Influence of machining parameters on the machinability of particulate reinforced Al/SiC–MMC

The paper presents the result of an experimental investigation on the machinability of silicon carbide particulate aluminium metal matrix composite during turning using a rhombic uncoated carbide tool. The influence of machining parameters, e.g. cutting speed, feed and depth of cut on the cutting force has been investigated. The influence of the length of machining and cutting time on the tool wear and the influence of various machining parameters, e.g. cutting speed, feed, depth of cut on the surface finish criteria has been analyzed through the various graphical representations. The combined effect of cutting speed and feed on the flank wear has also been investigated. The influence of cutting speed, feed and depth of cut on the tool wears and built-up edge is analyzed graphically. The job surface condition and wear of the cutting tool edge for the different sets of experiments have been examined and compared for searching out the suitable cutting condition for effective machining performance during turning of Al/SiC-MMC. Test results show that no built-up edge is formed during machining of Al/SiC-MMC at high speed and low depth of cut. From the test results and different SEM micrographs, suitable range of cutting speed, feed and depth of cut can be selected for proper machining of Al/SiC-MMC.     

Soft computing models and intelligent optimization system in electro-discharge machining of SiC/Al composites

In this paper, a multi-variable regression model, a back propagation neural network (BPNN) and a radial basis neural network (RBNN) have been utilized to correlate the cutting parameters and the performance while electro-discharge machining (EDM) of SiC/Al composites. The four cutting parameters are peak current (I_p), pulse-on time (T_on), pulse-off time (T_off), and servo voltage (S_v); the performance measures are material remove rate (MRR) and surface roughness (Ra). By testing a large number of BPNN architectures, 4-5-1 and 4-7-1 have been found to be the optimal one for MRR and Ra, respectively; and it can predict them with 10.61 % overall mean prediction error. As for RBNN architectures, it can predict them with 12.77 % overall mean prediction error. The multivariable regression model yields an overall mean prediction error of 13.93 %. All of these three models have been used to study the effect of input parameters on the material remove rate and surface roughness, and finally to optimize them with genetic algorithm (GA) and desirability function. Then, an intelligent optimization system with graphical user interface (GUI) has been built based on these multi-optimization techniques, in which users can obtain the optimized cutting parameters under the desired surface roughness (Ra).     

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.     

Solid particle erosion studies on biomorphic Si/SiC ceramic composites

Solid particle erosion tests were conducted on four different types of silicon carbide ceramic composites. The composites are cotton fabric based Si/SiC with and without chemical vapour infiltration, fine teak wood powder based Si/SiC and coarse teak wood powder based Si/SiC. The erodents used are angular SiC particles of average size 80, 250 and 450 μm. The velocities with which particles impacted on the target materials were varied from 20 to 50 m/s. Similarly the angle of impact was varied from 20° to 90°. Scanning electron microscopic observations on the eroded surface show brittle and cleavage like fracture. Fine teak wood powder based Si/SiC ceramic shows better erosion resistance than the other ceramics. Homogenous distribution of SiC grains with the presence of very fine grains of silicon and carbon is responsible for the improved erosion resistance. The higher erosion rate in cotton fabric based SiC arises from its microstructure. Here, the free carbon and free silicon grains are large in size and the SiC phase has very low hardness as compared to the erodent.     

SiCp/Al复合材料切削仿真与实验研究

由于SiCp/Al颗粒增强复合材料具有高比模量、高比强度、耐磨性好、耐高温和导热导电性能良好等优异性能,使其在工程应用中成为了传统金属的精良替代品。针对体积分数为45%的SiCp/Al颗粒增强复合材料进行切削研究,建立切削仿真模型,从应力场的分布情况、颗粒的断裂与破碎机理以及切屑表面的裂纹扩展等方面对切削机理进行仿真分析,并通过铣削实验进行了验证。结果表明,颗粒的断裂与破碎主要发生在剪切区和工件与切屑的分离面,同时由于颗粒的存在会使切屑表面产生微裂纹,微裂纹的扩展是影响切屑表面形态的重要因素。     

