Increasing Al Content Research Articles

Theoretical study on the lattice distortion and electronic structure in the Al–Co–Cr–Fe–Ni multicomponent alloys

At present, the phase structure design for multicomponent alloys (MCAs) is mainly based on the valence electron concentration (VEC). In this work, based on the classification of valence electrons by the empirical electron theory of solid and molecule (EET), the VEC is further dissected and found that the covalent electron concentration (CEC) can be used as a criterion for determining the phase structure of MCAs. The Alx(CoCrFeNi)1-x (x = 0, 1/24, 1/12 and 1/8) alloys are designed on the basis of the CEC. The effect of Al content on the lattice distortion in the FCC phase of the alloys by combining density functional theory (DFT) and EET. The results show that the degree of lattice distortion in the FCC phase gradually increases with the increase of Al content and the interatomic bonding decreases before the phase structure transition. The alloy reaches the criticality of the phase structure transition when the Al content is 9.48 at.%.

Effects of Al doping on structural, optical, morphological, and low-concentration CO2 gas sensing properties of ZnO nanoparticles synthesized by sol-gel method

Abstract This work examines the morphological, structural, optical, and gas-sensing characteristics of ZnO thin films doped with Al that were created by the sol-gel spin coating technique. The thin films, doped with varying aluminum concentrations (0%, 2%, and 5%), were characterized using XRD, UV-visible spectroscopy, and FE-SEM to assess their crystallinity, band gap, and surface morphology. XRD analysis confirmed the incorporation of Al into the ZnO lattice without forming secondary phases, while UV-visible spectroscopy revealed an increase in transmittance and band gap with higher Al doping. FE-SEM images showed a transition from agglomerated grains to smoother surfaces with increased Al content. Gas sensing performance was evaluated using low-concentration CO2 as the target gas. The results demonstrated that Al doping significantly enhances the CO2 sensing response, with the 5% Al-doped ZnO exhibiting the optimal sensitivity due to increased carrier concentration and improved surface interaction. These findings suggest that Al-doped ZnO thin films are promising candidates for efficient CO2 gas sensors, combining enhanced structural and optical properties with superior gas sensing capabilities.

Atomic simulation for the effect of short-range order and twin boundary on mechanical behavior of FeNiCrCoAl high-entropy alloys

Short-range order (SRO) structure has been considered a potential strengthening method to improve the mechanical properties of high-entropy alloys (HEAs). However, the reinforcement mechanism of SRO structure on the HEA is still unclear. Here, the effect of SRO degree, twin boundary (TB) and temperature on the mechanical properties of the FeNiCrCoAl HEAs with different Al contents under uniaxial tensile is investigated using molecular dynamics/Monte Carlo simulations. The results indicate that the strengthening effect caused by the SRO structure and the softening effect caused by the addition of Al atoms coexist in the HEAs, and their competition determines the mechanical properties of the HEAs. And the softening caused by Al atoms dominates the mechanical properties of the HEAs, and the mechanical properties of the HEAs decrease with the increase of Al content. The results show that Al content has a significant impact on the SRO structure of the HEAs and the degree of SRO decreases in the HEAs with the increase of Al content. It is worth noting that under the same alloy composition, the strengthening effect of the SRO structure on the alloys first increases and then decreases with increasing the degree of SRO. The results indicate that the strengthening effect of the SRO structure and TB together is greater than that of TB or SRO alone. In addition, the results also show that higher temperature is not conducive to the stability of SRO structure, and the strengthening effect of SRO on the HEAs decreases with the increase of temperature.

Thermophysical properties of AlxCoCrCuFeNi high entropy alloys

The AlxCoCrCuFeNi (x = 0.25, 0.5, 1, 2) high entropy alloys (HEAs) were prepared by arc melting and spray casting techniques. Their microstructures, hardness, and thermophysical properties such as fusion enthalpy, entropy, thermal diffusion coefficients, thermal expansion coefficients, were investigated. XRD results indicated that AlxCoCrCuFeNi (x = 0.25 and 0.5) alloys were composed of a high-entropy FCC phase and Cu-rich nanophase. As the Al content increased to 1 and 2, the phase structures included the AlNi-rich B2 phase, FeCr-rich A2 phase and Cu-rich nanophase. With the increased Al content, the microstructures of AlxCoCrCuFeNi HEAs transitioned from coarse dendrites to petal-like dendrites, and the grains were continuously refined. Moreover, the Al additions reduced the density whereas increased the Vickers hardness of the alloys. The maximum hardness observed in Al2CoCrCuFeNi HEA was approximately 2.4 times greater than that of the Al0.25CoCrCuFeNi HEA. The thermal diffusion coefficients of alloys initially increased and subsequently decreased as the temperature elevated. The phase transformation induced by Al content was an effective method for rapidly homogenizing the internal temperature of alloys. Furthermore, the crystal structure, elemental segregation, lattice distortion, enthalpy and entropy of fusion, and lattice vibration frequency all mutually affected the thermal diffusion and expansion coefficients of AlxCoCrCuFeNi HEAs.

