Influence of carbon nanotubes and dispersions of SiC on the physical and mechanical properties of pure copper and copper‐nickel alloy

This paper investigates the physical and mechanical properties of copper‐nickel alloy (at 50 wt.%–50 wt.%) and pure copper, mixed with various types of reinforcement materials such as carbon nanotubes (0.5 wt.%–2 wt.%) as nanoparticles, silicon carbide (1 wt.%–4 wt.%) as microparticles. The acquired composite specimens characteristics were estimated such as microstructure, density, electrical and thermal conductivity, hardness, and compression stress properties to determine the suitable reinforcement percentage that has the best physical and mechanical properties with different main matrix material whether copper‐nickel mechanical alloying or pure copper powder. The micron‐sized silicon carbide and nanosized carbon nanotubes were added to improve the mechanical and physical properties of the composite. The electrical and thermal conductivity of pure copper alloy enhanced compared with the copper‐nickel alloy matrix material. The hardness and compression yield stress of both pure copper and copper‐nickel composites have enhancement values and for copper‐nickel base composites hardness and compression yield stress have enhanced with the most positive enhancement values to examined an optimum percentage of reinforcing material.     

铜基石墨复合材料的研究进展

铜基石墨复合材料是一种广泛应用于摩擦材料和电接触材料等领域的金属基复合材料.综述了铜基石墨复合材料在改善铜基体与石墨增强体结合方面的研究进展,主要包括基体合金化、石墨的表面处理、添加粘结剂等,重点介绍了铜基石墨复合材料的制备工艺方法,并概述了其导电导热性能、摩擦磨损性能、工艺性能及应用,最后展望了铜基石墨复合材料的研究重点和发展方向,认为取代现有的易切削铅黄铜合金将成为铜基石墨复合材料今后研究和应用的一个亮点.     

In situ fabrication of titanium carbide particulates-reinforced iron matrix composites

Titanium carbide (TiC) particulates-reinforced iron matrix composites were prepared by in situ fabrication method combining an infiltration casting with a subsequent heat treatment. The effects of different heat treatment times (0, 1, 6 and 11 h) at 1138 °C on the phase evolution, microstructural features, and properties of the composites were investigated. The as-prepared composites were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and microhardness and wear resistance tests. The XRD results showed that the composites consisted of graphite, α-iron and titanium carbide after heat treatment at 1138 °C for 11 h. The SEM observation revealed that the formed TiC particulates were homogenously distributed in the iron matrix. The average microhardness of the composite heat treated at 1138 °C for 6 h increased depending upon the region: 209 HV_0.1 (iron matrix) < 787 HV_0.1 (titanium wire) < 2667 HV_0.1 (composite region). After being heat treated at 1138 °C for 11 h, the composite indicated no considerable change in microhardness value, and the average microhardness of the composite region was about 2354 HV_0.1. The highest microhardness value obtained for the composite region was due to the formation of titanium carbide particulates as reinforcement phase within the iron matrix. Relative wear resistance was determined by a pin-on-disc wear test technique under different loads, and as a result, the composites containing higher volume fraction of hard titanium carbide particulates presented higher wear resistance compared with the unreinforced gray cast iron.     

碳纤维增强铜基复合材料的性能研究

采用粉末冶金法制备了短碳纤维增强铜基复合材料。经对不同碳纤维含量试样的硬度及导电性能的测定，并在干摩擦的条件下研究了碳纤维增强铜基复合材料的摩擦磨损性能，同时对磨损表面的微观结构进行观察来分析其磨损机理。实验结果表明，随着碳纤维含量的增加，该材料的硬度和耐磨性均有所增加，但其导电性有所下降。     

Effect of the method for producing $$\hbox {}$$–$$\hbox {Cr}_{3}\hbox {C}_{2}$$Cr3C2 bulk composites on the structure and properties

