Effect of the SiC particle size on the dry sliding wear behavior of SiC and SiC–Gr-reinforced Al6061 composites

The effect of size of silicon carbide particles on the dry sliding wear properties of composites with three different sized SiC particles (19, 93, and 146 μm) has been studied. Wear behavior of Al6061/10 vol% SiC and Al6061/10 vol% SiC/5 vol% graphite composites processed by in situ powder metallurgy technique has been investigated using a pin-on-disk wear tester. The debris and wear surfaces of samples were identified using SEM. It was found that the porosity content and hardness of Al/10SiC composites decreased by 5 vol% graphite addition. The increased SiC particle size reduced the porosity, hardness, volume loss, and coefficient of friction of both types of composites. Moreover, the hybrid composites exhibited lower coefficient of friction and wear rates. The wear mechanism changed from mostly adhesive and micro-cutting in the Al/10SiC composite containing fine SiC particles to the prominently abrasive and delamination wear by increasing of SiC particle size. While the main wear mechanism for the unreinforced alloy was adhesive wear, all the hybrid composites were worn mainly by abrasion and delamination mechanisms.     

Different reinforcement strategies of hybrid surface composite AA6061/(B4C+MoS2) produced by friction stir processing

Aluminum surface composites have gained huge importance in material processing due to their noble tribological characteristics. The reinforcement of solid lubricant particles with hard ceramics further enriches the tribological characteristics of surface composites. In the current study, friction stir processing was chosen to synthesize hybrid surface composites of aluminum containing B₄C and MoS₂ particles with anticipated improved tribological behavior. B₄C and MoS₂ powder particles in 87.5: 12.5 ratio were reinforced into the AA6061 by hole and groove method. Microstructural observations indicated that reinforcement particles are well distributed in the matrix. The hardness and wear resistance of hybrid surface composites improved as compared to the base material, due to well distributed abrasive B₄C and solid lubricant MoS₂ particles in AA6061. The hybrid surface composites achieved ∼32 % increased average hardness as compared to the base material. Hole method revealed ∼13 % better wear resistance compared to the groove method for friction stir processed hybrid surface composite, attributing to an improved homogeneity of particle distribution shown by zigzag hole pattern. Moreover, friction stir processed AA6061 without reinforcement particles exhibited reduced hardness and wear resistance due to loss of strengthening precipitates during multi-pass friction stir processing.     

Mg_2B_2O_(5W),SiC和Gr颗粒增强6061Al基复合材料的摩擦磨损行为

采用粉末热挤压法制备2%Mg2B2O5w/6061Al,2%Gr/6061Al,2%SiCp/6061Al,2%Mg2B2O5w+2%Gr/6061A,2%Mg2B2O5w+2%SiCp/6061Al,2%Mg2B2O5w+2%Gr+2%SiCp/6061Al单一及混杂增强的铝基复合材料,并对其耐磨性和摩擦行为进行研究。结果表明:随着载荷的增大,各种复合材料的磨损率均增大,石墨的添加增大了铝基复合材料的磨损率;复合材料的摩擦因数随载荷的增大而降低并趋于稳定,摩擦因数均介于0.22~0.32之间。未加入石墨的复合材料的磨损机制以磨料磨损和轻微的黏着磨损为主,加入石墨后复合材料的磨损机制转变为剧烈的黏着磨损。     

基体各类对混杂复合材料摩擦磨损性能的影响

研究了基体种类对SiC和石墨（Gr)颗粒混杂增强铝基复合材料的摩擦磨损性能的影响。各种铝基体的混杂复合材料的耐磨性有明显差异,纯铝基混杂复合材料具有最好的耐磨性,其次是A356,2024和6061为基体的混杂复合材料。     

Microstructure and mechanical behavior of AA6082-T6/SiC/B4C-based aluminum hybrid composites

The microstructural and mechanical behavior of hybrid metal matrix composite based on aluminum alloy 6082-T6 reinforced with silicon carbide (SiC) and boron carbide (B₄C) particles was investigated. For this purpose, the hybrid composites were fabricated using conventional stir casting process by varying weight percentages of 5, 10, 15, and 20?wt% of (SiC?+?B₄C) mixture. Dispersion of the reinforced particles was studied with x-ray diffraction and scanning electron microscopy analyses. Mechanical properties such as micro-hardness, impact strength, ultimate tensile strength, percentage elongation, density, and porosity were investigated on hybrid composites at room temperature. The results revealed that the increase in weight percentage of (SiC?+?B₄C) mixture gives superior hardness and tensile strength with slight decrease in percentage elongation. However, some reduction in both hardness and tensile strength was observed in hybrid composites with 20?wt% of (SiC?+?B₄C) mixture. As compared to the un-reinforced alloy, the improvement in hardness and tensile strength for hybrid composites was found to be 10% and 21%, respectively. Reduction in impact strength and density with increase in porosity was also reported with the addition of reinforcement.     

