Melting Point Of Phase Research Articles

Effect of aging treatment on the microstructure, cracking type and crystallographic texture of IN939 fabricated by powder bed fusion-laser beam

This study aimed to provide a comprehensive understanding of how aging treatments (namely, HT1 and HT2) affect the microstructure, cracking behavior, and crystallographic texture of IN939 fabricated by powder bed fusion-laser beam (PBF-LB) method. Although both aged samples demonstrated similar grain structure and recrystallization behavior according to the electron backscatter diffraction (EBSD) analysis, as well as the precipitation of bimodal γ′ phase and MC- and M23C6-type carbides, notable differences were observed in the size and morphology, particularly the γ′ phase. The HT1 sample displayed coarsened primary γ′ phase, with sizes reaching up to 2 μm and exhibiting varied morphologies, including irregular and cuboidal shapes. Additionally, this treatment led to the formation of some γ′-γ eutectic regions and plate-like η phase, along with the decomposition of MC-type carbides into M23C6-type carbides. In contrast, the HT2 sample displayed uniformly distributed spherical primary γ′ phase with sizes ranging from 70 to 120 nm, accompanied by very fine secondary γ′ phase. Furthermore, it was found that changes in both aged sample microstructures could result in the formation of strain-age cracks due to the γ′ phase formation and liquation cracks due to the partial remelting of lower melting point phases. The findings also revealed that with the application of aging treatments, the hardness of the as-fabricated sample (339.8 ± 3.4 HV) increased to 440.2 ± 5.6 HV and 508.1 ± 4.8 HV for the heat treatment of HT1 and HT2, respectively.

Synthesis of Phenanthrene/Pyrene Hybrid Microparticles: Useful Synthetic Mimics for Polycyclic Aromatic Hydrocarbon-Based Cosmic Dust.

Polycyclic aromatic hydrocarbons (PAHs) are found throughout the interstellar medium and are important markers for the evolution of galaxies and both star and planet formation. They are also widely regarded as a major source of carbon, which has implications in the search for extraterrestrial life. Herein we construct a melting point phase diagram for a series of phenanthrene/pyrene binary mixtures to identify the eutectic composition (75 mol % phenanthrene) and its melting point (83 °C). The molten oil obtained on heating this eutectic composition to 90 °C in aqueous solution is homogenized in the presence of a water-soluble polymeric emulsifier. On cooling to 20 °C, polydisperse spherical phenanthrene/pyrene hybrid microparticles are obtained. Varying the stirring rate and emulsifier type enables the mean microparticle diameter to be adjusted from 11 to 279 μm. Importantly, the phenanthrene content of individual microparticles remains constant during processing, as expected for the eutectic composition. These new hybrid microparticles form impact craters and undergo partial fragmentation when fired into a metal target at 1 km s-1 using a light gas gun. When fired into an aerogel target at the same speed, microparticles are located at the ends of characteristic "carrot tracks". Autofluorescence is observed in both types of experiments, which at first sight suggests minimal degradation. However, Raman microscopy analysis of the aerogel-captured microparticles indicates prominent pyrene signals but no trace of the more volatile phenanthrene component. Such differential ablation during aerogel capture is expected to inform the in situ analysis of PAH-rich cosmic dust in future space missions.

Ablation mechanism of Cf/(Ti0.2Zr0.2Hf0.2Nb0.2Ta0.2)C-SiC composite during plasma ablation above 2000 °C

Air plasma ablation behavior of Cf/(Ti0.2Zr0.2Hf0.2Nb0.2Ta0.2)C-SiC composite was studied systematically with the surface temperature above 2000 °C at the ablation center. It presents a linear recession rate of 0.15 μm/s and a mass recession rate of 2.05 mg/s after ablation at 4 MW/m2 (2000 °C) for 300 s. Associated with the temperature gradient of the ablation surface, the oxidation products at different locations mainly consist of (TiZrHfNbTa)Ox, (ZrxHf1–x)6(NbyTa1–y)2O17, Ti(NbxTa1–x)2O7, (HfxZr1–x)SiO4, and SiO2. Due to the synergistic effect of the multi-component oxides, oxidation products form a protective structure composed of high melting point oxide skeleton filled with relatively low melting point phases. It retards oxygen inward diffusion and prevents the composite fragmentation caused by plasma mechanical scouring. It is believed that the results would be helpful for further improving the ablation resistance by component design of high entropy ceramics and their composites.

