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In this paper, the structures of structural steel for railway transport 1566 and tool steel w1-7 are investigated. For the analysis of the structures of these steels, two techniques are used: traditional optical microscopy (Neophot-21) and ASM (Solver PH47-PRO) with use of a contact method. The microstructure of the steels is studied after complete annealing. The temperature of complete annealing for structural steel 1566 is 770–790 °С. The annealing temperature for tool steel w1-7 is 760–780 °C. The atomic force analysis of the structure of the steels is carried out using different modes. The prospects of using atomic force microscopy in solving theoretical and applied problems of modern metallurgy are demonstrated. [ABSTRACT FROM AUTHOR]

An experimental study on superplastic forming behaviors and microstructure characters of commercial magnesium alloy sheet AZ31B is presented in this paper. The main experimental results show that the commercial magnesoium alloy AZ31B sheet has superplastic capability. For the received sheet without any pre-processing, the maximum elongation is 295%. The dynamic recrystallization and grain refinement can be found, In the case of temperature <350°C, and the grain growth appears if temperature >= 350°C. The superplastic behaviors can be improved by controlling the dynamic recrystallization and grain refinement. Some experimental results of free superplastic bulging are presented in this paper. The results show that influence of temperature on forming capability is much less than the influences of temperature on elongation. In addition, the maximum principle strain. © 2004 American Institute of Physics [ABSTRACT FROM AUTHOR]

The paper presents a shear strength model used to evaluate information of interest from shock experiments aimed at studying the properties of the hardened 30KhGSA steel and the MA14 magnesium alloy subjected to low- and high-intensity loadings. The model parameters are adjusted by experimental deformation curves obtained from static and dynamic tests at different temperatures and the data from shock experiments to account for strength variation at high strain rates. The simulation of low-intensity loading tests helped to improve the description of elastic-plastic properties and to adjust our failure model. The data from the shock experiments with high-intensity loading of 30KhGSA steel samples and unloading of the shocked samples in window materials were used to verify the phase diagram and the kinetics of direct and inverse phase transitions, and to determine more exactly how the changed phase state influences the strength. The model presented here has allowed us to reproduce the complicated strength behavior of the MA14 alloy at different loading intensities. [ABSTRACT FROM AUTHOR]

The paper is devoted to the analysis of the structural features, which determine an increase in the strength and fracture energy of the surface layers of a NiCr-TiC metal-ceramic composite modified by a pulsed electron beam, from the standpoint of bionic design of composite structures. The analogy of the structure and ratio of the mechanical parameters of the components in the surface layers of this composite and the biological one (mollusc shells) is discussed. Using computer simulation, we show that the key factors determining the increase in the mechanical properties of the modified surface layers of a cermet composite are the geometric and mechanical parameters of ceramic inclusions. We have estimated the ranges of the values of these parameters, which provide the optimal ratio of strength, stiffness and fracture energy. [ABSTRACT FROM AUTHOR]

The paper is concerned with the skin effect of plastic deformation, which was discovered circa ninety years ago. The study is carried out with the help of the hydrogen diagnostics. Accumulation of hydrogen is shown to occur due to the dissociation of atmospheric moisture under the process of plastic deformation of metals in a thin surface layer comparable to the grain size. Hydrogen is accumulated in pores and microcracks, whose volume in the surface layer increases hundred-fold. The zones of localization of plastic deformation coincide with the local surface zones of hydrogen storage. The obtained experimental data lead to the conclusion that the surface layer cannot be considered as a continuous medium. [ABSTRACT FROM AUTHOR]

This paper studies the influence of martensite content in the 09Cr17Ni5Al two-phase austenitic chromium-nickel steel on acoustic, magnetic and electrical properties. The non-contact electromagnetic-acoustic (EMA) method of excitation and reception of acoustic waves by means of a through-type transducer and the method of magnetic saturation and electrical resistance were used for the research. Acoustic wave velocities, the efficiency of EMA transformation and magnetic saturation intensity were considered as informative parameters. [ABSTRACT FROM AUTHOR]

Using the methods of modern physical materials science, the microstructure and characteristics of shear band propagation in wire-feed EBAM Ti-6Al-4V samples were investigated at different strain rates under uniaxial tension. The effect of shear bands on the fracture mechanism of wire-feed EBAM Ti-6Al-4V samples was revealed. [ABSTRACT FROM AUTHOR]

