Machining of Magnesium Matrix Composites

Several magnesium alloys with different particle and short fibre reinforcements have been machined for the investigations reported here. The main problem when machining metal matrix composites (MMC) is tool wear, which is caused by the very hard and abrasive reinforcements. Therefore it is necessary to find suitable cutting tools for the MMC and the different machining operations. In addition it is required to investigate the cutting conditions considering tool wear, surface quality, accuracy and surface integrity. In this papaer the results of investigations concerning drilling and reaming of different MMC are presented.     

增强相对铝基复合材料超精密加工表面的影响

采用聚晶金刚石（PCD）刀具对SiC增强铝基复合材料进行超精密车削加工试验,基于原子力显微镜（AFM）、扫描电子显微镜（SEM）和Talysurf-6型轮廓仪对加工表面进行检测和分析.结果表明,S iC增强相的切削变形机理对超精密级加工表面的影响重大（粗糙度Ra为0.025μm）.若增强相在解理面直接被切削刀具切断,则SiC增强相附近区域的表面粗糙度值范围为6~10 nm,故产生超精密级加工表面的可能性大;若增强相以拔出或压入的机理进行切削变形,则不易获得超精密级加工表面.较高的切削速度、较小的进给量、较小的刀具钝圆半径和较大的PCD刀具晶粒度都有助于获得超精密级的加工表面,而背吃刀量对其影响很小.SiC增强相的体积分数和类型也是影响超精密级表面质量的重要因素,增强相体积分数越高,表面质量越差,晶须增强铝基复合材料较颗粒增强铝基复合材料可获得更好的表面质量.     

Investigation on the cutting quality characteristics of abrasive water jet machining of AA6061-B4C-hBN hybrid metal matrix composites

Aluminum metal matrix composites (AMMCs) explicitly show better physical and mechanical properties as compared to aluminum alloys and results in a more preferred material for a wide range of applications. The addition of reinforcements embargo AMMCs employment to industry requirements by increasing order of machining complexity. However, it can be machined with a high order of surface integrity by nonconventional approaches like abrasive water jet machining. Hybrid aluminum alloy composites were reinforced by B₄C (5–15?vol%) and solid lubricant hBN (15?vol%) particles and fabricated using a liquid metallurgy route. This research article deals with the experimental investigation on the effect of process parameters such as mesh size, abrasive flow rate, water pressure and work traverse speed of abrasive water jet machining on hybrid AA6061-B₄C-hBN composites. Water jet pressure and traverse speed have been proved to be the most significant parameters which influenced the responses like kerf taper angle and surface roughness. Increase in reinforcement particles affects both the kerf taper angle and surface roughness. SEM images of the machined surface show that cutting wear mechanism was largely operating in material removal.     

Parametric optimization studies on drilling of sandwich composites using the Box–Behnken design

This study was carried out to investigate the parametric influence on the performance of drilling newly made sandwich composites. Sandwich composite was prepared by using steel and jute as reinforcements and polyester as the matrix material. Drilling experiments were carried out by considering input factors such as spindle speed, feed rate of the spindle, point angle of the drill and tool diameter. Three output factors, namely thrust force developed during drilling, surface roughness of the drilled hole and damage at the entrance surface, were studied. All output factors were optimized by using the Box–Behnken approach, and the best machining conditions were taken on the basis of the desirability approach. Confirmatory experiments were conducted and compared against the Box–Behnken model. The comparison showed only a minor error, and hence the optimization is satisfactory.     

Fabrication and Machining of Metal Matrix Composites: A Review

Intrinsically smart, metal matrix composites (MMCs) are lightweight and high-performance materials having ever expanding industrial applications. The structural and the functional properties of these materials can be altered as per the industrial demands. The process technologies indulged in fabrication and machining of these materials attract the researchers and industrial community. Hybrid electric discharge machining is a promising and the most reliable nonconventional machining process for MMCs. It exhibits higher competence for machining complex shapes with greater accuracy. This paper presents an up-to-date review of progress and benefits of different routes for fabrication and machining of composites. It reports certain practical analysis and research findings including various issues on fabrication and machining of MMCs. It is concluded that polycrystalline tools and diamond-coated tools are best suitable for various conventional machining operations. High speed, small depth of cut and low feed rate are a key to better finish. In addition, hybrid electrical discharge machining has proved to be an active research area in critical as well as nonconventional machining since last few years. This paper incorporates year-wise research work done in fabrication, conventional machining, nonconventional machining, and hybrid machining of MMCs. Conclusions and future scope are addressed in the last section of the paper.     