A comparative study on the slag resistance of MgO–C, low‐carbon MgO–C, and MgO–SiC–C refractories

AbstractThe corrosion of slag on refractories usually starts from the matrix, so improving the slag resistance of the matrix is of great significance for the slag resistance of the refractories. To clarify the influence of matrix on the slag resistance of magnesia–carbon refractories, the slag corrosion experiments were conducted at 1873 K on MgO–C refractories, low‐carbon MgO–C refractories, and MgO–SiC–C refractories. The results showed that the slag resistance of MgO–C refractories was higher than that of low‐carbon MgO–C refractories, and the slag resistance of MgO–SiC–C refractories was superior to that of low‐carbon MgO–C refractories. The interaction between MgO–SiC–C refractories and slag generated high melting point phases such as forsterite and spinel, reducing the routes for the slag to infiltrate the inside of the refractories. MgO–SiC–C refractories reacted with slag to increase the viscosity of the slag, the viscosity being 86.3% and 51.9% higher than in the case of low‐carbon MgO–C and MgO–C refractories, respectively. Compared with MgO–SiC–C refractories, MgO–C refractories did not exhibit overwhelming advantages in slag resistance. Due to the low‐carbon content and good slag resistance, MgO–SiC–C refractories were promising low‐carbon magnesia‐based refractories for high‐temperature industries.

Formation Mechanism of Deposits in Rotary Kiln during Steelmaking Dust Carbothermic Recycling

Rotary kiln has been widely used in hazardous waste treatment because of its strong adaptability to raw materials, high productivity, and simple processing technology. However, the formation of deposits reduces its performance period and profitability. This study characterized the deposit mineralogy and thermodynamically and experimentally investigated its formation mechanism. The results show that the main phases of the deposit are magnetite, monolithic iron, olivine, and yellow feldspar. They indicate that the deposit formation process was accompanied by the participation of alkaline and iron oxides. The intermediate product Ca2SiO4 can promote the generation of low melting point phases, such as CaFeSiO4 and Ca2Al2SiO7, which are the main phases of deposit materials. Additionally, the reduction intermediate product FeO facilitated the generation of a liquid ferrous mixture (Fe3O4-FeO and Fe3O4-FeO-Fe mixture), which in turn further promoted the growth of the initial deposit phase. The solid deposit formed and attached to the kiln inner wall, along with a decrease in temperature. These results are expected to provide an idea or approach for fundamentally solving the problem of deposits in the rotary kiln.

C/C-HfC-SiC composites with simultaneous the resistance to ultra-high temperature airflow erosion and high temperature oxidation

HfC-SiC modified C/C composites containing in situ formed Si-HfC-HfSi2 ablation resistant layer and SiC oxidation resistant layer were successfully prepared by reactive melt infiltration (RMI) combined with gaseous silicon infiltration (GSI). A comparative study was conducted on the anti-oxidation and anti-ablation performance of the C/C-HfC-SiC composites with GSI (noted as RG-CHS) and without GSI (noted as R-CHS). After oxidation at 1,500 °C for 200 min, the oxide film of RG-CHS remained intact. The mass and linear ablation rates decreased from 1.31 mg/s and 7.36 μm/s to 0.12 mg/s and −0.22 μm/s after GSI process, respectively. The introduction of low melting point phases and reducing surface defects can improve the high temperature oxidation resistance and plasma ablation resistance of the composites.

Effect of nano-oxides on corrosion resistance of Al2O3–ZrO2–C material

The Al2O3–ZrO2–C material was prepared using tabular alumina aggregates and fines, zirconia-corundum, zirconia-mullite, flake graphite, B4C powder, Si powder and different nano-oxides (nano-ZrO2, nano-TiO2, and nano-Al2O3) as raw materials, the effects of different nano-oxides on the corrosion resistance and microstructure evolution of Al2O3–ZrO2–C material were investigated. The results showed that the high reactivity nano-ZrO2, nano-TiO2, and nano-Al2O3 particles reacted with CaO to generate high melting point phases of CaZrO3, CaTiO3, CaO·6Al2O3 (CA6) at high temperature, which forms a protective layer at the interface between corroded media and samples, inhibiting CaO penetration into the material. Additionally, nano-oxides can fill the pores and increase the density of material, thereby contributing to improving the penetration resistance and corrosion resistance of material.