X-ray lithography is an ideal technique by which high aspect ratio and high spatial resolution micro/nano structures are fabricated using X-rays from synchrotron radiation source. The technique has been used for fabricating optics (X-ray, visible and infrared), sensors and actuators, fluidics and photonics. A beamline for X-ray lithography is operational on Indus-2. The beamline offers wide lithographic window from 1-40keV photon energy and wide beam for producing microstructures in polymers upto size ~100mm x 100mm. X-ray exposures are possible in air, vacuum and He gas environment. The air based exposures enables the X-ray irradiation of resist for lithography and also irradiation of biological and liquid samples. This paper gives a brief introduction of X-ray lithography beamline, complimentary processing steps to realize micro structures, and various high aspect ratio structures fabricated for different applications. Using X-ray lithography beamline various refractive and diffractive synchrotron optics for micro/nano focusing are being developed for second and third generation synchrotron sources. X-ray refractive lenses are produced in X-ray sensitive resist PMMA (poly methylmethaacrylate) and high radiation and temperature resistance material SU-8. The performances of these lenses at various photon energies are evaluated at Indus-2 and Diamond Light Source. Few 3D structures are also produced using this beamline. [ABSTRACT FROM AUTHOR]

The paper consists of two parts united by the central idea of the random field of the microstructure of the material. The first part addresses a discrete static approach to describing the localization effect of plastic deformation known with the help of finite-element analysis under the assumption that the deformation of each of the grains obeys a bilinear law with a normal distribution of the yield stress over the grains. The result is a surface relief in the form of diagonally directed strips, which allows one to treat the deformed surface as Panin’s "chessboard". The second part is concerned with a dynamic continuum approach to the description of the random microstructure of materials. The problem of the propagation of stochastic waves modeled by waves in media with random elastic and mass properties is solved by means of the integral decomposition of the wave amplitude over the wave numbers. [ABSTRACT FROM AUTHOR]

The machining of FRP composites has posed a serious challenge to industry and academia alike as far as the sub-surface damage is concerned caused by fiber-matrix debonding. Proper prediction of sub-surface damage is thus essential for different fiber orientations and fiber-matrix bonding. A Cohesive Zone Modeling (CZM) of the fiber-matrix debonding leading to interfacial separation is presented in this paper. The cohesive bonding strength existing between the fiber and matrix increases with increased separation, reaches a maximum value before causing permanent debonding when the cohesive strength between the interfaces vanishes. An effort is made to implement the Cohesive Zone Model (CZM) and to ascertain the extent of debonding below the trim plane at fiber failure. © 2004 American Institute of Physics [ABSTRACT FROM AUTHOR]

In this paper, statistical continuum mechanics modeling is applied to predict the elastic mechanical properties of an anisotropic Al-SiC composite. Two-point statistics are measured on vertical metallographic planes in three-dimensional microstructures. As a result of anisotropy the correlation functions are orientation dependent. Longitudinal and transverse elastic moduli are calculated for two samples with different PSR and clustering, and the results are compared with upper and lower bound and experimental data. It’s observed that the theoretical results are in good agreement with experimental data and two-point statistics significantly contribute to the estimation of the elastic modulus. © 2004 American Institute of Physics [ABSTRACT FROM AUTHOR]

Homogenization theory has been well accepted by the applied mechanics modeling community for its ability to integrate small-scale microstructure phenomena into bulk continuum equations using convergent features of asymptotics. This paper describes an extension of the method to handle asymptotically small atomic scale systems at zero temperature embedded within a deforming continuum. A so-called inner displacement naturally arises in the formulation that enables the consideration of distributed anharmonic crystalline effects that would otherwise be unapproachable with bulk continuum methods alone. The result is a simple computational mechanics method that, first, maps instantaneous continuum deformation gradients to deforming defected crystalline arrangements then, second, provides convergent effective material properties to be used for consistent continuum calculations. The intended applications are those involving patterned defects, either in bulk or on surfaces, which allude to possible manufacturing scenarios. Simple 2-D examples are shown for in-plane deformation of graphene possessing various types of point defects. © 2004 American Institute of Physics [ABSTRACT FROM AUTHOR]

In this paper, we propose a multi-time scale modeling technique for analyzing cyclic plastic deformation in crystalline solids subject to periodic loading. An asymptotic expansion of the variables in the time domain, together with homogenization forms the basis of multi-time scaling. In the macroscopic scale analysis, the oscillatory behavior of the load is averaged out and neglected, and the rate of averaged material behavior is quite slow in cyclic deformation. Implicitly, this means that the periodicity of some variables may be assumed for the oscillatory potion of the material behavior may be approximated. In this formulation, the governing equations are divided into two initial-boundary value problems with two different time scale: one is long time scale problem for describing the smooth averaged solution (global problem) and the other is for the remaining oscillatory potion (local problem). For the global problem, long time increments, which are longer than one cycle period, can be used and this multi-time scaling becomes an effective integrator. © 2004 American Institute of Physics [ABSTRACT FROM AUTHOR]

