Intermetallic Interlayer Research Articles

Recognition of Synthesized Intermetallic Interlayers at the Interface in Ti@Al "Core — Shell" Nanoparticles Based on Computer Molecular-Dynamic Simulation

The paper presents the results of applying a new method, previously developed by the authors, based on precalculated sets of 3D distributions of a matter density. The method is designed to recognize the spatial 3D distributions of the synthesized intermetallic compounds in the volume of a nanoparticle. A set of 3D distributions of a matter density in the volume of a cubic Ti@Al core — shell nanoparticle corresponds to a set of successive time points. It is calculated based on the results of the computer molecular dynamics simulation of self-propagating high temperature synthesis in the nanoparticle. Computational experiments are performed using the LAMMPS software package. Based on the obtained results, thermal and microstructural analyses are performed, confirming the multistage mechanism for the formation of intermetallic phases during the SHS reaction in the Ti-Al reaction medium. The sets of 3D distributions of the matter density and 3D distributions of synthesized intermetallic compounds in the volume of a nanoparticle corresponding to the sequence of time points are calculated. The paper shows the advantage of the method for recognizing 3D distributions of synthesized intermetallic compounds, proposed by the authors, over the methods of similar analysis built into the OVITO software package.

3D Visualization of Heterophase Intermetallic Structures Based on Computer Simulation of SHS in a Nanosized Ti-Al Layered-Block Structure

he paper presents the results of thermal and microstructural analysis of the SHS of intermetallic compounds in a nanosized atomic layer-block structure of Ti-Al, obtained using the freely available software packages LAMMPS and OVITO, as well as using the software of the authors of the paper. Using the LAMMPS package in the version of parallel computing, the software implementation of which is based on the "molecular dynamics" method, the SHS process is simulated. For 3D visualization of simulation results, the OVITO package is used. Among the results of microstructural analysis, noteworthy is the appearance of stable heterophase intermetallic structures during the SHS reaction, which were confirmed using the OVITO package and the software module developed by the authors for calculating a set of matter density profiles of the SHS-product. In heterophase intermetallic structures, it was possible to detect local features in the form of layered quasi-coherent intermetallic interlayers with the presence of two-dimensional defects in crystal lattices — twinning planes delimiting pairs of grains (twins) with symmetrical lattices reorientation.

Extension of the functionality of the software for MD-simulation of the SH-synthesis of intermetallides in Ni-Al and Ti-Al nanosystems

The subject of research: the methodological and functional capabilities of specialized software packages of free access LAMMPS and OVITO and author's programs used for simulation of SHS-microkinetics in heterogeneous systems.
 Purpose of research: to increase information content, 3D-visualization, and adequate interpretation of the processes of structural-phase transformations at interfaces of the layered, layered-block nanoscale Ni-Al and Ti-Al systems.
 Methods and objects of redearch: the molecular dynamics simulation method implemented in the basis of the LAMMPS software package simulates the process of initiation and propagation of the SHS combustion wave in the systems under study, and using the OVITO package, 3D-visualization of the processes of dissolution, diffusion, and motion of the SHS combustion wave front is carried out.
 Main results of research: it is shown that the development by the author of software modules for calculating one-dimensional temperature and density profiles of the synthesized material along the direction of combustion wave motion, as well as for calculating and visualizing the 3D-structure of the distribution of synthesized intermetallic interlayers at the interface in nanoparticles with the Ni-Al "core-shell" structure (and similarly for Ti-Al) allows, in contrast to the OVITO package, to detect heterophase intermetallic structures in such systems. As a result of a large series of computational experiments on simulation of microkinetics in the studied nanoscale Ni-Al and Ti-Al systems, it has been established that the software package created by the author with support for parallel computing, which, in addition to the licensed packages LAMMPS and OVITO, integrates author's software modules, has new broader functionality in the methodological aspect of the study of the problems of physical chemistry of the SHS process and is a vivid example of the created software engineering tools in this area of research.

