Metal Composite Materials Research Articles

Study of the corrosion-protection effect of electrodeposited coatings on objects of rapid prototyping technologies

It is shown that metal composite materials based on stainless steel and bronze, which are used for the layer-by-layer synthesis of products by the method of selective laser sintering (SLS), can be reliably protected from corrosion by electrodeposited coatings. It is established that, at equal thickness of the coatings (∼20 μm), the best characteristics in a 3% solution of NaCl are found for layers of chemically precipitated nickel, electrodeposited milky chromium, and a three-layer coating of Cu-Ni-Cr. The correlation between the corrosion and electrochemical activity of the coating materials and the value of the wetting angle for their surface and polar fluid is obtained.

Heterojunctions between metals and carbon nanotubes as ultimate nanocontacts.

We report the controlled formation and characterization of heterojunctions between carbon nanotubes and different metal nanocrystals (Fe, Co, Ni, and FeCo). The heterojunctions are formed from metal-filled multiwall carbon nanotubes (MWNTs) via intense electron beam irradiation at temperatures in the range of 450-700 degrees C and observed in situ in a transmission electron microscope. Under irradiation, the segregation of metal and carbon atoms occurs, leading to the formation of heterojunctions between metal and graphite. Metallic conductivity of the metal-nanotube junctions was found by using in situ transport measurements in an electron microscope. Density functional calculations show that these structures are mechanically strong, the bonding at the interface is covalent, and the electronic states at and around the Fermi level are delocalized across the entire system. These properties are essential for the application of such heterojunctions as contacts in electronic devices and vital for the fabrication of robust nanotube-metal composite materials.

Model reference adaptive control for an ionic polymer metal composite in underwaterapplications

Ionic polymer metal composite (IPMC) materials are in an early stage of development.Their response as actuators is still very unpredictable. Their dynamic response is stillsubjected to several critical parameters that vary with time, thus extracting an accurateand repeatable model is very difficult. This paper presents the design and implementationof an adaptive efficient position control system for an IPMC actuator workingin underwater conditions. The control system is an model reference adaptivecontrol (MRAC) based on a reference model and an adaptation that controls a1 cm × 0.5 cm length IPMC stripbased on a Nafion 117 Na+ membrane. As the reference model a second-order empirical model of the plant is used. Thecontrol system is first simulated and then experimentally implemented within theLabVIEW framework.

Structure and properties of the superelastic and hard carbon particles reinforcing wear-resistant composite materials obtained from mixtures of iron and fullerene powders under pressure

The structure and mechanical properties of hard and superelastic carbon particles formed at a pressure of 5 GPa at 1200–1400°C upon the consolidation of metal-fullerene powder mixture into a composite material have been studied by optical microscopy, high-resolution electron microscopy, nanoindentation, etc. The reinforcing carbon particles are characterized by an elastic hardness of up to 15 GPa, a high elastic recovery (80–90%), an elastic modulus of 60–90 GPa, a low density (about 2 g/cm3), and a high cracking resistance. The particles are X-ray amorphous, but they inherit the pattern of the initial fullerite crystals. The metallic composite materials reinforced by the hard and superelastic carbon particles in abrasive resistance surpass the well-known wear-resistant steels by an order of magnitude and approach diamond-like coatings in their friction coefficients (about 0.12).

Characterization of Interphase Environmental Degradation at Elevated Temperature of Fibre-Reinforced Titanium Matrix Composites