This paper discusses the forging process of a wayshaft with sector gear through computer simulation, including the forming technology and technology parameters. Combined with the microstructure of structure steel 20CrMnTi, the computing method for the evolution of microstructure is studied. The process is analyzed and simulated by thermo-mechanically-coupled method and the microstructure was predicted by using 3D rigid-plastic FE software. © 2004 American Institute of Physics [ABSTRACT FROM AUTHOR]

Additive-manufacturing technologies have been gaining tremendously in popularity for some years in the production of single-part series with complex, close-to-final-contour geometries and the processing of special or hybrid materials. In principle, the processes can be subdivided into wire-based and powder-based processes in accordance with the Association of German Engineers (VDI) Guideline 3405. A further subdivision is made with respect to the smelting technology. In all of the processes, the base material is applied in layers at the points where it is needed in accordance with the final contour. The process that was investigated was wire-based, multi-pass welding by means of gas–metal arc welding. This was accomplished in the present study by determining the material parameters (thermo-mechanical and thermo-physical characteristics) of the welding filler G3Si1 (material number: 1.5125) that were necessary for the numerical simulation and implementing them in a commercial FE program (MSC Marc Mentat). The focus of this paper was on simulation and validation with respect to geometry and microstructural development in the welding passes. The resulting minimal deviation between reality and simulation was a result of the measurement inertia of the thermocouples. In general, however, the FE model can be used to make a very good predetermination of the cooling behaviour, which affects the microstructural development and thus the mechanical properties of the joining zone, as well as the geometric design of the component (distortion, etc.). [ABSTRACT FROM AUTHOR]

A molecular dynamics analysis model is proposed to study the effects of parameters on nanoimprint process, for example: taper angle, imprint depth and spring back. The nanoimprint process comprises one punch and one specimen at an isothermal state of 400K, while the deformed material is a copper FCC single crystal and the punch material is a nickel FCC single crystal. There were a total of 10,080 atoms in copper measuring 12.02 nm × 5.72 nm in length and height, respectively. There were a total of 4,200 atoms in nickel where the typical length and depth in punch tooth are 6.24 nm × 3.52 nm, respectively. Computer simulation codes based on Hamiltonian dynamics, periodical boundary conditions and Morse potential function were used to simulate the nanoimprint processes. By varying the punch taper angle and the imprinting depth, useful information for nanoimprint process has been obtained. © 2004 American Institute of Physics [ABSTRACT FROM AUTHOR]

Aluminum matrix composite currently used in engineering applications due to their desirable combination of properties. Development of aluminium matrix composite has become an essential area of research interest in material science. Aluminium based graphene composite are finding increased application in electrical, automobile and aerospace applications because of its light weight. In this present work dealt with mechanical and microstructure properties AA8030 reinforced with 5 different wt% of Graphene. The bottom pouring stir casting machine was used to fabricate AA8030-Graphene composite. Fabricated samples were tested according to the ASTM standard. The microstructure and mechanical properties such as hardness, tensile strength, flexural strength of fabricated samples were evaluated. [ABSTRACT FROM AUTHOR]

Modeling of high-speed deformation of α-Ti at a pressure of 20 GPa and a temperature of 700 K simulating the conditions of high-energy effects is carried out. The mechanisms of plastic deformation, including sliding along prismatic planes and the α-ω transition, are established. A feature of the deformation process of titanium in the considered conditions, which leads to the formation of disperse inclusions of the α-phase in the ω-phase matrix, is revealed. [ABSTRACT FROM AUTHOR]

Two-phase (γ + α') structural states with high volume fractions of α'-martensite are formed by thermomechanical treatments of metastable austenitic steel specimens. The influence of short-term high-temperature annealing on the reverse martensite-austenite transformation, recrystallization, and mechanical properties of steel is investigated. It is shown that heightemperature annealing at T = 850 °C for 30 s in 4 cycles favors an increase in the volume content of martensite up to 95% and precipitation of dispersed TiC particles. The resulting structural state is characterized by high values of yield strength up to ≈1174 MPa and tensile strength up to ≈1179 MPa, with a relative elongation of 4.1%. Additional annealing for 70 s at the same temperature leads to the reverse (α'→ γ) martensitic transformation and the formation of submicrocrystalline structure. The volume fraction of austenite is increased to 70% after 4 annealing cycles. With an increase in the number of cycles up to 8, the austenite content reaches 91%, and the processes of recovery and recrystallization begin in the steel microstructure. Structural states with a high volume fraction of submicrocrystalline austenite provide high values of the yield, ≈873 to 1073 MPa, and tensile strength, ≈1045 to 1283 MPa, with a relative elongation of 5.2 to 5.4%. [ABSTRACT FROM AUTHOR]