SiC 和Gr 颗粒混杂增强Al 基复合材料的摩擦磨损特性的研究

比较了SiC 和Gr 颗粒混杂增强Al 基复合材料的干摩擦磨损行为, 并与单一SiC_P 和单一G_rP 增强Al 基复合材料的相应行为进行了比较。结果表明, 在低载荷(< 30 N ) 时, SiC_P 和G_rP 能协调作用, 使混杂复合材料的摩擦系数和磨损率均比单一SiC_P 和G_rP 增强复合材料低。在较高载荷(30～ 120 N ) 时, 混杂复合材料磨损以剥层磨损机制为主, 摩擦系数比单一SiC_P 增强复合材料低, 磨损率比单一G_rP 增强复合材料低得多, 比单一SiC_P 增强复合材料高。混杂复合材料对偶件的磨损比单一SiC_P 增强复合材料低得多。      

Processing of heat-treated silicon carbide-reinforced aluminum alloy composites

The present study investigates the processing of heat-treated silicon carbide (SiC) particle-reinforced 6061 aluminum alloy (AA) composites. As-received SiC powders were heat treated at 1300ºC, 1400ºC, and 1500ºC in nitrogen atmosphere for 2 h, and the 6061 AA–SiC composites were developed by spark plasma sintering at 560ºC and 60 MPa for 5 min in argon atmosphere. The amorphous silicon nitride is found to form in SiC particles as a result of heating at 1400ºC. The microstructure of the composites exhibited uniform distribution of SiC or SiC/Si₃N₄ particles in 6061 AA matrix. Further, the heat-treated SiC-reinforced 6061AA composites exhibited improved mechanical properties. A typical combination of UTS of 240 MPa and elongation of 21% is obtained for the 6061 AA composites prepared using SiC powders heated at 1400ºC.     

Characteristics evaluation of SiC/Si nanocomposites produced by spark plasma sintering

SiC–Si composites are widely used either as a bulk material or as a matrix for fibre reinforced ceramics. In the current research, nanocomposites of SiC–Si with different volume fractions of Si were sintered by spark plasma sintering (SPS) for the first time. The effect of Si content and different sintering parameters on relative density, microstructure, hardness and fracture toughness of the sintered materials have been investigated. The relative density increased from about 83 to 99% by increasing the sintering temperature to 1700°C, sintering time to 10?min, and pressure to 70?MPa for composites containing >20?vol.-% Si. The results revealed that the full dense SiC–20?vol.-%Si composite can be obtained by SPS at 1700°C, 10?min and 70?MPa. Moreover, in this condition, the hardness and toughness of the composites reached the optimum values.     

Tribological properties of powder metallurgy – Processed aluminium self lubricating hybrid composites with SiC additions

In this experimental study, aluminium (Al)-based graphite (Gr) and silicon carbide (SiC) particle-reinforced, self-lubricating hybrid composite materials were manufactured by powder metallurgy. The tribological and mechanical properties of these composite materials were investigated under dry sliding conditions. The results of the tests revealed that the SiC-reinforced hybrid composites exhibited a lower wear loss compared to the unreinforced alloy and Al–Gr composites. It was found that with an increase in the SiC content, the wear resistance increased monotonically with hardness. The hybridisation of the two reinforcements also improved the wear resistance of the composites, especially under high sliding speeds. Additionally, the wear loss of the hybrid composites decreased with increasing applied load and sliding distance, and a low friction coefficient and low wear loss were achieved at high sliding speeds. The composite with 5 wt.% Gr and 20 wt.% SiC showed the greatest improvement in tribological performance. The wear mechanism was studied through worn surface and wear debris analysis as well as microscopic examination of the wear tracks. This study revealed that the addition of both a hard reinforcement (e.g., SiC) and soft reinforcement (e.g., graphite) significantly improves the wear resistance of aluminium composites. On the whole, these results indicate that the hybrid aluminium composites can be considered as an outstanding material where high strength and wear-resistant components are of major importance, predominantly in the aerospace and automotive engineering sectors.     