Investigation of the structure and properties of a fivelayer titanium-steel explosion-welded composite material after technological stages

The paper presents the results of studies of a five-layer composite material consisting of three layers of titanium VT20 alloy and two layers of stainless 08Kh18N10T steel after explosion welding (EW) and subsequent processing, including hot rolling (HR) and heat treatment (HT) at temperatures of 800, 850 and 900 °C with a holding time of 1 to 100 h to form a layered intermetallic composite (LIC), which has a combination of plastic layers of the original alloys and intermetallic interlayers in contact with them, the presence of which provides the necessary strength characteristics at elevated temperatures. The structure, microhardness, and chemical composition of the diffusion zones of the composite were studied using optical and electron microscopy, X-ray spectral and X-ray diffraction analyses. It is shown that, after EW, the joint zones have a characteristic wavy profile with areas of melted and crystallized metal–flashes, which are solid solutions based on titanium, iron, and Cr(Fe)2Ti intermetallic compound. Hot rolling and HT under the specified conditions led to diffusion processes of main steel elements into the titanium alloy, resulting in the formation of diffusion interlayers adjacent to the steel and titanium alloy, the composition and thickness of which depend on temperature and holding time at certain ratios of chemical elements and phase composition.

Investigation into the Intermetallic Layers in Ti/Al Multi-Layer Composites Produced via Accumulative Rolling and Sintering

For anti-penetration applications, multilayer composites combining hard brittle elements confronting penetrators and ductile materials at the back are attractive. Because of the weak connection between the ductile and hard brittle layers, these composites usually lose their anti-penetration capability when the hard, brittle layer falls apart. In the present work, attempts to produce in-situ hard, brittle layers were carried out through accumulative roll bonding (ARB) and post-sintering. It is found that an intermetallic interlayer of TiAl3 can be produced between Ti and Al plates with full integrity under a proper sintering condition. The diffusion mechanism between Ti and Al layers was analyzed via microstructural characterization. It implies that Al serves as the primary diffusion phase between Ti and Al plates. This work may shed light on the development of high-performance anti-penetration multi-layer composites.

Control of fatigue failure mechanisms in multilayer coatings by varying the architectural parameters of an intermetallic interlayer

AbstractA multilayer overlay coating system containing an intermediate intermetallic layer is an architecture expected to show good fatigue resistance. Experimental characterization and modeling simulations were carried out to classify the different crack initiation mechanisms occurring during fatigue of this coating system (2IML coating system) and to reveal how changes in the layer architecture lead to fatigue improvement. Surface crack initiation seems to play the dominated role in the fatigue failure of this coating system as over 55% of observed cracks were surface cracks. Fatigue improvement is achieved by increasing surface initiation resistance via decreasing the IML‐Top layer thickness. However, subsurface initiation mechanisms inhibit the improvement (dominated by surface initiation mechanism) achieved by locating the IML‐Top layer closer to the top surface. Optimizing the design of 2IML multilayer coatings based on the fatigue performance should eliminate the unreacted nickel layer in the intermediate IML‐Top layer, increase the subsurface interface strength, and decrease the density of voids occurring in the annealing process.

Investigating the fatigue performance of soft multilayer coatings with varying locations of an intermetallic interlayer

A multilayer coating system containing two hard intermetallic layers (IMLs) within a soft metallic system provides improved fatigue performance. To further optimise this system, various coatings with different locations of the intermediate intermetallic (IML-Top) interlayer were manufactured and experimentally investigated. Their characteristics were assessed and fatigue performances were compared, revealing the improvement of fatigue resistance by locating the IML-Top layer close to the top overlay coating surface. The mechanisms, based on post-test observations of crack morphology, are identified as (1) improved retardation of crack initiation and (2) improved crack growth resistance provided by the shielding effect of the IML-Top layer.

Research of the boundary structure for the bimetal compound steel 08Kh18N10T + vanadium VnPl-1 + titanium VT1-0 at the influence of explosion energy

ABSTRACT The effectiveness of using a barrier layer of vanadium in a bimetallic composition consists of stainless steel 08Cr18Ni10T + vanadium VnPd-1 + titanium VT1-0 obtained by explosion welding meant to prevent the formation of an intermetallic interlayer under the effect of different temperatures was investigated. The evolution of the near-weld zone was investigated by analysis with scanning electron microscope of microsections from samples heated at 600, 700, 800 and 900 °C with 1, 3, 5 and 10 hours exposures. The researches indicated that the barrier layer of vanadium reliably prevents mutual diffusion between steel and titanium at high temperatures, thus eliminating the formation of intermetallic compounds in the adjacent zone. The limit of the barrier layer effectiveness was determined.

