FABRICATION OF SiCp-AI COMPOSITE MATERIALS

Liquid phase fabrication methods for aluminum matrix composites reinforced with SiC whiskers, or SiC particles have been investigated and the mechanical properties of fabricated composites have been evaluated. Three kinds of liquid phase fabrication methods; hot extrusion, hot pressing and pressure infiltration, were studied. Commercial SiC whiskers and SiC powders of alpha type and beta type were used as the reinforcements for an aluminum matrix. Among the fabrication methods investigated, the best results were achieved by the pressure infiltration. The mechanical properties and the wear resistance of the fabricated composites were measured. The SiC whisker reinforced aluminum matrix composites have high strength, so that they can be used as high specific strength materials. The SiC particulate reinforced aluminum matrix composites are not strong as the SiC whisker reinforced composites. However, the SiC particulate reinforced aluminum matrix composites have a good potential for use as wear resistant material. The hardening effect of beta type particles on the aluminum matrix was larger than that of alpha type particles.     

Production and characterization of AA6061–B4C stir cast composite

This work focuses on the fabrication of aluminum (6061-T6) matrix composites (AMCs) reinforced with various weight percentage of B₄C particulates by modified stir casting route. The wettability of B₄C particles in the matrix has been improved by adding K₂TiF₆ flux into the melt. The microstructure and mechanical properties of the fabricated AMCs are analyzed. The optical microstructure and scanning electron microscope (SEM) images reveal the homogeneous dispersion of B₄C particles in the matrix. The reinforcement dispersion has also been identified with X-ray diffraction (XRD). The mechanical properties like hardness and tensile strength have improved with the increase in weight percentage of B₄C particulates in the aluminum matrix.     

碳化硅颗粒增强铝基复合材料颗粒表面改性技术研究现状

SiC颗粒增强铝基复合材料因具有高的比强度、比刚度、耐磨性及较好的高温稳定性而被广泛应用于航空航天、电子、医疗等领域,但由于SiC颗粒高熔点、高硬度的特点以及SiC颗粒与铝基体间存在界面反应,碳化硅铝基复合材料存在加工性差、界面结合力不足等问题,已无法满足航天等领域对材料性能更高的要求,因此开展如何改善基体与颗粒之间界面情况的研究对进一步提升复合材料综合性能具有重要的科学意义。结合国内外现有研究成果,总结了SiC颗粒与铝基体界面强化机制、界面反应特点、表面改性技术原理及数值建模的发展现状,结果表明,现有经单一表面改性方法处理后的增强颗粒对铝基复合材料性能的提升程度有限,因此如何采用新的手段使复合材料性能进一步提升将成为后续研究热点,且基于有限元数值模拟方法进行复合材料设计也是必然趋势。最后针对单一强化性能提升有限的问题,提出了基于表面改性的柔性颗粒多模式强化方法,同时针对现有的技术难点展望了后续的研究方向,以期为颗粒增强复合材料的制备提供理论参考。     

Effects of particulate reinforcement and strain‐rates on deformation and fracture behavior of Aluminum 6061‐T6 under high velocity impact

Aluminum matrix composites (AMC) exhibit an attractive combination of mechanical and physical properties such as high stiffness and low density, which favors their utilization in many structural applications. Thus, increasing the structural applications of AMC is the driving force for the need to adequately understand their deformation and failure mechanisms under various types of loading conditions. In this study, plastic deformation of alumina particle reinforced Aluminum 6061‐T6 matrix composite is investigated and compared to that of an un‐reinforced Aluminum 6061‐T6 alloy at high strain‐rates under compressive loading. Dynamic stress‐strain curves are obtained using direct impact Split Hopkinson Pressure Bar (SHPB). Particulate reinforcement increases the deformation resistance of the aluminum alloy at high strain‐rates. Strain localization along narrow adiabatic shear bands is observed in both the reinforced and un‐reinforced alloy. Whereas the microstructure of shear bands in un‐reinforced alloy showed finer grain size compared to that of the bulk material, the shear bands observed in the AMCs are darker than the bulk material and the reinforcing particles are observed to be more closely spaced along the shear bands.     