Fibre reinforced metallic composite materials are being considered for a number of applications because of their attractive mechanical properties as compared to monolithic metallic alloys. An engineered interphase, including the bond strength between the composite's constituents, contributes to a large extent to the improvement of strength and stiffness properties of this class of materials. However, in high temperature applications, where combination of cyclic loading with environmental effects is expected, consideration should be given to interphase degradation, especially in the vicinity of stress risers, such as notches and holes. The applicability of damage tolerance analysis in structural components made of titanium matrix composite materials designed to operate under high temperature environments would depend on the availability of adequate characterization methods for the evaluation of interfacial degradation. The objective of this paper is to provide a basic understanding of interfacial degradation mechanisms due to oxidation in environmentally exposed titanium-based composites subjected to cyclic stresses. A non-destructive method has been developed enabling high-resolution monitoring of interfacial damage initiation and accumulation as well as surface/subsurface cracking behaviour during interrupted fatigue tests. This nondestructive technique is based on surface acoustic wave propagation in the composites and can detect minute changes in elastic properties of the interfacial region due to elevated temperatures as well as oxygen effects.

Metal Coated Functionalized Single-Walled Carbon Nanotubes for Composites Application

This study is considered as a method for producing multifunctional metal composite materials by using Single-walled Carbon Nanotubes (SWNTs). In this research, various metals (Ni, Cu, Ag ) were successfully deposited onto the surface of SWNTs. It has been found that homogenous dispersion and dense nucleation sites are the necessary conditions to form uniform coating on SWNTs. Functionalization has been applied to achieve considerable improvement in the dispersion of purified single-walled carbon nanotubes. A three-step electroless plating approach was used and the coating mechanism is described in the paper. The samples were characterized by using scanning electron microscopy (SEM), transmission electron microscopy (TEM), Raman spectroscopy, and energy-dispersive X-ray spectroscopy (EDX). The application of coated SWNTs in Titanium will be discussed in this paper.

Doping effects on robotic systems with ionic polymer–metal composite actuators

Ionic polymer–metal composite (IPMC) materials are one of the most promising electro-active polymer actuators for applications, and have good properties of response and durability. The characteristics of IPMC materials depend on the type of counter-ion. When applied to mechanical systems such as a robot, there exist possibilities to change the properties of the system dynamics by changing the counter-ions and system parameters according to the environment or purpose. We focus on this 'doping effect' property of the system and will verify the effect on robotic applications. In this paper, we consider dynamic walking of a small-sized biped robot and swimming motion of a snake-like robot, and demonstrate the doping effects by numerical simulations and experiments.

Strength and Plasticity of Metal and Nonmetallic Composites for Cryogenic and Aerospace Purposes

We present results of studying mechanical properties of four groups of metallic and nonmetallic composite materials in a temperature range of 300–4.2 K. Types of glass-reinforced and carbon-reinforced plastics with the best low-temperature strength and elastic characteristics have been specified. A deterioration of the strength characteristics of boron-fiber-reinforced aluminum alloy after temperature cycling in the temperature range 20–443 K has been detected. It has been shown that superconducting composites with ultra-fine filaments, fabricated by hydrostatic extrusion without intermediate annealings, possess optimal combination of mechanical and electrical characteristics.

Optimization of solar absorbing three-layer coatings

Abstract The optimization of spectrally selective solar-absorbing three-layer coatings was studied from both theoretical and experimental points of view. The base layer consists of a cermet (ceramic–metal composite) material, where small metal clusters are embedded in the dielectric surrounding. The results show considerable enhancement of the solar absorption due to the metal nanoparticles. Theoretical treatment of the optical properties of the cermet was carried out using effective medium theory. The experimentally determined optical constants of calibration samples were used to calculate the film reflectance of single or multiple layers. Theoretically optimized three-layer coatings show solar absorptance value as high as 0.97 and moderate reflectance at 2.5 μm giving low thermal emittance. Experimental optimization was carried out through control of the coatings layer by layer. The metal content and the film thickness are two important parameters for cermet films. Only thickness is sensitive to the middle and top layer. The optical properties are matched in such a way that the base layer functions as main absorber, the top layer reduces the reflectance from the front surface, and the middle layer links the base and the top layers. An experimentally optimized solar absorptance of 0.97 with a thermal emittance of 0.05 was obtained, which shows that the optimization procedure is reliable.

