Aluminum dross is a waste of the aluminum industry, and its improper disposal can pose negative environmental impacts. The metallurgical effects of utilizing nitrided aluminum dross in the smelting process of rebar steel are systematically investigated. Firstly, resistance furnace experiments were performed to evaluate the effects of nitrided aluminum dross addition on the oxygen content, aluminum content, and nitrogen content in steel, as well as the corresponding aluminum yield and nitrogen yield. Secondly, an analysis was conducted on the characteristics of inclusions resulting from the addition of nitrided aluminum dross to steel. Finally, based on the laboratory experimental parameters, industrial trials were conducted in steel plant. The laboratory results showed that as nitrided aluminum dross addition increased from 0.5 to 2.0 g per kilogram of molten steel, w[O] (reduction in oxygen content) increased from 0.0017 to 0.0028 wt.

Tin-based halide perovskites suffer from oxidation and interfacial energy mismatch, limiting their photovoltaic performance. Here we uncover a thermally driven interfacial reconstruction mechanism that differs in its driving force from previously reported light-induced doping pathways. FASnI3 solar cells stored in inert atmosphere exhibit spontaneous performance improvement over 144 h at room temperature, dramatically accelerating to just 4.5 h at 60 degrees C. Multimodal characterization reveals that mild thermal treatment induces relaxation within the topmost atomic layers of the perovskite surface without detectable change in bulk structure or optical properties. This surface reconstruction enhances coupling with the PCBM electron transport layer, as confirmed by density functional theory calculations showing increased binding energy. The strengthened interfacial coupling passivates trap states, enhances built-in potential, suppresses non-radiative recombination, and accelerates charge extraction, collectively boosting both open-circuit voltage and short-circuit current density. This work demonstrates the potential of controlled thermal annealing alone to drive beneficial interfacial reconstruction, offering a complementary route to optimized tin-based perovskite devices.

The magnetic properties of non-oriented silicon steel are affected by the composition and morphology of inclusions in the steel. It is necessary to minimize the number of inclusions and modify the inclusions during the manufacturing process. Rare earth modification of the non-oriented silicon steel is a common practice in steelmaking industry. At present, there is still insufficient research on the properties of rare earth alloys themselves, such as phase composition, inclusions in alloys, and the influence of alloy impurities on inclusions in non-oriented silicon steel. In this paper, the phase composition of Fe-RE-Si alloy was analyzed by X-ray diffraction (XRD) and electron probe microanalysis (EPMA). The inclusions in Fe-RE-Si alloy were analyzed by electrolytic extraction and scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS) methods. Subsequently, non-oriented silicon steel was melted in a high-temperature tubular resistance furnace and the Fe-RE-Si alloy was added for rare earth treatment. The evolution of inclusions in silicon steel after Fe-RE-Si alloy treatment was studied by thermodynamic calculation and SEM-EDS analysis. The results demonstrate that the Fe-RE-Si alloy is made up of two phases, i.e., the Fe-Si phase and the Ce-Si phase. The inclusions in the alloy are predominately Al-Fe intermetallic compounds and oxide inclusions. The effect of the Fe-RE-Si alloy on the size, morphology and composition of inclusions in non-oriented silicon steel was investigated through high-temperature melting experiments and thermodynamic calculations. The results of experiments show that after treatment with Fe-RE-Si alloy, the rare earth inclusions in non-oriented silicon steel are mainly AlN-RE2O2S composite inclusions, a small amount of AlN-RES and AlN-REAlO3 composite inclusions. The modification sequence of rare earth inclusions in heat A (with a rare earth content of 0.0017 wt%) is as follows: RES/RE2O2S/RE2O2S/REAlO3. Besides, the modification sequence in heat B (with a rare earth content of 0.0119 wt%) is as follows: RE2O3/RE2O2S/RES/RE2O2S. When the rare earth content increases from 0.0017 wt% to 0.0119 wt%, the type of rare earth inclusions changes from RE2O2S/REAlO3 to RES/ RE2O2S. The average size of inclusions in two heats increases slightly in 30 min after the addition of Fe-RE-Si alloy. The average size of inclusions in heat A and heat B increases from 1.89 to 2.59 mu m, and from 1.93 to 2.6 mu m, respectively. The average size of inclusions in the furnace cooling samples of heat A is larger than that of heat B. In both heats, after the addition of Fe-RE-Si alloy, the proportion of inclusions with the size of 0-2 mu m decreases and the proportion of inclusions with the size of 2-5 mu m increases. The effect of rare earth elements coarsening inclusions is significant. By calculating Gibbs free energy of the rare earth inclusions and the phase stability diagram, it is found that the thermodynamic stable inclusions in both heats are RE2O2S. (c) 2025 Chinese Society of Rare Earths. Published by Elsevier B.V. All rights are reserved, including those for text and data mining, AI training, and similar technologies.