纳米氮化硼增强金属基复合材料的研究进展

在金属中添加陶瓷增强相是调控和改善金属材料结构和性能的重要途径。传统硬质陶瓷增强相难以满足金属材料日益严苛的应用需求。以氮化硼纳米片（boron nitride nanosheet,BNNS）和氮化硼纳米管（boron nitridenanotube,BNNT）为代表的纳米氮化硼具有极大的比表面积和优异的力学性能、热稳定性、化学稳定性等,是制备性能优异的金属基复合材料的理想增强相。系统总结了纳米氮化硼的种类和特征,综述了纳米氮化硼增强金属基复合材料的制备方法,归纳了纳米氮化硼增强Cu、Al、Ti复合材料的研究成果,总结了纳米氮化硼/金属复合材料的力学和摩擦学性能,并揭示了复合材料性能改善的机理。最后,展望了纳米氮化硼/金属复合材料的发展趋势。     

Spanende Bearbeitung von Bauteilen aus Al‐Matrix‐Verbundwerkstoffen

Machining of Components of Al Matrix Composites The microstructure of metal matrix composites consists of hard reinforcements which are embedded in a metal matrix. The high hardness of the reinforcements leads to a difficult processing of these materials. The present paper demonstrates the machining of components of Al matrix composites for the automotive and the aircraft industry. The components are SiC particle reinforced brake drums, cylinder blocks with local Si particle and Al₂O₃ short fiber reinforced cylinder liners and TiB₂ particle reinforced extrusion molding profiles. The investigations illustrate that good results can be achieved when machining these components by turning, boring, drilling and milling with polycrystalline diamond (PCD) or CVD diamond thick‐film cutting tool materials.     

A CRITICAL STUDY ON MACHINING OF Al/SiC COMPOSITES

This study focused on the tool topography and chip formation during machining of aluminium-silicon carbide particulate composites. The Al/SiC composites with different volume fraction of reinforcements were machined with cemented carbide tool inserts. The effects of volume fraction, cutting speed, feed rate, depth of cut, and time of machining on chip disposability, chip thickness ratio, and shear angle were studied. The quick-stop sections and chip cross sections at different conditions were also observed. The tool topography was also analyzed.     

Fabrication of 6061 aluminum alloy reinforced with Si3N4/n-Gr and its wear performance optimization using integrated RSM-GA

In this research work the dry sliding wear behavior of a hybrid aluminum metal matrix composite is evaluated. Al 6061 is used as a matrix material while Si₃N₄ and nanographite powder (3–15 wt%) are used as reinforcements. These two reinforcements (50 wt% of each) were blended in a high-energy ball mill for homogeneous mixing to derive the sound aluminum matrix composite (AMC). The hybrid composite is made by the stir casting route and its wear rate was investigated against an EN32 steel disc surface, using a pin-on-disc tribometer. Integrated response surface methodology (RSM) and genetic algorithm (GA) are used to optimize the pin-on-disc process parameters. Analysis of variance (ANOVA) shows that sliding distance plays a major role on the dry sliding wear rate followed by load, sliding speed and reinforcements. Two-factor interactions and quadratic terms have also significant contributions. GA suggested a minimum wear rate value of 0.827 mg at optimized setting. Microstructural analysis by scanning electron microscopy (SEM) reveals that very fine grooves are obtained at optimized settings while at other settings severe ploughing is observed. Transition of wear mechanism takes place with the increase of speed (i.e., temperature between the two rubbing surfaces) from abrasive to adhesive.     

Impact of graphite particle on milling of Al/15Al2O3 and Al/15Al2O3/5Gr composites

ABSTRACT

Hybrid Metal Matrix Composites (MMCs) are a new class of composites, formed by a combination of the metal matrix and more than one type of reinforcement having different properties. Machining of MMCs is a difficult task because of its heterogeneity and abrasive nature of reinforcement, which results in excessive tool wear and inferior surface finish. This paper investigates experimentally the addition of graphite (Gr) on cutting force, surface roughness and tool wear while milling Al/15Al₂O₃ and Al/15Al₂O₃/5Gr composites at different cutting conditions using tungsten carbide (WC) and polycrystalline diamond (PCD) insert. The result reveals that feed has a major contribution on cutting force and tool wear, whereas the machined surface roughness was found to be more sensitive to speed for both composite materials. The incorporation of graphite reduces the coefficient of friction between the tool–workpiece interfaces, thereby reducing the cutting force and tool wear for hybrid composites. The surface morphology and worn tool are analyzed using scanning electron microscope (SEM). The surface damage due to machining extends up to 200 µm for Al/15Al₂O₃/5Gr composites, which is beyond 250 µm for Al/15Al₂O₃ composites.     