Large sized cubic BN reinforced nanocomposite with improved abrasive wear resistance deposited by cold spray

In this work, large sized cubic BN (cBN) reinforced nanocomposites are prepared by cold spray deposition of blended powder mixtures of mechanically alloyed 40 vol.% cBN–NiCrAl nanocomposite particles and large sized cBN particles. Deposition behavior of the blended powders, microstructure and mechanical properties including hardness, fracture toughness and two-body dry abrasive wear behavior of the sprayed composites, are investigated. Results show that dense composites with large cBN particle content of 13–20 vol.%, depending on composition of the spray powders, can be obtained. Declining deposition efficiency is detected as increasing large cBN content due to the gradually enhanced sand blasting effect. Increasing content of large cBN in spray powder results in an increment in hardness and a decrement in fracture toughness. Abrasive wear resistance of the 40 vol.% cBN–NiCrAl nanocomposite is doubled by incorporating 20 vol.% of the large cBN particles. Worn surface morphology observation indicates that the improvement is due to the shielding effect of the large protruding cBN particles against SiC abrasive. Material removal mechanism of the sprayed composites during abrasive wear test is also studied.     

Effect of silicon carbide particulates on wear resistance of graphitic aluminium matrix composites

Use of graphite (Gr) reinforcement in aluminium matrix composites has been reported to be beneficial in reducing wear due to its solid lubricant property, but it results in reduction of mechanical strength. Addition of silicon carbide (SiC), on the other hand, improves both strength and wear resistance of composites, but high amount of SiC makes machining difficult and composites become brittle. Thus, SiC can be advantageously used as a second reinforcement to overcome the problem of strength reduction of Gr reinforced composites, resulting in what is known as hybrid composites. Aluminium matrix composites reinforced with equal weight fraction of SiC and Gr particulates up to 10% are studied with regard to hardness improvement and modified dry sliding wear behaviour. Studies based on design of experiments techniques indicate that there is an increasing trend of wear in Al–SiC–Gr hybrid composites beyond % reinforcement of 7.5%. Hybrid composites exhibit better wear characteristics compared to Gr reinforced composites. Interaction between load and sliding distance is noticed in both the composites and this may be attributed to the presence of Gr particulates. Decrease of wear with increase of speed and increase of wear with increase of either load or sliding distance or both were noticed.     

Evaluation of microstructure and mechanical properties of Al/Al2O3/SiC hybrid composite fabricated by accumulative roll bonding process

In this investigation, a new kind of metal matrix composites with a matrix of pure aluminum and hybrid reinforcement of Al₂O₃ and SiC particles was fabricated for the first time by anodizing followed by eight cycles accumulative roll bonding (ARB). The resulting microstructures and the corresponding mechanical properties of composites within different stages of ARB process were studied. It was found that with increasing the ARB cycles, alumina layers were fractured, resulting in homogenous distribution of Al₂O₃ particles in the aluminum matrix. Also, the distribution of SiC particles was improved and the porosity between particles and the matrix was decreased. It was observed that the tensile strength of composites improved by increasing the ARB passes, i.e. the tensile strength of the Al/1.6 vol.% Al₂O₃/1 vol.% SiC composite was measured to be about 3.1 times higher than as-received material. In addition, tensile strength of composites decreased by increasing volume fraction of SiC particles to more than 1 vol.%. Scanning electron microscopy (SEM) observation of fractured surfaces showed that the failure mechanism of broken hybrid composite was shear ductile rupture.     

Studies on mechanical and dry sliding wear of Al6061–SiC composites

Particulate reinforced Al-MMCs exhibits better mechanical properties and improved wear resistance over other conventional alloys. In the present paper, the experimental results of the mechanical and tribological properties of Al6061–SiC composites are presented. The composites of Al6061 containing 2–6 wt% SiC were prepared using liquid metallurgy route. The experimental results showed that the density of the composites increase with increased SiC content and agrees with the values obtained through the rule of mixtures. The hardness and ultimate tensile strength of Al6061–SiC composites were found to increase with increased SiC content in the matrix at the cost of reduced ductility. The wear properties of the composites containing SiC were superior to that of the matrix material.     