The leaching of Cr6+ from chromium-containing stainless steel slag causes serious environmental pollution, limiting the large-scale application of stainless steel slag. Recovering chromium from stainless steel slag has become the key to fully utilizing chromium-containing stainless steel slag. In order to achieve sustainable recycling of chromium-containing stainless steel slag, this paper explores the synergistic treatment method of secondary aluminum dross and stainless steel slag. Secondary aluminum dross (SAD) contains a certain amount of Al2O3, which can replace Al2O3 as a modifier for chromium-containing stainless steel slag, and Al in SAD can also reduce Cr2O3. The article studied the effect of adding Al2O3 and different contents of SAD to chromium-containing stainless steel slag on chromium partition. The results calculated by FactSage thermodynamic software show that with the increase in the content of Al2O3 and SAD, the content of spinel precipitation increased, while the proportion of MgCr2O4 and FeCr2O4 decreased. After adding Al2O3 and SAD, the main component of chromium-containing spinel phase is Mg(Cr,Al)2O4. The experimental results indicate that the average size of the spinel phase increases with adding Al2O3 and SAD. The large-sized spinel phase is beneficial for its separation and recovery from slag. Meanwhile, the metal Al in SAD can undergo a reduction reaction with FeO and Cr2O3 in the slag to form Cr-Fe alloy, which can be directly separated and recovered from slag. Therefore, the synergistic treatment of secondary aluminum dross and chromium-containing stainless steel slag can selectively enrich chromium, making it a promising comprehensive utilization method.

A water model system that detects level fluctuation and surface velocity is established to study fluid flow and slag entrapment in mold. Results show that the flow field in mold is chaotic and transient. Characterized by two upward flows and a downward flow, a special triple-roll flow pattern is formed. The reason for this phenomenon is the upward SEN. Affected by triple-roll flow, the slag-metal interface can be divided into three parts: SEN zone, impinging zone, and reversed zone. With the increase in casting speed, the level fluctuation near SEN rises from 0.27 to 1.06 mm, and slagging frequency increases from 1.2 to 8.6 min-1. Therefore, the level fluctuation near the SEN can accurately reveal severity of slag entrapment. In this region, vortexing is the major mechanism that leads to slag entrapment. Based on mass conservation, momentum conservation, and Bernoulli equations, a new dimensionless number is found to evaluate slag entrapment caused by this special triple-roll flow. The accuracy of this indicator is compared with experiment and predicted results, and good agreement is obtained. This study offers new insights into surface defects that occur during the casting of stainless steel.