EDM machinability of SiCw/Alcomposites

Machinability of high temperature composites was investigated. Target materials, 15 and 25 vol % SiC whisker-2124 aluminium composites, were machined by electrodischarge sinker machining (EDM) and diamond saw. The machined surfaces of these metal matrix composites were examined by scanning electron microscopy (SEM) and profilometry to determine the surface finish. Microhardness measurements were also performed on the as-machined composites.     

Effects of roller burnishing process parameters on surface roughness of A356/5%SiC composite using response surface methodology

In this study,a simple roller burnishing tool was made to operate burnishing processes on A356/5%SiC metal matrix composite fabricated by electromagnetic stir casting under different parameters.The effects of burnishing speed,burnishing force and number of burnishing passes on the surface roughness and tribological properties were measured.Scanning electron microscopy(SEM) graphs of the machined surface with PCD(insert-10) tool and roller burnished surface with tungsten carbide(WC) roller were taken into consideration to observe the surface finish of metal matrix composites.The mechanical properties(tensile strength,hardness,ductility) of A356/5%SiC metal matrix composites were studied for both unburnished samples and burnished samples.The results revealed that the roller burnished samples of A356/5%SiC led to the improvement in tensile strength,hardness and ductility.In order to find out the effects of roller burnishing process parameters on the surface roughness of A35675%SiC metal matrix composite,response surface methodology(RSM)(Box-Behnken design) was used and a prediction model was developed relevant to average surface roughness using experimental data.In the range of process parameters,the result shows that roller burnishing speed increases,and surface roughness decreases,but on the other hand roller burnishing force and number of passes increase,and surface roughness increases.Optimum values of burnishing speed(1.5 m/s),burnishing force(50 N) and number of passes(2)during roller burnishing of A356/5%SiC metal matrix composite to minimize the surface roughness(predicted1.232 urn) have been found out.There was only 5.03%error in the experimental and modeled results of surface roughness.     

Electric discharge hole grinding in hybrid metal matrix composite

Moving toward a hybrid approach, a hybrid process, electric discharge hole grinding (EDHG) was used to machine a hybrid metal matrix composite (MMC) (Al6063/SiC/Al₂O₃/Gr). Here, holes were drilled and ground in a single step process (EDHG) using a novel tool electrode. The experiments were designed using response surface methodology (RSM). The objective of this study was to investigate the effect of electric discharge diamond hole grinding operation on the surface roughness (SR) of the hole. The input process parameters were current, duty factor, tool speed and flushing pressure. It was found that the process is very effective in producing a finished hole. A comparison of surface roughness was made between electric discharge drilling (EDD) and electric discharge diamond hole grinding, thereby showing the effectiveness of the electric discharge diamond hole grinding process. The grinding action of the process is clearly visible in the scanning electron microscopic (SEM) image. It was observed that the craters, globules of resolidified material and micro cracks, which are normally seen on surfaces machined by electric discharge machining (EDM), are completely ground off by electric discharge diamond hole grinding.     

基体各类对混杂复合材料摩擦磨损性能的影响

研究了基体种类对SiC和石墨（Gr)颗粒混杂增强铝基复合材料的摩擦磨损性能的影响。各种铝基体的混杂复合材料的耐磨性有明显差异,纯铝基混杂复合材料具有最好的耐磨性,其次是A356,2024和6061为基体的混杂复合材料。     

