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.     

Processing issues,machining, and applications of aluminum metal matrix composites

Aluminum metal matrix composites (AMMCs) used in different industries from automotive to aerospace for specific purposes. Many problems hinder the full-scale industrialization of AMMCs but the main problems include wettability, particle distribution, porosity, and chemical reaction. These problems have explicit effects on mechanical, wear, and corrosion resistance properties of the composite materials. Therefore, it is essential to cope up with these problems for better quality of AMMCs. This paper focuses on issues related to AMMCs fabrication, corrosion resistance, wear resistance, machining parameter optimization, and chip analysis of AMMCs. Literature provides a guideline to researchers about present scenario of AMMC fabrication using stir casting process. Moreover, paper presents properties and applications of AMMCs.     

Machining of aluminium based metal matrix composites

Although metal matrix composites (MMCs) are generally regarded as extremely difficult to machine, it is also acknowledged that their machining behaviour is not fully understood. The work reviewed here confirms this widely held view but also suggests that the machinability of these materials can be improved by appropriate selection of the reinforcing phase, its volume fraction, size, and morphology as well as the composition and hardness of the matrix material. Cemented carbide tools can be used to machine some of the less abrasive materials at slow speeds but if higher production rates are required or the more abrasive materials are to be machined, polycrystalline diamond tooling is required.     

Rotary Ultrasonic Machining: A Review

Rotary ultrasonic machining (RUM) is a mechanical type of nontraditional hybrid machining process that has been utilized potentially to machine a wide range of latest and difficult-to-machine materials, including ductile, hard and brittle, ceramics, composites, etc. In RUM, the basic material removal phenomenon of ultrasonic machining (USM) and conventional diamond grinding amalgamates together and results in higher material removal rate (MRR), improved hole accuracy with superior surface finish. In the current article, several investigations carried out in the domain of RUM for enormous materials have been critically reviewed and reported. It also highlights several experimental and theoretical ensues of RUM to improve the process outcomes and it is reported that process performance can be substantially improved by making the right selection of machine, diamond tooling, material and operating parameters. In recent years, various investigators have explored umpteen ways to enhance the RUM process performance by probing the different factors that influence the quality attributes. Among the various accessible modifications in RUM as employed in industries, rotary ultrasonic drilling is more strongly established compared to other versions such as rotary ultrasonic side milling, face milling, grinding, surface texturing, etc. The micro machining applications of RUM have also been discussed briefly. The final section of this paper discusses RUM developments and outlines the aspects for future research.     

Chemical vapour deposition (CVD) diamond coated tools performance in machining of PEEK composites

This paper presents a study about the chemical vapour deposition (CVD) diamond coated tool performance in machining unreinforced PEEK and composite PEEK CF30 (reinforced with 30% of carbon fibres).

The experimental procedure consisted of turning operations, during which cutting forces and surface roughness obtained in composite workpieces were measured.

The obtained results showed a best cutting performance for CVD diamond coated tool in machining PEEK composites, particularly in terms of cutting forces and power consumption, when compared with polycrystalline diamond (PCD) and cemented carbide (K10) cutting tools. This fact is very important due to the minor production costs of CVD diamond coated tools in comparison with PCD tools.     

Metal matrix composites – From science to technological significance

Over the past two decades – a period coinciding with publication of Composites Science and Technology – metal matrix composites (MMCs) have been transformed from a topic of scientific and intellectual interest to a material of broad technological and commercial significance. The worldwide MMC markets in 1999 accounted for 2500 metric tons valued at over $100M. Important MMC applications in the ground transportation (auto and rail), thermal management, aerospace, industrial, recreational and infrastructure industries have been enabled by functional properties that include high structural efficiency, excellent wear resistance, and attractive thermal and electrical characteristics. A suite of challenging technical issues has been overcome, including affordable primary and secondary processing, material design and development methodologies, and characterization and control of interfacial properties. This article describes the technological features that characterize the MMC industry. Matrix/reinforcement systems and primary and secondary processes of commercial significance will be broadly described. Several metrics that underscore the growing maturity of the MMC industry will be discussed, including the emergence of a second tier support industry and the growth of standardized materials and methods. MMC applications in the major markets of ground transportation, thermal management, aerospace, industrial, recreational and infrastructure will be described. Successful commercialization strategies will be discussed and insights for achieving expanded MMC applications will be given. A forward look at candidate approaches for the next generation of MMCs will be provided, including projections of new MMC paradigms.     

