Effect of spark plasma sintering and high-pressure torsion on the microstructural and mechanical properties of a Cu–SiC composite

This investigation examines the problem of homogenization in metal matrix composites (MMCs) and the methods of increasing their strength using severe plastic deformation (SPD). In this research MMCs of pure copper and silicon carbide were synthesized by spark plasma sintering (SPS) and then further processed via highpressure torsion (HPT). The microstructures in the sintered and in the deformed materials were investigated using Scanning Electron Microscopy (SEM) and Scanning Transmission Electron Microscopy (STEM). The mechanical properties were evaluated in microhardness tests and in tensile testing. The thermal conductivity of the composites was measured with the use of a laser pulse technique. Microstructural analysis revealed that HPT processing leads to an improved densification of the SPS-produced composites with significant grain refinement in the copper matrix and with fragmentation of the SiC particles and their homogeneous distribution in the copper matrix. The HPT processing of Cu and the Cu-SiC samples enhanced their mechanical properties at the expense of limiting their plasticity. Processing by HPT also had a major influence on the thermal conductivity of materials. It is demonstrated that the deformed samples exhibit higher thermal conductivity than the initial coarse-grained samples

Wytwarzanie, mikrostruktura i waściwości kompozytów Cu-Al2O3 otrzymywanych różnymi technikami

Alumina/copper composites are used where high thermal conductivity, high absorption and dissipation of heat, high resistance to thermal fatigue and good frictional wear resistance are required. The properties of these composites depend on a number of factors including the content, shape and distribution of the ceramic phase, the method of their obtaining, as well as the conditions under which they are obtained. All these variables have influence on mentioned properties and, in consequence, on the future applications of the final material. The aim of this paper was to develop Cu /Al2 O3 composites, processed using two techniques, namely sintering (of Cu /Al2 O3 high-energy mixed powders) and tape casting (of slurry of the following composition: 1, 3 and 5 vol.% of Al2 O3 phase; the remaining part: Cu). The compositions were determined taking into consideration the planned applications. The paper presents newly developed technologies, the results of both microstructure investigations as well as of the measurements of selected physical and mechanical properties (microhardness, wear resistance, thermal conductivity etc.) and contains the analysis of the influence of selected techniques and processing conditions on the properties and the interface morphology between ceramic and copper.Kompozyty na bazie miedzi znajdują zastosowanie tam, gdzie jest wymagane: wysokie przewodnictwo cieplne, wysoka absorpcja i rozpraszanie ciepła, wysoka odporność na zmęczenie cieplne i dobra odporność na zużycie ścierne. Właściwości tych kompozytów zależą od wielu czynników tj. zawartości, kształtu i rozkładu fazy ceramicznej w metalowej osnowie jak również od samego sposobu (warunków) ich wytwarzania. Celem niniejszej pracy było otrzymanie kompozytów Cu-Al2 O3 stosując dwie techniki: spiekania mieszaniny proszków pod ciśnieniem oraz odlewanie folii kompozytowych (tape casting), laminowanie oraz końcowe spiekanie otrzymanych materiałów. Ze względu na przyszłe zastosowania tych kompozytów (m.in. elementy w układach turbin w samolotach) wytypowane zostały następujące składy: 99%ob j:Cu-1%ob j:Al2 O3 , 97%ob j:Cu-3%ob j: Al2 O3 , 95%ob j:Cu-5%ob j: Al2 O3 : W prezentowanej pracy przedstawiono dwie technologie otrzymania kompozytów na bazie miedzi. Przeprowadzone zostały badania mikrostruktury otrzymanych kompozytów ze szczególnym zwróceniem uwagi na możliwość pojawienia się warstwy przejściowej ceramika/metal. Przeprowadzone zostały również badania właściwości fizycznych (twardość, gęstość), badania właściwości cieplnych (dyfuzyjność cieplna, przewodnictwo cieplne) oraz badania właściwości mechanicznych (zużycie ścierne) otrzymanych kompozytów

The influence of electrocorundum granulation on the properties of sintered Cu/electrocorundum composites

