A study of the mechanical behaviour on fibre reinforced hollow microspheres hybrid composites

This paper presents the results of an investigation into the effects of hollow glass microsphere fillers and of the addition of short fibre reinforcements on the mechanical behaviour of epoxy binding matrix composites. Properties like flexural stiffness, compressive strength, fracture toughness and absorbed impact energy, were studied. The specimens were cut from plates produced by vacuum resin transfer moulding having a microsphere contents of up to 50% and with fibre reinforcement up to 1.2% by volume. The tests performed with unreinforced composites show that flexural and compressive stiffness, maximum compressive stresses, fracture toughness and impact absorbed energy decrease significantly with increasing filler content. However, in terms of specific values, both flexural and compressive stiffness and impact absorbed energy increase with microsphere content. The addition of glass fibre produces only a slight improvement in the flexure stiffness and fracture toughness, while increasing significantly the absorbed impact energy. In contrast, the addition of a small percentage of carbon fibres produces an important improvement in both fracture toughness and flexure stiffness, when hybrid composites with 0.9% carbon fibre are compared to unreinforced foam, but did not improved absorbed impact energy.     

Metal fibre reinforced hydroxy-apatite ceramics

The reinforcement of hydroxy-apatite ceramics with metal fibres is discussed. Hastelloy X and FeCralloy fibres were dispersed in hydroxy-apatite powder slurry. The fibre-powder slurries were dried and sieved over a wide aperture sieve. The resulting granules were used for die pressing. Volume fractions used were 10, 20 and 30%. The compacts obtained in this way were isostatically repressed at 4 k bar. These compacts showed considerable strength and toughness. Hot-pressing of the compacts was done at about 1000'C and a pressure between 0.2 and 1.0 k bar for 15 min. The resulting materials were characterized by fractography and strength, fracture toughness, Young's modulus and hardness measurements. Both strength and fracture toughness increased while Young's modulus and hardness decreased with increasing volume fraction of fibres. The strength and fracture toughness of composites containing 20 vol % metal fibres showed an increase of the strength and fracture toughness by a factor of about 2 and 6, respectively, as compared with the strength of about 100 M Pa and a toughness of 1 .0 MPa m^1/2 for the sintered, pure matrix materials. The results obtained are also promising for other metal fibre-ceramic matrix composites.     

构型参数及方式对Al2O3p/高锰钢球形网络复合材料压缩性能的影响

传统的耐磨金属基复合材料普遍存在塑韧性低的问题。对氧化铝颗粒(Al₂O₃p)增强高锰钢复合材料进行球形网络构型设计,研究了构型方式、参数及热处理对复合材料压缩性能的影响。制备了3种构型参数(球径?分别为6 mm、7 mm、8 mm)结合两种构型方式(平行、错落)的Al₂O₃p/高锰钢球形网络复合材料、均匀复合材料和基体材料。结果表明：同构型方式下,随着构型参数(复合区体积分数)的增加,材料的压缩性能降低,其中?6材料的屈服强度、抗压强度和(抗压强度下)应变最佳,相比于均匀复合材料分别提升203.8%、236.1%和134.8%,屈服强度相比于基体材料提升107.5%;同构型参数下,错落排布比平行排布的屈服强度、抗压强度和应变分别提升10.9%、28.5%和16.3%;水韧处理后,错落排布材料的屈服强度降低35.2%,抗压强度提升11.0%,应变提升163.1%。裂纹易在基体区与复合区界面处萌生并进行扩展,基体能够阻碍裂纹的扩展;错落排布增大了复合区的最小间距,提升了塑性。     

Optimizations of wear resistance and toughness of hydroxyapatite nickel free stainless steel new bio-composites for using in total joint replacement

