Influence of addition of Grp/Al2O3p with SiCp on wear properties of aluminum alloy 6061-T6 hybrid composites via friction stir processing

Aluminum alloy base surface hybrid composites were fabricated by incorporating with mixture of (SiC+Gr) and (SiC+Al₂O₃) particles of 20 μm in average size on an aluminum alloy 6061-T6 plate using friction stir processing (FSP). Microstructures of both the surface hybrid composites revealed that SiC, Gr and Al₂O₃are uniformly dispersed in the nugget zone (NZ). It was observed that the addition of Gr particles rather than Al₂O₃ particles with SiC particles, decreases the microhardness but immensely increases the dry sliding wear resistance of aluminum alloy 6061-T6 surface hybrid composite. The observed microhardness and wear properties are correlated with microstructures and worn micrographs.     

真空压力浸渗制备SiCp/AZ91复合材料的显微组织、力学性能和磨损行为

采用真空压力浸透法制备SiC_p/AZ91复合材料,研究其显微组织、力学性能和耐磨性。结果表明,SiC颗粒均匀分布于金属基体中,并与基体界面结合良好。Mg₁₇Al₁₂相在SiC颗粒附近优先析出,SiC与AZ91基体的热膨胀系数失配导致高密度位错的产生,加速基体的时效析出。与AZ91合金相比,SiC颗粒的加入提高了复合材料的硬度和抗压强度,这主要是由于载荷传递强化和晶粒细化强化机制。此外,由于SiC具有优异的耐磨性,在磨损过程中形成稳定的支撑面保护基体。     

Taguchi approach to influence of processing parameters onerosive wear behaviour of Al7034-T6 composites

Taguchi technique was used to predict the influence of processing parameters on the erosive wear behavior Al7034-T6 composite reinforced with SiC and Al₂O₃ particles in different mass fractions. These hybrid metal matrix composites (HMMCs) were fabricated by using a simple technique called stir casting technique. Scanning electron microscope (SEM) was used to study the surface morphology of the composite and its evolution according to processing time. The design of experiment (DOE) based on Taguchi's L₁₆ orthogonal array was used to identify various erosion trials. The most influencing parameter affecting the wear rate was identified. The results indicate that erosion wear rate of this hybrid composite is greatly influenced more by filler content and impact velocity respectively compared to other factors. This also shows the significant wear resistance with the increase in the filler contents of SiC and Al₂O₃ particles, respectively.     

SiC contents and pin temperature effect on tribological properties of Al25Zn/SiC composites

In this investigations, an effect of silicon carbide addition on dry sliding wear behavior of Al25Zn/SiC composites was studied at different temperature, load and sliding speed for a sliding distance of 1400 m using a pin on disc tribometer with EN24 shaft steel disc as per Taguchi L₁₆ orthogonal array. Under equal test situation, highest wear resistance, hardness, tensile strength and lowest coefficient of friction were observed for the composite with 15 wt% of SiC. The pin temperature is identified as the most influencing factor for the wear and friction characteristics of the composites. Regression model and Artificial Neural network model developed were found capable of predicting wear behavior of the composite. The mechanism of wear observed is adhesion, abrasion and delamination.     

Microstructures and properties of graphite and Al2O3 short fibers reinforced Mg-Al-Zn alloy hybrid composites

Graphite and Al2O3 short fibers reinforced Mg-Al-Zn alloy hybrid composites were fabricated by perform squeeze-infiltration route. The effects of the volume of graphite particles on the microstructure, mechanical properties and tr/bological behavior were investigated under the conditions of constant size of graphite particle and volume of Al2O3 short fiber. The results reveal that the uniform distribution of the reinforced graphite particles and Al2O3 short fiber can be obtained by this technique, and they have strong bonding with the metal matrix. Increasing graphite volume results in decrease in hardness, the ultimate tensile strength whereas the Al2O3 short fiber makes contribution to the increase in hardness of the composite. The composite exhibits good wear resistance, small wear mass loss and low coefficient of friction as compared with the metal matrix. The wear mechanisms transit from oxidation wear, abrasion wear into delamination wear as the applied load is increased, and a film of lubricant covering almost entire surface of specimen, is found to be formed, which separates the wear surfaces from metal to metal contact and thus improves the tribological properties.     