Aluminum matrix composites based on preceramic-polymer-bonded SiC preforms

Polymethylsiloxane (PMS) was used as a binder to make self-supporting SiC preforms for pressurized aluminum melt infiltration. The SiC particles were coated with preceramic polymer by spray drying; this ensured a fine and homogeneous distribution coupled with a high yield of the binder. The conditioned SiC powder mixtures were processed into preforms by warm pressing, curing and pyrolysis. A polymer content of 1.25 wt.% conferred sufficient stability to the preforms to enable composite processing. Using this procedure, SiC preforms with various SiC particle size distributions were prepared. The resulting Al/SiC composites with SiC contents of about 60 vol.% obtained by squeeze casting infiltration exhibit a 4-point bending strength of ∼500 MPa and Young’s moduli of ∼200 GPa. These values are comparable to those of compositionally identical, but binder-free composites. It is thus shown that the PMS-derived binder confers the desired strength to the SiC preforms without impairing the mechanical properties of the resulting Al/SiC composites.     

Production and characterization of AA6082-(Si3N4 + Gr) stir cast hybrid composites

The present research work emphasizes the development of hybrid aluminum (AA6082) matrix composites (HAMCs) reinforced with different weight percentages (wt.%) of ball-milled (silicon nitride (Si₃N₄) + graphite (Gr)) ceramic particulates by conventional stir casting process. Si₃N₄ and Gr are ball milled to obtain a definite density of combined powder. The weight percentage of ball-milled ceramic powder is varied from 0 to 12 wt.% in a stage of 3%. The microstructures as well as mechanical properties of the fabricated hybrid composites are analyzed. The scanning electron micrograph reveals the uniform distribution of ball-milled (Si₃N₄ + Gr) ceramic particulates in the aluminum matrix. The distribution of ball-milled (Si₃N₄ + Gr) ceramic particulates has also been analyzed with x-ray diffraction (XRD) technique. Both the hardness and ultimate tensile strength have enhanced with a reduction in percentage elongation with increase in weight percentage of ball-milled (Si₃N₄ + Gr) ceramic particulates in the aluminum matrix.     

铝基钎料在SiC及SiC_p/6061复合材料上的润湿性研究

对多种铝基钎料在SiC、6 0 6 1及SiCp 6 0 6 1复合材料上进行了润湿性试验。结果表明 :炉中钎焊时 ,钎料与钎剂的成分、加热温度与保温时间、钎料与钎剂熔化温度的匹配等是影响铝基钎料润湿性的主要因素 ;真空钎焊时 ,镁含量不同的各种含镁Al 2 8Cu 5Si钎料在Al基复合材料连接的温度范围内都不能润湿SiC陶瓷表面 ;配合QJ2 0 1钎剂 ,Al 2 8Cu 5Si 2Mg钎料对 15 %SiCp 6 0 6 1Al复合材料具有良好的润湿性 ,但对 30 %SiCp 6 0 6 1Al复合材料却润湿不良 ;在加钎剂的情况下 ,钎料中的镁反而对在铝合金及铝基复合材料上的润湿性有不利影响 ;在Al 2 8Cu 5Si 2Mg钎料和 15 %SiCp 6 0 6 1Al复合材料的钎焊界面处存在SiC颗粒的偏聚现象     

SiC<Subscript>f</Subscript>/SiC composites reinforced by randomly oriented chopped fibers prepared by semi-solid mechanical stirring method and hot pressing