Data on structure formation in austenitic steel samples by electron beam wire-feed manufacturing have been obtained. Structural characterization demonstrates a complex and heterogeneous character of the material structure. In all cases, regardless of the manufacturing parameters, the material of the samples is represented by a dendritic structure. The structure of the samples shows a strong dependence of the metal microstructure on the 3D-printing parameters; e.g., the thickness of the metal layers changes depending on the parameters of the printing process. [ABSTRACT FROM AUTHOR]

A complex of performance characteristics of Ti-B-C coatings formed by the method of electron-beam treatment in the air atmosphere is investigated. No pores or cracks are found in the cladded surface-alloyed layers. The structure is characterized by carbide- and boride-phase particles uniformly distributed in the titanium matrix. The microhardness of the formed surface-alloyed layers reaches 5 650 MPa. The investigation of the coatings for oxidation resistance at elevated temperatures has shown that an increase in the mass of the samples containing titanium carbide and boride particles decreases by a factor of 6 at 900 °C compared with commercially pure titanium. However, electron-beam cladding of powders containing boron carbide leads to a reduction in the impact strength by a factor of 1.4 in comparison with the base material. [ABSTRACT FROM AUTHOR]

A current area of intense research involves the development and use of integrated computational materials engineering (ICME) approaches, which promise to develop next-generation material systems with significant cost and time savings. At its core, ICME synergistically combines material-centric models related to materials development, processing, manufacturing, and property/performance assessment, where key material property information is shared between the various models to enhance process and product outcomes. The integration of computational NDE models within the ICME framework represents an additional opportunity to advance material science and engineering processes through the development of advanced material state awareness (MSA) sensing methods. In particular, nondestructive sensing methods are needed for ICME model and process validation at all stages of the material development process. Several examples of this are presented, which show model-driven sensing for in-process monitoring, microstructure quality assurance, and damage state sensing in a dynamic loading environment. The results illustrate opportunities, challenges, and key linking opportunities for NDE and MSA within the ICME framework. [ABSTRACT FROM AUTHOR]

The recent development of the thermal spraying is to design the microstructure of coatings by controlling the sizes of the structural features within the coating. Improvements in performance can be in mechanical properties as well as functional properties. The sizes of these structural features depend essentially on the process conditions employed during production. Narrowing the crystal size distribution can be obtained from a carefully-controlled nucleation and growth process. This study describes a simple heat transfer model predicting the crystal nucleation and subsequent advance of the solidification front in an alumina sprayed splat. It involves melt undercooling, nucleation and crystal growth kinetics and the selection of the most likely nucleated alumina phase. It intends to investigate the effect of the oxide layer developed on low carbon steel substrate, on the grain sizes. Calculations were performed for various parameters: thermal contact resistance, substrate temperature. Results are presented in terms grain size densities, grain size distribution and solidification front velocity. [ABSTRACT FROM AUTHOR]

The addition of colloidal shear thickening fluids (STFs) to Kevlar fabrics has been shown to enhance the ballistic penetration resistance of the fabric, under conditions of low velocities and small target sizes. It is believed that this improvement in ballistic properties is related to the resistance of the STF to deformation at high strain rates, since the addition of Newtonian fluids to Kevlar fabric does not improve ballistic performance. However, the precise role of the STF, and its rheological properties, in the ballistic defeat process are not known. In this study, ballistic and rheological experiments are performed to determine the effect of fluid viscosity, particle loadings, and particle size and shape on the behavior of STF-Kevlar composites. These results will be help to determine which rheological parameters are most critical to achieving enhanced composite properties. © 2004 American Institute of Physics [ABSTRACT FROM AUTHOR]

The morphology and rheology of carbon nanofiber suspensions is studied. Untreated and acid-treated vapor-grown carbon nanofibers are dispersed in 90wt% glycerol water solutions. Microscopy analysis shows that the suspensions of the untreated fibers are poorly dispersed, containing some dispersed nanofibers, but also un-dispersed nanofiber clumps that interact during flow to form continuous networks. In contrast, the treated fibers are observed to be well-dispersed, and subsequent sonication further disperses the nanofibers, but with the cost of greatly shortening the nanofibers. The rheology of the CNF/glycerol-water suspensions is found to be highly non-Newtonian both in shear and extensional flows, with strong dependence on the dispersion, particle length, and concentration of the CNFs. We have developed kinetic theory-based models for the carbon nanofiber suspensions from SEM measurements of their morphology, and through these models deduce the bulk rheological properties of the composite systems from the microstructural SEM measurements. The rheology and morphology of nanofiber suspensions are related by identifying morphology of the suspensions with the assumptions of the elastic and rigid dumbbell constitutive models. Of those investigated, the elastic dumbbell model with anisotropic hydrodynamic drag is the most successful, quantitatively predicting the strongly non-Newtonian viscoelastic behavior of the composite system that we observe in our experiments. © 2004 American Institute of Physics [ABSTRACT FROM AUTHOR]

