Al4C3 Phase Research Articles

Interface design in 3D-SiC/Al-Si-Mg interpenetrating composite fabricated by pressureless infiltration

3D-SiC/Al-Si-Mg interpenetrating composites (IPCs) were fabricated by pressureless infiltration method. Interfaces in the 3D-SiC/Al-Si-Mg IPCs were modificated by using two different kinds of aluminum alloy Al-15Si-10Mg and Al-9Si-6Mg to infiltrate into 3D-SiC performs and different treated 3D-SiC preforms unoxidized or preoxidized in air at 1000 °C, 1100 °C and 1200 °C for 2 h respectively. Results showed that desired interfaces can be achieved in both IPCs made with those two aluminum alloys, as demonstrated by their excellent comprehensive properties. When the Al-15Si-10Mg alloy with excessive Si content is used for infiltration, interfaces in 3D-SiC/Al-Si-Mg IPC fabricated with the unoxidized 3D-SiC preform are directly bonded through atomic matching without any interfacial reaction and the composite has the properties of a thermal conductivity (TC) of 224.5 W/(m °C), a thermal expansion coefficient (CTE) (RT ~ 300 °C) of 7.04 × 10−6/°C and a bending strength (BS) of 277 MPa. When the Al-9Si-6Mg alloy with a lower Si content is used for infiltration, interface zone with a thickness around 200 nm forms in the 3D-SiC/Al-Si-Mg IPC fabricated with the 3D-SiC preform preoxidized at 1000 °C. The reaction-bonded interface is composed of AlN and MgAl2O4 which have better interface affinity with SiC and can isolate SiC effectively from liquid Al against the formation of detrimental Al4C3 phase. The composite has the properties of a TC of 219.5 W/(m °C), a CTE (RT ~ 300 °C) of 7.66 × 10−6/°C and a BS of 318 MPa.

Effect of Si addition on the stability of Al-10Ti-5Cu-xSi alloy/SiC interface

The effect of Si addition on the interfacial stability of Al-10Ti-5Cu-xSi (x = 0, 5, 10, 15) alloy/SiC is investigated. SiC and the Al-10Ti-5Cu-xSi alloys were compacted to obtain a stable interface with 10 wt% Si. Analysis of the processing conditions and the microstructures indicated that an excellent Ti3SiC2 phase had been formed and the deleterious Al4C3 phase had been eliminated successfully by the addition of 10 wt% Si to the Al-10Ti-5Cu alloy. Formation of Ti3SiC2 increased at first and then decreased, while the formation of Al4C3 was gradually inhibited with increasing Si content. Ti3SiC2 possesses good chemical stability, and flexibility. However, Al4C3 degrades within few days, in composites exposed to ambient conditions. The presence of Ti3SiC2 at the interface and the elimination of Al4C3 together ameliorate the bonding of Al-10Ti-5Cu-xSi alloy to SiC, thereby improving the interfacial stability of Al-10Ti-5Cu-xSi/SiC.

Aluminum carbide hydrolysis induced degradation of thermal conductivity and tensile strength in diamond/aluminum composite

Diamond particles reinforced aluminum matrix (diamond/Al) composite is receiving great interests as a thermal management material due to its superior thermal conductivity and light weight. The diamond/Al composite is, however, incurring a problem of aluminum carbide (Al4C3) hydrolysis in the applications. Here we propose an accelerated hydrolytic ageing method to assess the reliability of diamond/Al composite in water environment. The diamond/Al composite specimens have been immersed in distilled water at room temperature up to 115 days. The microstructural characterization shows that water diffuses into the composite and reacts with the interfacial Al4C3 phase to generate Al(OH)3 and CH4. The concentration of the collected methane gas was measured by using a gas chromatograph technique to monitor the hydrolysis reaction. With prolonging soaking time from 5 to 115 days, the normalized methane concentration increases from 4 × 10−4 to 2 × 10−3, the thermal conductivity decreases from 467 to 347 W/mK, and the tensile strength decreases from 105 to 61 MPa. The property degradation is ascribed to the hydrolysis of Al4C3, which is harmful to the structural integrity of the diamond/Al composite. The finding provides guideline for the protection of diamond/Al composite components in service environments.