SiC short fibers, with an average diameter of 13 μm, length of 300–1,000 μm and chopped from SiC continuous fibers, were surface modified by the semi-solid mechanical stirring method to produce a discrete coating of aluminum particles. Then the starting mixtures, which consist of SiC short composite fibers, aluminum powder less than 50 μm and α-SiC powder of an average diameter of 0.6 μm, were mechanically mixed in ethanol for about 3 h, dried at 80 °C in air, and hot pressed under 30 MPa pressure at 1,650, 1,750 and 1,850 °C with 1 h holding time to prepare SiC_f/SiC composites. Volume fraction of SiC short fibers in the starting powder for SiC_f/SiC composites was about 25 vol.%. The composites were characterized in terms of bulk density, phase composition, and mechanical properties at room temperature. In addition, the distribution of SiC short fibers in the matrix and the cracking pattern in the composites were examined by optical microscope. Fracture surface of the composites were performed by a scanning electron microscope (SEM). The effect of hot-pressing temperature on bulk density and mechanical properties was investigated. The results indicated that SiC short fibers were uniformly and randomly distributed in the matrix, bending strength and bulk density of the composites increased with increasing sintering temperature. The composite, hot-pressed at 1,850 °C, exhibited the maximum bulk density and bending strength at room temperature, about 3.01 g/cm³ and 366 MPa, respectively. SEM analyses showed that there were a few of fiber pullout on the fracture surface of samples sintered at 1,650 °C and 1,750 °C, which was mainly attributed to lower densities. But few of fiber pullout was observed on the fracture surface of sample sintered at 1,850 °C, the combined effects of high temperature and a long sintering time were considered as a source of too severe fiber degradation because of the large amount of oxygen in the fibers.     

SiC含量对混杂复合材料摩擦磨损性能的影响

研究了ＳｉＣ含量对ＳｉＣ和石墨（Ｇｒ）颗粒混杂增强铝基复合材料摩擦磨损性能的影响。Ａｌ／ＳｉＣ＋Ｇｒ的磨损率随ＳｉＣ含量升高先下降,在２０ｖｏ％时达到最低值;然后则随ＳｉＣ含量升高而升高。当载荷为２０Ｎ时,摩擦系数随ＳｉＣ含量同而升高。当载荷为６０Ｎ时,摩擦系数与ＳｉＣ含量关系不大。     

Comparison of Fatigue Life Between C/SiC and SiC/SiC Ceramic-Matrix Composites at Room and Elevated Temperatures

In this paper, the comparison of fatigue life between C/SiC and SiC/SiC ceramic-matrix composites (CMCs) at room and elevated temperatures has been investigated. An effective coefficient of the fiber volume fraction along the loading direction (ECFL) was introduced to describe the fiber architecture of preforms. Under cyclic fatigue loading, the fibers broken fraction was determined by combining the interface wear model and fibers statistical failure model at room temperature, and interface/fibers oxidation model, interface wear model and fibers statistical failure model at elevated temperatures in the oxidative environments. When the broken fibers fraction approaches to the critical value, the composites fatigue fracture. The fatigue life S–N curves and fatigue limits of cross-ply, 2D and 3D C/SiC and SiC/SiC composites at room temperature, 550 °C in air, 750 °C in dry and humid condition, 800 °C in air, 1000 °C in argon and air, 1100 °C, 1300 °C and 1500 °C in vacuum, have been predicted. At room temperature, the fatigue limit of 2D C/SiC composite with ECFL of 20 % lies between 0.78 and 0.8 tensile strength; and the fatigue limit of 2D SiC/SiC composite with ECFL of 20 % lies between 0.75 and 0.85 tensile strength. The fatigue limit of 2D C/SiC composite increases to 0.83 tensile strength with ECFL increasing from 20 to 22.5 %, and the fatigue limit of 3D C/SiC composite is 0.85 tensile strength with ECFL of 37 %. The fatigue performance of 2D SiC/SiC composite is better than that of 2D C/SiC composite at elevated temperatures in oxidative environment.     

Effect of dual size particle distribution on processing and properties of AZ91D/SiCp magnesium matrix composites prepared by rotation cylinder method

Abstract

Spiral fluidity and hardness and wear experiments were carried out to investigate the effect of dual size (5 and 50 μ m) SiC particle distributions on the fluidity, hardness, and wear resistance of Mg - 9.1Al - 0.7Zn (wt-%) alloy containing 10 vol.-% SiC particles, with the aim of tailoring properties to specific applications. Although a decrease in the fluidity of the composites is observed, as expected, in the presence of SiC particles, the fluidity of the composites with dual size particle distributions was in some instances better than that of composites containing the same volume fraction of single size particles. The hardness and wear resistance of the composites with dual size distributions were weakly dependent on the mixing ratio. In terms of complete molten processing and tailored mechanical properties, the optimum mixing ratio of 5 and 50 μm particles appears to be 1:2.