The aim of this work was to produce novel bio-composites made of hydroxyapatite and nickel free stainless steel (prepared by heat treating bone ash) and studying their mechanical properties including their tribology under various loads, toughness, and compressive and bending strengths. Different amounts of nickel free stainless steel powder (30, 40, 50 and 60 wt.%) was added to this hydroxyapatite powder to get bio-composites. Their hardness, wear resistance and friction coefficient, as a function of the metal (nickel free stainless steel) content were investigated. Hardness and wear resistance were decreased by increasing of the weight percentage of stainless steel, while friction coefficient was increased. Strength and toughness of composites increases considerably by increasing of NFSS content. The toughness enhancement is contributed mainly by crack bridging and plastic deformation of the nickel free stainless steel. The strengthening effect is contributed by both the matrix grain refinement and the toughness enhancement. According to results of all mechanical tests done on composites, composite with 50 wt.% nickel free stainless steel has the most appropriate mechanical properties among other composites for using in orthopaedic applications.     

钛氮合金的铸态组织与性能

采用熔铸工艺法制备了含氮量为0.045%～0.27%的原位自生氮化物增强钛基复合材料,分析并测试了合金的铸态组织和力学性能.研究结果表明:在Ti-N合金中,随着氮含量的增加,合金中氮化物的形态和相组成发生了明显的改变;当氮含量在0.045%～0.18%时,合金的基体为α-Ti,增强相为TiN0.3;氮含量增加到0.225%时,增强相转变为块状Ti2N;复合材料的硬度、抗压强度和弹性模量均高于纯钛基体且随着氮含量的增加而增加;当增强相由TiN0.3转变为Ti2N时,抗压强度显著增加;由压缩断口分析可知,基体为韧性断裂,随着氮含量增加合金由韧窝 解理断口向具有解理特征的脆性断裂转变.     

Influence of grain refining elements on mechanical properties of AISI 430 ferritic stainless steel weldments – Taguchi approach

The effect of grain refining elements such as copper, titanium and aluminum on transverse tensile strength, ductility, impact toughness, microhardness and austenite content of AISI 430 ferritic stainless steel welds through Gas Tungsten Arc Welding (GTAW) process in as-welded condition was studied. Taguchi method was used to optimize the weight percentage of copper, titanium and aluminum for maximizing the mechanical properties and austenite content in the weld region of ferritic stainless steel welds. Based on Taguchi orthogonal array the regression equations were developed for predicting the mechanical properties of ferritic stainless steel welds within the range of grain refining elements. The observed mechanical properties and austenite content have been correlated with microstructure and fracture features.     

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。     

真空退火对原位Al2O3/Fe-Cr-Ni增强复合材料性能的影响

铁铬镍合金具有良好的高温强韧性和抗蠕变性,被广泛应用于制造航空发动机、工业燃气轮机等设备。利用原位合成和热压烧结工艺制备Al2O3/Fe-Cr-Ni复合材料。为减少脆性相对复合材料性能的影响,将热压烧结试样在1000℃下真空保温2h后退火。采用XRD和SEM等测试方法,研究热处理后Al2O3/Fe-Cr-Ni复合材料的微观结构和常温力学性能。结果表明:Al2O3/Fe-Cr-Ni复合材料主要由Fe-Cr-Ni合金相、Fe-Cr相和Al2O3陶瓷增强相组成。热压烧结试样的维氏硬度、抗弯强度和断裂韧度分别为4.16GPa、298.31MPa和8.04MPa·m1/2。经1000℃高温热处理后,复合材料中Fe-Cr相发生奥氏体转变和合金基体晶粒长大,导致硬度下降至2.98GPa。Fe-Cr-Ni合金基体中韧性相含量和基体连续性增加,使该复合材料的抗弯强度和断裂韧度明显上升,其值分别为459.33MPa和12.81MPa·m1/2。     

Microstructure and mechanical behavior assessment of Al–Cu composites fabricated through stir casting

In this work, Al–Cu composite metallic materials are produced by dispersing copper particulates in an aluminum matrix using stir casting technique. In order to know the effect of reinforcement content, composites with varying weight fractions were fabricated. For comparison purpose, Al–Cu alloy is also fabricated and investigated. Increased densities have been observed with increasing particulate contents. Homogenization treatment has improved the hardness to a larger extent for both alloy and composites, particularly for rich composites. Composite with lean mixture of reinforcements has shown improvement in specific strength, whereas drop in specific strength has been observed for rich mixture of reinforcements. However, hardness is improved from 5% to 15% reinforcement content. Drop in strain has been observed for higher reinforcement composites. Response to cold upsetting is noticeable for lean composite which is on par with the alloy.     