The formation of atomic-level interfacial layer and its effect on thermal conductivity of W-coated diamond particles reinforced Al matrix composites

Diamond particles coated with a 45 nm-thick W layer were used to produce diamond particles reinforced Al matrix composites (Al/diamond(W)) by a gas pressure infiltration method. The results show that W atoms have diffused into Al matrix and replaced Al atoms during infiltration. As a result, a uniform 0.5 nm-thick Al5W interfacial layer is formed in the composite produced with 20 min infiltration time. The generation of the Al5W layer strengthens not only the interfacial bonding but also impedes the formation of hydrolysable Al4C3 phase. With increasing infiltration time from 10 to 60 min, the thermal conductivity increases from 520 to 620 W/m K, which manifests the influence of interfacial layer thickness on thermal properties of the Al/diamond(W) composite. The study provides a new strategy to modifying the interfacial structure of Al/diamond composites on the aspects of both enhancing the thermal conductivity and preventing the formation of hydrolysable Al4C3 phase.

Microstructure and mechanical properties of graphene nanoplates reinforced pure Al matrix composites prepared by pressure infiltration method

In the present work, microstructure and mechanical behavior of the graphene nanoplates (GNPs) reinforced pure Al (GNPs/Al) composites prepared by the pressure infiltration method was investigated. No Al4C3 phase was detected in the composites, while GNPs have been well bonded with the Al matrix. It is suggested that the reaction between pure Al matrix and graphene could also be inhibited by using graphene with fewer defects. It has been found that the mechanical properties of the composites could be significantly improved by the addition of graphene. After addition of 0.54 wt% GNPs, the improvement of the yield and tensile strength before the extrusion was 116% and 45%, respectively. However, after the extrusion treatment, the corresponding increment of the yield and tensile strength was increased to 228% and 93%, respectively. Moreover, the fracture surface of the GNPs/Al composites before and after the extrusion treatment was mainly characterized by the lamellar structure with bridging of GNPs and the fine equiaxed structure with the pulling-out of the GNPs, respectively. Based on the modified shear-lag model, the strengthening mechanism of the GNPs/Al composites has been discussed, and the effect of GNPs and the extrusion treatment on the yield strength of the composites have been analyzed.

Direct formation of graphene shells on Al2O3 nano-particles using simple thermal treatment under C2H2-H2 atmospheric conditions

Graphene shells were directly formed on Al2O3 nano-particles (NPs) without the use of catalytic materials using simple thermal treatment in a C2H2 and H2 environment. The stacking number of graphene layers increased from 3 to 7 depending on the treatment temperature. The sheet resistance of films formed using Al2O3-graphene core-shell (CS) paste was 1665 Ω/□ at 1000 °C and 60 Ω/□ at 1100 °C. The proposed chemical reactions on Al2O3 NPs could be summarized as formation of liquid Al due to H2 reduction, thermal decomposition of the AlO(OH) phase, graphene shell formation due to super-saturation of C-elements in the liquid Al layer, and formation of an Al4C3 phase. Moreover, the existence of trapped H2O played an important role in additional reactions and led to decomposition of the Al4C3 phase, resulting in the appearance of the α-Al2O3 phase. The method developed in this study is a simple one-step technique that allows Al2O3-graphene CSs to be easily fabricated within a short time. Thus, this method is expected to be applied to the formation of various metal oxide-graphene CSs.

Vacuum hot pressed AZ31/UCF/AZ31 composite sheets: Microstructure and mechanical properties

AZ31 Mg alloy/unidirectional carbon fiber (UCF)/AZ31 composite sheets were fabricated with AZ91 Mg alloy powder as an adhesive using vacuum hot pressing (VHP) at various temperatures. Both the wettability and bonding strength of the UCF/AZ91 interfaces increased with increasing VHP temperature, resulting in an improvement of the mechanical properties of the composite sheets. The fracture mechanism of the composite sheets at low VHP temperature (500 °C) was the pullout of UCFs and delamination. In contrast, at 560 °C, partial debonding between the UCFs and AZ91 was the dominant failure mechanism, and an S-type fracture path surrounding the UCFs was observed. The bonding strength of the UCF/AZ91 interface was weaker than that of the AZ91/AZ31 interface for this composite. The sheet prepared at 585 °C exhibited the largest ultimate tensile strength of 252 MPa and an elongation of 13.2%. This behavior was attributed to the enhancement of the interfacial bonding strength due to the formation of Al4C3 and MgAl2C2 phases at the UCF/AZ91 interface. The hardness and modulus reached maximum values of 9.9 and 61 GPa, respectively, near the UCF/AZ91 interface.

