Characterization of ZrC reinforced AA6061 alloy composites produced using stir casting process

In the present study, effect of ZrC vol.% on mechanical properties of AA6061 metal matrix composites (MMCs) produced via stir casting technique was investigated. The vol.% of ZrC particles was varied as 5,10 and 15. The composites were characterized for its microstructure and mechanical properties and their relationships were obtained. The scanning electron microscope (SEM) images revealed uniform distribution and good bonding between the AA6061 alloy and the ZrC particles. The mechanical properties of the AA6061 alloy was found to significantly improve with the addition of ZrC particles from 5 to 15 vol.%, the hardness increased from 32 to 68 HV, yield strength increased from 50 to 86 MPa and the ultimate tensile strength increased from 118 to 165 MPa. However, the % of elongation of the composite samples decreased with 15 vol.% addition of ZrC particles. Sliding wear behaviour of the composites was investigated using a pin-on-disc wear tester at a load of 9.8 N and addition of ZrC particles was significantly found to reduce the wear rate of AA6061 alloy.

     

Characterization & evaluation of Al7075 MMCs reinforced with ceramic particulates and influence of age hardening on their tensile behavior

Aluminium has a massive demand in the areas of automobile, aerospace and diverse engineering applications in order to furnish the requirement in those fields. But this technological evolution needs something more than aluminium. Materialogists are struggling hard to find out a material which owns sound mechanical and thermal properties and also superior than aluminium in each extent. Metal matrix composite (MMC) is a solution. Generally, metal matrix composites contain a low density material, i.e. aluminium or magnesium, reinforced with fibers or particulate of a ceramic material, i.e. silicon carbide or graphite. They show greater specific strength, high stiffness, elevated operating temperature, and superior wear resistance, along with the possibility to customize these properties for a specific use. In this study, Al 7075 is taken as a base matrix material, whereas ceramic materials like SiC, Al₂O₃, B4C and TiB₂ are used as reinforcements. There are different methods available for fabricating metal matrix composite materials and in this work, stir casting technique, which is a liquid state process, is used. Four different MMC specimens were produced with 15 % SiC, 15 % Al₂O₃, 15 % B4C and 15 % TiB₂. Mechanical properties i.e. tensile strength, hardness, and impact strength were studied for the prepared specimens. The results were charted and presented graphically to describe these materials characteristics.     

Fabrication of copper–TiC–graphite hybrid metal matrix composites through microwave processing

The significant requirements such as wear resistance and better tribological properties in addition to good electrical conductivity necessitate the development of copper-based advanced metal matrix composites for electrical sliding contact applications. Though the addition of graphite to copper matrix induces self-lubricating property, the strength of the composite reduces. The improvement in the strength of the composite can be achieved by reinforcing harder ceramic particles such as SiC, TiC, and Al₂O₃. In this paper, the development of hybrid composite of copper metal matrix reinforced with TiC and graphite particles through microwave processing was investigated. The effects of TiC (5, 10, and 15 vol.%) and graphite (5 and 10 vol.%) reinforcements on physical and mechanical properties of microwave-sintered copper–TiC–graphite hybrid composites are discussed in detail. Micrographs show the uniform distribution of reinforcements in copper matrix. Microwave-sintered composites exhibited higher relative density, sintered density, and hardness compared with conventionally sintered ones.     

B4C/6061Al复合材料焊接接头组织与力学性能研究*

基于碳化硼中¹⁰B同位素优良的热中子吸收能力,铝基碳化硼复合材作为中子吸收材料越来越多的应用于核电站中。但碳化硼颗粒的加入使该材料的可焊性变差,因此研究其焊接行为变得十分必要。采用钨极氩弧焊(Tungsten inert gas,TIG)和搅拌摩擦焊(Friction stir welding,FSW)对体积分数为30%的B₄C/6061Al复合材料进行焊接,研究不同焊接方法、焊缝填充材料对复合材料对接接头微观组织及力学性能的影响。B₄C/6061Al复合材料焊接接头拉伸性能如下：FSW焊>TIG焊(Al-Si焊丝)>TIG焊(6061Al焊丝)>TIG焊(6061Al-Mg焊丝)>TIG焊(无填充)。TIG焊缝区容易产生气孔、B₄C颗粒分布不均匀及有害生成相是导致其力学性能不佳的主要原因。FSW可以有效避免基体金属与增强相的高温化学反应,使得焊缝区的晶粒细化,增强相颗粒的分布比TIG焊均匀,为30%B₄C/6061Al复合材料最佳焊接方法,其接头的室温拉伸强度达247 MPa,为母材强度的85%。     