Dry Sliding Wear Behavior of a Novel 6351 Al-(Al4SiC4 + SiC) Hybrid Composite

In this research study, the dry sliding wear behaviors of 6351 Al alloy and its composites with single and hybrid reinforcements (ex situ SiC and in situ Al₄SiC₄) were investigated at low sliding speed (1 ms^?1) against a hardened EN 31 disk at different loads. In general, the wear mechanism involved adhesion (coupled with subsurface cracking) and microcutting-abrasion at lower loads. With higher loads, abrasive wear involving microcutting and microplowing along with adherent oxide formation was observed. At higher loads, the abrasive wear mechanism caused rapid wear loss initially up to a certain sliding distance beyond which, by virtue of frictional heat generation and associated temperature rise, an adherent oxide layer was developed at the pin surface, which drastically reduced the wear loss. Moreover, the overall wear rates of all the composites (either single or hybrid reinforcement) were found to be lower than that of the 6351 Al alloy at all applied loads. The ex situ SiC particles were found to resist abrasive wear; while, in situ Al₄SiC₄ particles offered resistance to adhesive wear. Accordingly, the 6351 Al-(SiC + Al₄SiC₄) hybrid composite exhibited the best wear resistance among all composites.     

Centrifugal casting of functionally graded aluminium matrix composite components

Abstract

Centrifugal casting is one of the potential manufacturing techniques used for producing near net shaped components with improved properties. The emergence of new class of functionally graded materials has made it an important technique for the fabrication of engineering components and structures with graded property. The present paper describes the studies carried out on processing and characterisation of functionally graded Al matrix composites components based on Al–SiC ex situ and Al–Si in situ composites. The microstructural and mechanical characteristics of the composites are evaluated. In the case of Al–SiC functionally graded metal matrix composites discs, the particles are segregated gradiently towards the outer periphery of the casting exhibiting high strength and hardness towards the outer periphery. The Al–Si in situ composite cylinder shows the dispersion of primary Si particles towards the inner periphery of the casting which can lead to higher hardness and wear resistance.     

Formation of surface layer based on Al3Ti on aluminum by laser cladding and its compatibility with ceramics

Intermetallic compound Al₃Ti or intermetallic compound matrix composite (IMC) surface layers were formed on Al surface by laser cladding. To form sound IMC surface layers, laser conditions must be controlled to suppress the melting of base metal. With increasing the volume fraction of ceramics in the IMC layer, it needed higher laser power to obtain IMC layer although the control of laser conditions became easier. During laser cladding, TiB₂ melted by laser irradiation and then homogeneously precipitated as fine particles at a cooling stage. On the contrary, TiC and SiC hardly melted and were dispersed in Al₃Ti matrix. SiC reacted with Ti to form titanium-silicide or TiC, which made the composition of matrix richer in Al than Al₃Ti and caused degradation of the wear property. IMC surface layer improved the wear property of Al substrate. The particle size as well as volume fraction of dispersoid ceramics affected the wear property.     

预制块重熔法制备的SiC/Al复合材料的磨损性能研究

本文采用含高体积分数SiC颗粒预制体在高能超声搅拌下加入铝熔体的方法制备SiCP/Al复合材料,研究了复合材料的微观组织特征、硬度和摩擦磨损性能。实验结果表明：高能超声重熔预制块的方法制备的复合材料基体组织形态均匀细小,SiCP颗粒在复合材料中弥散分布,与基体间结合良好;随着SiCP颗粒体积分数的增加,复合材料的硬度上升,耐磨性显著提高。通过对复合材料磨损表面的SEM观察分析表明,在干摩擦条件下,复合材料的磨损机理为微切削磨损和表层剥落及部分粘着磨损的综合作用。     

Property improvement of stainless-steel-base surface composites fabricated by high-energy electron-beam irradiation

This is a study on the fabrication of surface composites of SiC, TiC particulates, and AISI 304 substrate by high voltage electron beam irradiation. Using CaF₂ powders as flux, two kinds of surface composites were fabricated for a comparative analysis of the microstructural modification and mechanical properties. Through the employed process, the powders and substrate surface were melted and surface composite layers were successfully formed in both cases. In the specimen fabricated with SiC powders, a volume fraction of Cr₂₃C₆ particles (−22 vol.%) were homogeneously distributed along solidification cell boundaries. The large amount of Cr₂₃C₆ particles in combination with solid solution hardening of Si in the matrix resulted in the improved hardness and wear resistance of the surface composite layer, that are 2 to 3 times those of the substrate. In the specimen fabricated with SiC and Ti+SiC powders, TiC and Cr₂₃C₆ particles were precipitated without precipitation of SiC.     