Over the years several methods have been proposed for the determination of the effective elastic properties of particle reinforced composites. The material microstructures used in the present analysis is a real microstructure and a numerically generated microstructure. X-ray microtomography is used to determine the material microstructure and with this method the interior microstructure is determined in a non-destructive way. Using the commercially available equipment, SkyScan 1072, the maximum resolution is approximately 5 microns. The data obtained from the tomographic examination is used to generate three-dimensional finite element models of the microstructure. The models contain a large number of elements, up to 1 million, and are solved iteratively using an element-by-element formalism. Models containing 100 particles have been statistically generated and the material properties of each particle is assigned using a Gaussian distribution of the properties. Various distributions have been used to determine how the variation of particle properties influences the effective elastic properties. From this examination it was found that the larger the variation of the particle properties is the softer the composite material gets. © 2004 American Institute of Physics [ABSTRACT FROM AUTHOR]

A finite element-based, integrated process model is presented for precise prediction of the thermo-mechanical-metallurgical behavior that a strip would reveal as it passes through the entire finishing mill. The validity of the proposed model was examined through comparison with measurements. Then, a series of simulation is conducted to investigate the variation of the distributions of the grain size and fraction of recrystallized microstructure and mechanical properties both along the strip thickness and length. © 2004 American Institute of Physics [ABSTRACT FROM AUTHOR]

A preliminary study of the alumina nanoparticles were conducted using density functional theory based first principles approach. The clusters consist of 5 – 32 atoms, with a size up to 1.4 nm. Both stoichiometric and nonstoichiometric clusters were included in the investigation. The structural change and energetics of these clusters were investigated. The results showed a trend of increasing stability with increasing size for the clusters. Stoichiometric clusters are generally more stable than the under-oxidized counterparts. Electronic structure analysis showed that these nanosized alumina particles have a narrower band gap than the bulk alumina material, and some particles are magnetic. © 2004 American Institute of Physics [ABSTRACT FROM AUTHOR]

In this work, a new technique utilizing an automated approach of combining a Focused Ion Beam (FIB) and Electron Back-Scatter Diffraction (EBSD) system was implemented for the collection of 3-D orientation data that can be used to more accurately model grain and sub-grain particle structures. The process is currently capable of sectioning a sample with inter-slice thicknesses as low as 100 nanometers and capturing an orientation map of each slice. Automation of this technique allowed for rapid data collection with the ability to update settings in real time. The orientation data obtained by the EBSD scans consists of each grid point’s position, three Euler angles and phase. Reconstruction of the 3-D orientation data involves combining or “stacking” the 2-D slices obtained by the FIB-EBSD process. The orientation data of each slice is combined into one data file containing orientation information for each point on the 3-D grid, which can have spacing as little as 100 nanometers in all three directions. A program developed in this work, Micro-Mesher, uses the reconstructed orientation information to define microstructural features such as grains and second phase particles. Micro-Mesher constructs grain boundaries with line and plane segments using an error per unit length approach to approximate the complex grain boundaries. Important microstructural statistics that are used to define and characterize the 3-D microstructure are also calculated by Micro-Mesher. Such important parameters include: grain size, no. of neighboring grains, orientations and misorientations, second phase particles size and inter particle spacing as well as others. The 3-D statistical information gained from this process improves the ability to accurately characterize the microstructure. © 2004 American Institute of Physics [ABSTRACT FROM AUTHOR]

In the present work a numerical procedure for identification of clustered distributions of spherical inclusions is presented for two- and three-dimensional cases. The procedure is based on the plane (2D) and spatial (3D) tessellation of the observation window and parameters that characterize a relative density of inclusions within a cluster and background. The identification is performed on simulated dispersions with different radii distributions of spherical inclusions and different volume fractions. The procedure can be applied to images of real microstructures obtained using X-ray microtomography and it is extended so that percolation paths in 2D and 3D can be detected. This might be important to study transport phenomena in polymers filled with particulate inclusions. © 2004 American Institute of Physics [ABSTRACT FROM AUTHOR]