Effect of Fe2O3 content on microstructure of Al powder consolidated parts via selective laser melting using various laser powers and speeds

In situ constituents were formed inside an aluminium matrix via selective laser melting (SLM) of Al powder mixed with 5, 10, and 15 wt% Fe₂O₃ powder (using various laser powers and speeds), in order to investigate the effect of Fe₂O₃ content on the microstructural characteristics of novel aluminium matrix composites. The unique microstructures such as coralline-like Al–Fe intermetallics were formed by the in situ reaction, being Fe₃Al at first but Al₁₃Fe₄ soon after that. These coralline-like intermetallics were fragmented (under appropriate laser parameters and/or higher Fe₂O₃ contents) and mixed up with Al oxide particles, reinforcing the matrix. The higher Fe₂O₃ increased the formation of other combinations such as Al₂Fe, AlFe, and Fe₃Al as well as metastable Al oxides in addition to equilibrium Al₁₃Fe₄ (Al₃Fe) and stable α-Al₂O₃. A very fine, well-bonded, and homogeneous distribution of hard particles was achieved in high Fe₂O₃ contents, efficiently increasing the hardness and providing an advanced Al matrix composite.     

Mechanical and tribological behavior of the metal matrix composite AA6061/ZrO<Subscript>2</Subscript>/C

This study investigates the influence of zirconium dioxide (ZrO₂) and graphite (C) on the mechanical and tribological behavior of aluminum-based metal matrix composite (AA6061) fabricated through the stir casting. Metal matrix composites (MMC) are prepared with the following weight percentages: 100 % AA; 96 % AA-2 % ZrO₂-2 % C; 88 % AA-6 % ZrO₂-6 % C; 92 % AA-6 % ZrO₂-2 % C; and 96 % AA-2 % ZrO₂-6 % C. The microstructure and the mechanical and tribological behavior are characterized, and their correlations are obtained. Microstructural studies of the MMC reveal a uniform distribution of ZrO₂ and C particles in the AA6061 matrix. The addition of ZrO₂ improves the hardness from 6 % to 12 % (30 HRC to 40.94 HRC) and the ultimate tensile strength from 8 % to 15 % (128 MPa to 166.3 MPa) of the base metal (AA6061). The tribological behavior of wear and the frictional properties of the MMC are also studied by performing dry sliding wear test using pin-on-disc method. Result shows that the minimum and maximum wear rates of MMC are 5 E-9 and 6.2 E-9 (g/mm), respectively, at speed of 850 rpm and constant sliding distance of 1000 m.     

Effect of graphite and granite dust particulates as micro-fillers on tribological performance of Al 6061-T6 hybrid composites

Aluminium and its alloys have an ever growing demand in many industries such as aerospace, automotive due to their high strength to weight ratio and corrosion resistance. Our current work focuses on synthesis and tribological studies of precipitation hardened Al 6061–Gr_p–granite dust hybrid composites. Liquid stir casting technique is used for synthesis, precipitation hardening treatment imparted for maximising the hardness before subjecting to two-body sliding wear tests. The variation of wear for different levels of load, speed and composition along with SEM micrographs of the worn surfaces has been investigated. Hybrid combinations of granite dust (2 wt% and 4 wt%) with graphite (2 wt%) show higher tensile strength, hardness and significantly improved wear resistance as compared to the base alloy.     

Effect of graphene addition and tribological performance of Al 6061/graphene flake composite

Graphene, no wonder has attracted a significant research interest due to its extensive physical properties at its single atomic thickness and 2D morphology. The current studies focus on the role of graphene in reducing the wear and frictional coefficient of Al 6061–graphene-reinforced metal–matrix composites (MMC’s). Reinforcement chosen is 0.3, 0.6 and 0.9 wt% of graphene to investigate the self-lubricating property under dry wear condition and processed through the ultrasonic liquid processor. The dry frictional wear test was carried out using pin-on-disc tribometer to evaluate the effect of graphene content in the composites under various normal load (5, 10, 15 N) and disc sliding speed (0.4, 0.8, 1.2 m/s) conditions. The results show that there is a significant increase in the hardness and wear resistance and a reduction in the coefficient of friction (μ) values compared to pure alloys. Arithmetic mean surface roughness values (R_a), max profile peak (R_p) and max valley depth (R_v) are found to be comparatively lower than the pure alloy. Due to the tribological potential coupled with improved strength and surface roughness values, Al 6061–graphene composite are excellent candidates for all applications where it is subjected to Friction and wear.     