Laser Welding of Dissimilar Materials Based on VT20 Titanium and V-1461 Aluminum Alloys

This paper describes the experimental study of strength characteristics and the microstructure of a permanent joint of dissimilar materials (VT20 titanium alloy and V-1461 aluminum alloy), obtained by laser butt welding. Optical and electron microscopy, X-ray spectral and phase analysis, and the transmission diffraction method with the help of synchrotron radiation are all used to investigate the properties of a weld. It is shown that the laser radiation offset relative to the contact surface of dissimilar materials significantly changes the microstructure and phase composition of the intermetallic interlayer formed between the materials welded, thereby affecting the strength of dissimilar welded joints.

The effect of mechanical surface pre-treatment on the strength of the adhesive joint of high strength sheets

Nowadays, in the car body parts production, the quenching is often replaced by adhesive joints. The adhesive joints have a lot of advantages – they allow to keep the protective layer, enable to join different material and prevent from the formation of heat affected zones. With respect to passenger’s passive safety, plenty of car body parts are manufactured of high strength steel sheets. The body parts are hot-formed at a temperature of 900 °C to the desired shape followed by subsequent rapid quenching to achieve the required strength. The sheets are covered with an AlSi 60/60 layer which should protect them from high-temperature oxidation during the forming process. However, brittle intermetallic interlayers form during the high-temperature treatment due to the reaction of iron from the substrate with Al/Si from the protective cover, which negatively affects the final strength of adhesion joint. The paper deals with the comparison of different possible ways of removing the layer on the final strength.

Characterization of low temperature Cu/In bonding for fine-pitch interconnects in three-dimensional integration

This study presents the results for Cu/In bonding based on the solid–liquid interdiffusion (SLID) principle for fine-pitch interconnects in three-dimensional integration. The microbumps were fabricated on Si wafers (55 µm pitch, 25 µm top bump diameter, 35 µm bottom bump diameter). In was electroplated directly on Cu only on the top die microbumps. Two different In thicknesses were manufactured (3 and 5 µm). The interconnects were successfully fabricated at a bonding temperature of 170 °C. High temperature storage was carried out at 150 and 200 °C for different times between 2 and 72 h directly after the interconnect formation in order to investigate the temperature stability. The microstructure was analyzed by scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX). The intermetallic compound (IMC) found in the microbumps after electroplating was CuIn2. The intermetallic interlayer consists of Cu11In9 and a thin layer of Cu2In after bonding and isothermal storage.

Joining of Aluminium Alloy and Steel by Laser Assisted Reactive Wetting

Compounds of dissimilar materials, like aluminium and steel offer an interesting opportunity for the automotive industry to reduce the weight of a car body. Thermal joining of aluminium and steel leads to the formation of brittle intermetallic compounds, which negatively affects the properties of the welded joint. Amongst others, growth of such intermetallic compounds depends on maximum temperature and on the time at certain temperatures. Laser welding with its narrow well seam and its fast heating and cooling cycles provides an excellent opportunity to obtain an ultrathin diffusion zone. Joining of sheet metal DC01 with aluminium alloy AW6016 has been chosen for research. The performed experimental studies showed that by a variation of the beam power and scanning speed it is possible to obtain an ultrathin diffusion zone with narrow intermetallic interlayers. With the aim of supporting further investigation of laser welding of the respective and other dissimilar pairings a multi-physical simulation model has been developed.

The Simulation of Titanium-Aluminium Composite with Intermetallic Inclusions Behavior under Compression

3D finite element simulation of behavior of composite VT6-AD1-D20 with the intermetallic layer at axial compression was carried out. The properties of the intermetallic interlayer were described using the model of Johnson-Holmquist. The effect of the aluminum layer thickness on failure deformation was defined.