The characteristics of the multi-phased oxide-TiN-TiC-(delta-Fe) heterostructures in Fe-Cr-based alloys are essential for TiN refinement and resultant grain refinement. While the refining phenomena of TiN and as-cast grains in FeCr-based alloys were well reported, the detailed refining mechanisms for TiN and delta-Fe grains remain to be further elucidated. In order to evaluate the oxide-TiN-TiC-(delta-Fe) heterostructures, three foils for transmission electron microscope (TEM) examination were prepared, denoted as the I0, R1, and MR1 samples, respectively. Here, the atomic lattice matching modes and orientation relationships (ORs) across the (Mg and /or RE bearing oxide)-TiNTiC-(delta-Fe) heterostructures were revealed. Based on the results, the simulated multilayer /3D atomic matching models for the interfaces of each heterostructure were established, revealing the actual atomic-scale structures of the heterostructures and their formation processes originating from the oxides. Furthermore, a newly developed long-range lattice matching (LRLM) model was established to provide a new method of the OR verifications. In summary, this study does provide new insights into interfacial engineering and new ideals on refining TiN and ascast grains in industrial production of Fe-Cr-based alloys.

Three steels were prepared using Ti–Mg, V and Ti–Mg–V microalloying treatments and rolled into steel plates with a thickness of 20 mm. In this article, the inclusions, second phase particles, grain size and mechanical properties of three steels were studied. It was shown that Mg was able to refine inclusions in steel, and the average sizes of inclusions in Ti–Mg-microalloyed and Ti–Mg–V-microalloyed steels were 2.56 μm and 2.87 μm respectively, which were smaller than the average size of inclusions in V-microalloyed steel (3.58 μm). The austenite grain sizes of Ti–Mg-microalloyed and Ti–Mg–V-microalloyed steels (73.34 μm and 68.70 μm) were significantly smaller than those of V-microalloyed steel (289.38 μm) because of the ability of TiN precipitated at high temperatures to pin austenite. V-microalloyed steel had the largest number of second phase particles with the smallest particle size, resulting in the best precipitation strengthening effect. Ti–Mg-microalloyed steel had TiN particles that grow and had a weakened precipitation strengthening effect. Ti and V tend to form larger sized (Ti, V) (C, N), which reduces the amount of precipitates and thus makes the precipitation strengthening effect weaker.

To investigate the nucleation behavior during the single-phased metallic solidification process, the commercial ultrapure ferritic stainless steels with no (Initial steel) and various melt treatments (R1, MR1, Y2, MY1, and M1 steels) were used to carry out the differential scanning colorimetry (DSC) and high-temperature confocal laser scanning microscope (HT-CLSM) experiments. Based on the results of DSC experiments, the equilibrium solidification process as well as the relationship among the critical undercooling degree ( ΔT_c^DSC ), latent heat of fusion/crystallization ( ΔH_f / ΔH_c ), equiaxed grain ratio (ER), and average grain size ( D_ave.^ingot ) was revealed. ER is increased with the decreasing ΔT_c^DSC and increasing ΔH_f / ΔH_c ; however, D_ave.^ingot is decreased with them. Referring to the results of HT-CLSM experiments, the average sizes of micro-/macrostructures ( d_ave. / D_ave. ) are decreased with the increasing cooling rate, as well as the difference between ΔT_c^DSC and apparent critical undercooling degree ( ΔT_c^CLSM ) was revealed. The heterogeneous nucleation of the crystal nuclei occurs only if ΔT_c^CLSM > ΔT_c^DSC . Combining with the interfacial wetting-lattice mismatch heterogeneous nucleation model, the dynamic mechanism of the metallic solidification was revealed. The as-cast grains of the melt-treated samples were obviously refined, owing to the much higher actual heterogeneous nucleation rates ( I_heter., i ) obtained through melt treatments, and the heterogeneous nucleation rates ( I_heter., ij ) for all samples are increased with the cooling rates, firmly confirming that the as-cast grains of each sample could be refined by the increasing cooling rates.