Ti-enhanced exfoliation of V2AlC into V2C MXene for lithium-ion battery anodes

Abstract Two-dimensional V 2 C (MXene) derived from layered V 2 AlC phase attracts increasing interest due to its various promising applications such as lithium-ion batteries. Yet it is a great challenge to obtain completely exfoliated V 2 C MXene by etching Al from V 2 AlC. Here, in this work, we highlight that alloying Ti can significantly enhance the exfoliation of (V 1- x Ti x ) 2 C MXene from (V 1- x Ti x ) 2 AlC based on our systematic studies of experiments and first-principles calculations. Furthermore, the exfoliated (V 1- x Ti x ) 2 C MXene shows better multilayered morphology characterized by X-ray diffraction and scanning electron microscopy. Meanwhile, by analyzing the exfoliation process and electron localization functions, we have demonstrated that the micro-origin of Ti enhancement effect on the exfoliation of (V 1- x Ti x ) 2 AlC is due to the significantly weakened interlayer bonding between the VC and Al layers in (V 1- x Ti x ) 2 AlC induced by alloying Ti. Finally, we have shown that the performance of (V 1- x Ti x ) 2 C as anode materials for Li-ion batteries is improved with the increase of Ti content. Our results provide a useful way to improve the synthesis of V-based MXenes and are beneficial to the applications as well.

Microstructure and properties of an Al–Ti–Cu–Si brazing alloy for SiC–metal joining

An Al–Ti–Cu–Si solid–liquid dual-phase alloy that exhibits good wettability and appropriate interfacial reaction with SiC at 500–600°C was designed for SiC–metal joining. The microstructure, phases, differential thermal curves, and high-temperature wetting behavior of the alloy were analyzed using scanning electron microscopy, X-ray diffraction analysis, differential scanning calorimetry, and the sessile drop method. The experimental results show that the 76.5Al–8.5Ti–5Cu–10Si alloy is mainly composed of Al–Al2Cu and Al–Si hypoeutectic low-melting-point microstructures (493–586°C) and the high-melting-point intermetallic compound AlTiSi (840°C). The contact angle, determined by high-temperature wetting experiments, is approximately 54°. Furthermore, the wetting interface is smooth and contains no obvious defects. Metallurgical bonding at the interface is attributable to the reaction between Al and Si in the alloy and ceramic, respectively. The formation of the brittle Al4C3 phase at the interface is suppressed by the addition of 10wt% Si to the alloy.

Prediction on structural, mechanical and thermal properties of Al4SiC4, Al4C3 and 4H-SiC under high pressure by first-principles calculation

A theoretical study is conducted by first-principles theory to study the structural, electronic, elastic and thermal properties of Al4SiC4, Al4C3 and 4H-SiC phases under pressure. The calculated results indicated that the volumetric shrinkage of Al4SiC4 declines to 16% compared with 4H-SiC for 12% and its length of lattice parameter along c-axis decreases faster than that of along other axes in cell structures. The mechanical properties of Al4SiC4 like elastic constants and elastic moduli increase continuously under pressure. The thermal expansion coefficient of three compounds under pressure are studied first. When temperature is lower than 500 K, the coefficient increases rapidly first then gradually tends to a linear accession at higher temperature and the propensity of increment becomes moderate. The [Formula: see text] data decreases slightly with pressure but increases dramatically with temperature for all compounds.

Effect of Spark-Plasma-Sintering Conditions on Tensile Properties of Aluminum Matrix Composites Reinforced with Multiwalled Carbon Nanotubes (MWCNTs)

In this study, aluminum (Al) matrix composites containing 2 wt.% multiwalled carbon nanotubes (CNTs) were fabricated by powder metallurgy using high-energy ball milling (HEBM), spark plasma sintering (SPS), and subsequent hot extrusion. The effect of SPS conditions on the tensile properties of CNT/Al composites was investigated. The results showed that composites with well-dispersed CNTs and nearly full-density CNT/Al can be obtained. During HEBM, CNTs were shortened, inserted into welded Al powder particles, bonded to Al, and still stable without CNT-Al reaction. After consolidation, Al4C3 phases formed in composites under different sintering conditions. With the increase of sintering temperature and holding time, the strength decreased. Conversely, the ductility and toughness noticeably increased. As a result, a good balance between strength (367 MPa in ultimate tensile strength) and ductility (13% in elongation) was achieved in the as-extruded CNT/Al composite sintered at 630°C with a holding time of 300 min.