Fe-based metallic glass particles reinforced Al-7075 matrix composites prepared by spark plasma sintering

Metallic glass (MG) reinforced aluminum matrix composites (AMCs) have attracted the interest of many researchers in the past few years. In this study, Fe₅₀Cr₂₅Mo₉B₁₃C₃ metallic glass (FMG) particles reinforced 7075 aluminum matrix (Al-7075) composites were prepared by spark plasma sintering (SPS) technique. The microstructure of the composites showed good interface bonding between the FMG particles and the matrix. The micro-hardness of the composite with 30 vol% FMG particles reached 160.63 HV, which was increased by 30% compared with that of Al-7075 (119.3 HV). The ultimate compression strength (UCS) of the composite was also improved significantly from 596 MPa for Al-7075 matrix to 749 MPa for the composite reinforced with 30 vol% FMG particles, and the compression strain of the composite reached 22%. These results indicate that the mechanical properties of the composites can be enhanced by adding high volume fraction FMG particles. The enhancement of the strength is resulted from multiple strengthening mechanisms, and the main contributions come from the thermal mismatch and grain refinement.     

Microstructure and some mechanical properties of fly ash particulate reinforced AA6061 aluminum alloy composites prepared by compocasting

Fly ash has gathered widespread attention as a potential reinforcement for aluminum matrix composites (AMCs) to enhance the properties and reduce the cost of production. Aluminum alloy AA6061 reinforced with various amounts (0, 4, 8 and 12 wt.%) of fly ash particles were prepared by compocasting method. Fly ash particles were incorporated into the semi solid aluminum melt. X-ray diffraction patterns of the prepared AMCs revealed the presence of fly ash particles without the formation of any other intermetallic compounds. The microstructures of the AMCs were analyzed using scanning electron microscopy. The AMCs were characterized with the homogeneous dispersion of fly ash particles having clear interface and good bonding to the aluminum matrix. The incorporation of fly ash particles improved the microhardness and ultimate tensile strength (UTS) of the AMCs.     

微纳米SiO2/PP复合材料增强增韧的实验研究

为了研究无机刚性颗粒对通用塑料聚丙烯 (PP) 的力学性能的影响, 采用熔融共混方法制备了经硅烷偶联剂A-151处理的SiO₂/PP 复合材料, 并通过其缺口冲击、 拉伸、 弯曲试验和冲击断面的形貌观察, 分析研究了微纳米SiO₂颗粒大小、 填充量、 表面改性以及不同颗粒大小SiO₂混合物对PP复合材料增韧、 增强效果的影响。实验结果表明: 纳米SiO₂的加入可以同时改善其韧性、 刚性和强度; 填充量相同, 颗粒越细, SiO₂/PP复合材料的力学性能越好。SiO₂经改性后填充到PP基体中, 明显改善了颗粒在基体中的分散性及基体与颗粒之间界面结合性能, 使复合材料的综合力学性能得到提高。不同颗粒大小的SiO₂混合后填充到PP基体中, 混合SiO₂的协同效应使复合材料拉伸、 弯曲性能进一步提高, 对PP基体具有更好的增强效果, 但其冲击性能下降。      

Microstructure and Mechanical Properties of B4C/6061Al Nanocomposites Fabricated by Advanced Powder Metallurgy

In this study, B₄C/6061Al nanocomposites reinforced with various volume fractions of nano‐sized B₄C particles (B₄C/6061Al NCs) are successfully fabricated by a powder metallurgy route consisting of spark plasma sintering (SPS) and hot extrusion and rolling (HER). The microstructure evolution, phase composition, and mechanical properties of B₄C/6061Al NCs are experimentally investigate. The results show that nearly fully dense (maximum ≈99.21%) as‐SPSed NCs can be fabricated, and this can be attributed to joule heating at the particle contacts and tip spark plasma at the gaps. Nanosized B₄C particles mainly distributed in the 6061Al particles boundaries and formed inhomogeneous network materials in as‐SPSed NCs, while B₄C particles distributed relatively homogeneously in the 6061Al matrix after HER. No new phases are found in the B₄C/6061Al NCs over three deformation stages. The pin effect of the nanosized B₄C can suppress dynamic recovery and improve the driving force for dynamic recrystallization. The mechanical properties are further improved after HER, and the maximum ultimate tensile strength and yield strength for as‐rolled NCs are 305 and 168 MPa. The strengthening mechanisms mainly included load transfer strengthening, dislocation strengthening, Orowan strengthening, and fine‐grain strengthening.

