Layers Of Different Metals Research Articles

Identification of the wood species in the wooden sheath of Indonesian kris by synchrotron X-ray microtomography

A kris is a traditional dagger that originated in Indonesia. A kris is distinguished by its asymmetrical blade, which has layers of different metals bonded on its surface. Wood is the main material used to make the kris sheath. To preserve the knowledge about wood selection of the sheath, wood identification is a crucial first step. In the present study, we identified the wood species used to make the kris sheath. We performed synchrotron X-ray microtomography, which allows microscopic observation with minimum sample availability. Seven wooden kris sheaths were investigated. The results showed that synchrotron X-ray microtomography is suitable for observing the important microscopic anatomical features of the wood species in kris sheaths. We found that Dysoxylum spp., Tamarindus indica, and Kleinhovia hospita were used as sheath materials. We also visualized the spatial distribution of the prismatic crystals inside the T. indica and K. hospita xylem cells. Abundant crystals were present in T. indica arranged in longitudinal alignment inside the chambered axial parenchyma cells. The crystals were arranged in radial alignment inside the ray cells of K. hospita. The existence of abundant crystals in series may be important for the mechanical support of certain xylem cells.

Experimental and Numerical Investigation on the Perforation Resistance of Double-Layered Metal Shield under High-Velocity Impact of Armor-Piercing Projectiles.

In the case of protection of transportation systems, the optimization of the shield is of practical interest to reduce the weight of such components and thus increase the payload or reduce the fuel consumption. As far as metal shields are concerned, some investigations based on numerical simulations showed that a multi-layered configuration made of layers of different metals could be a promising solution to reduce the weight of the shield. However, only a few experimental studies on this subject are available. The aim of this study is therefore to discuss whether or not a monolithic shield can be substituted by a double-layered configuration manufactured from two different metals and if such a configuration can guarantee the same perforation resistance at a lower weight. In order to answer this question, the performance of a ballistic shield constituted of a layer of high-strength steel and a layer of an aluminum alloy impacted by an armor piercing projectile was investigated in experimental tests. Furthermore, an axisymmetric finite element model was developed. The effect of the strain rate hardening parameter C and the thermal softening parameter m of the Johnson–Cook constitutive model was investigated. The numerical model was used to understand the perforation process and the energy dissipation mechanism inside the target. It was found that if the high-strength steel plate is used as a front layer, the specific ballistic energy increases by 54% with respect to the monolithic high-strength steel plate. On the other hand, the specific ballistic energy decreases if the aluminum plate is used as the front layer.

Experimental and numerical investigation on the perforation resistance of double-layered metal shields under high-velocity impact of soft-core projectiles

Multi-layered metal shields have been extensively investigated in the past, mainly studying the effect of layering, spacing and order of plates of different materials. However, at present is not feasible to predict the effect of layering and spacing for a particular case but only general pattern can be considered. Some investigations based on numerical simulations showed that the multi-layered configuration made by layers of different metals could be a promising solution in terms of weight reduction of the shield but, different authors obtained contradictory results and comprehensive experimental investigation is still missing. Thus, the scope of this study is to evaluate the perforation resistance of double-layered metal shields constituted by a high-strength steel and an aluminum layer when impacted by a soft-core projectile. It was found that the multi-layered configuration constituted of two layers of different metals, is less efficient than the monolithic configuration. Furthermore, numerical models were developed to increase the understanding of the problem. It was necessary to use an alternative to the commonly used FE method to model extreme deformation occurring in soft-core projectiles in such kinds of scenario. In particular, the SPH method was implemented providing a detailed parametric study of the most relevant numerical parameters. The SPH method was thus exploited to study different configurations of the double-layer target, and it was found that the specific ballistic energy depends on the ratio between the two layers of the target.