Machinability of Metal Matrix Composites Reinforced by 3-D Network Structure

Metal matrix composites reinforced by three-dimensional (3-D) continuous network structure reinforcement (3DCNRMMC) are difficult to machine due to serious tool wear and poor surface roughness caused by the brittle and hard reinforcement which interpenetrate into ductile matrix. In order to achieve the approach of low cost of 3DCNRMMC, the machinability of it needs to be understood. The influences of three cutting parameters and volume fraction of reinforcement on cutting force were analyzed in detail. The results indicate that: (1) Due to the brittle phase(s) introduced into ductile matrix of composites, there is a large fluctuation of cutting force causing deterioration of machinability. The fluctuation ranges of cutting forces, initially increase rapidly with the increase of volume fraction of reinforcement and then decrease finally, are largest at the range of the volume fraction of 55–65%; (2) The influence of cutting parameters on cutting force is obvious. With the increases of cutting speed, cutting force decreases gradually unless cutting speed exceeds the value of 209 m/min. Cutting forces increase with increasing feed rate and depth of cut; (3) Owing to the large fluctuation of cutting force, there were some cratered surfaces caused by Si₃N₄ reinforcement pulling-out and flaking-off. Some brittle phase protruding from the machined surface caused the deterioration of machined surface.     

Experimental investigation and optimization of machining parameters in drilling of fly ash-filled carbon fiber reinforced composites

Particle-filled polymer composites have become attractive because of their wide applications and low cost. Carbon fiber reinforced polymer (CFRP) is well known as a difficult-to-cut material, which has very strong physical and mechanical characteristics. Machining of carbon fiber reinforced composites is essential to have functional upshots, out of which drilling is the key operation needed for fabrication. In this paper Taguchi L₂₇ experimental design is coupled with grey relational analysis (GRA) to optimize the multiple performance characteristics in the drilling of fly ash-filled carbon fiber reinforced composites. Experiments were conducted on a vertical machining center, and Taguchi L₂₇ experimental design was chosen for the experiments. The drilling parameters, namely spindle speed, feed rate, drill diameter and wt% of fly ash, have been optimized based on the multiple performance characteristics including thrust force, surface roughness, and delamination. The GRA with multiple performance characteristics indicates that the wt% of fly ash and drill diameter are the most significant factors that affect the performance. Experimental results have shown that the performance in the drilling process can be improved effectively by using this approach.     

Study of Magnetic Field-Assisted ED Machining of Metal Matrix Composites

The present study deals with an investigation of the hybrid electric discharge (ED) machining process executed in a magnetic field for improving process performance. Previous magnetic field-assisted electric discharge machining (MFAEDM) techniques, however, are limited to use with a class of magnetic workpieces. In this particular study, the magnetic field was coupled with the conventional EDM plasma zone to test the hybrid process on Al-based metal matrix composites (MMCs). The machining parameters, for instance, peak current as well as duration of pulse-on were selected to nail down thereafter effects on the response parameters like the material removal rate (MRR) and the surface integrity. The experimental results show an improvement of 12.9% MRR and reduction in recast layer formation at higher spark energy in the magnetic field environment. As the experimental outcome implied that the MFAEDM imparted appreciable process stability, a highly efficient pertinent process of EDM with high quality of the machined surface could be accomplished to satisfy modern industrial applications.     

Optimization of delamination factor in drilling GFR–polypropylene composites

Glass fiber-reinforced polypropylene composites often replace the conventional materials due to their special or unique mechanical properties. As the applications of these composites increase for a number of industries, drilling of these composites is inevitable for subsequent composite product manufacturing stage. In the drilling of composites, the thrust force is induced during the drilling operation; as a result, it causes damage. This damage is characterized by the delamination factor, which depends on the machining parameters such as speed of the spindle, feed rate, and drill diameter. The study on the delamination in the drilling of glass fiber-reinforced polypropylene is limited and has been carried out comprehensively. The effect of machining parameters on delamination in the drilling of glass fiber-strengthened polypropylene (GFR-PP) composites is studied through the Box–Bhenken design. Response surface method, along with the desirability analysis, is used for modeling and optimization of delamination factor in the drilling. The result proves that the models are effectively used to forecast the delamination in the drilling of GFR-PP composites. Also, the result indicates that the foremost issue that influences the delamination is the feed rate.     

铝基复合材料增强体涂层与界面

基体与增强体间的界面对金属基复合材料的性质起着重要的作用。为改善复合材料增强体与基体合金的浸润性,避免有害界面产物的形成,往往通过增强体表面涂层处理加以解决。本文综述了增强体涂层种类、涂覆方法及其对复合材料的界面和性能的影响。     

Recycling of Metal Matrix Composites

Fundamental ideas of recycling of metal matrix composites are introduced. Two fundamentally different ways for separating reinforcements from the matrix metal exist. One is the mechanical method and another is the chemical method. In this report the separation of fibers in an aluminum matrix composite is demonstrated by a chemical method.