Microstructure and mechanical properties of MoNbVTa0.5Alx refractory high entropy alloys

The specific strength of refractory high entropy alloys (RHEAs) is usually impaired due to the high density of constituent elements. In order to develop a low-density RHEA, the microstructure and mechanical property of MoNbVTa0.5-based RHEAs with various Al additions have been investigated in this study. All samples exhibited a monolithic BCC solid solution structure. The addition of Al resulted in improved yield strength but a degraded plasticity at ambient temperature. In contrast, the yield strength consistently decreased with increasing Al content at elevated temperatures, and the softening occurred at ~1000 °C. MoNbVTa0.5Al0.3 exhibited high specific strengths of 119.2 MPa cm3/g, 108.6 MPa cm3/g and 97.3 MPa cm3/g at 600 °C, 800 °C, and 1000 °C, respectively.

Effect of Al content on mechanical properties and corrosion performance of novel Fe-Cr-Al alloy steels in a CO2-O2 coexistence environment

The present study involved preparing five novel Fe-Cr-Al alloy steels with varying Al content based on commercially available 3Cr steel. The effect of Al content on the mechanical properties and corrosion performance in a CO2-O2 coexistence environment was investigated in novel Fe-3Cr-(0–2.5)Al alloy steels, and the microhardness, impact, and tensile properties were measured and compared. The corrosion rate, corrosion product film, and corrosion mechanism were studied using a weight-loss method, microscopic characterization, and electrochemical tests. The results showed that the tensile and impact properties of Fe-Cr-Al alloy steels exhibited a decreasing trend with increasing Al content. No localized corrosion was observed at an Al content of 2 wt%, attributed to the formation of a dense amorphous corrosion product film on the material surface and pre-passivation. Among the alloy steels examined in this study, the 3Cr2Al alloy steel exhibited the most optimal balance between mechanical properties and corrosion resistance.

LG = 50 nm T-gated and Fe-doped double quantum well GaN‒HEMT on SiC wafer with graded AlGaN barrier for future power electronics applications

High-performance LG = 50 nm graded double-channel (GDC)-HEMT featuring AlN top barrier, recessed T-gate and graded-AlGaN bottom barrier is designed and investigated. Two quantum wells are formed in the AlN-GaN-graded AlGaN-GaN multilayer structure developed on a SiC substrate and the clear double hump feature of the transconductance (GM), cut-off frequency (fT), and capacitance plots clearly illustrates the double-channel (DC) behavior. The investigations carried out to explore the impact of barrier thickness (both AlN & graded-AlGaN) revealed superior performance with the GM showing two peaks at 181.5 & 488.1 mS/mm, the peak-drive-current (ID_peak) with VGS biased at 3 V is 1.81 A/mm, maximum saturation drain current of 3.08 A/mm (VGS = 3V), and the fT derived from the left- and right-hump are 263.7 GHz & 354.2 GHz, respectively, when both barriers are 6 nm thin, attributable to enhanced 2DEG density due to the coordination of channels because of proximity and lower leakage. It has been noticed that when the bottom barrier is thick, the DC behaviour is less obvious due to insufficient gate access to the lower channel. We investigated the impact of varying the Al % in AlGaN top barrier on the DC/RF performance of GDC-HEMTs, demonstrating enhanced performance with increased Al content, particularly for Al0.35Ga0.65N. By using various metals, this study also investigates how gate engineering affects the electrical characteristics of the GDC-HEMT. The lower ϕm (work function) of the Al-gate led to better DC/RF performance. When the Schottky barrier rises as a result of the conduction band edge being elevated, the performance reduces, and the threshold voltage (Vth) increases. Since it is essential to comprehend the role that source resistance (Rs) & drain resistance (Rd) play in RF design, we have also conducted simulations by varying the source-gate gap (LGS) & drain-gate gap (LGD). Due to low Rs & Rd, it was determined that the GDC-HEMT performed better at the smallest LGS & LGD. The extraordinary performance strongly highlights the immense potential and applicability of the GDC-HEMTs for future broadband power amplifiers.