Synthesis of Cu-Based Bulk Metallic Glass Matrix Composites by Warm Processing of Gas Atomized Powders

The bulk metallic glass matrix composite comprising Cu54Ni6Zr22Ti18 metallic glass powder and ductile brass powder was fabricated by the warm process. The warm process was carried out by spark plasma sintering, which led to the homogeneous distribution of both phases of brass and metallic glass without pores. The metallic glass matrix composite material exhibits the same crystallization behavior of the metallic glass powder. A compressive strength of 1.0 GPa with a plastic strain of 3 % was obtained in the present metallic glass composite. The composite with enhanced strength and ductility was successfully achieved by introducing a ductile phase in the hard bulk metallic glass.

Separation of grain growth and glass transition during structural evolution of the bulkNd60Fe30Al10alloy

In this paper we report in situ high-energy x-ray diffraction studies and differential scanning calorimetry measurements during structural transformation of die-cast ${\mathrm{Nd}}_{60}{\mathrm{Fe}}_{30}{\mathrm{Al}}_{10}$ bulk samples. The real-time evolution of the structure was recorded as a function of temperature allowing to follow the grain growth and the crystallization of the amorphous matrix which take place in the system. The two processes could be independently investigated by the two different experimental methods, while the theoretical models used for the data interpretation allow us to calculate their activation energies, to separate the grain growth process from the glass transition, and to obtain the continuous heating transformation diagram of the ${\mathrm{Nd}}_{60}{\mathrm{Fe}}_{30}{\mathrm{Al}}_{10}$ system. The relevance of the combination of these two techniques for the investigation of metallic glasses or complex composite materials is discussed.

Adhesively-bonded joints in metallic alloys, polymers and composite materials: Mechanical and environmental durability performance

The factors affecting the mechanical and environmental durability (or stability), and performance of the adhesively bonded joints in various adherends including metallic alloys, polymers and composite materials are studied in detail. The primary function of a joint is to transfer load from one structural member to another. In most bonded joints the load transfer takes place through interfacial shear. At present, the use of adhesive bonded joints are largely applied to secondary non-critical structures. Whereas the use of adhesive bonding in primary structural applications has been somewhat limited because of the difficulty in defining and predicting joint strength, and designing the joint geometry to optimize strength and reliability. The determination of adhesive joint strength is complicated primarily by the nature of the polymeric material itself. Since these problems are mainly mechanical in nature, stress analysis is required to understand how the force loads are distributed along the adherends and adhesive layer. Most structural engineers consider the durability or stability of a joint to be fatigue related. This is only partly true for adhesive bonds as most durability issues are driven by environmental resistance rather than fatigue loads. The environmental resistance of an adhesive bond is determined by the chemical bonds formed during cure of the adhesive and the resistance of the chemical bonds to environmental degradation. Environmental resistance is fundamental to the durability of a bonded joint or repair. Most in-service failures are caused by environmental degradation of the interface between the bonding surface and the adhesive. Although the use of adhesive bonding is increasing rapidly, there are still important issues which need to be addressed in joint analysis, design, durability, and performance considerations. Therefore, the study of joints usually involves consideration of (a) joint geometries, (b) materials (i.e., adhesives and adherends), (c) loading conditions (i.e., static and dynamic loadings), (d) failure modes (i.e., cohesive, adhesive or mixed failure modes), and (e) temperature and moisture or environmental effects (humidity, solvents, corrosion, temperature extremes, thermal cyling etc.). Therefore, in the present paper the adhesive joints are critically assessed in terms of these factors which affect the durability and performance of them. There are two basic mathematical approaches for the analysis of adhesively bonded joints: (a) closed-form or analytical model and (b) numerical solutions (i.e., finite element analysis, FEA). In the closed-form approach, a set of differential equations and boundary conditions is formulated. The solutions of these equations are analytical expressions which give values of stresses at any point of joint. The analytical approach for the solution of complex stress distributions in the joints has been progressively refined until recent times. In the second approach, solutions of differential equations are obtained by numerical methods or the continuum is represented by a discrete model at the outset. The solution of these equations gives displacements at the determined points from which strains and stresses can be obtained for any point within the model. Among the numerical methods, finite element analysis (FEA) has been extensively used with success. The two- and three-dimensional finite element analyses approaches have been extensively applied by many workers to analyse the adhesive joints considering the linear and geometric nonlinearities.