     

搅拌摩擦加工制备颗粒增强铝基复合材料的研究现状及展望

铝合金作为现代工程和高新技术领域发展的关键材料之一,具有密度小、比强度和比刚度高、耐蚀性好等特点。通过在铝基体中添加增强相颗粒,制备得到的颗粒增强铝基复合材料既有铝合金良好的强度、韧性、易成形性等特点,又有颗粒的高强、高模等优点,是近年来应用最广的一类金属基复合材料。 目前,制备铝基复合材料的方法主要有粉末冶金法、铸造以及超声波法等,但这些方法在制备过程中需要较高的温度,颗粒与金属基体容易发生不良的界面反应,从而影响界面结合效果,降低复合材料的性能。搅拌摩擦加工(FSP)作为一种新型的固相加工技术,可同时实现材料微观组织的细化、致密化和均匀化。目前,FSP直接法已在铝基复合材料制备方面取得应用,主要是将增强相颗粒通过打盲孔或开槽的方式预置在金属基体内再进行FSP,进而制备出高致密度的颗粒增强铝基复合材料。因为FSP过程的温度低,颗粒与铝基体不会发生界面反应,所以该方法也被用于制备具有形状记忆效应(SME)的铝基功能复合材料。 近年研究结果表明,颗粒相对FSP制备的铝基复合材料晶粒细化起到显著作用,这有助于提高复合材料的拉伸强度、显微硬度及疲劳强度等力学性能。随着颗粒含量的增加和颗粒尺寸的减小,复合材料的力学性能得以增强。再者,减小颗粒尺寸有利于改善颗粒与基体之间的结合。另外,通过优化搅拌头的结构、形状和尺寸,以及FSP工艺参数,已经可以实现加工后颗粒相在基体中的均匀分布。 鉴于搅拌摩擦加工(FSP)直接法在制备颗粒增强铝基复合材料方面所具备的短流程、高效能以及基体与增强相颗粒界面无杂质等优势,本文对目前FSP直接法制备颗粒增强铝基复合材料的最新研究现状进行了总结。主要综述了FSP制备颗粒增强铝基复合材料过程中颗粒的含量、类型及尺寸对复合材料组织与力学性能的影响,并对颗粒分布均匀性以及颗粒与铝基体的界面问题做了阐述。文章最后深入分析了当前研究中的不足之处并展望了未来的研究方向。     

颗粒增强铜基复合材料的研究进展

为了研究颗粒增强相对铜基复合材料的性能的影响,对不同类型铜基复合材料的特点及其制备方法进行对比分析,探讨了颗粒相的生成机制,重点论述了颗粒增强相的类型及铜基复合材料的制备工艺.结果表明在铜基体中引入纳米分散相进行复合,可以使铜合金的力学性能得到极大改善,其中机械合金化和原位复合化学反应获得的纳米陶瓷颗粒在铜基复合材料中效果最佳;反应喷射沉积成型法、液相反应原位生成法和机械合金化法在制备纳米粒子增强铜基复合材料方面有着良好的应用前景.     

纳米颗粒分布对镁基复合材料强化机制的影响

Orowan强化、 热错配强化和Hall-Petch强化是纳米颗粒增强镁基复合材料的主要强化机制, 纳米颗粒在基体中的分布状态对起主导作用的强化机制具有重要影响。本文中对现有强化机制模型进行了适当修正, 以纳米SiC颗粒增强AZ91D复合材料为例, 通过理论计算分析了纳米颗粒完全分布于晶内、 完全分布于晶界、 在晶内晶界上均有分布的三种状态对镁基复合材料屈服强度的影响, 并与实验结果进行对比。结果表明: 颗粒完全分布于晶内时, 增强效果最好, 主要增强机制为Orowan强化; 颗粒完全分布于晶界上时, 增强效果最差, 主要增强机制为Hall-Petch强化。颗粒在晶内晶界上均有分布时, 多种强化机制共同发挥作用, 增强效果随着晶内与晶界上颗粒比例的减小而逐渐减弱。     

Synthesis and characterization of in situ formed titanium diboride particulate reinforced AA7075 aluminum alloy cast composites