Copper–chromium carbide composites containing a carbide phase of 20–30 vol% were obtained with the use of solid- and liquid-phase mechanosyntheses, followed by magnetic pulse compaction (MPC) and spark plasma sintering. The morphology, structural-phase composition, density, hardness and electrical conductivity of the composites were investigated. The structure of composites obtained by MPC represents regions of copper matrix hardened by superfine carbide precipitates surrounded by a layer of chromium carbide. In the composites obtained by spark plasma sintering, the copper matrix hardened by superfine carbide precipitates was divided into areas surrounded by a copper–chromium layer. A composite obtained by the MPC of the powders synthesized using solid-phase mechanosynthesis (MS) (copper, chromium and graphite) had the highest values of Vickers microhardness (4.6 GPa) and Rockwell hardness (HRA 69). The best value of electrical conductivity (36% IACS) was achieved using liquid-phase MS (copper, chromium and xylene) and spark plasma sintering. Liquid-phase MS is the only way to synthesize the powder with a small amount of the carbide phase and without contamination.     

Laser cladding nickel-titanium carbide composite coating on a 45 carbon steel: Preparation,microstructure and wear behavior

Almost fully dense nickel-titanium carbide composite coatings with varied titanium carbide content were deposited on 45 carbon steel by laser cladding. High content of titanium carbide particles up to 50 wt.% with bimodal microstructure could be homogeneously distributed in the nickel based matrix. Due to the presence of the harder nickel-titanium carbide composite coating on the 45 carbon steel, the surface hardness and wear properties were significantly improved. The Vickers hardness (HV 3) increased from about 260 HV 3 for the 45 carbon steel to 300 HV 3 – 360 HV 3 for nickel based composite coating containing 30 wt.% titanium carbide and 550 HV 3 – 680 HV 3 for nickel based composite coating containing 50 wt.% titanium carbide composite coating, respectively. The coefficient of friction and volume wear rate was reduced down to 0.41×10⁻⁶ mm³ N⁻¹ m⁻¹ and 9.3×10⁻⁶ mm³ N⁻¹ ⋅ m⁻¹ when a nickel based composite coating containing 50 wt.% titanium carbide was coated on the 45 carbon steel, respectively. The enhanced wear performance of the composite coating was due to presence of harder nickel-titanium carbide composite coating and formation of varied soft and lubricant metal oxides consisting of mainly titanium oxides and minor iron and nickel oxides.     

Influence of the interface structure on the thermo-mechanical properties of Cu–X (X = Cr or B)/carbon fiber composites

This study focuses on the fabrication, for power electronics applications, of adaptive heat sink material using copper alloys/carbon fibers (CF) composites. In order to obtain composite material with good thermal conductivity and a coefficient of thermal expansion close to the ceramic substrate, it is necessary to have a strong matrix/reinforcement bond. Since there is no reaction between copper and carbon, a carbide element (chromium or boron) is added to the copper matrix to create a strong chemical bond. Composite materials (Cu–B/CF and Cu–Cr/CF) have been produced by a powder metallurgy process followed by an annealing treatment in order to create the carbide at the interphase. Chemical (Electron Probe Micro-Analysis, Auger Electron Spectroscopy) and microstructural (Scanning and Transmission Electron Microscopies) techniques were used to study the location of the alloying element and the carbide formation before and after diffusion. Finally, the thermo-mechanical properties have been measured and a promising composite material with a coefficient of thermal expansion 25% lower than a classic copper/carbon heat sink has been obtained.     

In‐situ composite coating on powder metallurgy master alloy fabricated by vacuum hot‐pressing sintering technology

A material consisting of an in‐situ titanium carbide reinforced nickel‐aluminide (Ni₃Al) coating and a powder metallurgy master alloy was fabricated by vacuum hot‐pressing sintering technology. A metallurgical bonded, pores‐free interface between composite coating and powder metallurgy master alloy was formed at the sintering temperature of 1050 °C, pressure of 10^‐4 Pa and pressing pressure of 40 MPa. The phase, microstructure and wear behavior of composite coating were investigated. The results showed that polygonal titanium carbide particulates with various sizes were homogeneously distributed in nickel‐aluminide matrix. The sintering temperature, pressing pressure and heat from as‐reactions‐formed coating green compact facilitated the pore infiltration with transiently generated liquid phases and ensured the high‐intensity metallurgical bonding between composite coating and powder metallurgy master alloy. Due to the abnormal elevated‐temperature properties of nickel‐aluminide matrix, titanium carbide particulates reinforcement and the mechanically mixed layer protection, TiC/Ni₃Al‐coated parts demonstrated superior wear resistance and lower friction coefficient while compared with Ni₃Al‐coated parts and H13 steel.     