Dynamic interaction between refractory and low‐carbon low‐silicon Al‐killed steel

AbstractTo investigate the dynamic interaction between refining refractory and low‐carbon low‐silicon Al‐killed steel, the “refractory‐molten steel‐inclusion” system was analyzed using dynamic erosion experiments and the FactSage database. This study discussed the formation of interfacial layers between various refining refractories and molten steel, as well as the transformation of nonmetallic inclusions in steel. The findings indicate that the interaction between refractories and molten steel produces a distinct interface layer. The influence of various refining refractories on inclusions varies significantly. MgO‐C refractory promotes the formation of MgO·Al2O3 inclusions in steel, while Al2O3‐MgO refractory leads to the formation of SiO2‐MnO‐Al2O3 inclusions. Both Al2O3‐SiC refractory and Al2O3‐MgO‐C refractory result in Al2O3 inclusions with trace levels of MgO. Steel refined with Al2O3‐MgO‐C refractory has increased MgO content within Al2O3 inclusions but still does not reach the stoichiometric ratio of MgO·Al2O3. As the initial Al content increases, the influence of MgO‐C refractory inclusions becomes increasingly noticeable. The average MgO content within the inclusions rises with the reaction duration, achieving as high as 62.9%. The transition path of Al2O3 inclusions in molten steel follows “Al2O3→MgO·Al2O3→MgO.”

Aluminium bioavailability and toxicity disrupted chloroplast structure and inhibited inorganic carbon utilization and nutrient uptake in Vallisneria natans at acidic and alkaline pH

Vallisneria natans, as submerged aquatic plants, face significant threats from aluminium (Al) toxicity. While the effects of Al at low pH on terrestrial plants have been extensively studied, there is a lack of research on the impacts of both low and high pH on chloroplast ultrastructure and nutrient uptake in submerged plants. This research is important as it aims to fill this gap by exposing the leaves of Vallisneria natans to 100 μM Al at varying pH levels (4.5, 5.5, 7.5, and 9.5) for 48 hours. The results showed that inorganic carbon (CT), CO2, and HCO3 content increased at extreme pH levels (4.5 and 9.5), suggesting decreased inorganic carbon utilization under Al stress. Additionally, photosystem II efficiency and electron transport rate were significantly reduced at extreme pH levels, highlighting the sensitivity of V. natans to Al. Chlorophyll a and total chlorophyll content were significantly lower at pH 4.5 compared to pH 7.5. Chloroplast structural disruptions were evident at extreme pH levels coupled with Al exposure, whereas minimal injury was observed at pH 5.5 and 7.5. The study also noted vacuole enlargement, altered plasma membrane permeability, and hematoxylin staining, indicating Al accumulation in leaves. ICP analysis revealed increased Al content at extreme pH levels, underscoring heightened Al bioavailability and toxicity. Significant reductions in macro and micronutrient content (P, Mg, K, Fe, Zn, B, Mn) were observed, likely due to Al-induced root and cell damage and altered nutrient uptake. These findings emphasize the complex interplay between Al exposure, pH fluctuations, and their cascading effects on the physiology and elemental composition of Vallisneria natans, highlighting the need for further research and environmental management strategies.

Microstructure evolution and high-temperature erosion behaviors of laser cladded AlxCoCrFeNi2.1 HEA coatings

High entropy alloys (HEAs) are anticipated to be candidates for high-temperature applications. In this work, high-speed laser cladding has prepared AlxCoCrFeNi2.1 (1≤x≤1.4) HEA coatings with high Al content. The effects of Al content on the microstructure, microhardness, and high-temperature erosion behaviors have been systematically investigated. With the increase of Al content, the coating’s microstructure transforms from the dual-phase structure of FCC and BCC to a single-phase BCC structure. Correspondingly, the microhardness of HEA coating gradually increases at room temperature due to the increment of BCC proportion. The Al1.4 HEA coating, consisting of a single BCC phase, exhibits the highest resistance to solid-particle erosion at 600℃, while Al1.0 coating with FCC and BCC dual-phase structure takes the second place. Ploughing, fracture, and spalling occurred during the high-temperature erosion process of AlxCoCrFeNi2.1 HEA coatings. The synergistic interaction between the FCC and BCC phases in dual-phase coatings primarily influences erosion behaviors. However, oxidation resistance is critical to erosion resistance for single-phase BCC coatings.