Porous Zn scaffolds are considered promising next-generation biodegradable antibacterial bone implants. This work provides insight into the influence of Cu content and porous structure on the evolution of corrosion degradation and tribocorrosion mechanisms of porous Zn-Cu scaffolds, offering guidance for the design and application of porous materials in bone tissue engineering. Porous Zn-Cu scaffolds with 0, 1, 2, and 3 wt% Cu and a 60 % porosity were effectively fabricated using the space-holder technique. The microstructure, microhardness, corrosion degradation, and tribocorrosion behavior were systematically studied. The results show that porous ZnCu scaffolds, with an average pore diameter of 311.57 +/- 125.69 mu m, consist of eta-Zn, ZnO, and epsilon-CuZn5 phases. The CuZn5 phase significantly increases the microhardness of porous Zn-Cu while reducing both corrosion and degradation rates. The corrosion degradation progresses through three stages, with the corrosion modes exhibiting both uniform corrosion and pitting. Notably, the degradation rates of porous Zn-(0, 1, and 2 wt%) Cu were consistent with the requirements for bone implants. Tribocorrosion testing revealed that the porous structure can effectively suppress the fluctuation of OCP. However, increasing Cu content promotes the removal of passive film. Wear mechanisms include a mixture of abrasive and adhesive wear, with higher Cu content intensifying corrosion and promoting wear. Four typical wear modes were identified in the Tcell, while in the Tstrut, increasing Cu content led to the formation of prominent cracks and micropits.

To meet the requirement of low magnetic permeability, which, in turn, lowers the ferrite content of castings, of special interest is 316 stainless steel, whose low ferrite content renders it suitable also for nuclear power applications. Therefore, the effects of the composition and cooling rate of 316 stainless steel castings on the ferrite content are investigated. Three 316 stainless steel continuous casting samples with different compositions (primarily differing in the Ni content) are studied, i.e., low-alloy type (L-316), medium-alloy type (M-316), and high-alloy type (H-316). The austenite-forming element nickel of three different industrial samples is 10%, 12%, and 14%, respectively. The effect of the cooling rate on the ferrite content and precipitation phases of the high Ni content of the 316 stainless steel casting (H-316) is studied by remelting experiments and different methods of quenching of liquid steel. In both cases, the ferrite content and the precipitate phases in the microstructure are analyzed using SEM and EBSD. The results indicate that compositional changes within the 316 stainless steel range lead to changes in the solidification mode. In the L-316 casting, solidified by the FA mode (ferrite–austenite mode), ferrite precipitates first from the liquid phase, followed by the formation of austenite, and the ferrite content is 11.2%. In contrast, the ferrite content in the M-316 and H-316 castings, solidified by the AF mode (austenite–ferrite mode), is 2.88% and 2.45%, respectively. The effect of the solidification mode on the ferrite content is more obvious than that of the composition. The microstructure of the L-316 casting is mainly composed of the austenitic phase and the ferritic phase. The microstructure of the M-316 casting is composed of austenite, ferrite, and a small amount of sigma phase, with a small amount of ferrite transformed into the sigma phase. The microstructure of the H-316 casting is basically composed of austenite and the sigma phase, with the ferrite has been completely transformed into sigma phase. Changes in composition have a greater influence on the precipitate phases, while the solidification mode has a lesser impact. In the remelting experiments, the ferrite content in the H-316 ingot obtained through furnace cooling and air cooling is 1.49% and 1.94%, respectively, and the cooling rates are 0.1 °C/s and 3.5 °C/s, respectively. Under oil- and water-cooling conditions, with cooling rates of 11.5 °C/s and 25.1 °C/s, respectively, the ferrite content in the ingot is controlled to below 1%. The effect of the cooling rate on the precipitation phase of the H-316L ingot is that the amount of precipitated phase in the ingot decreases with an increase in cooling rate, but, when the cooling rate exceeds a certain value (air cooling 3.5 °C/s), the change in cooling rate has little effect on the amount of the precipitated phase.