Determination Of Formability Of Bimetallic Sheet Using Forming Limit Diagram

Abstract The Formability of a sheet plays an important role in all sheet metal forming operations. It is required to determine the formability of sheet to know the behavior of the sheet under various loading conditions. By determining the formability, it will be easier to predict the failure point of a sheet metal. Further it suggests us the maximum permissible value of load to be applied on the sheet material so that it will not fail. Forming Limit Diagram is a graphical way of depicting the forming behaviour of a sheet metal. FLD estimates various regions of sheet metal of plastic deformation and suggests a permissible value of load to be applied. However FLD of Aluminium, MS, Copper etc are known from the record books but FLD for bimetallic sheet is not yet determined. Bimetal refers to an object that is composed of two separate metals joined together. Instead of being a mixture of two or more metals, like alloys, bi-metallic objects consist of layers of different metals. Generally, these bimetals are used for thermal applications like the thermostat, thermocouple and other electrical devices which need circuit breakers. But these bi-metallic sheets have better strength, thermal resistance and ductility than the singular sheet metal. Hence, the aim of this work is to determine whether these bi-metallic sheets are suitable for deep drawing operation or not. This can be determined by finding out the formability of these sheets. The main objective of this work is to draw the Forming Limit Diagram of bimetallic sheet made of Aluminium and Copper and to find the formability of the sheet. To achieve this objective the strength of the bimetallic sheet is determined first and then Chemical Etching of the bimetallic sheet is done which creates a grid pattern of circles on the surface of the sheet. The sheet is then cut into different widths by keeping the height of the specimen constant. Erichsen cupping test is performed for different widths of bimetallic strips. During the experimental process the sheet is initially fixed between die and punch. Then the punch is made to advance through specimens until a fine hair line fracture appears. The circles on the surface of the sheet will be deformed into ellipse. Deep drawing is carried out for the same bimetallic sheet where the blank of the bimetallic sheet is drawn into cup. The major and minor axes of the ellipse which corresponds to major and minor strains are measured. The strains are measured along different portions of the cup namely flange portion, side walls and the base of the cup and this is included in the Forming Limit Diagram of Bimetallic sheet. By taking major strain on Y-axis and minor strain on X-axis, a curve is obtained which is called as Forming Limit curve or Forming Limit Diagram.

A microscale explosive initiator integrated with a reactive thin-filmed metallic bridge of boron/titanium laminated layers

Aided by the advancement of microfabrication technologies, the electro-pyrotechnical initiators are being miniaturized into micron sizes to gain higher safety and reliability as well as lower mass manufacturing cost. One of the most important innovations proposed for the explosive initiator design in recent years would be the device integration with reactive thin-film metallic bridge which is composed of many laminated layers of different metals. The nanoscale boron and titanium (B/Ti) multilayers would be a feasible candidate for substantially improving the thermal initiation performance due to their fast reaction speed and high exothermic heat release. This study introduces the numerical modeling of ohmic heating in thin-film metallic bridge and the self-propagating intermetallic reaction in B/Ti laminated layers coupled with pulse-forming circuit in order to investigate the feasibility of such an initiator design. The computational results show that the ignition of intermetallic reaction and propagation of reaction wave in B/Ti multilayers of reactive initiator bridge are successfully modeled and simulated. The effects of several reactive bridge design parameters are investigated such as B/Ti layer thickness and its set number on bridge, electrical energy input in pulse form, and the existence of pre-mixing zone at bimetallic interface.

Extended Simulations of the Roll Bonding Process

AbstractRoll bonding is a joining‐by‐forming process in which two or more layers of different metals are passed through a pair of flat rolls. Under the high pressure, a permanent bond between the metals is generated by plastic deformation. The main factors influencing this process and the creation of bond strength are the size of the surface area and the normal pressure in the interface. In order to numerically predict the bond strength the FE implementation of a contact algorithm is performed. Simultaneously, the physical mechanisms typical of plastic deformation are taken into consideration. The focus particularly lies on the micro‐mechanical modeling of strain hardening by dislocation slip. A first study is given on the effects of the chemical impurities on the dislocation density and motion.

