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.

Fine-sized oxide particles are often used to improve the mechanical properties and service life of materials. Particularly, rare earth-silicate particles have high deformability and promising applications in metallic materials and ceramic coatings. To study the formation of rare earth-silicate particles and control their physical characteristics, we apply first-principles calculations and investigate the nucleation mechanism of Ce 2 Si 2 O 7 particles at the atomic scale. The estimated thermodynamic properties of (Ce 2 Si 2 O 7 ) n (n = 1 – 4) agree reasonably well with the experimental data, indicating that the first-principles calculation is reliable. Furthermore, the potential of a preformed nuclear phase for Ce 2 Si 2 O 7 particles is thermodynamically demonstrated. Four formation pathways of Ce 2 Si 2 O 7 particles are proposed and discussed. Based on thermodynamic principles, the most probable formation pathway is [Ce]+[Si]+[O]→(Ce 2 Si 2 O 7 ) n →Ce 2 Si 2 O 7(s) , and another formation pathway is considered the least likely, (SiO 2 ) n +(Ce 2 O 3 ) n →(Ce 2 Si 2 O 7 ) n →Ce 2 Si 2 O 7(s) .

In this study, two typical commercially used CaO-SiO2-CaF2-based mold fluxes with different basicities were adopted. Solid slag films of the two mold fluxes were obtained by immersing an improved water-cooled copper probe in the molten fluxes for different probe immersion times and molten slag temperatures. The film thickness, closed porosity, and roughness of the film surfaces in contact with the copper probe were measured. The heat flux through the solidified films and the comprehensive thermal conductivity of the films were both calculated. The results indicated that compared with the heat flux through high-basicity films, the heat flux through low-basicity films exhibited high fluctuation due to the evolution of fusion cracks within the glass layer. High-basicity mold fluxes resulted in higher thickness, growth velocity, surface roughness, and devitrification velocity of the films. With the growth and crystallization of the slag films, the comprehensive thermal conductivity of the high-basicity films increased significantly. For the low-basicity films, their comprehensive thermal conductivity first decreased and then increased after the solidification time exceeded 30 s. The comprehensive thermal conductivity of the high- and low-basicity films ranged from 0.63 to 0.91 and 0.62 to 0.81 W/(m·K), respectively. The results provide a novel method for analyzing the potential effect of the structural factors of slag films on heat transfer control and controlling the heat transfer behavior of slag films.

This work investigates the localized corrosion behavior of zirconium-treated P110 oil-casing steel in 3.5 wt% NaCl solution. The influence of inclusions containing zirconium on localized corrosion is analyzed in detail by combining experiments with theoretical calculations. Inclusions primarily exist in the form of ZrO2-Al2O3. Slight corrosion of micro-cracks is observed at later stages of immersion. Zirconium treatment promotes passivation, transforming poorly corrosion-resistant CaS-MgAl2O4 inclusions into ZrO2 inclusions which mitigate the stress concentration induced by Al2O3 inclusions. The thermodynamic results indicate that stable ZrO2 inclusions form in P110 steel with Zr content exceeding 0.014 wt%, effectively inhibiting inclusion-driven localized corrosion.

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.

The characteristics of inclusions have a significant influence on the performance and fatigue life of Ni-based alloy and some cracks usually initiate and propagate from inclusions. High-temperature experiments were carried out at 1823 K to study the effect of Al and Ti addition on the characteristics of oxide inclusions in Ni-based alloy. The size, number, distance, distribution of oxide inclusions and degree of homogeneity in inclusion dispersion in Ni-based alloy with [%Al] i = 0.3–0.7 and [%Ti] i = 0.7–1.2 ( i represent initial addition of deoxidant) were analyzed systematically. It is found that the oxide inclusions in alloys with [%Al] i = 0.7, [%Ti] i = 0.7/1.2 had smaller average size of 2.4 µm and distributed more homogeneously. The Ostwald ripening theory and collision model were applied to point out the relationships among compositions of Ni-based alloy, behaviors of oxide inclusions and their characteristics under the condition of no external stirring. The calculated results were in good agreement with experimental results. The mechanism on obtaining fine and dispersed oxide inclusions in Ni-based alloy was summarized.