An industrial experiment was conducted at a certain steel plant in China to compare and analyze the effects of Ca treatment and Mg-Ca treatment on inclusions in 45MnVS non-quenched and tempered steel. Through scanning electron microscopy-energy dispersive scanning analysis of the morphology and composition of inclusions, as well as Aspex quantitative analysis of their quantity, type and size, the formation mechanism of MnS-oxide (MnS inclusions with oxide cores) was intensively studied. The influence of sulfide morphology on the impact properties of steel was also analyzed. The results show that the quantity percentage of spindle-shaped sulfides in Ca-treated steel is 19.99%, and that in Mg-Ca-treated steel is 35.38%. Compared with Ca-treated steel, there are more MnS-oxide inclusions in Mg-Ca-treated steel. Controlling the content of Ca and Mg in the oxide core of MnS-oxide inclusion above 10 wt.% and the area ratio below 5 would contribute to the formation of spindle-shaped inclusions after rolling. The mismatch between MnS and oxides decreases with the increase in MgO content in the oxides, which is beneficial to nucleation and precipitation of MnS with this type of oxides as the core. Under the same deformation conditions, the size of sulfide does not affect its aspect ratio. Under the experimental conditions, the inclusion containing a certain amount of MgO can enhance its sulfur capacity, facilitating the formation of composite sulfides. The transverse impact energy of Ca-treated steel is 25.785 J, and that of Mg-Ca-treated steel is 32.119 J. Compared with the traditional Ca-treatment, Mg-Ca treatment can increase the number of spindle-shaped sulfides in the steel, thereby improving the transverse impact toughness of the steel and reducing the anisotropy of the mechanical properties of the material.

The phenomena and mechanisms for TiN and corresponding as-cast grain refinement in magnesium-treated ultra-pure ferritic stainless steel (ultra-FSS) have been systematically investigated in this study, and two samples were prepared as the Initial and magnesium-treated samples. A new research method, X-ray diffraction coupled with electrochemical impedance spectroscopy, was conducted to reveal the relationship among the solute atoms, TiN, and solidification structure; after magnesium treatment, the solidification structure is refined resulting from the promoted precipitation of TiN and the corresponding decrease of solute Ti atoms. From the results of TiN inclusions coupled with mechanism analysis, it is concluded that the promoted precipitation and refinement of TiN can be attributed to (i) the pure oxides possessing low lattice misfits with TiN along at least one orientation relationship, (ii) multiphase complex oxides including at least one phase possessing extremely low lattice misfits with TiN, and (iii) sufficient oxides. Based on the results of macro−/microstructures and solidification processes, the general rule of solidification for metallic materials can be perfected as: the metal with more finer nucleating particles inoculated, higher latent heat of fusion/crystallization, smaller critical undercooling degree, wider nucleation-growth interval, and narrower solidification interval usually yields finer grains. Grain refinement of ultra-FSS through TiN is comprehensively evaluated by the interfacial wetting-lattice mismatch heterogeneous nucleation model; the higher value of the heterogeneous nucleation rate is, the higher equiaxed grain ratio and finer as-cast grain for the solidification structure are. Focused ion beam-transmission electron microscope was utilized to reveal the orientation relationships among magnesium-bearing oxide, TiN, TiC, and δ-Fe, directly confirming that the TiN refinement through oxides can be ascribed to the highly similar crystal structures.

The removal of inclusion particles is an important function of tundish metallurgy. During ladle change, the liquid level fluctuation around the ladle shroud is severe, which may affect the effectiveness of inclusion removal. In the present study, the fluid flow characteristics and inclusion‐removal behavior in the tundish during ladle change are investigated by numerical simulation method. And the effectiveness of flow control devices on the flow characteristics of molten steel is evaluated. It is found that the escape rate of inclusion particles during ladle change is ordered as emptying process < steady process < filling process. The proper combination of weir, dam, and turbulence inhibitor can optimize the conditions for the floating and removal of inclusion particles to the greatest extent. In the tundish with weir and dam, the escape rates of inclusion particles with sizes of 10, 50, and 100 μm throughout the entire ladle change period are respectively reduced by 9.8%, 1.6%, and 1.4%, compared to not using flow control devices. With a combination of weir, dam, and turbulence inhibitor, the escape rates of the three types of inclusion particles are reduced by 24.7%, 9.9%, and 1.2%, respectively.