Возможность снижения роста интерметаллидной прослойки при пайке стали припоями медь–фосфор

Возможность снижения роста интерметаллидной прослойки при пайке стали припоями медь–фосфор

Possibilities of reduction of growth of intermetallic interlayer in steel brazed using brazing filler metals of copper-phosphorus system

Possibilities of reduction of growth of intermetallic interlayer in steel brazed using brazing filler metals of copper-phosphorus system

Surface potential analysis on initial galvanic corrosion of Ti/Mg-Al dissimilar material

A surface potential analysis was carried out to establish a new materials design of pure Ti/Mg-Al alloy dissimilar materials with an excellent galvanic corrosion resistance. The formation of Ti-Al intermetallic interlayer and Al diffusion layer at interface effectively reduced the surface potential difference at the interface. As a result, a formation of local cells, causing a galvanic corrosion phenomenon of Ti/Mg alloy dissimilar material, was prevented because the potential difference of Mg alloy with Ti-Al interlayer completely decreased. A salt water immersion test obviously indicated no Mg(OH)2 corrosion product on Mg alloy surface due to Ti-Al interlayer formation, and the initial galvanic corrosion phenomenon was effectively obstructed.

Structure Formation Mechanisms during Solid Ti with Molten Al Interaction

The study discuses advantages and disadvantages of previously proposed mechanisms of the formation of structure between solid Ti and molten Al and presents a new mechanism based on the reviewed and experimental data. The previously proposed mechanisms were classified into three groups: mechanisms of precipitation, mechanisms of destruction and mechanisms of chemical interaction between intermetallics and melt. The reviewed mechanisms did not explain the formation of heterogeneous interlayer with globular aluminide particles and thin layers of pure Al, while the present study reveals variation in the solid Ti/molten Al reaction kinetics during various phases of laminated metal-intermetallic composite formation. The proposed mechanism considers formed during composite fabrication thin oxide interlayers between Ti and Al evolution and its impact on the intermetallic compound formation and explains the initial slow rate of intermetallic interlayer formation and its subsequent acceleration when the oxide foils are ruptured.

Initiation of thermal explosion in Ti/Al nanofoils

Temperature conditions for initiation of thermal explosion (volume reaction) in multilayer Ti/Al nanofoils were explored both experimentally and by numerical simulation. It is shown that there exists a critical heating rate below which thermal explosion of foil is not observed. Upon heating at rates above the critical value, the initiation temperature of thermal explosion (Tig) was found to decrease with increasing heating rate (Vh). A non-monotonous dependence of Tig on Vh was associated with formation of an intermetallic interlayer at the interface between Ti and Al layers in the solid-state reaction thermally induced during heating. Numerical simulation has shown that the interlayer gets thicker with decreasing heating rate, thus promoting an increase in Tig.

Formation of Metal-Intermetallic Laminate Composites by Spark Plasma Sintering of Metal Plates and Powder Work Pieces

Laminate composites with an intermetallic component are some of the most prospective constructional and functional materials. The basic formation method of such materials consists in heating a stack composed of metallic plates reacting at elevated temperatures to form intermetallic phases. The temperature of the process is usually approximately equal to a melting point of a more easily fusible component. In this study, an alternative technology of producing a titanium – titanium aluminide composite with a laminate structure is suggested. It consists in combining metallic (titanium and aluminum) powder mixtures pre-sintered at 400 оС with titanium plates, alternate stacking of these components and subsequent spark plasma sintering (SPS) of the fabricated workpieces. Applying this technology allowed for the fabrication of metal-intermetallic laminate (MIL) materials with an inhomogeneous structure of intermetallic interlayers. The phases revealed in the composite by X-Ray diffraction (XRD) were α-Ti, Al, Al3Ti and Al2Ti. Moreover, the results of the energy-dispersive analysis gave the evidence of the formation of Ti-enriched phases in powder layers after SPS. A small number of voids were observed between the structural components of the intermetallic layers. Voids were also detected at “metal-intermetallic” interfaces; however, the quality of connection between different layers in the composite was very high. The microhardness of an intermetallic layer formed in the composite was comparable to the microhardness of the Al3Ti compound. The microhardness of titanium was equal to 1600 MPa.

Structural changes in magnesium-aluminum composite obtained by explosion welding after bending and thermal treatment

The effect of bending deformation and subsequent thermal treatment on the behavior of the micromechanical properties and characteristics of a fine structure of the AD1-MA2-0 magnesium-aluminum composite material (CM) after explosion welding (EW) is investigated. It is found that an intermetallic interlayer is formed after the thermal treatment (t = 300 and 400°C, τ = 1 h) of the composite welded by explosion and subjected to bending, which substantially affects the behavior of the characteristics of a fine structure.