Effect of Al(OH)<Subscript>3</Subscript> Particle Fraction on Mechanical Properties of Particle-Reinforced Composites Using Unsaturated Polyester as Matrix

The effect of particle fraction on mechanical properties of particle-reinforced composites was studied using tensile and hardness testing. Unsaturated polyester (UP) was used as polymer matrix, and aluminum hydroxide as the reinforcing particles. The fracture morphology of tensile samples was observed by scanning electron microscopy (SEM). The results showed that the tensile strength and absorbed energy increased to a maximum at 10% particle content and then decreased. With increasing content of aluminum hydroxide, the elastic modulus increased, and the fracture elongation decreased. The SEM showed that the failure of the Al(OH)₃/UP composites was one of macroscopically brittle fracture. In addition, the study showed that appropriate amount of filler can enhance the surface hardness of Al(OH)₃/UP composite.     

Interpenetrating Microstructure and Properties of Si3N4/Al–Mg Composites Fabricated by Pressureless Infiltration

Si₃N₄/Al–Mg composites based on Al–Mg alloy reinforced by ceramic interpenetrating network structure were fabricated via pressureless infiltration technology. Infiltration temperature and infiltration time are the key parameters distinctly effecting on infiltration processes. Moreover, the increasing of Mg content (2–8 wt.%) resulted in an increased amount of infiltration. Microstructural characterization of the composites reveals a special topology of skeleton and good integrity of metal/ceramic interface. The presence of second reinforced phase results in a significant increase in 0.2% offset yield and ultimate tensile strength of composites materials. However, when the volume fraction of reinforcement is large than 6%, there are a distinctly reduction of strength. The presence of additional secondary brittle phase in matrix results in the reduction in ductility and increase in hardness of 3-DNRMMCs. The failure features as cracking and void in reinforcement, interface cracking and interface debonding as well as matrix damage result in the decreases of fracture toughness. With the increases of volume fraction of reinforcement, 3-DRMMC exhibits excellent wear-resistance property.     

Combustion synthesis and mechanical properties of molybdenum disilicide composites reinforced with SiC particulate

Intermetallic composites of molybdenum disilicide reinforced with silicon carbide were produced by combustion synthesis of the elemental powders. The combustion reaction was initiated near 700°C and completed within a few seconds. The end product was a porous composite which was subsequently hot pressed to >97% theoretical density. The grains of the matrix were 8–14 m in size surrounded by SiC particulate reinforcement of 1–5 m. The mechanical properties of the composites improved with increasing SiC reinforcement. The hardness of the materials increased from 10.1 GPa to 12.7 GPa with the addition of 20 vol% SiC reinforcement, while the strength increased from 195 MPa to 299 MPa. The fracture toughness also increased from 2.79 MPa m1/2 to 4.08 MPa m1/2 with 20 vol% SiC. © 1998 Chapman & Hall     

Fracture behavior and microstructure of steel fiber reinforced cast iron

In this study, improvement of fracture toughness and strength of gray cast iron by reinforcing steel fiber was investigated. Three point bend specimens were used to calculate the flexural strength and fracture toughness. Fracture toughness of the reinforced cast iron with two distinct volume fraction (Vf = 0.05 and 0.08) were calculated by compliance method and J-integral method using single specimen technique. The study shows that fiber reinforced composite has higher fracture toughness and flexural strength than cast iron without reinforcement. Also, fracture toughness increases with increasing volume fraction of reinforcement. Optical and scanning electron microcopy (SEM) analyses were used to examine the microstructure and fracture surface. It is noted that the carbon diffuses from gray cast iron to steel fiber and graphite free transition regions with high hardness were observed due to the carbon diffusion.     