Growth of Al-Cu Thin Films on LiNbO3 Substrates for Surface Acoustic Wave Devices Based on Combinatorial Radio Frequency Magnetron Sputtering

Al-Cu thin films were fabricated by RF magnetron sputtering from aluminum (Al) and copper (Cu) metal targets to improve the acoustic performance of SAW devices on LiNbO3 substrates. To optimize the electrode material for SAW devices, Al-Cu films with various compositions were fabricated and their electrical, mechanical, and acoustic properties were comprehensively evaluated. The Al-Cu films exhibited a gradual decrease in resistivity with increasing Al content. The double-electrode SAW devices composed of Al-Cu films demonstrated a resonant frequency of 70 MHz and an average insertion loss of −16.1 dB, which was significantly lower than that of devices made with traditional Au or Al electrodes. Additionally, the SAW devices showed an increase in the FWHM values of the resonant frequency and a decrease in the insertion loss as the Al content in the IDT electrode decreased. These findings indicate that improving the performance of SAW devices can be achieved by reducing the density of the IDT electrodes, rather than focusing solely on their electrical characteristics.

Study on the surface performance strengthening of AlCrN coated cemented carbide by micro-texture laser preparation process

The combined application of coating and surface texture technology on the material surface can enhance its performance. However, the two procedure and their joint mechanism have not been fully revealed. Therefore, this paper takes the micro-textured coated cemented carbide as the research object, and focuses on the influence of preparation procedure and process parameters on surface characteristics and friction behavior. The results show that compared with the coating textured (XT) sample, the textured coating (XW) sample has more advantages in micro-hardness, microstructure and wear degree. The Rockwell hardness of the XT sample is better. Compared with the single coating sample, the coating micro-hardness of the XW sample is increased by 10 %, the Rockwell hardness is reduced by 2 %, the average grain size is reduced by 7.9 %, and the friction force is reduced by 6.2 %. Additionally, within a certain range, the increase of Al content will increase the sample hardness, reduce friction, and inhibit the Cr content and the growth of CrN phase grains. Complete process parameter optimization based on the ideal solution.

The effects of Ni and Al elements on microstructure and mechanical properties of low carbon CoCrMo alloy coatings

Low-carbon cobalt-based alloy coatings with high ductility and low thermal fatigue crack propagation rates were prepared using laser cladding (LC) technology. The microstructure of the coatings was characterized using SEM, EBSD, and TEM, while the mechanical properties were tested and analyzed. The CoCrMo alloy primarily consists of γ-Co and a minor amount of ε-Co. The addition of Ni increased the stacking fault energy (SFE), resulting in the retention of γ-Co in the alloy. However, the increase of Al content reduced the SFE, leading to the precipitation of Al3Ni intermetallic compound along with a eutectic region with Al3Ni, Cr23C6, and ε-Co. More ε-Co phase appeared after tensile deformation due to the stress-induced transformation induced plasticity (TRIP) effect. Ni addition increased the content of face-centered cubic (fcc) γ-Co, enhancing the coating's ductility by approximately 85 % compared to CoCrMo. With higher Al content, the ε-Co phase increased, and the dispersion of Al3Ni improved the coatings' strength. The jagged structure of the eutectic region increased the resistance to thermal fatigue crack propagation, causing the crack propagated along the grain boundary. Optimal mechanical properties were achieved with the addition of 13 wt% Ni and 7 wt% Al, which achieved a 53 % increase in ductility and a 40 % reduction in the thermal fatigue crack propagation rate compared to CoCrMo.

High Temperature Oxidation Behaviours of NiCoCrAlY alloys with High Al Content

Abstract MCrAlY coatings are of paramount importance in the protection of hot-end components from thermal oxidation and corrosion. The Al content is a crucial factor in enhancing the oxidation resistance properties of the coatings. This paper studies the oxidation behaviors of Ni-27.5Co-17Cr-xAl-0.5Y (x = 12 and 16 wt.%) alloys with high Al content. Following an oxidation process at 1100 °C over a period of 100 h, both alloys exhibit the oxide scales primarily consist of Al2O3 with minor amount of Co(Ni)Al2O4 spinels. The increased Al content results in a higher proportion of β phase, thereby promoting the development of an oxide scale in response to thermal exposure. This study provides insights into the fabrication of high Al content MCrAlY coatings with potential applications in next-generation thermal barrier coatings.