聚晶金刚石的高温高压制备及其性能研究进展

聚晶金刚石(PCD)刀具在加工非铁基材料时,尤其是一些超硬、耐磨材料时,其寿命和加工精度远高于传统刀具。聚晶金刚石的性能与原材料和烧结条件密切相关。概述了不同因素对以陶瓷为粘结剂的聚晶金刚石和无粘结剂的纳米聚晶金刚石的硬度、断裂韧性的影响并比较了不同种类PCD的热稳定性能。分析得到以过渡金属硼化物和碳化硅为粘结剂所制备的PCD的热稳定性能较好,优于以钴为粘结剂制备的PCD;在Hall-Petch定律作用下,以纳米尺寸陶瓷为粘结剂的PCD硬度更高,韧性更强;无粘接剂的纳米聚晶金刚石的力学、热学性能最为优异。最后,结合实际应用对聚晶金刚石的制备提出了参考性的建议。     

Dry machining of silicon-aluminium alloys with CVD diamond brazed and directly coated Si3N4 ceramic tools

Silicon-aluminium alloys (Al-Si), with Si contents up to 20%, are important materials in automotive and aeronautical industries due to their low density and high wear resistance. The turning of these alloys has been done mainly by superhard tools like polycrystalline diamond (PCD). CVD diamond either as thin coatings on silicon nitride ceramics or as thick brazed tips on hard metals is alternative material. In this work, CVD diamond thin films were grown on Si₃N₄ ceramic substrates and thick CVD diamond plates were brazed onto WC-Co tools. These different inserts were used in dry turning of silicon-aluminium alloys with 12 wt% and 18 wt% Si. Both directly diamond coated and brazed tools are able to machine the Al-12 wt% Si alloy with negligible wear. In turning of Al-18 wt% Si, sharp edged tools yield lower cutting forces than the chamfered ones, with the occurrence of tool failure at about 500 and 100 m, respectively. CVD brazed tools proved to be able for dry turning this hypereutectic alloy, keeping the cutting forces below 60 N. Minimal wear was observed after 1500 m of cutting length, mainly caused by diamond chipping at the flank face.     

金属基复合材料的现状与发展趋势

在过去的二十多年里,金属基复合材料凭借其结构轻量化和优异的耐磨、热学和电学性能,逐渐在陆上运输(汽车和火车)、热管理、民航、工业和体育休闲产业等诸多领域实现商业化的应用,确立了作为新材料和新技术的地位。但是,金属基复合材料的未来发展仍然面临不确定性,既有可能持续扩大应用领域和市场规模,也有可能在其它材料和技术的竞争下停滞甚至萎缩。在综述金属基复合材料的研究与应用现状的基础上,对其可预期的增长点和发展趋势进行了展望。     

Single-point scratching of 6061 Al alloy reinforced by different ceramic particles

Aluminium alloys reinforced by ceramic particles have been widely used in aerospace and automotive industries for their high stiffness and wear resistance. However, the machining of such materials is difficult and would usually cause excessive tool wear. The effect of ceramic particles on the cutting mechanisms is also unclear. The purpose of this study is to investigate the cutting mechanisms and the relationship between specific energy of scratching and depth of cut (size effect). The single-point scratch test was carried out on 6061 Al and its composites reinforced by Al₂O₃ and SiC ceramic particles using a pyramid indenter. The results indicated that the scratch process was composed of rubbing, ploughing, plastic cutting and reinforcement fracture. A simple model was proposed to interpret the apparent size effect. The effect of reinforcement on the specific energy was correlated to the ratio of volume fraction to particle radius. The paper found that for machining MMCs, a larger depth of cut should be used to maintain a lower machining energy, especially for those with a larger ratio of volume fraction to particle radius.     

Acousto-ultrasonic decay in metal matrix composite panels

Acousto-ultrasonic (A-U) decay rates (UD) were measured in metal matrix composite (MMC) panels. The MMC panels had fiber architectures and cross-sectional thicknesses corresponding to those designed for aerospace turbine engine structures. The wavelength-to-thickness ratio produced by the combination of experimental frequency setting conditions and specimen geometry was found to be a key parameter for identifying optimum conditions for UD measurements. The ratio was shown to be a useful rule of thumb when applied to ceramic matrix composites (CMCs) and monolithic thermoplastics. No conjectures are presented as to the source of UD in undegraded MMCs such as those used in the present work.     

Particulate reinforced metal matrix composites — a review

The physical and mechanical properties that can be obtained with metal matrix composites (MMCs) have made them attractive candidate materials for aerospace, automotive and numerous other applications. More recently, particulate reinforced MMCs have attracted considerable attention as a result of their relatively low costs and characteristic isotropic properties. Reinforcement materials include carbides, nitrides and oxides. In an effort to optimize the structure and properties of particulate reinforced MMCs various processing techniques have evolved over the last 20 years. The processing methods utilized to manufacture particulate reinforced MMCs can be grouped depending on the temperature of the metallic matrix during processing. Accordingly, the processes can be classified into three categories: (a) liquid phase processes, (b) solid state processes, and (c) two phase (solid-liquid) processes. Regarding physical properties, strengthening in metal matrix composites has been related to dislocations of a very high density in the matrix originating from differential thermal contraction, geometrical constraints and plastic deformation during processing.     