Analysis of deformation during simultaneous plastic deformation of dissimilar powder metallurgical preforms

Metal composite materials are heterogeneous materials consisting of two or more different components bonded together internally. Special kinds of metal composites are produced by simultaneous plastic deformation of different metals. Process variables and characteristics of materials deformed simultaneously have an effect on the amount of deformation in each material, plastic zone, influencing the results of simultaneous plastic deformation. The present paper investigates the ability of dissimilar powder metallurgical (P/M) preforms to undergo simultaneous deformation using a special laboratory test. The influence of density ratio, thickness or volume ratio, type of deformation and total plastic strain on the strain experienced by individual metals are studied to establish the conditions of sound flow during simultaneous deformation. The results indicate that the simultaneous plastic deformation of dissimilar P/M preforms with different properties makes the deformation heterogeneous. The difference in the plastic strain experienced by each material increases with increase in the total plastic strain, volume or thickness ratio and deviation from the unit density ratio. The consolidation and metal matrix hardening mechanisms associated with the P/M preform deformation, strongly affect the deformation behavior of each metal and the onset of steady state deformation, during simultaneous deformation. Parameters such as volume ratio and type of deformation also strongly influence the simultaneous deformation results.

Adhesively-bonded joints and repairs in metallic alloys, polymers and composite materials: Adhesives, adhesion theories and surface pretreatment

In the present paper, the following topics are reviewed in detail: (a) the available adhesives, as well as their recent advances, (b) thermodynamic factors affecting the surface pretreatments including adhesion theories, wettability, surface energy, (c) bonding mechanisms in the adhesive joints, (d) surface pretreatment methods for the adhesively bonded joints, and as well as their recent advances, and (e) combined effects of surface pretreatments and environmental conditions on the joint durability and performance. Surface pretreatment is, perhaps, the most important process step governing the quality of an adhesively bonded joint. An adhesive is defined as a polymeric substance with viscoelastic behavior, capable of holding adherends together by surface attachment to produce a joint with a high shear strength. Adhesive bonding is the most suitable method of joining both for metallic and non-metallic structures where strength, stiffness and fatigue life must be maximized at a minimum weight. Polymeric adhesives may be used to join a large variety of materials combinations including metal-metal, metal-plastic, metal-composite, composite-composite, plastic-plastic, metal-ceramic systems. Wetting and adhesion are also studied in some detail in the present paper since the successful surface pretreatments of the adherends for the short- and long-term durability and performance of the adhesive joints mostly depend on these factors. Wetting of the adherends by the adhesive is critical to the formation of secondary bonds in the adsorption theory. It has been theoretically verified that for complete wetting (i.e., for a contact angle θ equal to zero), the surface energy of the adhesive must be lower than the surface energy of the adherend. Therefore, the primary objective of a surface pretreatment is to increase the surface energy of the adherend as much as possible. The influence of surface pretreatment and aging conditions on the short- and long-term strength of adhesive bonds should be taken into account for durability design. Some form of substrate pretreatment is always necessary to achieve a satisfactory level of long-term bond strength. In order to improve the performance of adhesive bonds, the adherends surfaces (i.e., metallic or non-metallic) are generally pretretead using the (a) physical, (b) mechanical, (c) chemical, (d) photochemical, (e) thermal, or (e) plasma method. Almost all pretreatment methods do bring some degree of change in surface roughness but mechanical surface pretreatment such as grit-blasting is usually considered as one of the most effective methods to control the desired level of surface roughness and joint strength. Moreover, the overall effect of mechanical surface treatment is not limited to the removal of contamination or to an increase in surface area. This also relates to changes in the surface chemistry of adherends and to inherent drawbacks of surface roughness, such as void formations and reduced wetting. Suitable surface pretreatment increases the bond strength by altering the substrate surface in a number of ways including (a) increasing surface tension by producing a surface free from contaminants (i.e., surface contamination may cause insufficient wetting by the adhesive in the liquid state for the creating of a durable bond) or removal of the weak cohesion layer or of the pollution present at the surface, (b) increasing surface roughness on changing surface chemistry and producing of a macro/microscopically rough surface, (c) production of a fresh stable oxide layer, and (d) introducing suitable chemical composition of the oxide, and (e) introduction of new or an increased number of chemical functions. All these parameters can contribute to an improvement of the wettability and/or of the adhesive properties of the surface.