石墨烯含量对铜基石墨烯复合材料力学和电学性能的影响

为改进铜基复合材料的力学和电学性能,向铜基体分别加入0.2%、0.3%、0.4%(质量分数)的石墨烯,充分混合后,采用放电等离子烧结技术(SPS)制备了石墨烯/铜(G/Cu)复合材料。通过扫描电镜(SEM)、拉曼(Raman)光谱和XRD等表征了复合材料微观结构,测试了其硬度、屈服强度、抗压强度和导电率等性能,以确定石墨烯在铜基体中的合适掺杂量。结果表明:随着石墨烯含量的降低,其力电性能显著提高。当石墨烯质量分数为0.2%时,G/Cu复合材料的综合性能(力学及电学性能)达到最好匹配,实现了铜基材料的高强度、高导电性:其抗压强度和屈服强度分别为557.23 MPa和256 MPa,相对于用SPS方法制备的纯铜分别提高了59.21%和70.7%;电导率为52.3 MS/m,其IACS高达91.8%。     

Grundlagen,Herstellung und Anwendungsaspekte des Supersolidus Flüssigphasensinterns von hochlegierten Werkzeugstählen und Metallmatrix‐Verbundwerkstoffen

Principles, manufacturing and application aspects of super solidus liquid phase sintering of high‐alloyed tool steels and metal matrix composites Iron‐based metal matrix composites (MMC) are applied for abrasive wear resistant applications. A common production route uses hot isostatic pressing (HIP) of metal and carbide powders, a comparatively cost intensive process. Using high‐alloyed tool steels as matrix materials it is possible to obtain dense materials by liquid phase sintering with an internally formed liquid phase. This contribution describes the basic principles of densification of the matrix materials taking thermodynamic calculations into consideration. It points out a production route for processing particulate reinforced, high wear resistant composite materials by sintering. Beside the sintering behaviour concepts for heat treatment as well as the abrasive wear resistance are discussed.     

Production and wear characterisation of AA 6061 matrix titanium carbide particulate reinforced composite by enhanced stir casting method

Metal matrix composite (MMC) focuses primarily on improved specific strength, high temperature and wear resistance application. Aluminium matrix reinforced with titanium carbide (Al–TiC_p) has good potential. The main challenge is to produce this composite in a cost effective way to meet the above requirements. In this study Al–TiC_p castings with different volume fraction of TiC were produced in an argon atmosphere by an enhanced stir casting method. Specific strength of the composite has increased with higher % of TiC addition. Dry sliding wear behaviour of AMC was analysed with the help of a pin on disc wear and friction monitor. The present analyses reveal the improved specific strength as well as wear resistance.     

碳化硼颗粒增强Cu基复合材料的研究

研究了用表面涂覆含钛金属涂层的碳化硼颗粒增强Cu基复合材料[B4Cp/(TiB2 TiN)/Cu],并与未经涂覆的B4C颗粒增强Cu基复合材料（B4Cp/Cu)进行了对比。实验结果表明,前者的致密度和电导率比后者好。磨损实验结果表明,使用有涂层颗粒的复合材料的耐磨性比无涂层颗粒的好。通过对复合材料界面和磨损表面的电镜观察表明,B4C颗粒经过涂覆处理后,改善了复合材料的界面粘结性能,颗粒与基体间有良好的浸润性。     

Solidification microstructures and mechanical properties of vertical centrifugal cast high speed steel