Spray forming of Al/SiC metal matrix composites

This paper describes the as-sprayed microstructure of a model Al-4wt%Cu/SiC particulate (Al4Cu/SiC_p) metal matrix composite (MMC) manufactured by spray forming, and the relationship between microstructure and solidification conditions during manufacture. Injection of SiC_p into the melt atomization region during the spray forming of Al4Cu results in significant SiC_p incorporation into molten droplets during atomization, and relatively little incorporation during flight to the substrate and at deposition. SiC_p clustering is evident in the Al4Cu droplets and results in clustering in the as-sprayed MMC deposit. Matrix dislocation and precipitation microstructures are dependent upon local solidification conditions during spray forming. Increased dislocation density and increased quantity of fine-scale θ′-Al₂Cu precipitation is found in the α-Al(Cu) matrix where local deposit cooling rates are high, i.e. in the vicinity of the substrate/deposit interface and when increased spray distances are used in manufacture. Lower dislocation density and increased quantity of grain-boundary θ-Al₂Cu is found where deposit cooling rates are relatively low, i.e. distant from the substrate/deposit interface and at decreased spray distances. In all cases, dislocation densities are higher in α-Al(Cu)/SiC_p interfacial regions than in the α-Al(Cu) matrix. There is no evidence of α-Al(Cu)/SiC_p interfacial reaction in the as-sprayed condition indicating that cooling rates during spray forming are sufficiently rapid to prevent reaction.     

Study of electrochemical machining characteristics of Al/SiCp composites

Non-conventional machining is increasing in importance due to some of the specific advantages which can be exploited during machining operation. Electrochemical machining (ECM) appears to be a promising technique, since in many areas of application, it offers several special advantages including higher machining rate, better precision and control, and a wider range of materials that can be machined. The present work is, therefore, initiated to investigate the influence of some predominant electrochemical process parameters such as applied voltage, electrolyte concentration, electrolyte flow rate and tool feed rate on the metal removal rate (MRR), and surface roughness (Ra) to fulfill the effective utilization of electrochemical machining of LM25 Al/10%SiC composites produced through stir casting. The contour plots are generated to study the effect of process parameters as well as their interactions. The process parameters are optimized based on Response Surface Methodology (RSM).     

Drilling of a hybrid Al/SiC/Gr metal matrix composites

The present study investigates the influence of cutting parameters on cutting force and surface roughness in drilling of Al/20%SiC/5%Gr and Al/20%SiC/10%Gr hybrid composites fabricated by vortex method. The drilling tests are conducted with diamond-like carbon-coated cutting tools. This paper is an attempt to understand the machining characteristics of the new hybrid metal matrix composites. The results indicate that inclusion of graphite as an additional reinforcement in Al/SiCp reinforced composite reduces the cutting force. The cutting speed and its interactions with feed rate are minimum. Feed rate is the main factor influencing the cutting force in both composites. The surface roughness value is proportional with the increase in feed rate while inversely proportional with cutting speed in both composites. For all cutting conditions, Al/20%SiC/10%Gr composite has lower surface roughness values than Al/20%SiC/5%Gr composite. The surface is analyzed using scanning electron microscope.     

Wear of rotary carbide tools in machining of Al/SiCp composites

With the projected widespread application of Metal Matrix Composites, it is necessary to develop an appropriate technology for their efficient and cost-effective machining. This paper deals with the study of feasibility of rotary carbide tools in the intermittent machining of Al/SiCp composites. A rotary tool holder was designed and fabricated for this work. Experiments were designed using Taguchi Methods to analyse the influence of various factors and their interactions on the flank wear of rotary carbide tools during machining. A tool-life model describing the effect of process, tool and material dependent parameter on the magnitude of flank wear of a rotary carbide tool is proposed.     

多孔预制体对SiC/Al复合材料孔隙率的影响

采用无压浸渗法制备了SiC含量较高的SiC/Al复合材料,分析了造孔剂添加量对多孔预制体孔隙率的影响,利用铝液浸渗多孔体理论分析了多孔顸制体孔隙结构对复合材料孔隙率的影响.结果表明:通过添加造孔剂可以调节多孔预制体的孔隙结构,使预制体的孔隙率增加;多孔预制体的孔隙结构的变化可以调节复合材料的孔隙率.多孔预制体的孔隙率越高、孔隙尺寸越大,则铝液浸渗畅通,复合材料的孔隙率越小.     