The effect of magnesium treatment and calcium treatment on the microstructure and mechanical properties of industrial H13 steel after quenching and tempering was investigated. The impact toughness and tensile tests were mainly carried out, and the microstructure was observed by scanning electron microscopy, electron backscattered diffraction, and X-ray diffraction. The results show that magnesium treatment is still feasible in industrial trials. It is mainly manifested in the refinement of lath martensite and carbides. Compared with calcium treatment, the prior austenite grains and carbides size of industrial H13 steel treated with magnesium decreased by 3.17 μm after quenching. After quenching and tempering, the carbides (especially V-rich carbides) in Mg treatment obviously spheroidized and distributed uniformly and increased in quantity significantly. The lath martensite size is reduced from 2.45 to 2.31 μm. This suggests that magnesium treatment was able to yield smaller grains and more evenly distributed carbides. Moreover, the impact toughness, yield strength, and ultimate tensile strength of industrial H13 steel with magnesium treatment increased by 28%, 65.5 MPa and 123.7 MPa, respectively. The increment of strength mainly comes from dislocation strengthening, grain refinement strengthening, and precipitation strengthening, among which precipitation strengthening accounts for the largest proportion.

The desulfurization effect of CaO-secondary aluminum dross (SAD) composite desulfurizer in hot metal was studied in present work. The thermodynamic reaction mechanism of desulfurization with CaO as desulfurizer under the action of SAD was discussed. The experimental results indicated that the desulfurization ability of CaO significantly improved with the addition of SAD. Metallic aluminum can effectively reduce the oxygen potential in molten melt, which is conductive to the thermodynamics conditions of desulfurization reactions. When CaO-SAD composite desulfurizer is used, C3A calcium aluminate with low melting point can be generated, which improves the fluidity of desulfurizer at experimental temperatures. Meanwhile, it prevents the formation of high melting point 2CaO·SiO2 on the surface of lime particles and promotes a sustainable desulfurization reaction. When the ratio of CaO/SAD is 0.9 and 1.0, the utilization rate of CaO in desulfurizer is about 10%, which is higher than that of calcium-aluminate based desulfurizer. The application of SAD as a desulfurizer for hot metal in the steel industry can provide a new approach for the comprehensive utilization of SAD.

Microinclusions in steel will significantly affect mechanical performance of final products and therefore require serious concern during metallurgical process. Herein, the collision, coalescence as well as floatation of bubble–inclusion coexisting system is fully studied through a new mathematical model. It comes to the following conclusions: as bubbles rise, they induce a flow of liquid steel from their upper surface to their lower surface, and inclusion droplets rise and collide in the wake of the bubble. The velocity of the bubbles is affected by their deformation, with deformation rates being linked to the Weber number. The coalescence time of these inclusions is primarily influenced by viscosity and surface tension. Coalescence accelerates with higher surface tension or reduced viscosity, and this phenomenon can be described by a formula, which is developed by simulation results. According to this formula, coalescence time of 3CaO·Al 2 O 3 is 20% longer than that of 12CaO7·Al 2 O 3 . Consequently, 12CaO7·Al 2 O 3 is more prone to coalescence. The movement of inclusions can be controlled by adjusting gas volume and flow rate. Moreover, promoting coalescence can be achieved by altering the viscosity of inclusions and the surface tension coefficient, making it easier to remove these unwanted inclusions.