碳纳米管含量对铝基复合材料力学性能的影响

采用搅拌摩擦加工技术制备了多壁碳纳米管增强铝基(MWCNTs/Al)复合材料,研究了碳纳米管含量对复合材料力学性能的影响规律。结果表明,MWCNTs的添加对铝基复合材料的力学性能影响显著,随着MWCNTs含量的增加,MWCNTs/Al复合材料的硬度、弹性模量、强度都逐渐提高;当碳纳米管含量为6.6%(体积分数)时,复合材料强度达218 MPa,为基体材料的2.24倍;随MWCNTs含量的增加,MWCNTs/Al复合材料的塑性逐渐变差,拉伸延伸率逐渐降低,断口韧窝逐渐变小、变浅。     

凝胶注模成型技术制备氧化石墨烯/HA复合材料的研究

以氧化石墨烯和纳米羟基磷灰石(HA)粉体为原料,采用凝胶注模成型技术制备了氧化石墨烯/HA复合材料。研究了有机单体、浆料固相含量和石墨烯含量对氧化石墨烯/HA浆料粘度的影响,观察了陶瓷浆料的凝胶固化过程并测量了固化后生坯的密度和抗压强度,分析了氧化石墨烯含量对烧结后复合材料抗弯强度和断裂韧性的影响,观察了试样断口的显微组织。研究结果表明,有机单体含量为15%(质量分数,下同),固相含量为45%,氧化石墨烯含量为1.5%时,氧化石墨烯/HA浆料的粘度最佳,为362.9mPa·s,浆料的分散性良好,固化后生坯具有较高的密度和抗压强度。随氧化石墨烯含量的增加,复合材料的抗弯强度和断裂韧度均先增加后降低。当氧化石墨烯含量为1.5%时,1 150℃烧结样品的抗弯强度为81.5MPa,断裂韧性为1.52MPa·m1/2,分别比HA基体提高了151.8%和74.7%,因此添加氧化石墨烯后的HA复合材料的力学性能更佳。     

Effect of metal volume fraction on the mechanical properties of alumina/aluminum composites

The influence of metal volume fraction on the mechanical properties of Al₂O₃/Al composites with constant diameter of metal ligaments was studied. Alumina/aluminum composites with interpenetrating networks and metal content between 12 and 34 vol.% were fabricated by gas-pressure infiltration technique. The fabricated composites exhibited good mechanical properties, e.g. the bending strength of 740 MPa for samples containing 12 vol.% of Al. The bending strength of the composites decreased with increasing volume fraction of metal phase. High strength of the fabricated composites was explained by strong interfacial bonding between alumina and aluminum. The fracture toughness of the composites increased, however, with increasing volume fraction of aluminum. The highest fracture toughness values of 6 MPa m were measured for the composites containing 25 vol.% of Al. Fractographic analysis of fractured surfaces showed deformed metal ligaments which demonstrated that crack bridging by plastic deformation of the metal phase is the main toughening mechanism in Al₂O₃/Al composites.     

Mechanical properties of novel aluminum metal matrix metallic composites: Application to overhead conductors

The mechanical behavior and microstructural evolution of aluminum metal matrix metallic composites fabricated under various process conditions were investigated to understand their process-structure–property relations. The novel techniques for arranging the matrix and reinforcement materials and controlling the processing atmosphere were applied to the extrusion process. The composites were comprised of matrix 1050 and reinforcement 6061 aluminum alloys with varying percent weight compositions and were arranged in a tailorable concentric annular pattern. The composites were shown to substantially increase compressive strength when the atmosphere of composite arrangement was evacuated prior to extrusion. Mechanical response of the composites were compared to the pre-extruded 1050 and 6061 aluminum alloys. The yield strengths of each composite, with varying percent weight compositions, were found to lie between those of matrix and reinforcement alloys, and abided by a simple rule-of-mixtures when considering weight composition. Highly elongated grains were oriented in the as-extruded composites along the extrusion direction and grains near the interface between two constituent alloys showed higher aspect ratio than in the interior region. The present study could lead to the optimum composite design for various industrial applications including all aluminum alloy overhead conductors with high strength and improved electric conductivity.     