Effect of machining parameters on the milling process of 2.5D C/SiC ceramic matrix composites

Abstract

The C/SiC ceramic matrix composites are widely used for high-value components in the nuclear, aerospace and aircraft industries. The cutting mechanism of machining C/SiC ceramic matrix composites is one of the most challenging problems in composites application. Therefore, the effects of machining parameters on the machinability of milling 2.5D C/SiC ceramic matrix composites is are investigated in this article. The related milling experiments has been carried out based on the C/SiC ceramic matrix composites fixed in two different machining directions. For two different machining directions, the influences of spindle speed, feed rate and depth of cut on cutting forces and surface roughness are studied, and the chip formation mechanism is discussed further. It can be seen from the experiment results that the measured cutting forces of the machining direction B are greater than those of the in machining direction A under the same machining conditions. The machining parameters, which include spindle speed, feed rate, depth of cut and machining direction, have an important influence on the cutting force and surface roughness. This research provides an important guidance for improving the machining efficiency, controlling and optimizing the machined surface quality of C/SiC ceramic matrix composites in the milling process.     

制备空间光机结构件的高体份SiC/Al复合材料

采用无压浸渗复合新方法和自行研制的专用工艺设备,低成本地制备了用作空间光机结构件的高体份(55%~57%)SiC/Al复合材料大尺寸坯锭,并对其微观结构特征、基本的力学及热物理性能和断裂机制予以表征。此外,还通过线切割、电火花成型等特种加工手段将该种复合材料制造成反射镜背板、焦面板等一系列空间光机结构用典型样件。研究结果表明,该材料既有优异的结构承载功能(弹性模量213 GPa,而比模量则比铝合金、钛合金及钢高出近两倍),又有卓越的热控功能(其热膨胀系数比钛合金还要低,热导率接近纯铝,达到235 W/m·K),若以其替代钛合金用于空间光机结构可望获得显著的轻量化效果并降低热控负荷、改善热控效果。     

Wear behavior of Al-Mg-Cu-based composites containing SiC particles

The friction and wear behavior of Al-Mg-Cu alloys and Al-Mg-Cu-based composites containing SiC particles were investigated at room conditions at a pressure of 3.18 MPa and a sliding speed of 0.393 m/s using a pin-on-disk wear testing machine. This study is an attempt to investigate the effects of adding copper as alloying element and silicon carbide as reinforcement particles to Al-4 wt% Mg metal matrix. The wear loss of the copper containing alloys was less than that for the copper free alloys. It was observed that the volume losses in wear test of Al-Mg-Cu alloy decrease continuously up to 5%. Also it was found that the silicon carbide particles play a significant role in improving wear resistance of the Al-Mg-Cu alloying system. The formation of mechanically mixed layer (MML) due to the transfer of Fe from counterface disk to the pin was observed in both Al-Mg-Cu alloys and Al-Mg-Cu/SiC composites.     

Wear properties of Saffil/Al,Saffil/Al2O3/Al and Saffil/SiC/Al hybrid metal matrix composites

The purpose of this study is to investigate the wear properties of Saffil/Al, Saffil/Al₂O₃/Al and Saffil/SiC/Al hybrid metal matrix composites (MMCs) fabricated by squeeze casting method. Wear tests were done on a pin-on-disk friction and wear tester under both dry and lubricated conditions. The wear properties of the three composites were evaluated in many respects. The effects of Saffil fibers, Al₂O₃ particles and SiC particles on the wear behavior of the composites were elucidated. Wear mechanisms were analyzed by observing the worn surfaces of the composites. The variation of coefficient of friction (COF) during the wear process was recorded by using a computer. Under dry sliding condition, Saffil/SiC/Al showed the best wear resistance under high temperature and high load, while the wear resistances of Saffil/Al and Saffil/Al₂O₃/Al were very similar. Under dry sliding condition, the dominant wear mechanism was abrasive wear under mild load and room temperature, and the dominant wear mechanism changed to adhesive wear as load or temperature increased. Molten wear occurred at high temperature. Compared with the dry sliding condition, all three composites showed excellent wear resistance when lubricated by liquid paraffin. Under lubricated condition, Saffil/Al showed the best wear resistance among them, and its COF value was the smallest. The dominant wear mechanism of the composites under lubricated condition was microploughing, but microcracking also occurred to them to different extents.     