Abstract

This study was undertaken to investigate the influence of Nb and V alloying elements and manufacturing conditions on the microstructural behaviour and mechanical characteristics of HSS (high speed steel) roll manufactured by a VCC (vertical centrifugal casting) process. In the Fe - 2C - 6Cr-1.5W - 3Mo - 4V alloy, the amount of MC carbide was increased and the the amount of M₇C₃ carbide decreased with an increase in V and Nb content. In steel containing 3%Nb, primary NbC carbide was formed within the cell in the matrix. The hardness of steel containing 6.5%V but no Nb was increased a little but when 9%V was added, the hardness decreased in the specimen owing to the soft ferritic matrix. The hardness of the matrix in steel containing 1.5%Nb increased, but decreased for 3%Nb addition. In wear tests, wear loss decreased with increasing rotational wear speed.     

Improvement of thermal conductivity in 2D carbon–carbon composites by doping with TiC nanoparticles

Titanium-doped CC composites were prepared by liquid impregnation of a 2D carbon fibre preform using a mesophase pitch doped with TiC nanoparticles as matrix precursor. The effect of the addition of titanium carbide on the microstructure and thermal properties of CC composites is investigated. A higher degree of order was developed in the matrix of the Ti-doped composite which is the result of the catalytic graphitisation of carbon promoted by titanium. As a consequence, the thermal conductivity is higher in this doped material, despite the low dopant content introduced in the matrix, which points out the relevant contribution of the matrix to the thermal properties of the whole composite.     

Heat treatment and wear characteristics of Al/SiCp composites fabricated by duplex process

This study was undertaken to investigate the effects of alloying elements and heat treatment on the microstructures, wear resistance, and heat resistance of Al–Si–Cu–Mg–(Ni)/SiC_p composites fabricated by a duplex process that consists of squeeze infiltration (1st step) followed by squeeze casting (2nd step). This duplex process produces a homogeneous distribution of SiC_p in Al alloy. The hardness of the composites increased with decrease in SiC_p size, and also with Ni addition in both the as-cast and the as-aged specimens. Compared with 5 and 10 μm SiC_p reinforced Al composites, the aging time to obtain the peak hardness was shortened for 3 μm SiC_p reinforced Al composite, because of higher density dislocations on the periphery of SiC_p in the matrix. However, the Al composite reinforced with 10 μm SiC_p was found to have the lowest wear amount as compared with 3 and 5 μm SiC_p composites. The amount of wear in Al/SiC_p composites decreased with increase of the sliding speed because abrasive wear occurred under low sliding speed and block-type wear debris occurred under high sliding speed.     

Mechanical properties of Cu/SiCp composites fabricated by composite electroforming

The silicon carbide particles (SiC_p) dispersion-strengthened copper matrix composites (Cu/SiC_p) were fabricated by composite electroforming technology. The microstructure, tensile property and wear behavior of Cu/SiC_p composites were investigated. The results showed that composites with different SiC_p contents were obtained. The microstructure of the composite presented a uniform distribution of SiC_p in the matrix and good interfacial integrity. The hardness, yield strength and rigidity of the composites increased with increasing SiC_p content, but at the cost of ductility. Increasing SiC_p content in the composite was not always beneficial to the ultimate tensile strength and wear resistance. The ultimate tensile strength increased with SiC_p content increasing up to 16 vol.% and decreased as exceeding 16 vol.%, and the wear mass loss decreased with SiC_p content increasing up to 21 vol.% and increased again as exceeding 21 vol.%.     