Laboratory experiments were carried out to study the effect of a MgO-CaO-ZrO2-based refractory (MCZ refractory) on the cleanliness of a K4169 Ni-based superalloy. The chemical composition and characteristics of the refractory, alloy, and inclusions were analysed by X-ray fluorescence (XRF), X-ray diffraction (XRD), and scanning electron microscopy-energy-dispersive spectroscopy (SEM-EDS). Characterisation results indicated that the CaZrO3 phase was stable, the amount of the spinel phase increased whereas that of the MgO phase decreased, and Ca2Al2SiO7 and Ca2SiO4 transformed into Ca3Ti8Al12O37 and CaSiO3, respectively, in the refractory during the melting of the Ni-based superalloy. In addition, a new phase of Mg8Cr16O32 was simultaneously formed. The MCZ refractory penetrated the liquid alloy and reacted with it, which increased the Mg and Ca contents of the alloy. The erosion depth of the refractory in the alloy was more than 20 mu m after melting for 100 min. Inclusions composed of MgO-Al2O3-TixOy wrapped with TiN were observed in the alloy after melting in the MCZ refractory. The inclusions were large, numerous, and distributed inhomogeneously in the alloy near the side and bottom of the refractory. The chemical reactions among the refractory, liquid alloy, and inclusions were analysed, and FactSage software was used to investigate these interactions. The effect of the dissolution of the MCZ refractory on the composition and transformation of the liquid alloy and inclusion was estimated. The thermodynamic results agreed well with the experimental results.

Understanding the interactive forces of inclusions on the surface of molten nickel-based superalloys and finding methods to disperse these inclusions help improve performance and service life. The aggregation behavior of aluminum oxide (Al2O3) and calcium aluminate inclusions with different sizes and spacings on the surface of molten nickel-based superalloys was observed in-situ using a high-temperature confocal laser scan microscope. The attractive force acted on Al2O3 inclusions with radii of 3.5–6 μm was found ranging from 6.2 × 10–18 to 3.6 × 10–15 N, and that of CaO·2Al2O3 (CA2) inclusions with radii of 3–5.5 μm ranging from 3.5 × 10–19 to 8.3 × 10–15 N. The capillary force acted on inclusions on the surface of nickel-based superalloy was calculated based on the Kralchevsky–Paunov model and investigated as a function of inclusion size, spacing, and composition. The calculated results were in the same trend as the experimental results. The capillary force acted on inclusions was also affected by their contact angle, the density, surface energy, and oxygen content of the molten alloy. It decreased with increasing alloy density and decreasing contact angle between inclusion with alloy. Thus, the attractive force acted on Al2O3 inclusions was smaller on the surface of molten nickel-based superalloy than that of molten steel. Decreasing the oxygen content in the molten nickel-based alloy could increase its surface energy, and the attractive force acted on the inclusions would decrease. When the oxygen content in the molten nickel-based alloy decreased from 0.05 to 0.0001 wt.

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.