Two heats of steel are melted using a vacuum induction furnace in the laboratory, with one heat undergoing magnesium treatment and the other being subjected to a combined magnesium-calcium treatment. The precipitation and agglomeration behaviors of inclusions of these two steel samples are observed using a high-temperature confocal laser scanning microscopy. MnS precipitates form around oxide cores and undergo rapid growth during the solidification process of molten steel, and these MnS precipitates with oxide cores react with the cores, resulting in the transformation of the MnS into complex sulfides. In comparison with Al2O3 inclusions, MgOAl2O3 inclusions have a lower critical velocity (V c), making them more susceptible to being engulfed by the solid-liquid interface. As the size of colliding inclusions increases, the coalescence-collision frequency (E 0) initially decreases until it reaches a minimum value. After that, with further size increments, the frequency starts to increase. During the inclusions growth process through collision, there is a distinct zone where coalescence-collision frequency is low. Inclusions that reach this zone struggle to grow further due to reduced collision coalescence, consequently leading to a predominance of inclusions with diameters in this zone. This article investigates the formation and collision behavior of inclusions in steels treated with Mg and Ca-Mg-Ca composite treatment. The study includes calculations of the critical velocity and coalescence-collision frequency of the inclusions. MgOAl2O3 have a lower critical velocity compared to Al2O3. Additionally, a distinct zone with a low coalescence-collision frequency is observed. image (c) 2024 WILEY-VCH GmbH

Rare earth element played an important role in the carbide and solidification structure of high carbon steel. Reasonable control of rare earth content in electroslag remelting (ESR) of special steel can obviously improve the quality of steel. This paper focused on the thermodynamics between rare earth slag and steel to improve the homogeneous distribution control of rare earth element along the height of ESR ingot. The melting temperature, viscous characteristics of CaF2-CaO-Al2O3-Ce2O3-based slags were measured. The results showed that the CaO played an important role in activity coefficients of SiO2, Al2O3, Ce2O3. The content of Ce in ESR ingot increased with the increase of CaO content in slags, but the excessive CaO deteriorated the physical properties of the slag and the surface quality of electroslag ingots. When the slag compositions met the condition of CaF2: CaO: Al2O3: Ce2O3 = 50: 10: 20: 20, it not only had the low melting temperature and appropriate viscous characteristics but also could control the rare earth content in steel to a greater extent. Finally, ESR ingots with good surface and homogeneous distribution of Ce along the height of ingot were obtained.

To investigate the refining phenomena of TiN inclusion and macro-/microstructure through heterogeneous nucleation of δ-Fe at TiN encapsulating oxide during solidification in ultrapure ferritic stainless steel, five samples were prepared, denoted as the initial, low-yttrium-treated, moderate-yttrium-treated, high-yttrium-treated, and magnesium-yttrium-treated samples. Based on the results of TiN inclusions, the minimum value of the average size (2.61 μm) and the maximum value of the number density (346.70 mm−2) were observed after magnesium-yttrium (Mg–Y) treatment. Combined with the mechanism analysis, these results reveal that the TiN can be refined because of the following three reasons: (ⅰ) the pure oxides, possessing low planar and/or linear disregistry with TiN; (ⅱ) the complex oxides, including the phase, which possesses extremely low disregistry with TiN; and/or (ⅲ) the increasing number of the oxides. By comparison, finer macrostructures were yielded with the addition of Y-/Mg–Y-based modifiers because of the decreasing nucleation barrier, and the finest macrostructure with equiaxed grain ratio of 100% and average grain size of 1.099 mm was observed in the Mg–Y-treated sample. Coupled with the results of TiN inclusions, therefore, the refining efficiency of macrostructure increases with the number of TiN. Referring to the results of differential scanning colorimetry, a general rule of solidification for metallic materials has been revealed. In addition, the in-situ nucleation-growth of δ-Fe was observed using high temperature laser confocal microscopy, and the microstructures were refined after Y/Mg–Y treatment. Eventually, the interfacial wetting-lattice mismatch heterogeneous nucleation model is successfully applied to evaluate the refining phenomenon of macro-/microstructures.