Mechanical and tribological behaviour of tungsten carbide reinforced aluminum LM4 matrix composites

Aluminum-based metal matrix composites (AMCs) play a vital role for potential applications in aerospace and automotive industries. This paper explores the experimental analysis of a composite with aluminum LM4 alloy as the matrix and tungsten carbide (WC) as the reinforcement material. The composite specimens were fabricated by the stir casting process. The reinforced ratios of 5, 10 and 15?wt.% of WC particulates were stirred in molten aluminum LM4 alloy (AALM4). Once the composite is solidified, the specimens are prepared to the required ASTM dimensions and tested for various mechanical properties such as tensile strength, impact strength and hardness. Moreover, the tribological behavior of the composite was studied using the pin-on-disc wear test apparatus. X-ray diffraction (XRD) analysis was conducted to analyze the various elements present in the composites. Finally, the scanning electron microscope (SEM) analysis reveals the uniform distribution of WC particles in Aluminum LM4 alloy matrix. The improvement in mechanical properties – hardness, impact strength and tensile strength – was achieved for the increase in the addition of wt.% of WC particles in the LM4 matrix. The decrease in mass loss was observed for the composite containing 15?wt.% of WC during the wear test among the various composites tested.     

原位TiB/Ti复合材料的熔铸制备及其显微组织

结合Ti-B-Al体系的热力学及Ti-B相图,提出了可制备薄壁、复杂形状原位自生钛基复合材料构件的SMIF工艺.采用XRD、SEM和TEM等手段研究用该工艺制备的复合材料的相组成和显微组织.结果表明,钛基复合材料中生成了TiB增强相,且在基体中分布均匀,呈短纤维状;并且Al的加入使得TiB相具有较高的长径比,最高可达110.TiB增强相/基体界面清洁、无污染.受熔模精铸陶瓷型壳的激冷作用,钛基复合材料铸锭表层中TiB相垂直于铸锭的表面分布.与基体合金相比较,钛基复合材料的力学性能有了很大程度的提高.     

Thermisch gespritzte titankarbidverstärkte Eisenbasisschichten als Alternative zu konventionellen karbidischen Werkstoffen

Thermal sprayed titanium carbide strengthened iron coatings as alternative for conventional carbide materials High velocity oxygen fuel (HVOF) sprayed carbide based materials are industrially well established as wear and corrosion protection coatings. Because of the high carbide content of typically 75 weight percent and more they are providing a very high hardness and excellent wear resistance. However, at the same time this characteristic is resulting in major difficulties during post‐processing steps. Cost‐effective machining processes such as turning and milling are usually not applicable and any sprayed oversize has to be reduced by grinding. To overcome these drawbacks a novel carbide‐based material concept, which is already in use for sintering processes, is offering promising properties. Titanium carbides at a reduced content of 33 weight percent embedded in a ferrous matrix can provide distinctly improved characteristics for optimal machinability. Depending on the carbon content the iron‐base material can additionally offer a temperable matrix for enhanced wear behaviour. Within this study spray trials have been carried out to investigate the sprayability of titanium carbide strengthened iron powders with a gaseous and a liquid fuel driven high velocity oxygen fuel spraying system. Optimised parameters were developed by implementing the statistical method of design of experiment (DoE). The resulting coatings were analysed with respect to microstructure, hardness and phase composition and compared to sintered reference materials. Furthermore thermally sprayed iron‐based coatings strengthened with titanium carbides were heat treated to proof the retained temperability of the iron matrix after thermal spray processing.     

Abrasive wear behavior of various reinforced AA6061 matrix composites produced with hot pressing process: A comparative study

The effects of various reinforcements (boron carbide ‐silicon carbide‐alumina) with constant volume fraction (20 %) on the abrasive wear properties of AA6061 matrix composites produced with hot pressing process were investigated. The wear tests were carried out using a pin‐on‐disk wear tester by sliding at sliding speeds of 1.2 m/s against silicon carbide paper. Applied normal loads have 5, 10 and 15 N magnitude at room temperature. The wear morphologies of the worn surfaces were analyzed using a scanning electron microscope in order to examine the wear characteristics and to investigate the wear mechanisms. The effects of reinforcement type on the wear behavior of AA6061 matrix composites were observed. Results exhibited that the optimum wear resistance obtained with the boron carbide reinforced composite parts. All reinforced samples showed better wear resistance compared to as‐received samples in all the studied conditions. Scanning electron microscope characterization showed that test specimens have complex combination of wear mechanisms on the worn surface.