Effect of particle size, forging and ageing on the mechanical fatigue characteristics of Al6082/SiCp metal matrix composites

Addition of inexpensive silicon carbide particulates (SiC_p) in the aluminium alloy matrix results in materials with properties non-obtainable in monolithic materials. The forging process results in improved properties as well as forms a shape of the final product. The age-hardening processes accelerate the coarse hardening process of the composites and improve strength and ductility. The size, morphology and volume fraction are the key controlling factors that control the plasticity and the thermal residual stresses in the matrix and thereby it’s mechanical and fatigue properties. This research paper focuses on the effect of particle size, forging and ageing on the mechanical and fatigue properties of the cast, forged and age-hardened aluminium 6082 (AI6082) reinforced with SiC_p. Al6082 reinforced with three different particle sizes of SiC_p (average particles size of 22, 12 and 3 µm) in the forged and ageing conditions were studied. The samples were characterised by optical microscopy, hardness, tensile and fatigue tests. The forged microstructure shows a more uniform distribution of SiC_p in the aluminium matrix. The addition of SiC_p results in improved tensile strength, yield strength and elastic constants of the composites with reduction in ductility. It also increases the fatigue strength of the composites by increasing the number of cycles required for fatigue failure of the composites for the given value of stress. The results also show considerable improvements in mechanical fatigue properties due to forging and ageing heat treatment of the metal matrix composites     

Effect of microwave heat treating processing on frictional behaviour of aluminium alloy 2900 composites

The sliding wear behaviour of microwave processed, SiC_p and Al₂O_3p reinforced aluminium alloy 2900 and 2024 metal matrix composites prepared by powder metallurgy method was investigated in a pin on disc system. The objective is to determine the effects of novel alloying elements of AA 2900, ceramic addition and microwave aging process on the strength to tribological properties. This composite is evaluated to be an effective replacement for conventionally available AA 2024 composites in brake applications. Compared to conventional heat treating processes, microwave processing used for heat treating the samples is observed to be novel method in improving the strength–microstructural–tribological properties. AA 2900 with 6 wt-% Al₂O₃ exhibited good strength to microstructure relationship with excellent wear characteristics compared to AA 2024 composites which are governed by alloying elements in AA 2900. 2 H aged AA 2900 with 6 wt-% Al₂O₃ sample exhibited good frictional coefficient values with good density and strength characteristics. Hence, it is observed that alloying elements in AA 2900 and microwave processing have enhanced the strength to tribological behaviour where the property enhancement is achieved only through ceramic reinforcements.     

Effect of reinforcement coatings on the dry sliding wear behaviour of aluminium/SiC particles/carbon fibres hybrid composites

Dry sliding wear of an AA 6061 alloy reinforced with both modified SiC particles and metal coated carbon fibres has been studied. SiC particles were used to increase the hardness of the composite while short carbon fibres are supposed to act as a solid lubricant. SiC particles were coated with a silica layer deposited through a sol–gel procedure to increase the processability of the composite and to enhance the particle–matrix interfacial resistance. The metallic coatings on carbon fibres were made of copper or nickel phosphorus which was deposited through an electroless process. The metallic coatings favoured the wetting of the fibres during processing and then dissolved in the aluminium matrix forming intermetallic compounds that increased its hardness. Wear behaviour of AA 6061–20%SiC and AA 6061–20%SiC–2%C was compared with that of the composites with the same reinforcement content but using coated particles and fibres. The influence that the modification of the matrix because of the incorporation of coatings on the reinforcements had on the mild wear behaviour was investigated. The wear resistance of the composites increased when carbon fibres were added as secondary reinforcement and when coated reinforcements were used.     