In situ fabrication of aluminum matrix composites (AMCs) has gathered widespread attention of researchers due to inherent advantages over ex situ methods. Aluminum alloy AA7075 reinforced with various amounts (0, 3, 6 and 9 wt.%) of TiB₂ particles were prepared by the in situ reaction of inorganic salts such as K₂TiF₆ and KBF₄ to molten aluminum. X-ray diffraction patterns of the prepared AMCs clearly revealed the formation of TiB₂ particles without the presence of any other intermetallic compounds. The microstructures of the AMCs were studied using optical and scanning electron microscopy. The in situ formed TiB₂ particles were characterized with uniform distribution, clear interface, good bonding and various shapes such as cubic, spherical and hexagonal. The formation of TiB₂ particles enhanced the microhardness and ultimate tensile strength (UTS) of the AMCs.     

颗粒增强镁基复合材料的研究现状及发展趋势

综述了颗粒增强镁基复合材料的研究概况,着重介绍了颗粒增强镁基复合材料的制备技术,界面行为和制备热力学与动力学三大研究热点,另外,对颗粒增强镁基复合材料的增强机理及常温力学性能作了简单介绍,最后,对颗粒增强镁基复合材料的研究方向进行了一些看法和展望,指出原位颗粒增强镁基复合材料的制备技术交城为制备镁基复合材料的发展趋势,镁基复合材料由于具有高的比强度,比模量和良好的耐磨性、耐高温性能和减震性能,在航空航天,特别是汽车工业具有在的应用前景和广阔的市场。     

Recent progress in graphene-reinforced aluminum matrix composites

Recent years witnessed a growing research interest in graphene-reinforced aluminum matrix composites(GRAMCs).Compared with conventionalreinforcements of aluminum matrix composites(AMCs),graphene possesses manyattractive characteristics such as extremely high strength and modulus,unique self-lubricating property,high thermal conductivity(TC)and electrical conductivity(EC),andlow coefficient of thermal expansion(CTE).A lot of studies have demonstrated that theincorporation of graphene into Al or Al alloy can effectively enhance mechanical andphysical properties of the Al matrix.The purpose of this work is aimed to trace recentdevelopment of GRAMCs.Initially,this paper covers a brief overview of fabricationmethods of GRAMCs.Then,mechanical,tribological,thermal and electrical properties ofrecently developed GRAMCs are presented and discussed.Finally,challenges andcorresponding solutions related to GRAMCs are reviewed.     

Effects of particle size and distribution on the mechanical properties of SiC reinforced Al-Cu alloy composites

This paper studied the combined effects of particle size and distribution on the mechanical properties of the SiC particle reinforced Al-Cu alloy composites. It has been shown that small ratio between matrix/reinforcement particle sizes resulted in more uniform distribution of the SiC particles in the matrix. The SiC particles distributed more uniformly in the matrix with increasing in mixing time. It has also been shown that homogenous distribution of the SiC particles resulted in higher yield strength, ultimate tensile strength and elongation. Yield strength and ultimate tensile strength of the composite reinforced by 4.7 μm sized SiC particles are higher than those of composite reinforced by 77 μm sized SiC particles, while the elongation shows opposite trend with yield strength and ultimate tensile strength. Fracture surface observations showed that the dominant fracture mechanism of the composites with small SiC particle size (4.7 μm) is ductile fracture of the matrix, accompanied by the “pull-out” of the particles from the matrix, while the dominant fracture mechanism of the composites with large SiC particle size (77 μm) is ductile fracture of the matrix, accompanied by the SiC particle fracture.     

无机颗粒增强聚合物基复合材料耐磨性能影响因素研究进展

为了更好地指导无机颗粒增强聚合物基耐磨复合材料的优化设计,全面回顾了复合材料各组分对复合材料耐磨性能的影响。根据复合材料组成,将无机颗粒增强聚合物基复合材料耐磨性能影响因素分成5类:纳米/微米无机颗粒填充量、纳米/微米填充颗粒粒径、不同粒径无机颗粒的级配、无机颗粒与纤维的协同增强和无机颗粒表面处理。从能量角度,即各因素对材料内部结合键的断裂所吸收的外部冲击功和摩擦功的影响,分析了各因素对复合材料耐磨性能的影响。在回顾前两个因素对复合材料耐磨性影响时,发现都存在使材料耐磨性能最佳的最佳颗粒填充量和最佳颗粒粒径。对于微米颗粒(粒径50μm),颗粒填充量比粒径对复合材料耐磨性能影响更大,应尽可能提高颗粒最佳填充量。对于纳米颗粒,颗粒粒径则是影响材料耐磨性能的关键因素,应尽可能降低最佳颗粒粒径。另外,颗粒的表面改性和级配都能通过提高颗粒最佳填充量和综合力学性能来提高复合材料的耐磨性能。无机颗粒与纳米纤维的混杂填充使复合材料同时具备最优的耐磨性能、摩擦系数以及优异的变载荷适应性。     