Synthesis of bimetallic nanostructures by nanosecond laser ablation of multicomponent thin films in water

The paper presents results on nanosecond laser ablation of thin films immersed in a liquid. The thin films were prepared by consecutive deposition of layers of different metals by thermal evaporation (first layer) and classical on-axis pulsed laser deposition (second layer); Ni/Au, Ag/Au and Ni/Ag thin films were thus deposited on glass substrates. The as-prepared films were then placed at the bottom of a glass vessel filled with double distilled water and irradiated by nanosecond laser pulses delivered by a Nd:YAG laser system at λ = 355 nm. This resulted in the formation of colloids of the thin films’ material. We also compared the processes of ablation of a bulk target and a thin film in the liquid by irradiating a Au target and a Au thin film by the same laser wavelength and fluence (λ = 355 nm, F = 5 J/cm2). The optical properties of the colloids were evaluated by optical transmittance measurements in the UV– VIS spectral range. Transmission electron microscopy was employed to estimate the particles’ size distribution.

Electroless Metallization of Stereolithographic Photocurable Resins for 3D Printing

In the last few years the introduction of affordable 3D printing techniques like fused deposition modeling (FDM) and stereolithography (SLA) is slowly changing the way mass production has always been intended. The possibility to obtain complex shapes in a short time directly at home, without using conventional manufacturing techniques, is a revolutionary concept that is finding a lot of different applications. However some limitations exist for 3D printing, the most important one being the manufacture of metallic objects. Metals offer many attractive properties like electrical and thermal conductivity or a good mechanical resistance, and for this reason the 3D printing of metallic objects is a strategic research field in additive manufacturing. Some techniques able to directly print using metals are available, but many limitations are present in this case. For this reason the most used method to obtain bulk metallic parts is the use of the printed polymeric version as a mold to cast the final object. In most applications however only a thin layer of metal is required and different methods can be used to coat a printed part, including PVD and all-wet metallization. The latter is in general preferred due to the low cost and the optimal coverage in the case of critical shapes of the printed part. Optimized methods are available for the metallization of FDM printed objects [1], while in the case of SLA manufactured samples only some aspects of the plating process are treated in the existing literature [2, 3]. The present work investigates an optimized method to metallize parts obtained with SLA 3D printing by mean of an all-wet process based on electroless plating. The behavior of different proprietary and custom made photocurable resins printed using a commercial laser stereolithographic printer is investigated. The coatings employed include nickel-phosphorus and copper, two metals typically deposited via electroless plating on polymers. The metallization is characterized from the fundamental point of view on planar samples, while in a second time some examples of complex shapes metallization are provided. In particular the metallization of micrometric parts is studied. Finally the possibility to deposit other layers of different metals via electrodeposition on the first coating obtained by electroless plating is analyzed. [1] R. Bernasconi et al.; ECS Trans., 66 (19), 23 (2015) [2] A. Macor et al.; Rev. Sci. Instrum., 83, 046103 (2012) [3] B. Luan et al.; Appl. Surf. Sci., 156, 26 (2000)

Development of ITO thin film sensor for the detection of formaldehyde at room temperature

Thin films of indium tin oxide were grown by the direct evaporation technique. The sensors fabricated under the optimized deposition conditions were exposed at room temperature (303K) to different concentrations of formaldehyde vapours and the relative change in resistance was measured. The effect of the film thickness on the response to test vapours was studied. In order to enhance the sensitivity, sensors with thin promoting layers of different metals and oxide like Cu, Ag and MgO deposited on the top of the film were fabricated and tested. The sensors with improved sensitivity were studied for the elaborate response to formaldehyde vapours at room temperature.

Experimental and numerical study of surface alloying by femtosecond laser radiation

Here we report on experimental studies of femtosecond laser induced surface metal alloying. We demonstrate that layers of different metals can be mixed in a certain range of laser pulse energies. Numeric simulations demonstrate that the sub-surface melting and mixing is advantaged through the difference in the electron–phonon coupling constants of the metals in the multi-layer system. Dependence of the depth of the mixed layer on the number of laser pulses per unit area is studied. Numeric simulations illustrate physical picture of the laser alloying process.