The composition of the refractory strongly affects the cleanliness of the alloy. K4169 Ni-based superalloys were melted in different types of refractories in this study. The cleanliness of the Ni-based superalloy and phase transformation of the refractory were observed by X-ray fluorescence (XRF), X-ray diffraction (XRD), and scanning electron microscopy energy dispersive spectroscopy (SEM-EDS). The high-temperature stabilities of a Y2O3-based refractory, MgO-based refractory, and Al2O3-based refractory during melting with a Ni-based alloy were compared. The oxygen content was also lowest, and no Y2O3-containing inclusions were observed in the Nibased alloy melted with the Y2O3-based refractory at 1823 K. Inclusions with 21%-29% MgO and a phase composed of Al, Mg and O with an area of approximately 1300 mu m(2) were observed in the alloy. This indicates that the dissolution and erosion of the Y2O3-based refractory were weak, and obvious physical erosion and chemical dissolution of the MgO-based refractory occurred during the melting process of the Ni-based alloy. The width of the refractory phase adhered to the boundary of the Ni-based alloy increased in the order Y2O3-based refractory (15 mu m- 23 mu m)< Al2O3-based refractory (93 mu m- 285 mu m)< MgO-based refractory (3.5 mm-3.6 mm), indicating that the adhesive strength of the MgO-based refractory with the Ni-based alloy was strongest. The interaction between the refractory material, Ni-based alloy and inclusions was analyzed based on thermodynamic calculations by Factsage software. The effects of dissolution of the three refractory types on the formation and transformation of the new phases and inclusions were estimated. The thermodynamic results were in good agreement with the experimental results.

Al 2 O 3 encapsulated by TiN inclusion is a common inclusion in nickel-based superalloys, which affects the performance of nickel-based superalloys. In this paper, typical Al 2 O 3 –TiN composite inclusions in nickel-based superalloy K4169 were observed by scanning electron microscopy and energy-dispersive spectrometer. The first principles calculation based on density functional theory was carried out to study the formation of TiN–Al 2 O 3 composite inclusions at an atomic scale. The surface energy of Al 2 O 3 and the adsorption energy of Ti and N atoms on the Al 2 O 3 surface were estimated, and the stable structures of Ti and N atoms adsorbed on the lowest energy surface of Al 2 O 3 were analyzed. The density of States (DOS) and Partial Density of States (PDOS) were analyzed to investigate the bonding nature and interaction between Ti and N atoms with Al 2 O 3 . The adsorption pathway of Ti and N atoms on the Al 2 O 3 surface and the formation mechanism of TiN–Al 2 O 3 composite inclusions was discussed.

Scrap steel is a kind of resource that can be recycled indefinitely. However, the enrichment of arsenic in the recycling process will seriously affect the performance of the product, making the recycling process unsustainable. In this study, the removal of arsenic from molten steel using calcium alloys was investigated experimentally, and the underlying mechanism was explored based on thermodynamic principles. The results show that the addition of calcium alloy is an effective means of reducing the arsenic content in molten steel, with the highest removal percentage of 56.36% observed with calcium aluminum alloy. A thermodynamic analysis revealed that the critical calcium content required for arsenic removal reaction is 0.0037%. Moreover, ultra-low levels of oxygen and sulfur were found to be crucial in achieving a good arsenic removal effect. When the arsenic removal reaction occurs in molten steel, the oxygen and sulfur concentrations in equilibrium with calcium were wO=0.0012% and wS=0.00548%, respectively. After successful arsenic removal, the arsenic removal product of the calcium alloy is Ca3As2, which usually does not appear alone. Instead, it is prone to combining with alumina, calcium oxide, and other inclusions to form composite inclusions, which is beneficial for the floating removal of inclusions and the purification of scrap steel in molten steel.