Regulations of Thermal Expansion Coefficients of Yb1−xAlxTaO4 for Environmental Barrier Coatings Applications

Environmental barrier coatings (EBCs) are widely used to protect ceramic matrix composites (CMCs, SiCf/SiC, and Al2O3f/Al2O3), and they should have low thermal expansion coefficients (TECs) matching the CMCs and excellent mechanical properties to prolong their lifetime. Current EBC materials have disadvantages of phase transitions and insufficient mechanical properties, which affect their working temperatures and lifetime. It is necessary to develop new oxide EBCs. Ytterbium tantalate (YbTaO4) is a stable and novel EBC material, and we have improved the mechanical properties and TECs of Yb1−xAlxTaO4 (x = 0.05, 0.1, 0.2, 0.3, 0.4, 0.5) ceramics by replacing Yb with Al. XRD, SEM, and EDS are used to verify the crystal and microstructures, and nano-indentation is used to measure the modulus and hardness when changes in TECs are measured within a thermal expansion device. The results show that the phase structure of Yb1−xAlxTaO4 (x = 0.05, 0.1, 0.2, 0.3, 0.4, 0.5) is stable at 25–1400 °C within air atmosphere, and their high-temperature TECs (6.4–8.9 × 10−6 K−1, 1400 °C) are effectively regulated by introductions of different contents of Al, which enlarge their engineering applications for SiCf/SiC and Al2O3f/Al2O3 CMCs. The evolutions of TECs are analyzed from structural characteristics and phase compositions, and the increased TECs make Yb1−xAlxTaO4 potential EBCs for Al2O3 matrixes. Due to the high bonding strength of Al–O bonds, hardness, as well as Young’s modulus, are enhanced with the increasing Al content, with Yb1−xAlxTaO4 (x = 0.05, 0.1, 0.2, 0.3, 0.4, 0.5) having a nano-hardness of 3.7–12.8 GPa and a Young’s modulus of 100.9–236.6 GPa. The TECs of YbTaO4 are successfully regulated to expand their applications, and they match those of Al2O3 and SiC matrixes, as well as displaying improved mechanical properties. This work promotes applications of YbTaO4 as potential EBCs and provides a new way to regulate the TECs of tantalates.

Liberalizing the effects of Al and Cr in coatings for enhanced interface stability with Mo-rich Ni3Al-based superalloys

The interfacial behaviors between protective coatings and substrate single-crystal superalloys significantly impact their service performances. This work focuses on the elements interdiffusion and microstructural evolution at the interface between a NiCrAlY coating and a series of high-Mo Ni3Al-based single-crystal superalloys, through the coupled phase-field simulations and DICTRA kinetics calculations of their model systems. The critical roles of Al and Cr played in the microstructural evolution at coating/superalloy interface have been confirmed, which requires the appropriate content decreases of Al and Cr in the coating at 1100 °C. However, the addition of Mo reduces the driving force of element diffusion from coating to substrate by increasing the activities of Al and Cr in superalloy. Moreover, increasing the Mo content in superalloy from 8 wt% to 10 wt% could also counteract the promoting effect of Al on Ni mobility and mitigate the γ′ coarsening and detrimental TCP precipitation. Therefore, the effects of Mo enable the reasonable increase of Al content in coating to better balance the interfacial stability and oxidation resistance of coated superalloy, besides its advantage in reducing the anisotropy of TCP precipitate. The obtained interfacial evolution mechanisms resulting from the phase transformation thermodynamics and element interdiffusion kinetics are expected to aid the coating design for advanced single-crystal superalloys servicing at ultra-high temperature.