Optimization of large cast Haynes 282 based on thermal induced cracks: formation and elimination

Haynes 282, a wrought material, attracts the attention from casting application due to its excellent mechanical properties. Fracture of large cast Haynes 282 were found before yielding during tensile test in previous researches, but the reasons have not been fully understood. In this study, various heat treatments were designed and applied for large cast Haynes 282 to reveal the fracture before yielding. Thermodynamic calculation, residual stress calculation combined with microstructural examination were utilized to analyze the reasons of fracture. It has been found that there are grain boundary cracking and grain boundary precipitate cracking in the tensile sample. The grain boundary cracking is mostly attributed to the melting of the low melting point phases such as some segregated matrix and μ phases. The grain boundary precipitate cracking is associated with the blocky Ti, Mo rich MC carbides, and it is more likely to be caused by the quenching after the second homogenization treatment. Optimized heat treatment has been proposed and proven to be workable for the large cast Haynes 282.

The influence of vanadium and titanium oxides in slag on the wetting and corrosion of dense Al2O3 ceramics

The present study investigates the wetting and corrosion behaviour of slags on dense Al2O3 ceramics, focusing on the influence of varying vanadium- and titanium oxide content. Physicochemical properties of the slag were assessed by measuring wetting angles, heights and diameters of the molten slags on the alumina at different temperatures. Microscopic observations and elemental composition analysis were conducted on the interface between the corroded Al2O3 ceramics and the slags. Our findings demonstrated that the V2O3 addition in the slag leads to its oxidation to V2O5, which further reacts with Fe2O3 and MnO to form low melting point phases such as FeVO4 and MnVO6. Consequently, the melting point of the slag decreases significantly, resulting in a decreased wetting angle with the Al2O3 ceramics. The presence of unsaturated alumina in the slag leads to the dissolution of aluminium ions from the ceramics into the slag, which reacts with Fe2O3 and MnO to form spinel phases, contributing to material loss of the ceramics. Infiltration of the slag into the Al2O3 predominantly occurs through the alumina grain boundaries. Two types of infiltration are identified: one involving reactions with alumina to form low melting point phases like Fe2O3 and the other involving inherent low melting point phases such as MnVO6. In contrast, the penetration of SiO2 into the alumina substrate is limited. Additionally, the dissolution of Al2O3 into the slag creates pathways for further infiltration. This study highlights the significant influence of Ti and V content on the physicochemical properties of the slag and provides insight into the corrosion mechanism of Al2O3 ceramics by Ti and V containing slags.

Optimization of corrosion resistance and mechanical properties of Al2O3‐Cr2O3 refractories for waste incinerator

AbstractThe corrosion resistance and mechanical properties directly affects the operation and service life of Al2O3‐Cr2O3 refractories used in waste incinerators. In this study, ZrO2 particles were introduced via vacuum impregnation to adjust microstructure and properties of Al2O3‐Cr2O3 refractories. The results showed that the impregnated ZrO2 particles and increasing impregnation times resulted in the decreased median pore size and increased compactness, and mechanical strengths of refractories were elevated from the inhibited cracks propagation by ZrO2 particles. The decreased amounts of large pores and increased amounts of small pores from the filled ZrO2 particles inhibited penetration of low melting point phases, and the formed CaZrO3 phase from the reactions between corrosion reagent and ZrO2 particles increased the viscosity of penetrated corrosion reagent, resulting in the decreased penetration index from 8.57% to 2.58%. Meanwhile, the filled ZrO2 particles around alumina particles prevented reactions between molten corrosion reagent and alumina, leading to the decreased corrosion index from 3.78% to .74%. The decreased pore size and formation of CaZrO3 phase were primary factors that enhanced the penetration resistance. And formation of wrapped layers from ZrO2 particles around alumina particles presented prominent effects on the strengthened corrosion resistance of Al2O3‐Cr2O3 refractories.

Effects of Aluminium Oxide Content on the Regenerated Magnesia-Calcium Bricks for Cement Rotary Kiln

Regenerated magnesia-calcium brick samples with different aluminium oxide (Al2O3) contents were prepared using spent magnesia-calcium bricks and fused magnesia as the main raw materials and Al2O3 powders as the additive. The phase compositions, microstructures, room temperature, hot flexural strength, and kiln coating adherence of the regenerated samples were investigated. This indicates that the Al2O3 content increased, mainly resulting in the content of tetracalcium aluminoferrite (C4AF) and tricalcium aluminate (C3A) increasing in the regenerated samples. The bulk density, room temperature flexural strength, and kiln coating adherence all increased, whereas the hot flexural strength and corrosion resistance to cement clinker both deteriorated with an increase in the Al2O3 content. This was because, on the one hand, the low melting point phases of C4AF and C3A improved the sinterability of the regenerated samples during the burning stage, and on the other hand, they melted or existed in the liquid phase at the experimental temperature, which degraded the hot flexural strength and corrosion resistance but enhanced the kiln coating adherence as the wettability of the liquid phase. The content of Al2O3 in the regenerated magnesia-calcium brick should not be higher than 1.1 wt.%, considering its comprehensive performance for cement rotary kiln.