COPPER/INVAR/COPPER

Abstract Copper/Invar/Copper is a wrought metallic composite material used in printed circuit boards, power planes, metal cores, hybrid enclosures, heat sinks, and other applications where coefficients of thermal expansion (CTE) match or where constraint of thermal expansion is required or beneficial. The laminated Cu/Invar/Cu composite material is metallurgically bonded by roll bonding and normally used in the fully annealed condition. This datasheet provides information on composition, physical properties, hardness, elasticity, and tensile properties. It also includes information on corrosion resistance as well as forming, heat treating, and joining. Filing Code: FE-125. Producer or source: Engineered Materials Solutions Inc.

Fabrication of Various Nano Noble Metal Composite Materials by Ecological Sono-Process

The ultrasonic irradiation differs from traditional energy sources in duration, pressure, and energy per molecule, and it is a unique means on the interaction between energy and matter. It is well known that the chemical reactions which take place under conventional conditions can be accelerated by ultrasonic irradiation. In this study, the process of nano-sized metal deposition on various kinds of materials were investigated for ecological sonochemical process. By choosing suitable conditions, it is reasonable to expect that these simple sonochemical processes can be extended to obtain various nano-sized metal particles. Thus applications by using these reactions were investigated to prepare the nano-sized metal particles on various materials at ecology and economy, and mechanisms were investigated.

A Metamaterial for Directive Emission

In this paper we present the first results on emission in metamaterial. We show how the specific properties of metallic composite material can modify the emission of an embedded source. We show that under proper conditions the energy radiated by a source embedded in a slab of metamaterial will be concentrated in a narrow cone in the surrounding media. An experimental demonstration of this effect is given in the microwave domain, and the constructed antenna has a directivity equivalent to the best reported results with photonic-crystal-based antennas but using a completely different physical principle [B. Temelkuaran, J. Appl. Phys. 87, 603 (2000)]].

Metallurgical special features of the production of welded joints in dispersion‐filled metallic composite materials

Metallurgical special features of the production of welded joints in dispersion‐filled metallic composite materials

Use of mechanical alloying in preparation of metal powders and composite materials

Use of mechanical alloying in preparation of metal powders and composite materials

Interface toughness under combined mode I, II and III loadings

Realizing improved strength in composite metallic materials remains a challenge using conventional welding and joining systems due to the generation and development of brittle intermetallic compounds caused by complex thermal profiles during solidification. Here, wire arc additive manufacturing (WAAM) process was used to fabricate a steel-nickel structural component, whose average tensile strength of 634 MPa significantly exceeded that of feedstock materials (steel, 537 MPa and nickel, 455 MPa), which has not been reported previously. The as-fabricated sample exhibited hierarchically structural heterogeneity due to the interweaving deposition strategy. The improved mechanical response during tensile testing was due to the inter-locking microstructure forming a strong bond at the interface and solid solutions strengthening from the intermixing of the Fe and Ni increased the interface strength, beyond the sum of parts. The research offers a new route for producing high-quality steel-nickel dissimilar structures and widens the design opportunities of monolithic components, with site-specific properties, for specific structural or functional applications.