initial precipitation of TiN in the FCC phase of the superalloy from 963 to 1403 K. The precipitation temperature of TiN decreased with the decrease of N content and increase in Ti content in the superalloy. The precipitation of TiN was not only dependent on the contents of Ti and N in a sample but also on the cooling conditions. (c) 2022 Elsevier B.V. All rights reserved.

To investigate the thermodynamic stability and the evolution process of inclusions in the Al–Ti deoxidized steels, both laboratory experiments and thermodynamic calculations were conducted in the present work. Scanning electron microscope-energy dispersive spectrometer (SEM-EDS) and Al2O3–Ti2O3–TiO2 phase diagrams were used to investigate the composition of oxide inclusions after adding various contents of Al and Ti. The results show that the TiOx content of inclusions increases with the increase in titanium addition in steel ranging from 0.31 to 1.88%, and the typical inclusions are transferred from pure Al2O3 to multi-phase Al–Ti complex inclusions and Al2O3–TiOx complex inclusions with uniform composition. The TiOx content in the inclusions first increased and then decreased with the extension of deoxidation time in the steels with deoxidants of [% Al] = 0.055 and [% Al] = 0.71, and the content of TiOx in the inclusions is highest at 360 s of deoxidation. There is a small amount of pure titanium oxide and liquid Al2O3–TiOx composite inclusions in the steel with deoxidants of [% Al] = 0.13 and [% Ti] = 1.88 at 120 s of deoxidation, and then this part of inclusions gradually turns into the Al2O3-rich phase. The predominance diagrams of the Al–Ti–O–Fe system were obtained based on the classical thermodynamic calculation and FactSage calculation with different databases and products. The calculated results were compared with the experimental data, and the discrepancies on the stable region of oxides in the predominance diagrams were discussed. The evolution and transformation of inclusions during the solidification process were analyzed based on FactSage calculation.