Fracture behaviour of boride-dispersed composites fabricated by hot-pressing amorphous Ni60Mo30B10 powder

Microstructural and mechanical property characteristics were investigated for three boride-dispersed composites fabricated by hot-pressing amorphous Ni60Mo30B10 powder. The first composite was tested in the as-hot-pressed condition (HP) whilst the other specimens were subjected to a solution treatment (ST) and further ageing (STA). X-ray diffraction showed the HP and ST composites to consist of Mo2NiB2 particles in a Ni-rich matrix whilst the STA material contained Mo2NiB2 particles in a NiB3Mo matrix. The hardness and fracture toughness decreased and increased, respectively, for the ST material compared to the HP case whilst the STA case showed increased and decreased hardness and fracture toughness, respectively, compared to the ST composite. These results were explained in terms of the brittle–ductile–brittle fracture modes for the HP–ST–STA specimens. In addition, the HP specimen showed only a 15% decrease in compressive strength at 973 K compared to 303 K.     

Physico‐mechanical characterization of garnet and fly ash reinforced Al7075 hybrid composite

The aim of present work was to study the effect of adding garnet and fly ash on the physical and mechanical performance of Al7075 hybrid composites. Al7075 hybrid composites reinforced with varying weight percentage (0 wt.%–15 wt.%) of each of garnet and fly ash were fabricated and characterized for the comparative assessment of their physical and mechanical properties. The physical and mechanical tests such as void content test, hardness test, tensile strength test, impact strength tests, flexural and fracture toughness test were performed for both garnet and fly ash reinforced composites. The finding of results indicated that the addition of 0 wt.%–15 wt.% of garnet increased the void content, hardness, flexural strength, tensile strength, impact strength and fracture toughness in the range of 1.01 %–2.69 %, 33 HRB–88 HRB, 165 MPa–275 MPa, 205 MPa–263 MPa, 12 J–22 J and 0.11 MPa ? m^1/2–0.58 MPa ? m^1/2 at crack length 0.1 respectively whereas addition of 0 wt.%–15 wt.% of fly ash increased the void content, hardness test, flexural strength, tensile strength, impact strength and fracture toughness in the range of 1.010 %–1.351 %, 33 HRB‐80 HRB, 165 MPa–225 MPa, 205 MPa–236 MPa, 12 J–20 J, 0.11 MPa ? m^1/2–0.48 MPa ? m^1/2 at crack length 0.1 respectively. Apart from the economic concern and void issue, Garnet indicated better choice of reinforcement as compared to fly ash in terms of mechanical properties.     

Microstructure and Mechanical Properties of Si_3N_4 Composites Containing SiC Platelet

Hoppressed Si3N4/SiC platelet composites had been investigated with respect to their microstructure and mechanical properties. The results indicate that Vickers hardness, elastic modulus and fracture toughness of the composites were increased by the addition of SiC platelet until the content up to 20 vol pct. A slight decrease in flexural Strength was measured at room temperature with increasing SiC platelet content. The high temperature flexural strength tests at 1150, 1250, and 1350℃ were conducted. It was found that the flexural strength at elevated temperature was degraded with the rising temperature, and the downward trend of flexural strength for the composite containing 10 vol. pct SiC platelet was less. The results indicate that SiC platelet had a positive influence on the high temperature strength. Effects of SiC platelet reinforcement were presented