Battery Thermal Runaway Preventive Time Delay Strategy Using Different Melting Point Phase Change Materials

<div>The production of alternative clean energy vehicles provides a sustainable solution for the transportation industry. An effective battery cooling system is required for the safe operation of electric vehicles throughout their lifetime. However, in the pursuit of this technological change, issues of battery overheating leading to thermal runaways (TRs) are seen as major concerns. For example, lithium (Li)-ion batteries of electric vehicles can lose thermal stability owing to electrochemical damage due to overheating of the core. In this study, we look at how a different melting point phase change material (PCM) can be used to delay the TR trigger point of a high-energy density lithium-iron phosphate (LiFePO<sub>4</sub>) chemistry 86 Amp-hour (Ah) battery. The battery is investigated under thermal abuse conditions by wrapping heater foil and operating it at 500-W constant heat conditions until the battery runs in an abuse scenario. A comparative time delay methodology is developed to understand the TR trigger points under a timescale factor for different ambient conditions such as 25°C, 35°C, and 45°C. In the present study, two different types of PCMs are selected, that is, paraffin wax which melts at 45°C and Organic Axiotherm (ATP-78) which melts at 78°C. Modeling results suggest that the TR trigger point and peak onset temperature are greatly influenced by the battery operating temperature. The concluded results indicate that by submerging the battery in PCM, the TR trigger point can be greatly delayed, providing additional time for the driver and passenger to evacuate the vehicle. However, the present findings also reflect that fire propagation cannot be completely extinguished due to the volatile hydrocarbon content in the PCM. Hence from this study, it is recommended that whenever using a PCM-equipped passive cooling strategy, thermal insulation should be provided at the wall of the PCM to delay the TR propagation from one battery to another at pack-level configuration.</div>

Microstructure control and hot cracking behavior of the new Ni-Co based superalloy prepared by electron beam smelting layered solidification technology

The prevention of hot cracking formation is of utmost importance in the production of the new Ni-Co based superalloys through the utilization of the electron beam smelting layered solidification technique (EBSL), as it ensures exceptional homogeneity and dependable consistency of the specimens. In contrast to previous studies that focused on minimizing the liquid film and solidification range, our methodology adopts a distinct approach. In this research, a novel methodology was employed to mitigate internal stresses through the implementation of equiaxed grain layers via an alternately reduced cooling method. This ultimately resulted in the elimination of hot cracking. To be more specific, the transition from a columnar to an equiaxed structure was observed during the layer-by-layer construction process in the fabrication of the new Ni-Co based superalloy in EBSL. The EBSL-Ni-Co superalloy, when subjected to the alternating reduction cooling method, exhibited an internal stress of 49 MPa. This value represents a significant reduction of 83.8% compared to the internal stress observed when employing the linear reduction cooling method. Additionally, the solvus temperature of the γ-γ' eutectic phases in EBSL-Ni-Co superalloys produced by the alternating reduction cooling method is significantly higher. Intriguingly, the Nth layer of the EBSL-Ni-Co based superalloys produced by EBSL simultaneously heats treated with the preceding layers. And the low melting point phase gradually dissolved back into the matrix. The implementation of an alternating reduced cooling method successfully mitigated the formation of the liquid film in the γ-γ' eutectic phase and the buildup of internal stresses in the EBSL-Ni-Co superalloy during its manufacturing process. These discoveries open up a novel preparation procedure pathway for the manufacture of crack-free superalloys with superior mechanical characteristics using EBSL.