Copper/alumina composites are extensively used in automotive and aerospace industry for products that are subjected to severe thermal and mechanical loadings, such as rocket thrusters and components of aircraft engines. These materials are well-known for their good frictional wear resistance, good resistance to thermal fatigue, high thermal conductivity and high specific heat. In this paper, the sintering process of copper/electrocorundum composites reinforced by electrocorundum particles with diameters of 3 or 180 μm and 1, 3, 5 vol.% content is presented. The effects of different particle sizes of the ceramic reinforcement on the microstructure, physical, mechanical, tribological and thermal properties of the fabricated composites are discussed

The relationship between microstructure and mechanical properties of directly bonded copper-alumina ceramics joints

The effect of phase transformations induced in the surface layer of alumina ceramics during its direct joining with copper activated with oxygen or titanium on the mechanical strength of the ceramic/copper joints was examined. The materials used in the experiments were an alumina single crystal, alumina ceramics (97.5 wt% Al2O3), the cermet mixtures: Cu-Cu2O with 10-50 wt% of Cu2O, copper with 5 wt% of Ti, and copper with 5 wt% of Ti and 10 wt% of Ag. The microstructure of the transition layer was examined by the X-ray diffraction method (XRD), scanning electron microscopy method (SEM) and energy dispersive x-ray spectroscopy (EDX). The mechanical strength of the joints was measured using the three-point bending method. The amount of oxygen optimal for the joining process was determined. It has been demonstrated that the cohesion of the joints depends not only on the formation of the individual phases but also, or even primarily, on the microstructure of the transition layer formed between them

Investigations of Interface Properties in Copper-Silicon Carbide Composites

This paper analyses the technological aspects of the interface formation in the copper-silicon carbide composite and its effect on the material’s microstructure and properties. Cu-SiC composites with two different volume content of ceramic reinforcement were fabricated by hot pressing (HP) and spark plasma sintering (SPS) technique. In order to protect SiC surface from its decomposition, the powder was coated with a thin tungsten layer using plasma vapour deposition (PVD) method. Microstructural analyses provided by scanning electron microscopy revealed the significant differences at metal-ceramic interface. Adhesion force and fracture strength of the interface between SiC particles and copper matrix were measured. Thermal conductivity of composites was determined using laser flash method. The obtained results are discussed with reference to changes in the area of metal-ceramic boundary

Copper-Carbon Nanoforms Composites - Processing, Microstructure and Thermal Properties

The main current of publication is focused around the issues and problems associated with the formation of composite materials with Cu matrix and reinforcing phases in the various carbon nanoforms. The core of the research has been focused on thermal conductivity of these composites types. This parameter globally reflects the state of the structure, quality of raw materials and the technology used during the formation of composite materials. Vanishingly low affinity of copper for carbon, multilayered forms of graphene, the existence of critical values of graphene volume in the composite are not conducive to the classic procedures of composites designing. As a result, the expected, significant increase in thermal conductivity of composites is not greater than for pure copper matrix. Present paper especially includes: (i) data of obtaining procedure of copper/graphene mixtures, (ii) data of sintering process, (iii) the results of structure investigations and of thermal properties. Structural analysis revealed the homogenous distribution of graphene in copper matrix, the thermal analysis indicate the existence of carbon phase critical concentration, where improvement of thermal diffusivity to pure copper can occur

Influence of Material Coating on the Heat Transfer in a Layered Cu-SiC-Cu Systems

This paper describes the process of obtaining Cu-SiC-Cu systems by way of spark plasma sintering. A monocrystalline form of silicon carbide (6H-SiC type) was applied in the experiment. Additionally, silicon carbide samples were covered with a layer of tungsten and molybdenum using chemical vapour deposition (CVD) technique. Microstructural examinations and thermal properties measurements were performed. A special attention was put to the metal-ceramic interface. During annealing at a high temperature, copper reacts with silicon carbide. To prevent the decomposition of silicon carbide two types of coating (tungsten and molybdenum) were applied. The effect of covering SiC with the aforementioned elements on the composite’s thermal conductivity was analyzed. Results were compared with the numerical modelling of heat transfer in Cu-SiC-Cu systems. Certain possible reasons behind differences in measurements and modelling results were discussed

The effect of ceramic type reinforcement on structure and properties of Cu-Al2O3 composites