SiC颗粒增强铝基复合材料的制备及性能

利用粉末冶金法制备出了SiC颗粒增强铝基复合材料(SiCp/Al),研究了SiC颗粒添加量对复合材料布氏硬度、抗拉强度及显微结构的影响。结果表明:SiC颗粒在基体材料中分布均匀,界面清晰;SiCp/Al复合材料的硬度与抗拉强度随SiC颗粒含量的增加先升高后降低,在SiC颗粒添加量为7 Wt%时,硬度与抗拉强度达到最大值,分别为89.4HBS与311MPa。     

Wear behaviour of Al/(Al2O3p+SiCp) hybrid composites

In this study, dry sliding metal–metal and metal–abrasive wear behaviours of the aluminium matrix hybrid composites produced by pressure infiltration technique were investigated. These composites were reinforced with 37 vol% Al₂O₃ and 25 vol% SiC particles and contained up to 8 wt% Mg in their matrixes. While matrix hardness and compression strength increased, amount of porosity and impact toughness decreased with increasing Mg content of the matrix. Metal–metal and metal–abrasive wear tests revealed that wear resistance of the composites increased with increasing Mg addition. On the other hand, abrasive resistance decreased with increasing test temperature, especially above 200 °C.     

Existence of Good Bonding between Coated B4C Reinforcement and Al Matrix via Semisolid Techniques: Enhancement of Wear Resistance and Mechanical Properties

An Al 6061 alloy matrix reinforced with the coated B₄C particles was used for the present study. The cohesion of the reinforcing ceramic particles is poor at temperatures near the melting point of aluminum and leads to inferior mechanical and tribological properties of developed aluminum matrix composites with nonuniform distribution of the reinforcement. The main reason for coating the particles is to improve the bond between the reinforcement and molten alloy and thus to eliminate interfacial reactions. The great enhancement in strength values of the composites in this study can be ascribed to the effective load-bearing capacity of disintegrated B₄C particles that are adherently bonded to the matrix alloy. Homogeneity and reduction in the particle size of B₄C during the extrusion process is evidenced in the microstructural studies.     

Investigations on mechanical and structural aspects of ultrasonic hybrid polymer mixture welding for industrial applications

Two-dimensional C_f/Al composites were fabricated by liquid-solid extrusion following vacuum infiltration technique (LSEVI), and defects were studied and analyzed through optical microscope (OM), scanning electron microscope (SEM), transmission electron microscope(TEM), and the tests of ultimate tensile strength (UTS). Through research, it was found that gas impurities were the main factors to generate hole defects within the 2D-C_f/Al composites, so vacuum level of the test system should be higher than 0.09 MPa. The infiltration of composites would not be sufficient and uniform under the low squeeze pressure of 50 MPa and low squeeze temperature of 590 °C. However, when squeeze pressure was larger than 90 MPa, fiber damage appeared, and macro internal cracks even occurred if it was over 100 MPa. Poor tensile behavior of composites between carbon fibers and matrix might arise because of the inappropriate process parameters. Brittle tensile fracture of composites was observed under the higher preform preheating temperature of 640 °C, and Al₄C₃ was found. Separated fibers and aluminum alloy of tensile fracture might occur under the lower preheating temperature of 580 °C. These defects hindered the improvement of property of C_f/Al composites greatly, and they should be avoided. Through contrast of UTS, internal cracks and poor tensile behavior were the most detrimental factors. Their UTSs were 45 and 117 MPa, respectively, which were less than 120 MPa of matrix. Improved process parameters were used to prepare the 2D-C_f/Al composite, and its defects were seldom found, so UTS of composite was improved 93.3 % than that of matrix.     

Mechanical characterization of jute-basalt hybrid composites with graphene as nanofiller

Natural fibre composites, due to their biodegradable and eco friendly nature, are being explored for potential application in wide areas. But their strengths need to be enhanced. Hybridization of the natural fibres with incorporation of nanofillers helps to tailor the properties of nanofillers, and individual fibers and enhance the properties of resultant composite. The present work aims to explore the mechanical propertis of jute-basalt hybrid composites by incorporating graphene nanofillers of varying concentrations. Basalt, jute and jute-basalt hybrid composites with varying concentrations of graphene (0 wt%, 0.2 wt%, 0.4 wt%, 0.6 wt%, 1 wt%) are prepared. Effect of hybridization of different fibers and influence of graphene on mechanical properties are analyzed. The effect of nature of top and bottom laminates on mechanical properties is also observed. Maximum improvement in tensile strength, flexural strength and hardness is found to be 13 %, 29 % and 55 %, respectively, with hybrid composite containing 1 wt.% graphene compared to hybrid composite without graphene. Impact strength is found to be highest for hybrid composite containing 0.4 wt.% graphene with 17 % increase compared to hybrid composite without graphene.