Exploring secondary phases in the Sm–Fe–V system beneficial for coercivity

Magnetic isolation of hard magnetic grains with an intergranular phase is a key factor in obtaining high coercivity, which has been established in the microstructure of Nd-Fe-B magnets owing to the phase equilibrium of hard magnetic Nd2Fe14B with a low melting point phase. In this work, we investigated the phase equilibrium in the Sm-Fe-V system to establish an optimum composition range to develop high coercivity SmFe12-based permanent magnets. In addition to the solid 1:12/liquid Sm-rich phase equilibrium, an additional V-rich phase is found for the first time in the Sm-Fe-V phase diagram for V contents between 19 and 35 at.% at 1500 K. The equilibrium between the 1:12 phase and the two phases with low melting points is computationally modeled for Sm-Fe-V metastable phase diagram. This is experimentally confirmed by analyzing the microstructure of the Sm8Fe72V20 thin film, where anisotropic columnar 1:12 grains are enveloped with predominantly V-rich phases along with some Sm-rich intergranular phases resulting in a coercivity (µ0Hc) of 0.9 T. Although this large V content in Sm(Fe,V)12-based alloy is not beneficial for achieving a large magnetization, the finding of a new V-rich intergranular phase can benefit the development of anisotropic sintered magnets via two alloy powder methods; one alloy powder with large V-content for forming intergranular phase and the other with V-lean content to maintain a large magnetizations. To further improve the coercivity to its highest limit μ0Hc ≈0.2–0.3Ha ≈2–3 T, decreasing the ferromagnetic elements in the intergranular phase is essential.

Structural characteristics and microwave dielectric performances of ZnZrNb2-xVx/2O8-1.25x-based ceramics for LTCC applications

The ZnZrNb2-xVx/2O8-1.25x-based (0.2 ≤ x ≤ 0.6) ceramics with monoclinic wolframite structure were prepared by the solid-phase method at low temperature. The microscopic morphology, phase structure, low-temperature sintering mechanism, and microwave dielectric performances of ZnZrNb2-xVx/2O8-1.25x-based (0.2 ≤ x ≤ 0.6) ceramics were thoroughly analyzed. Low-temperature sintering densification of microwave dielectric ceramics was made achievable by substituting non-dense vanadium at the Nb location. The sintering temperature of ZnZrNb2-xVx/2O8-1.25x (x = 0.4) ceramics was reduced by 340 °C when compared to pure ZnZrNb2O8 ceramics due to the mechanism of liquid phase aided sintering. The self-generated low melting point phase forms a liquid phase during the sintering process reducing the sintering temperature. It is noteworthy that when sintered at 900 °C, the ZnZrNb2-xVx/2O8-1.25x (x = 0.4) ceramic exhibits extremely exceptional microwave dielectric performances: εr = 25.15, Q×f = 17,600 GHz (at 8.01 GHz), and τf = −53.25 ppm/°C. The proposed material configuration provides a candidate material with extremely broad application potential for LTCC applications and a practical and effective strategy for low-temperature sintering of Nb-based monoclinic wolframite structured microwave dielectric ceramics.

Encapsulation of paraffin-magnetite, paraffin, and polyethylene glycol in concretes as thermal energy storage

These investigations analyze the encapsulation of phase change materials (PCMs): paraffin-magnetite composite, paraffin, and polyethylene glycol (PEG) in concretes. The research aimed to analyze PCMs as a thermal energy storage medium. The concretes were fabricated using the composition of lightweight aggregate, cement, sand, and water. Copper tubes (diameter of 12.7 mm and length of 50 mm) with various formations were installed in the concretes (50 × 50 × 50 mm). The arrangements of the copper tube consist of four-square, four-cross, and six-rectangular tubes. The concretes were then cured for 28 days at an ambient temperature. The copper tubes were filled with the melting paraffin-magnetite composite, paraffin, and PEG. The PCMs analyses include morphology, melting point, latent heat, thermal conductivity, and melting phase transition. The temperature distributions on the concretes filled with the PCMs were monitored using thermocouples and a data logger. The DSC test suggested the highest melting point of 61.65 °C and latent heat of 161.53 J/g obtained in the PEG sample. Adding magnetite particles in paraffin could improve the thermal conductivity to 0.53 W/m·°C compared to paraffin only (0.32 W/m·°C) and PEG (0.28 W/m·°C). The melting phase behavior on the PCMs was affected by the melting point, latent heat, and thermal conductivity. The highest thermal resistance occurred on the concrete where the copper tube only contributes to the low thermal resistance.