Investigation of wire electrical discharge machining characteristics of Al6063/SiCp composites

In this investigation, the effect of wire electrical discharge machining (WEDM) parameters such as pulse-on time (T _ON), pulse-off time (T _OFF), gap voltage (V) and wire feed (F) on material removal rate (MRR) and surface roughness (R _a) in metal matrix composites (MMCs) consisting of aluminium alloy (Al6063) and silicon carbide (SiC_p) is discussed. The Al6063 is reinforced with SiC_p in the form of particles with 5%, 10% and 15% volume fractions. The experiments are carried out as per design of experiments approach using L₉ orthogonal array. The results were analysed using analysis of variance and response graphs. The results are also compared with the results obtained for unreinforced Al6063. From this study, it is found that different combinations of WEDM process parameters are required to achieve higher MRR and lower R _a for Al6063 and composites. Generally, it is found that the increase in volume percentage of SiC resulted in decreased MRR and increased R _a. Regression equations are developed based on the experimental data for the prediction of output parameters for Al6063 and composites. The results from this study will be useful for manufacturing engineers to select appropriate WEDM process parameters to machine MMCs of Al6063 reinforced with SiC_p at various proportions.     

Optimization of machining characteristics in electric discharge machining of 6061Al/Al2O3p/20P composites by grey relational analysis

Present investigation applied the designs of experiments and grey relational analysis (GRA) approach to optimise parameters for electrical discharge machining process of 6061Al/Al₂O₃p/20P aluminium metal matrix composites. Planning of experiments was based on an L18 (2^1?×?3^5) orthogonal array to determine an optimal setting. The process parameters included one noise factor, aspect ratio having two levels and five control factors, viz. pulse current, pulse ON time, duty cycle, gap voltage and tool electrode lift time with three levels each. The material removal rate, tool wear rate and surface roughness were selected as the evaluation criteria, in this study. Optimal combination of process parameters is determined by the grey relational grade (GRG) obtained through GRA for multiple performance characteristics. Analysis of variance for the GRG is also implemented. It is shown that through GRA, the optimization of the multiple performance characteristics can be greatly simplified.     

Effect of SiC particles on the friction and wear behavior of Ti3Si(Al)C2-based composites

The non-lubricated, sliding friction and wear behavior of Ti₃Si(Al)C₂ and SiC-reinforced Ti₃Si(Al)C₂ composites against AISI 52100 bearing steel ball were investigated using a ball-on-flat, reciprocating tribometer at room temperature. The contact load was varied from 5 to 20 N. For monolithic Ti₃Si(Al)C₂, high friction coefficients between 0.61 and 0.90 and wear rates between 1.79 × 10⁻³ and 2.68 × 10⁻³ mm³ (N m)⁻¹ were measured. With increasing SiC content in the composites, both the friction coefficients and the wear rates were significantly decreased. The friction coefficients reduced to a value between 0.38 and 0.50, and the wear rates to between 2.64 × 10⁻⁴ and 1.93 × 10⁻⁵ mm³ (N m)⁻¹ when the SiC content ranged from 10 to 30 vol.%. The enhanced wear resistance of Ti₃Si(Al)C₂ is mainly attributed to the facts that the hard SiC particles inhibit the plastic deformation and fracture of the soft matrix, the oxide debris lubricate the counterpair, and the wear mode converts from adhesive wear to abrasive wear during dry sliding.     

高体份SiC/Al复合材料在无人机载光电稳定平台中的应用

采用无压浸渗复合方法并利用自行研制的专用工艺设备, 用高体份(55%～57%)SiC/Al复合材料制备了机载光电稳定平台的内框架,并将其作为有效载荷的主承力框架.由于该材料结构承载功能优异(弹性模量为213 GPa,比模量比铝合金、钛合金及钢高出近2倍),热控功能好(其热膨胀系数低于钛合金,热导率接近纯铝,达到235 W/(m·K),与常用的铝合金材料相比,整个内框架最大变形量减少了60%,基频提升了65%,轻量化效果的并减低了热控负荷.检测结果表明,系统的稳定精度达到20 μrad.本项研究首次将SiC/Al复合材料应用于机载光电稳定平台,为航空新材料的应用做出了有效的探索.