Discontinuously-reinforced aluminum matrix composites

This article reviews the literature relating to aluminum matrix composites reinforced by ceramic particles, short fibers or whiskers. The main reinforcements which have been used are presented with respect to their nature, morphology and mechanical behavior. The influence of matrix alloying elements on ceramic-metal compatibility is discussed. Most fabrication techniques which have been proposed are described and particular attention is paid to the methods suitable for large scale production. The mechanical characteristics of this kind of composite are reported and compared in relation to processing parameters. Finally, models giving a rough prediction of the mechanical behavior of the composites are discussed.     

Aluminum Dross Particles as Cost Effective Reinforcement for Aluminum Composites

In this work, the potential of Finely powdered aluminum dross by-product (d₅₀ = 67 (μm) as a cost effective reinforcement in discontinuously reinforced aluminum matrix composites (A356) was investigated on the basis of quality-cost modeling. Using a standard rheocasting procedure, samples of composite material were obtained consisting of 20 vol.% of as-received and laboratory processed grades of dross particles which differed mainly in particle size and level of impurities.

Inspection of the tensile properties of these different composite materials showed that a slight improvement in strength over the unreinforced matrix is achievable only by the introduction of fine dross particles with an average particle size less than 10 μm. In composites with larger dross particles the strengthening effect was not observed. In contrast, evaluation of the wear properties demonstrated that the introduction of coarse and as-received dross particles in an aluminum matrix results in a significant improvement in the wear resistance of the composite material. However, in that case, there is a sacrifice in strength. Quality-cost modeling of these two grades of dross reinforced aluminum based composites indicates that both may be applicable for some less critical engineered and wear resistant components, with possible widespread application in the transportation industry.     

Mechanical and tribological behaviour of tungsten carbide reinforced aluminum LM4 matrix composites

Aluminum-based metal matrix composites (AMCs) play a vital role for potential applications in aerospace and automotive industries. This paper explores the experimental analysis of a composite with aluminum LM4 alloy as the matrix and tungsten carbide (WC) as the reinforcement material. The composite specimens were fabricated by the stir casting process. The reinforced ratios of 5, 10 and 15?wt.% of WC particulates were stirred in molten aluminum LM4 alloy (AALM4). Once the composite is solidified, the specimens are prepared to the required ASTM dimensions and tested for various mechanical properties such as tensile strength, impact strength and hardness. Moreover, the tribological behavior of the composite was studied using the pin-on-disc wear test apparatus. X-ray diffraction (XRD) analysis was conducted to analyze the various elements present in the composites. Finally, the scanning electron microscope (SEM) analysis reveals the uniform distribution of WC particles in Aluminum LM4 alloy matrix. The improvement in mechanical properties – hardness, impact strength and tensile strength – was achieved for the increase in the addition of wt.% of WC particles in the LM4 matrix. The decrease in mass loss was observed for the composite containing 15?wt.% of WC during the wear test among the various composites tested.     

Al2O3颗粒增强纯铝基复合材料的研究

本文探讨了用粉末冶金法,采用常规的冶金加工设备和工艺,制造Al₂O₃颗粒增强纯铝基复合材料的可行性。研究了不同Al₂O₃体积含量复合材料的显微组织及力学性能。初步试验了二次热挤压变形对颗粒分布和对基体强化的影响。结果表明,Al₂O₃颗粒与纯铝粉混合,加压烧结制备的复合材料,组织致密,颗粒分布均匀,随Al₂O₃含量增加,复合材料强度、硬度及弹性模量大大提高,Al₂O₃含量小于10%时,塑性不降低。二次热挤压有助于提高颗粒分布的均匀性;并使基体显著强化。