Pulsed metall inert gas (MIG) welding and its effects on the microstructure and element distribution of an aluminum matrix reinforced with SiC composite material

This study aims to demonstrate the effects of pulsed current on the welding pool and fusion zone microstructures of the aluminum 2014 alloy matrix composite material reinforced with 14 and 20 vol% SiC particles. A programmable synergic controlled MIG welding machine with pulsed power supply was used. One hundred Ampere and 120 Ampere pulsed current values were used to determine the effect of heat input on microstructures. A 1 mm diameter SG‐AlSi5 wire was used as filler material. The microstructures were studied using a scanning electron microscope (SEM) with energy dispersive X‐ray (EDX) spectroscopy, and the phase analyses were performed via X‐ray diffraction analyzer (XRD). The study showed that increasing the SiC rate has a greater effect on the formation of Al4C3 phase than increasing the heat input values. Al4C3 formation was not formed as a needle‐like structure.

Fabrication and Characterization of In Situ Synthesized SiC/Al Composites by Combustion Synthesis and Hot Press Consolidation Method.

The in situ SiC/Al composites were fabricated in Al-Si-C systems with different Si/C mass ratios and holding time by the method of combustion synthesis and hot press consolidation. The influences of Si/C mass ratio and holding time on the phase constitution, microstructure, and hardness of the composites were investigated. The results indicate that the increase of Si/C mass ratio leads to more uniform size distribution of the SiC particles in the Al matrix. Moreover, by improving the Si/C mass ratio from 4 : 1 to 5 : 1, the maximum size of SiC particle was reduced from 4.1 μm to 2.0 μm. Meanwhile, the percentage of submicroparticles was increased from 22% to 63%, and the average hardness value of the composites was increased by 13%. In addition, when the holding time is set to be fifteen minutes, the Al4C3 phase did not exist in the composites because of its total reactions with Si atoms to form SiC particles, and the average hardness value was 73.8 HB.

E2<sub>1</sub>-（Co, Ni）<sub>3</sub>AlCを強化相とするCo基耐熱合金において二相組織形態が機械的性質に及ぼす影響

E2<sub>1</sub>-（Co, Ni）<sub>3</sub>AlCを強化相とするCo基耐熱合金において二相組織形態が機械的性質に及ぼす影響

石墨烯铝基复合材料的界面反应研究

石墨烯具有极其优异的力学性能，是理想的复合材料增强体。本文以商业纯铝为基体，石墨烯为增强相，通过超声混合法制备石墨烯-Al复合粉末，通过真空热压烧结制备石墨烯-Al复合材料，通过扫描电镜(SEM)、差热分析(DSC)、X-射线衍射分析(XRD)、显微硬度计表征了材料的宏观形貌、微观形貌、反应温度、相组成和显微硬度等。结果表明：石墨烯和Al在400℃时便开始发生反应，但在600℃以下时，两者反应速度较慢，在Al熔点以上时，石墨烯和Al反应速度明显增加，石墨烯和Al反应生成Al4C3；少量的Al4C3可以增强石墨烯和Al基体的结合力，有利于提高材料的力学性能，但是大量脆性Al4C3生成时，材料的力学性能下降。 Graphene has excellent mechanical properties and is considered as an excellent strengthening material in composite. In this paper, ultrasonic mixing was used to obtain uniformly dispersed graphene into Al powder and hot pressing was used to fabricate Graphene-Al composite bulk. The samples were characterized by scanning electron microscopy (SEM), differential thermal analysis (DSC), X-ray diffraction (XRD); the mechanical properties were tested by microhardness test. The results showed that the graphene could react with Al at 400˚C and form Al4C3 phase, and the reacting rates were relative low under 600˚C, the reacting rates increased significantly above the melting point of aluminum. Slight formation of Al4C3 could increase the mechanical property of composites, but massive Al4C3 would greatly decrease the mechanical property of composites.

Effects of graphene content on microstructures and tensile property of graphene-nanosheets / aluminum composites

The graphene nanosheets (GNSs) reinforced Al matrix composites were successfully fabricated by high-energy ball milling and vacuum hot pressing. Effects of graphene content (0.25 wt%, 0.5 wt% and 1.0 wt%) on microstructures and tensile properties of GNSs/Al composites were investigated. Microstructures and the distribution of GNSs were analyzed with scanning electron microscope (SEM), X-ray diffraction (XRD) and transmission electron microscope (TEM). Tensile properties and hardness were studied at room temperature. The results show that the GNSs/Al composites with the high relative density and dispersed distribution of GNSs were fabricated. A good interfacial bonding was obtaned in GNSs/Al composites. The aluminum carbide Al4C3 phases with granular and short rod-like morphology were found at interface. With the increase of GNSs content, the content of Al4C3 phases increases. The dislocations were also found near the interface, and the density of dislocation reduced with the increase of Al4C3 content. The Vickers hardness of GNSs/Al composites increases obviously with the increase of GNSs content. The yield strength and ultimate tensile strength of GNSs/Al composites have an obvious improvement compared to that of pure Al, but the elongation show a slight decrease. The yield strength and ultimate tensile strength of Al-0.25GNSs composites increase by 38.27% and 56.19% compare with that of pure Al. The GNSs pull-out is detected at the edges of dimples, and the number of dimples slight decreases with the increase of GNSs content.