Superior Tribological Properties of Particulate Aluminum Matrix Nano Composites

Aluminum is the best metal for producing metal matrix composites which are known as one of the most useful and high-tech composites in our world. Combining aluminum and nano Al₂O₃ particles will yield a material with high mechanical properties. Characterization of tribological properties revealed that the presence of nano particles significantly increased wear resistance of the composite. In case of unreinforced Al alloy, the depth of penetration is governed by the hardness of the specimen surface and applied load. But, in case of Al matrix composite, the depth of penetration of the harder asperities of hardened steel disk is primarily governed by the protruded hard ceramic reinforcement. The hard Al₂O₃ particles act as a protrusion over the matrix, carries a major portion of the applied load and protect the abrasives from penetration into the specimen surface.     

纳米稀土CeO2掺杂对Ni-Fe-Co-P合金镀层性能的影响

利用喷射电沉积技术制备了Ni-Fe-Co-P-CeO_2复合镀层。通过SEM、XRD、EDS等测试了复合镀层的表面形貌、截面形貌、物相结构和组成成分,同时,表征了复合镀层的硬度、耐磨和耐蚀性能,探究和分析了纳米稀土CeO_2颗粒浓度对镀层性能的影响。结果表明:该多元复合镀层为非晶态结构;随着镀液中CeO_2颗粒浓度的增加,复合镀层的显微硬度、耐磨性和耐蚀性均呈先增强后减弱的趋势;镀液中CeO_2颗粒浓度为1 g/L时,复合镀层的表面均匀致密,其HV_(0.1)显微硬度达到最大值5982 MPa,且具有最优的耐磨和耐蚀性能。     

硅含量对TIG焊Al-Si/SiCp复合层包覆A380铝合金显微组织的影响

采用钨极惰性气体（TIG）在铸态A380铝合金表面制备复合涂层。将Al,Si和SiC粉末混合物与硅酸钠溶液混合后涂覆在基材上,采用TIG焊进行表面熔化,在基体表面制备Al-SiC涂层。采用XRD、SEM和EDS研究显微组织的变化,采用显微硬度和滑动磨损试验研究包覆层的性能。结果表明,SiC粒子均匀分布在树枝状的铝基体中。加入过量的硅造成包覆层共晶和粗大硅粒子的形成,从而导致包覆层具有较高的硬度和耐磨性。     

离心铸造自生Zn—Al—Si表面复合材料的组织与性能

采用热膜金属型离心铸造Zn-27Al-5Si合金,获得了内层含大量初晶Si,外层有少量初晶Si,中层为细小共晶Si的表面复合材料,考察了复合材料的组织形貌和复合材料的,吧及模温和转速对组织的影响。结果,随着模温的提高,初晶Si、共晶Si和基体组织变得粗大;随着模转速的增加,初晶Si在内侧富集层厚度减小,初晶Si面积比增大。复合材料的内层由于聚集了大量初晶Si而具有较高的硬度和较优的耐磨性。复合材料的断裂方式为脆性断裂,含共晶Si的中层在断裂中比含块状初晶Si的内层经历了更多的塑性变形。     

Aluminum-silicon carbide coatings by plasma spraying

An aluminum base composite (Al-SiC) powder has been developed for producing plasma sprayed coatings on Al and other metallic substrates. The composite powders were prepared by mechanical alloying of 6061 Al alloy with SiC particles. The concentration of SiC was varied between 20 and 75 vol%, and the size of the reinforcement was varied from 8 to 37 μm in the Al-50 vol% SiC composites. The 44 to 140 μm composite powders were sprayed using an axial feed plasma torch. Adhesion strength of the coatings to their substrates were found to decrease with increasing SiC content and with decreasing SiC particle sizes. The increase in the SiC content and decrease in particle size improved the erosive wear resistance of the coatings. The abrasive wear resistance was found to improve with the increase in SiC particle size and with the SiC content in the composite coatings.     