     

High-Temperature Tribological Behavior of Al-20Si-5Fe-2Ni/ZrB2 Composites

Abstract

In this work, Al-20Si-5Fe-2Ni/ZrB₂ composites with 0–20?wt% ZrB₂ were fabricated by spark plasma sintering. The effects of ZrB₂ content on the microstructure, mechanical properties and high-temperature tribological behavior of the composites were investigated. The results indicate that Si, Al₅FeSi, and ZrB₂ particles are uniformly distributed in the aluminum matrix. The density, hardness, and compressive strength increase with increasing ZrB₂ content. The friction coefficient and wear rate are dependent on the ZrB₂ content and test temperature. At a certain temperature, the friction coefficient increases with an increase in ZrB₂ content, whereas the wear rate shows a reverse trend. Due to the improvement in thermal stability and high-temperature softening resistance, the composite shows improved wear resistance and increased transition temperature from mild wear to severe wear.     

增强体与粉末冶金316L不锈钢的反应性

在316L不锈钢粉中分别添加10％的TiC、WC、NbC、Al2O3、Si3N4五种增强体,研究了各种增强体与不锈钢基体的反应性及对烧结过程的影响。结果表明：TiC、WC、NbC与不锈钢基体有良好的相容性,能均匀分布到不锈钢基体中,可以有效提高其强度,添加TiC的不锈钢还表现出优越的耐腐蚀性;由于Al2O3与基体不锈钢相容性过差,不能发挥增强体的作用,使材料的强度和耐蚀性不良;添加Si3N4的不锈钢在烧结过程中Si3N4发生分解,弥散强化了基体,硅有促进烧结的作用,而氮均匀渗透到不锈钢中,有利于形成高强度的高氮钢,从而使其相对密度、硬度及耐蚀性都高于其他材料。     

Microstructure and High-Temperature Frictional Wear Property of Mo-Based Composites Reinforced by Aluminum and Lanthanum Oxides

In this article, we developed Mo-based composites reinforced with aluminum and lanthanum oxides using a sol-gel method combined with a sintering process and researched the microstructure and frictional wear properties under high-temperature conditions. The microstructure of composites was characterized by α-Al₂O₃ and composite oxide (La_0.62Mo_0.38)AlO₃, which were uniformly distributed in the molybdenum matrix. The composite oxide (La_0.62Mo_0.38)AlO₃ was mainly attached to α-Al₂O₃. The interfaces of α-Al₂O₃/Mo and α-Al₂O₃/(La_0.62Mo_0.38)AlO₃ were well bonded. The α-Al₂O₃ refined the molybdenum grains, increased the relative density and hardness of Mo-based composites, and had an obvious effect on the frictional wear properties of the composites. With increasing α-Al₂O₃ content, the friction coefficient first increased and then decreased, and the wear weight loss decreased continuously. The wear failure mode varied from microcutting to fatigue with increasing α-Al₂O₃ content. The better wear resistance of Mo-based composites, compared to pure molybdenum, was mainly attributed to the characteristics of α-Al₂O₃, such as high microhardness, good morphology, well-bonded phase interface, and high hardness matrix due to the effects of α-Al₂O₃ reinforcement.     

Drilling of hybrid Al-5%SiCp-5%B4Cp metal matrix composites

Hybrid metal matrix composites consist of at least three constituents—a metal or an alloy matrix and two reinforcements in various forms, bonded together at the atomic level in the composite. Despite their higher specific properties (properties/unit weight) of strength and stiffness, the nonhomogeneous and anisotropic nature combined with the abrasive reinforcements render their machining difficult. The work piece may get damaged and the cutting tools experience high wear rates, which may lead to an uneconomical production process or even make the process impossible. This work reports on the drilling of Al-5%SiC_p-5%B₄C_p hybrid composite with high-speed steel (HSS), not expensive PCD, or carbide drills in an attempt to explore the viability of the process. Drilling of Al-5%SiC-5%B₄C composites with HSS drills is possible with lower speed and feed combination. The cutting conditions for minimized tool wear and improved surface finish are identified. Characterization of tool wear and surface integrity are also carried out.