Effect of The Reinforcing by WC on Microhardness, Roughness and Corrosion Behavior of Al-12Si Alloy

This work investigated the effect of Tungsten Carbide as reinforcement with 1, 2 and 3 wt.% on some properties of matrix Al-12Si alloy. Al-12Si/WC composites were fabricated by stir casting method. Micro hardness and roughness have been tested to investigate the role of WC reinforcing. Corrosion behavior of these composites also investigated in 0.2M HCl solution using the potentiostat instrument. The results show a good incorporation between the matrix and WC particles with probability to form Al12W and Al4C3 phase in addition to eutectic structure of Al-12Si alloy. The micro hardness was increased with increasing the weight percent of WC, while the roughness was decreased due to the better interfacial bonding. Corrosion protection properties of composites were better than that of base alloy due to the behavior of WC as a cathodic site which reduces the dissolution of metals from the metallic surface.

Enhanced thermal conductive 3D-SiC/Al-Si-Mg interpenetrating composites fabricated by pressureless infiltration

A high thermal conductive 3D-SiC/Al-Si-Mg interpenetrating composite (IPC) with three dimensional mutually interpenetrated structure was fabricated by mold-forming and pressureless infiltration method. Al-15Si-10Mg was used as the infiltration aluminum alloy. The obtained composite was treated with a T6 procedure. The composed phases, microstructure, thermal conductivity, mechanical strength and fractography of the prepared 3D-SiC/Al-Si-Mg IPC were either analyzed or measured with X-ray diffraction (XRD), optical metallography, laser thermal conductivity instrument, universal testing machine, field emission electron scanning microscopy (SEM) with energy dispersive spectroscopy (EDS), high-resolution transmission electron microscopy (HRTEM), and etc. The results showed that both SiC ceramic and aluminum alloy phases distribute evenly and form a three-dimensional mutually interpenetrated structure in the obtained IPC. No clear brittle and harmful Al4C3 phase was found in the composite. The obtained IPC contains a SiC volume fraction of 67vol% and has the properties of a density of 3.02g/cm2, a thermal conductivity of 233.6W/(m°C), a thermal expansion coefficient (RT~300°C) of 7.03×10−6/°C and a bending strength of 288MPa.

Tailoring microstructure and properties of bilayer-graded Al/B4C/MgAl2O4 composites by single-stage pressureless infiltration

The quantitative effect of the following parameters on the one single step pressureless infiltration characteristics of bilayer (B4C)p/rice-husk ash (RHA) porous preforms by aluminum alloys was investigated using the Taguchi method and analysis of variance (ANOVA): infiltration temperature and time, B4C particle size, RHA percentage, preform porosity and alloy magnesium content. Contribution determinations of each of the parameters on the bending strength of the resulting bilayer composites indicated that the parameter with the most significant effect is process temperature, with a contribution percentage of 79%. Verification tests conducted using the established optimum parameters show good agreement with those of projected values. A detailed examination of microstructure and potential chemical reactions, aided by thermodynamic analysis, allowed establishing conditions for suppressing or diminishing the impact of the deleterious Al4C3 phase.

Synthesis by Vacuum Infiltration, Microstructure, and Thermo‐Physical Properties of Graphite–Aluminum Composite

Graphite prefabricated blocks are fabricated using natural flake graphite and pore‐forming agent of urea, and then high volume fraction graphite–aluminum (Gr–Al) composites are fabricated applying graphite prefabricated blocks and aluminum alloy (ZL101) by vacuum infiltration process for the electronic packaging materials. The microstructures of graphite prefabricated block and Gr–Al composites are observed in detail, which shows that the graphite maintains a good integrity and arranges uniformly in aluminum alloy. Besides, the result shows the formation of a tightly adhered interface between the side surfaces of the graphite and aluminum alloy matrix, and no detrimental Al4C3 phase is found. Thermal properties of Gr–Al composites are researched perpendicularly to the pressing direction. Thermal conductivity increases from 282 to 398 W mK−1 whereas the volume fraction of flake graphite increases from 40 to 75% in the composites, this reveals that the vacuum infiltration is a very promising method to synthesize Gr–Al composites.