Low-Stress Bond Pad Design for Low-Temperature Solder Interconnections on Through-Silicon Vias (TSVs)

Low-temperature bonds are thin intermetallic (IMC) bonds that are formed between devices when plated layers of different metals on each side of the component come into contact under relatively low temperature and high pressure. These joints, comprised of completely of IMC compounds, will fail in a sudden unexpected manner as compared to normal solder joints, which fail in a ductile manner, where cracks grow more slowly. This problem of weak interconnects is further exacerbated when these thin interconnections are formed on pads located above through-silicon vias (TSVs). When a change in temperature occurs, the mismatch in coefficient of thermal expansion causes the copper inside the TSV to expand or contract much more than the surrounding silicon. This could result in unexpectedly high tensile stresses in the joints. This additional tensile stress, during post-formation cooling down to room temperature, increases the likelihood of joint failure. This paper presents a novel pad design to overcome the situation of high stress in the joints. The proposed design does not involve any additional fabrication or material cost. Simulation results show that, with the proposed pad design, the maximum tensile stress in the interconnect decreases by 50%. Reliability assessment has also been performed in order to compare the proposed pad design with the conventional design. It is found that the samples with the proposed design have a better drop impact reliability performance than the samples with the conventional full pad design.

An experimental setup for obtaining metallic multilayer coatings with layers of nanometer thickness

An automated PC-controlled electrochemical setup for deposition of a specified number of different metal nanodimensional layers onto conducting substrates is described. Metallic layers are deposited in galvanic cells from solutions of corresponding electrolytes on a sample that serves as a cathode, while the anode is a plate of an inert material or a material dissolved during electrolysis. The electroplating is conducted by passing rectangular current pulses through the electrolyte solution between the sample and the anode. The amplitude (1 mA–1 A) and duration (1 ms–1 s) of the current pulses are set by a program. Samples are treated in the galvanic cells and rinsing baths according to a programmed route. In combination with efficient electrolytes for electrodeposition, the setup enables one to obtain multilayer structures of specified configuration with alternation of nanometer layers of different metals: normal metals, ferromagnets, paramagnetics, antiferromagnets, or superconductors. The characteristics of a normal metal (copper)-ferromagnet (palladium-nickel alloy) multilayer coating are presented.

Influence on the laser induced backside dry etching of thickness and material of the absorber, laser spot size and multipulse irradiation

Laser induced backside dry etching method (LIBDE) was developed – analogously to the well-known laser induced backside wet etching (LIBWE) technique – for the micromachining of transparent materials. In this procedure, the absorbing liquid applied during LIBWE was replaced with solid metal layers. Fused silica plates were used as transparent targets. These were coated with 15–120 nm thick layers of different metals (silver, aluminium and copper). The absorbing films were irradiated by a nanosecond KrF excimer laser beam through the quartz plate. The applied fluence was varied in the 150–2000 mJ/cm 2 range, while the irradiated area was between 0.35 and 3.6 mm 2. At fluences above the threshold values, it was found that the metal layers were removed from the irradiated spots and the fused silica was etched at the same time. In our experiments, we investigated the dependence of the main parameters (etch rate and threshold) of LIBDE on the absorption of the different metal layers (silver, copper, aluminium), on the size of the irradiated area, on the film thickness and on the number of processing laser pulses.

Preparation of ternary alloy libraries for high-throughput screening of material properties by means of thick film deposition and interdiffusion: Benefits and limitations

Several techniques have been investigated for making alloy libraries for combinatorial materials development. In this investigation, we demonstrate a method for Ni–Fe–Cr ternary alloy library preparation by deposition of three layers of different metals with a linear thickness gradient rotated by 120° for each layer. The layers were interdiffused and alloyed by annealing in vacuum. The resulting specimens were analyzed and compared with the well-known phase diagram for this system by means of rapid x-ray diffraction mapping with synchrotron radiation.

Innovative steel strip coatings by means of PVD in a continuous pilot line: process technology and coating development

Based on PVD coating of already conventionally zinc-coated steel strip novel approaches to highly corrosion resistant zinc alloy coatings have been developed on a laboratory scale. In this paper, the successful up-scaling of such an approach to a continuous pilot line with line speed up to 60 m/min and strip width of 300 mm is reported. The PVD technology of the pilot line comprises different plasma cleaning processes, thermal evaporation by means of radiation heating as well as electron beam evaporation. First results of coating development by means of evaporating thin additional layers of different metals on already conventionally zinc coated steel strip will be presented.