The purpose of this paper is to elaborate on mechanical alloying conditions for a composite powder consisting of copper and brittle aluminium oxides. Detailed analysis of the Cu-Al2O3 powder mixture structure obtained in the mechanical alloying process allows for the study of the homogenization phenomena and for obtaining grains (in composite form) with a high degree of uniformity. The Cu-5vol.%Al2O3 composites were obtained by means of the spark plasma sintering technique. The results presented herein were studied and discussed in terms of the impact of using a different form of aluminium oxide powder and a different shape of copper powder on composite properties. Research methodology included microstructure analysis as well as its relation to the strength of Cu-Al2O3 interfaces. It transpires from the results presented below that the application of electrocorundum as a reinforcement phase in composites decreases porosity in the ceramic phase, thus improving thermal properties and interfacial strength

Spiekane kompozyty molibden-Al2O3 - struktura i właściwości

Brittleness is the main technical limitation on a wide use of advanced ceramic materials. To overcome this problem, ceramic-metal composites are commonly applied. A principal advantage of ceramic-metal composite materials is their higher resistance to brittle fracture. An increase of fracture toughness depends on the type, amount, size and shape of a metallic component. The metallic phase can additionally modify physical, mechanical and thermal properties of materials. The results of experiments concerning a manufacturing process of Mo-Al2O3 composite materials obtained by the hot pressing method were presented. Two powder mixtures with different volume fraction of aluminium oxide were prepared in a planetary ball mill. The hot pressing process allowed to obtain well-densified metal matrix composites (˜99% of a theoretical density). Microstructural observations of sinters were conducted using scanning electron microscopy, energy-dispersive X-ray spectroscopy, and transmission electron microscopy. Very stable bonding between metal and ceramic grains was observed. Complex investigations of the physical and mechanical properties of obtained molybdenum-alumina composite materials seem to be very promising from an application point of view.Główna przyczyną ograniczenia stosowalności zaawansowanych materiałów ceramicznych jest ich kruchość. W celu pokonania tego problemu powszechnie stosuje sie kompozyty ceramiczno-metalowe, których zaletą jest wyższa odporność na kruche pękanie w porównaniu z materiałami ceramicznymi. Zależy ona od wielu czynników m.in. rodzaju, ilości, wielkości oraz kształtu zastosowanego metalu. Ostatecznym zmianom ulegają równiez inne właściwości tj. fizyczne, mechaniczne, termiczne. W pracy przedstawiono wyniki technologicznych prób otrzymywania materiałów kompozytowych Mo-Al2O3 przy wykorzystaniu techniki spiekania pod ciśnieniem. Mieszaniny proszków o różnych udziałach objętosciowych fazy ceramicznej przygotowano w planetarnym młynku kulowym. Ostateczny proces zageszczania pozwolił uzyskac materiały o wysokiej gestości względnej (powyżej 99% gęstości teoretycznej). Analizowano mikrostrukturę spieków z wykorzystaniem skaningowej i transmisyjnej mikroskopii elektronowej. Stwierdzono występowanie bardzo dobrego połączenia fazy ceramicznej z osnową metalową. Przeprowadzono szeroką analizą właściwosci fizycznych i mechanicznych uzyskanych kompozytów, co powinno pozwolić na rozszerzenie możliwości aplikacyjnych opracowanych tworzyw

Corrosion and thermal shock resistance of metal (Cu, Al) matrix composites reinforced by SiC particles

This paper presents the results of studies concerning the production and characterization of Al-SiC/W and Cu-SiC/W composite materials with a 30% volume fraction of reinforcing phase particles as well as the influence of corrosion and thermal shocks on the properties of selected metal matrix composites. Spark plasma sintering method (SPS) was applied for the purpose of producing these materials. In order to avoid the decomposition of SiC surface, SiC powder was coated with a thin tungsten layer using plasma vapour deposition (PVD) method. The obtained results were analysed by the effect of the corrosion and thermal shocks on materials density, hardness, bending strength, tribological and thermal properties. Qualitative X-ray analysis and observation of microstructure of sample surfaces after corrosion tests and thermal shocks were also conducted. The use of PVD technique allows us to obtain an evenly distributed layer of titanium with a constant thickness of 1.5 µm. It was found that adverse environmental conditions and increased temperature result in a change in the material behaviour in wear tests