Effect of slag composition on corrosion resistance of high chromia refractory bricks for industrial entrained-flow gasifier

The slag composition corresponding to different coals varies significantly, which directly affects the operation of industrial entrained-flow gasifier and the service life of refractory bricks. In this study, the corrosion resistance of several typical coal slags for gasification on high chromia refractory bricks was comparatively investigated by static laboratory crucible tests and thermodynamic simulations. The results demonstrated that the corrosion degree of high chromia refractory bricks by different coal slags was high-Ca/Na slag > high-Fe slag > high-Si/Al slag. The surface structure of the refractory was relatively flat after corrosion by high-Si/Al slag, and the primary corrosion reaction was the partial dissolution of the matrix by the slag. High-Fe slag was prone to the precipitation of iron phases as well as the formation of (Mg, Fe) (Al, Cr)2O4 composite spinel layer at the slag/refractory interface. The high-Ca/Na slag was susceptible to react with the refractory to yield a low melting point phase, which led to the destruction of the matrix structure of the refractory and an isolated distribution of particles. In addition, the monoclinic ZrO2 in the refractory reacted with CaO in the slag to formed calcium zirconate, which loosened its phase toughening effect, was the primary factor that aggravated the refractory corrosion.

Study on the effect of Al2O3 on the crystallization behaviour of MnO–SiO2–MgO inclusions in tire cord steel

ABSTRACT Aiming at avoiding the formation of high melting point inclusions containing Al2O3 and reducing the wire breakage rate of the tire cord steel. MnO–SiO2–10wt.%MgO–(5wt.%, 10wt.%, 15wt.%, 20wt.%) Al2O3 system were designed to investigate the crystallization behaviour by XRD, SEM-EDS, FactSage 8.0. The results indicate that the Mn/Mg element ratio of the Mg-Mn olivine phase precipitated from the system varies. Mg–Mn olivine phase is formed by the interaction of the components in the melt or by the occurrence of homogeneity and the liquidus temperature of the system decreases with the increase of Al2O3 content. Al2O3 lowers the melting point of the whole system by forming the low melting point phase Mn3Al2Si3O12. To obtain low melting point plasticized inclusions, the Al2O3 content of the system needs to be controlled in the range of 15–20 wt.%.

Molecular structure and the twist-bend nematic phase: the role of spacer length in liquid crystal dimers

ABSTRACT The liquid crystal dimers, the 1-(4-substitutedazobenzene-4′-yloxy)-4-(4-cyanobiphenyl-4′-yl)butanes (CB4OABX), are reported in which the terminal substituent is either a methyl, methoxy, butyl, butyloxy, cyano or nitro group. The butyloxy spacer endows these dimers with the required molecular curvature to exhibit the twist-bend nematic phase in addition to showing the conventional nematic phase. Their transitional properties are compared to those of the corresponding dimers with either a pentyloxy or hexyloxy spacer. As expected, the even-membered pentyloxy-based dimers show the highest nematic–isotropic transition temperature, TNI, and exhibit smectic behaviour. These observations are attributed to their linear molecular shapes. The values of both the twist-bend nematic–nematic transition temperature, TN TB N, and TNI increase on passing from the butyloxy to hexyloxy spacer, but the change in TNI is greater than that in TN TB N. Thus, the ratio TN TB N is greater for the shorter spacer reinforcing the view that molecular curvature drives the formation of the NTB phase relative to the N phase. By comparison, the melting point decreases on passing from the butyloxy to hexyloxy spacer. Thus, increasing molecular curvature simultaneously increases both the melting point and NTB phase stability and this highlights the design challenge in obtaining dimers that exhibit enantiotropic NTB–I transitions.

Slag resistance mechanism of MgO–Mg2SiO4–SiC–C refractories containing porous multiphase aggregates

The slag resistance of MgO–SiC–C (MSC) refractories should be improved because of the mismatch in the thermal expansion coefficient between the aggregates and matrix, as well as the defects caused by the affinity between periclase and slag. In this study, MgO–Mg2SiO4–SiC–C (MMSC) refractories were prepared using porous multiphase MgO–Mg2SiO4 (M-M2S) aggregates to replace dense fused magnesia aggregates. Compared to MSC, the slag penetration index of MMSC decreased by 43.5%. The structure of the porous aggregates increased the surface roughness, and the multiphase composition of the aggregates decreased the mismatch of the thermal expansion coefficient with the matrix, thus reducing debonding between the aggregates and matrix. The aggregates and matrix in the MMSC formed an interlocking structure, which bound them more tightly to improve the slag resistance. The slag viscosity at different depths from the initial slag/refractory interface was calculated using the Ribond model. The M-M2S aggregates increased SixOyz− in the slag, which increased the slag polymerization and slag viscosity. The aggregates and matrix in the MMSC reacted with the slag to form high melting point phases, which reduced the channel of the slag. In addition, the penetration depth and velocity derived from the Washburn Equation were modified for the CaO–SiO2–Al2O3–MgO–FeO slag and magnesia based refractory to accurately evaluate slag penetration.