Comparative study of jetting machining technologies over laser machining technology for cutting composite materials

There has been a great interest for improving the machining of composite materials in the aerospace and other industries. This paper focuses on the comparative study of jetting techniques and laser machining technics. This paper concentrates on the machining of composite materials like epoxy pre-impregnated graphite woven fabric and fibre reinforced plastic materials that are used in aerospace industries. While considering machining these materials with the traditional machining there are many disadvantages projected. One of these advantages is that all the traditional machining processes involve the dissipation of heat into the workpiece. This serious shortcoming has been dealt by the jetting technologies, which, contrary to the traditional machining, operate under cold conditions. The two methods in the jetting technologies used for processing materials are water jet machining and abrasive water jet machining. The first of these, water jet machining, has been around for the past 20 years and has paved the way for abrasive water jet technology. Water jet machining and abrasive water jet machining have been used for processing composite materials because of the advantages offered by this technologies as compared to traditional techniques of processing. The high surface and structural integrity required of any technique used for processing composite materials has created an opportunity for abrasive water jet machining. Cutting of composites using laser is also an option, and experiments were also conducted to reveal the extent of using laser technique.     

Commercial Viability of Al-Based MMCs in the Automotive Segment

Based on the cost-to-quality ratio evaluation related to automotive applications of discontinuously reinforced aluminum-based composites, R & D efforts, directed toward a further lowering of the cost of composite material, are considered. The results of the study indicate that a viable business concept for applications of discontinuously reinforced metal matrix composites (MMCs) in the automotive segment should be built up on the development of an end user-friendly and preferably one step production technology. This should be capable of producing near net-shaped automotive parts in MMC grade consisting of fine ceramic particles of average particle size around 1 μm or less and keeping the production cost at the current level.     

Acousto-Ultrasonic Decay in Metal Matrix Composite Panels

Abstract

Acousto-ultrasonic (A-U) decay rates (UD) were measured in metal matrix composite (MMC) panels. The MMC panels had fiber architectures and cross-sectional thicknesses corresponding to those designed for aerospace turbine engine structures. The wavelength-to-thickness ratio produced by the combination of experimental frequency setting conditions and specimen geometry was found to be a key parameter for identifying optimum conditions for UD measurements. The ratio was shown to be a useful rule of thumb when applied to ceramic matrix composites (CMCs) and monolithic thermoplastics. No conjectures are presented as to the source of UD in undegraded MMCs such as those used in the present work.     

铝基碳化硅精密铣削刀具磨损实验研究

针对铝基碳化硅切削加工中刀具易磨损、寿命低、切削难度大和加工成本高等问题,选用不同材料的硬质合金铣刀及金刚石铣刀进行切削加工实验,并利用扫描电镜和工具显微镜对高体积分数铝基碳化硅铣削时刀具磨损形态进行了分析研究.研究表明:硬质合金刀具前刀面和刃口磨损主要形式为粘结磨损和微崩刃,后刀面磨损主要为刻划磨损,而金刚石铣刀加工时刀具磨损很小;YG6X铣刀材料微观组织致密,抗磨损能力较强,宜粗加工时选用;金刚石刀体的硬度远大于SiC颗粒,且金刚石与工件的摩擦系数小,金刚石铣刀寿命远大于硬质合金铣刀,宜精加工时选用.     

High-speed turning experiments on metal matrix composites

The hard abrasive ceramic component which increases the mechanical characteristics of metal matrix composites (MMC) causes quick wear and premature tool failure in the machining operations. The aim of the paper is to compare the behaviour of high rake angle carbide tools with their diamond coated versions in high-speed machining of an Al₂O₃Al 6061 MMC. The influence of the cutting parameters, in particular cutting feed and speed, on tool wear and surface finish has been investigated. The higher abrasion resistance of the coatings results in increased tool life performances and different chip formation mechanisms.     

Al matrix composites fabricated by solid-state cold spray deposition:A critical review

Cold spraying(CS),or cold gas dynamic spray(CGDS),is an emerging solid-state powder deposition process,allowing fast and mass production and restoration of metallic components.CS of metal matrix composites(MMCs)has attracted increasing attention from academia and industry over the last decades,especially in the area of Al matrix composites(AMCs),which have demonstrated a high potential for applications in aerospace,automotive,and electronics industries.This article aims to summarize the recent development of CS-processed AMCs in terms of composite powder preparation,deposition pro-cessing,microstructure evolution,mechanical and corrosion properties.Furthermore,this review also reports the relevant research progress with the focus on post-treatments of the AMCs for CS additive manufacturing applications including heat treatment,hot rolling,and friction stir processing.Finally,the challenges and perspectives on the fabrication of advanced AMCs by CS are addressed.     

新一代高导热金属基复合材料界面热导研究进展

热物理性质不同的材料之间存在界面热阻,界面热阻对热传输过程产生极大的影响,并在很大程度上决定了复合材料的导热性能。金刚石颗粒增强金属基复合材料(Metal matrix composites,MMCs)充分发挥了金刚石的高热导率和低热膨胀系数的优点,有望获得高的热导率以及与半导体相匹配的热膨胀系数,可满足现代电子设备在散热能力上提出的越来越高的要求,作为新一代电子封装材料已引起广泛关注。界面热导(界面热阻的倒数)既是决定复合材料导热能力的关键因素,也是研究的难点,复合材料制备工艺、界面改性方式(金属基体合金化或金刚石表面金属化)以及改性金属种类均会影响界面热导。详细论述了界面热导理论及实验研究的最新成果,并对金刚石/金属复合材料在未来研究中面临的主要问题进行探讨。