Effect of Al content on microstructure and mechanical properties of the (FeCoNiV)100-xAlx high-entropy alloys

It is well known that face-centered cubic (FCC) high-entropy alloys (HEAs) typically have excellent ductility at room temperature but relatively low strength, which greatly limits their structural applications. To address the strength-ductility trade-off, researchers synthesized a series of (FeCoNiV)100-xAlx (x = 0–20 at. %) HEAs, investigated the effect of alloying Al on microstructure and tensile properties, then analyzed the strengthening mechanism. It was found that the crystalline structure changed from an initial single FCC structure to a duplex FCC plus body-centered cubic (BCC) structure and then to a single BCC structure with increasing Al concentration. After homogenization process, the FCC and BCC phases can be transformed to ordered L12 and B2 phases, respectively. These HEAs with duplex FCC/L12 plus BCC/B2 structure exhibit the potential for excellent mechanical properties, and their properties can be modulated by Al content and heat treatment. The properties can be tuned by both Al content and heat treatment, as the Al content can modulate the BCC phase content and the heat treatment can change the ordered structure. A careful analysis reveals that the solid solubility of Al element in this system was only 3.6 at. %, which has a limited effect on the strength. FCC/L12 bears the main plastic strain and the high tensile strength of the alloy is achieved thanks to the contribution of the BCC/B2 phase to the work-hardening rate of the alloy during the early stages of deformation and the unique work-hardening ability of the L12 phase.

Effect of Al or Cu Content on Microstructure and Mechanical Properties of Zn Alloys Fabricated Using Continuous Casting and Extrusion

The effect of Al or Cu content on the microstructure and mechanical properties of continuous casting and extrusion Zn alloys has been studied by a room temperature tensile test, X-ray diffraction, and scanning electron microscope. With the increase in Al content, the microstructure of continuous casting and extrusion Zn alloys slightly coarsens, and the lamellar eutectic structure increases. The changes in the above structural factors result in a slight decrease in strength and a significant increase in the elongation of Zn-Al alloys. The strength of Zn alloys increases as the Cu content increases due to the increased content and size of the second phase in the Zn alloys. This means that the mechanical properties of Zn alloys can be adjusted by a continuous casting and extrusion process, and the improvement of equipment capacity can improve the structure and morphology of the alloys.

Solidification microstructure and properties of Ni(60-y)Fe20Co10Cr10Aly high-entropy alloys

A series of eutectic high-entropy alloys Ni(60-y)Fe20Co10Cr10Aly (y = 0, 5, 10, 15, 20, 25) were synthesized via non-consumable vacuum melting, followed by investigation into their solidification microstructures and compression properties. The research results reveal that the solidification microstructures transition from a well-distributed FCC phase (y-0, y-5) to a coarse FCC+B2 isometric crystal structure (y-10), subsequently to a primary FCC phase with a (FCC+B2) eutectic structure (y-15), succeeded by a predominant B2 phase with a (FCC+B2) eutectic microstructure (y-20), and ultimately to a BCC+B2 biphasic structure characterized by periodic braided sheets (y-25). The FCC phase demonstrates a substantial concentration of Ni and Fe, the BCC phase shows substantial enrichment primarily in Fe and Cr, while the B2 phase exhibits significant enrichment in Ni and Al. As the Al content increases, the alloys exhibit higher strength but reduced plasticity. Specifically, alloys with y values of 20 and 25 exhibit yield strengths of 1012 MPa and 1477 MPa, respectively, coupled with remarkable plasticity of 41 and 23%, thereby demonstrating robust mechanical properties.

Effect of Interface Property on the Agglomeration Characteristic of Inclusions in High Al Steel with Different Al Contents

Herein, a 3D stability diagram is established in the AlON system. Based on that, four sets of experiments with different Al contents are designed to prepare different inclusions. Subsequently, the agglomeration behavior of inclusion is observed in situ by using confocal laser scanning microscopy (CLSM) combined with an infrared image furnace. The sample with inclusions is heated to melt and the agglomeration behavior of inclusion is recorded by the CRT monitor of CLSM. The calculated agglomeration force of inclusion shows that when the Al content increases from 0.5 to 3 pct, the agglomeration force of Al2O3 inclusions decreases from 7.2 × 10−16 ≈ 6.0 × 10−14 N to 1.2 × 10−16 ≈ 3.2 × 10−15 N. As the Al content increases from 6.5 to 10 pct, the agglomeration force of AlN inclusions increases from 2.2 × 10−17 ≈ 1.1 × 10−15 N to 1.7 × 10−16 ≈ 7.9 × 10−15 N. The theoretical calculation also shows that the agglomeration force of Al2O3 inclusions decreases and that of AlN inclusions increases with the increasing Al content. When the Al content is >4.7 pct, the agglomeration force of AlN inclusions is larger than that of Al2O3 inclusions.