The properties of functional particles are intrinsically linked to their nucleation process. However, for such particles at high temperature, it is difficult to observe their nucleation in real time, and so the corresponding properties are rarely well understood. In the reported study, the nucleation of titanium oxide particles was systematically investigated by means of both classical nucleation theory and first principles. In high-temperature experiments, three samples (T1-T3) with differing titanium content were processed into metallographic samples and subjected to electrolytic extraction for observations via scanning electron microscopy-energy dispersive spectroscopy, X-ray microdiffraction, and transmission electron microscopy. It was determined that the titanium oxide particles in the three samples were Ti2O3, Ti3O5, and TiO2. The nucleation rate and radius of these particles were calculated using classical nucleation theory, and the results were consistent with the experimental results for the Ti2O3 particles but not the Ti3O5 ones. The theoretical and experimental values for T1–T3 decreased in the order T1>T2>T3, and there were considerable differences of as much as an order of magnitude between some of the theoretical and experimental values. The size effect on the nucleation was analysed by constructing (Ti2O3)n, (Ti3O5)n, and (TiO2)n (n = 1–6) nanoclusters, and the thermodynamic properties of the nanoclusters and nano-sized titanium oxide particles were analysed. The thermodynamic properties of the titanium oxide particles estimated using density functional theory generally coincided with those determined experimentally. Based on cluster-assisted nucleation, four nucleation pathways for titanium oxide particles were summarized as follows: (i) [Ti]atom + [O]atom → (TiO2)n → (TiO2)5 → TiO2 particle or (TiO2)5-cluster core–shell nanoparticle → (TiO2)bulk, (ii) [Ti]atom + [O]atom → (Ti3O5)n → (Ti3O5)2 → Ti3O5 particle or (Ti3O5)2-cluster core–shell nanoparticle → (Ti3O5)bulk, (iii) [Ti]atom + [O]atom → (Ti2O3)n → (Ti2O3)3 → Ti2O3 particle or (Ti2O3)3-cluster core–shell nanoparticle → (Ti2O3)bulk, and (iv) [Ti]atom + [O]atom → (TiO2)n, (Ti3O5)n, (Ti2O3)n → (Ti2O3)3 → Ti2O3 particle or (Ti2O3)3-cluster core–shell nanoparticle → (Ti2O3)bulk.

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.

Understanding the mechanism of particle aggregation and dispersion at a liquid surface is important for the design and fabrication of novel materials. The behaviors of particles with various compositions at the interface of high-temperature melts, including the rapid growth of particles, the linear aggregation or curvilinear motion, and the wetting and separation processes, were observed in situ by high-temperature confocal laser scanning microscopy (HT-CLSM). We experimentally investigated the interaction force on particle pairs as a function of the interparticle distance and the size, composition and shape of particles. The experimental results indicate the attractive force between particle pairs decreases with increasing distance, and it increases as the size of the guest particle increases. The acting length of particles increases in the order of the alumina-magnesia particle (30 mu m) < calcium aluminate particle with low CaO contents (80 mu m)< alumina particle (110 mu m). The estimated attractive interaction between particle pairs based on in situ observation increases in the order of Al2O3 center dot 35%CaO < Al2O3 center dot 19%MgO < Al2O3 center dot 38%MgO < Al2O3 center dot 15%CaO < Al2O3. The complex selective attraction has been observed in the in situ experiments which is attributed to the polydirectional attractive force and anisotropy in the particle morphology. The relationship between the roundness with acceleration rate of particles indicates that the attraction between spherical particles tends to be less than the attraction between irregular particles with edges.

通过扫描电镜和能谱仪等设备,检测分析镍基高温合金中铝和钛含量对夹杂物的成分、形貌、尺寸、数量、夹杂物间的界面间距和面分布等参数的影响.通过经典热力学计算方法、FactSage软件,计算和分析冶炼过程中夹杂物的生成和演变.结果表明,镍基高温合金中夹杂物主要成分为Al2O3、TixOy、TiN,经典热力学计算和Fact-Sage软件计算结果与夹杂物成分检测结果基本吻合.冶炼后期,高铝钛镍基合金、低铝钛镍基合金中夹杂物尺寸相差不多,但是高铝钛镍基合金中夹杂物数量明显较少,夹杂物界面间距较大,夹杂分布更加均匀.通过经典形核理论计算得出,高铝钛镍基合金中夹杂物形核半径是低铝钛镍基合金的3倍,在结合氧相同的情况下,增加合金中铝钛添加量,有利于减少夹杂物的形核数量,从而增加夹杂物的界面间距,减少夹杂物间的碰撞,减弱夹杂物间吸引,减少夹杂物间的聚集.