固溶处理对TiB2/6061复合材料硬度及耐磨性的影响

采用氟盐法制备了TiB₂质量分数为3%的原位合成TiB₂/6061复合材料,研究了固溶温度和固溶时间对复合材料硬度和耐磨性能的影响。结果表明:TiB₂颗粒弥散分布在6061铝合金基体中,明显细化6061铝合金基体晶粒。当固溶温度一定时,随固溶时间延长,复合材料的硬度和耐磨性可获得明显提高,但固溶时间在6~10 h时,复合材料的性能变化不显著。当固溶时间一定时,随固溶温度升高,复合材料硬度和耐磨性呈现先上升后下降的趋势。3wt%TiB₂/6061复合材料经530 ℃×10 h固溶处理后,硬度和耐磨性能最佳,相较于铸态硬度值提高了79.5％,磨损量减少了59.1%。固溶处理后复合材料的磨损表面犁沟变细变浅,材料脱落现象减少。     

超细晶Al5083合金和碳化硼增强Al5083基复合材料的室温和高温干滑动摩擦磨损行为

讨论机械球磨Al5083合金和Al5083?5wt.％B4C复合材料在室温和200°C下的摩擦行为和磨损机制.结果表明,由于常温下的氧化磨损,形成可保护试样表面的机械混合层.在室温和80 N载荷下,Al5083和Al5083?5wt.％B4C球磨样品有磨损迹象,但体积磨损量有限,磨损率分别为5.8×10?7和4.4×1...     

Fabrication and characterization of Al356/SiCp semisolid composites by injecting SiCp containing composite powders

Al356/5 vol.% SiC_p cast composites were fabricated by the injection of reinforcement particles into the melt in three different forms, i.e. as untreated SiC_p, milled particulate Al-SiC_p composite powder, and milled Al-SiC_p-Mg composite powder. The resultant composite slurries were then cast in the semisolid temperature range of the alloy, upon which the effects of the type of injected powder on the distribution and incorporation of the reinforcement particles, along with the hardness of the cast composites, were investigated. Injection of milled composite powders resulted in considerable improvement in SiC_p wetting as well as the incorporation and distribution of SiC_p in the Al356 matrix alloy. Al356/5 vol.% SiC_p composite with well dispersed reinforcement particles of less than 3 μm average diameter was successfully produced by injecting Al-SiC_p-Mg composite powder into the melt. The best microstructural characteristics in terms of the reinforcement incorporation and distribution, and the highest hardness value of the cast composites, were achieved when magnesium was added through the injected composite powder and not directly into the melt.     

铝合金表面化学镀 Ni-Co-P / SiC 复合镀层的组织与性能研究

通过化学镀的方法,在铝合金表面成功地制备了Ni-Co-P/SiC复合镀层。对复合镀层的表面形貌、化学成分、晶态结构、硬度进行了表征分析,通过电化学测试对其耐腐蚀性进行了研究。结果表明:SiC纳米微粒起到了提高Ni-Co-P合金镀层硬度的作用,向镀液中加入12 g/L SiC纳米微粒时,复合镀层的硬度达到最大值524HV;Ni-Co-P/SiC复合镀层能增强铝合金材料的耐蚀性能,镀液中SiC微粒的质量浓度为9 g/L时,复合镀层的耐腐蚀性相对最好。     

Investigation on the constitution and mechanical characteristic of composite containing silicon-carbide produced by electroless co-deposition

The constitution and mechanical characteristics of the composites containing silicon carbide and Ni-P alloy matrix produced by electroless co-deposition were investigated in this article. The experimental results indicate that SiC particles with high hardness obviously strengthen the Ni-P alloy matrix, leading to an increase in both the hardness and surface roughness of the composites in comparison with pure Ni-P alloy. The hardness of the composites reaches the maximum value when heat treated at 673 K for 1 h. During the friction and wear process, the wear resistance of SiC composites is higher than that of Ni-P alloy and hard chromium plating, although the friction coefficient of the composite is comparatively high, which is attributed to the worn-resistant hard phase.