Structural and magnetoresistive properties of Co/Cu multilayers

Co/Cu multilayers (ML) were thermally evaporated at very low deposition rates on Si substrates covered with buffer layers of different metals (Ag, Cu, In, Pb, Bi). Structural characterisation of samples was performed by X-ray reflectometry (XRR), X-ray diffraction (XRD) and atomic force microscopy (AFM). Magnetoresistance measurements were carried out at room temperature using a standard four-probe DC method with current in the plane of the sample. It seems that a choice of buffer type has no significant effect on the magnitude of GMR. Since the thickness of single layers is of similar magnitude as the interfacial roughness in samples we suggest that the observed small value of GMR effect can be attributed rather to the interruption of film continuity and creation of magnetic bridges between Co layers, resulting in direct ferromagnetic coupling of magnetic films.

Magnetic nanowires

We review recent developments in the research on magnetic nanowires electrodeposited into pores of membranes. Typical nanowires fabricated by this method have a diameter in the range 30–500 nm for a length of the order of 10 μm, and can be composed of a stack of layers of different metals with thicknesses in the nanometer range (multilayered nanowires). We describe the preparation methods and present typical examples of structural characterization. We review the magnetic properties with examples of results on both arrays of nanowires and isolated nanowires. We then describe the magnetoresistance properties of multilayered nanowires, and their interest for their understanding of the CPP–GMR and the determination of spin diffusion lengths. The last section is an overview on the perspectives of future research.

An analysis of broken-layer characteristics in laser alloying for coinage applications

In laser surface alloying the distribution of alloying elements is mainly attributable to the convective behavior of the melt pool which is influenced by a number of factors including laser power density, size of the melt pool, interaction time, beam profile and the material physical properties. Any variation of the treatment conditions can change the flow pattern and the distribution of alloying elements in the melt pool. The laser alloying process reported in this article includes the steps of predeposition of multiple layers of different metals and subsequent alloying of these layers using a high power CO2 laser. A visible distinction between the alloyed and unalloyed regions or a difference in other physical properties is obtained. The work involves a study of the alloying types and the influence of the laser operating parameters and the thermal properties of the materials. It was found that properties such as the difference of the melting points between the coating layer and the substrate materials and thermal diffusivity (or thermal conductivity) of the substrate materials played an important role in the process. Laser control variables required for localized alloying for different substrates and coatings types were determined. The influence of both thermal properties and laser control variables on alloy types was investigated. A mathematical model was developed to establish an understanding of the process and the proper selection of the materials combinations required to achieve specific alloying types for coinage applications. Initial work on coin validation has shown promising results for automatic recognition of laser treated coins.

Methods for electrodepositing composition-modulated alloys

Materials exhibiting unique mechanical, physical and chemical properties can be obtained by combining thin layers of different metals or alloys forming a multilayered structure. Two general techniques exist for electrodepositing composition-modulated alloy (CMA) materials; dual-bath and single-bath plating. For both techniques a number of variation exist. The most suitable technique and variation for the manufacture of a certain CMA material is highly dependent on the metals included in the given CMA system and on the dimensions of the multilayered structure. In this paper, the main principles of the two electrochemical techniques and their variants are discussed.

Electrochemical Formation of Laminar Deposits of Controlled Structure and Composition: II . Dual Current Pulse Galvanostatic Technique

A dual current pulse technique was developed for plating two layers of different metals, or any number of pairs of layers, from a single bath. The key condition is to maintain the current density from the first current pulse below the diffusion limiting current density of discharge of the more noble metal and that from the second pulse well above the former and below the limiting current density of deposition of the less noble metal. If the content of the first metal in the second layer is to be small, the concentration of its ions in solution must be much smaller than that of the ions of the second metal. Example of plating several layers of copper and nickel upon each other is given.