通过扫描电镜-能谱仪检测和分析了不同铝钛脱氧顺序下钢中夹杂物的形貌、成分、尺寸、数量和分布等参数,通过热力学计算分析了脱氧过程中钢液中的化学反应和夹杂物优势区图.结果表明,脱氧剂添加顺序对夹杂物形貌影响很大,先加钛后加铝的脱氧方式下,钢液中形成了较多含有铁相("空心")的具有浓度梯度的铝钛复合夹杂物.夹杂物径向长度增加,夹杂物也更容易偏聚.所以先加钛后加铝不利于夹杂物尺寸细小化,不利于夹杂物弥散分布.先加铝后加钛的脱氧方式下,钢中形成氧化铝夹杂,不会被溶解的钛还原,因此夹杂物内部不含有铁相.夹杂物主要为Al-Ti-O(-N)类夹杂.夹杂物尺寸和数量小于先加钛后加铝钢中的夹杂物.通过FactSage计算结果、化学反应分析和试验检测结果,探究了不同铝钛脱氧顺序下夹杂物形成和演变机理,分析了具有浓度梯度的"空心结构"的铝钛复合夹杂物形成机理,讨论了脱氧剂添加顺序对夹杂物尺寸、数量和分布等特征的影响规律.发现先加钛后加铝的脱氧方式下,钛氧化物会与金属铝反应,钛氧化物逐渐转变为"空心"氧化铝壳,同时溶解的铝、钛和氧发生氧化反应,形成了具有浓度梯度的Al2O3-TiOx复合夹杂物,最终钛氧化物完全转变为氧化铝壳而消失.随着铁液的填充,形成了含有铁相的铝钛夹杂物.

This study aims to investigate the effect of Mg treatment on the homogenized distribution of inclusions. Deoxidized experiments with Al (0.05%Al) and Al-Mg (0.05%Al + 0.03%Mg) were carried out at 1873 K respectively and the degree of homogeneity in inclusion dispersion, area density, average size and inter-surface distance of inclusions were studied. The attractive capillary force acts on inclusions was analyzed by in-situ observation by confocal laser scanning microscopy and Kralchevsky-Paunov model. The results show that the proportion of inclusions with inter-surface distance at the range of 10–100 µm is up to 60% after Al-Mg deoxidized 1800 s. Compared with Al2O3 inclusion, the area density of MgAl2O4 inclusions is generally more homogeneous. The in-situ observed results indicate that the inclusions in the steel deoxidized by Al are easy to aggregate and small size Al2O3 inclusions tend to gather around large size Al2O3 inclusions, while the inclusions in the steel deoxidized by Al-Mg tend to distribute more homogeneously. Moreover, the calculated results suggest that the attractive capillary force is larger between inclusions with larger size. The attractive capillary force is larger when the value of smaller size inclusions R1 is gradually close to the value of larger size inclusions R2. The relationship between attractive capillary force and the degree of homogeneity in inclusion dispersion is discussed based on Kralchevsky-Paunov model.

This study aimed to investigate the effect of Mg treatment on the nucleation and ostwald growth of inclusions. Deoxidized experiments with Al (0.05%Al) and Al-Mg (0.05%Al + 0.03%Mg) were carried out at 1873 K, and the composition, number, and size of inclusions were studied as a function of holding time. Homogeneous nucleation theory and ostwald ripening were utilized to calculate the nucleation rate, the critical size of nuclei, and coarsening rate of inclusions. The results show that small inclusions were more easily found in the steels with Al-Mg complex deoxidation, and the number of inclusions with Al-Mg complex deoxidation is larger at an early stage of deoxidation. The critical size of nuclei increases in the order of MgAl2O4 (0.3–0.4 nm) < Al2O3 (0.4–0.6 nm), and the nucleation rate increases in the order of Al2O3 (1100 cm−3 s−1) < MgAl2O4 (1200 cm−3s−1), which is consistent with the experimental results. Moreover, the coarsening rate of MgAl2O4 inclusions was smaller than Al2O3 inclusions in both the value of kd(cal.)from ostwald growth and the value of kd(obs.)from inclusion size. The effect of Mg addition on coarsening of inclusion was analyzed and their mechanism was discussed based on ostwald ripening theory and Factsage calculation.