Showing papers in "International Journal of Materials Research in 2008"
TL;DR: In this paper, the authors describe the use of thin film high-throughput experimentation methods for the efficient development of multifunctional materials, using Ni-Ti-X and ferromagnetic shape memory alloys as examples.
Abstract: This paper describes the use of thin film high-throughput experimentation methods for the efficient development of multifunctional materials, using Ni – Ti – X and ferromagnetic shape memory alloys as examples. The thin films were fabricated in the form of binary, ternary, and quaternary materials libraries by special magnetron sputter deposition processes. These materials libraries were subsequently processed and characterized by high-throughput experimentation methods in order to relate compositional information with structural and functional properties. For this, appropriate visualization of the data is necessary. Results show that the martensitically transforming regions in ternary thin films are generally larger than was known from literature. Within these regions, the variation of the functional properties can be mapped with respect to the composition and microstructure, and thus the most suitable materials for applications can be effectively selected.
112 citations
TL;DR: In this paper, a new approach to modeling bainite nucleation is presented, where the authors assume that the average volume of bainitic sub-units is constant over the extent of the transformation and the growth of sub-unit is very fast.
Abstract: Using a new approach to modeling bainite nucleation, the kinetics of isothermal bainite formation have been calculated under the assumption of displacive growth. The nucleation rate is assumed to depend on the number density of potential nucleation sites Ni, a factor λ accounting for autocatalytic nucleation, and an activation energy Q*. Compatible with the theory for athermal martensite nucleation, Ni is assumed to be proportional to the driving pressure. Analogous to the Koistinen – Marburger model for martensite formation, the average volume of bainitic sub-units is assumed to be constant over the extent of the transformation and the growth of sub-units is very fast, and thus the change in fraction is directly related to the nucleation rate of bainite. The model results in an analytical expression for the fraction bainite as a function of time that contains only two adjustable parameters: a (temperature independent) autocatalytic parameter λ and a rate parameter κ, which has a temperature depe...
92 citations
TL;DR: In this article, the ω-phase formation after high pressure torsion under a wide range of pressures and shear strains was investigated by means of X-ray diffraction and transmission electron microscopy.
Abstract: It is well known that a high pressure ω-phase is formed in Ti at high pressures in the range between 2 and 8 GPa. This martensitic-type transformation demonstrates very large hysteresis, and hence the ω-phase can be retained in the material after release of pressure. Additionally, applied shear stresses are known to facilitate the α → ω transformation. This paper describes an investigation on the ω-phase formation after high pressure torsion under a wide range of pressures and shear strains by means of X-ray diffraction and transmission electron microscopy. We show that the ω-phase forms in Ti upon high pressure torsion deformation after 300 s under a pressure of 3 GPa. This suggests that the transformation kinetics are notably increased as compared with the kinetics of pressure-induced transformation.
90 citations
TL;DR: In this article, a model has been developed that links the viscosities of silicate melts to their thermodynamic properties, by optimizing viscosity parameters that are related to the structure of the liquid.
Abstract: A model has been developed that links the viscosities of silicate melts to their thermodynamic properties. Over the past several years, through critical evaluation of all available thermodynamic and phase equilibrium data, we have developed a quantitative thermodynamic description of multicomponent silicate melts using the Modified Quasichemical Model for short-range ordering. The local structure of the liquid, in terms of the bridging behavior of oxygen, calculated using our thermodynamic model allows us to characterize the structure of the liquid semi-quantitatively using the concepts of Q-species and connectivity of Q-species. The viscosity is modeled by optimizing viscosity parameters that are related to the structure of the liquid. The viscosity of pure liquid silica is modeled using four model parameters and every other unary liquid is modeled using two. The viscosity of all binary liquids is reproduced within experimental accuracy by optimizing one or at most two binary viscosity parameter...
72 citations
TL;DR: In this article, the authors measured densities and thermal expansion coefficients of liquid Al-Ag and Al-Cu alloys using the technique of electromagnetic levitation, which involves producing shadow images of the sample from which the volume is calculated by an image processing algorithm.
Abstract: Densities and thermal expansion coefficients of liquid Al–Ag and Al–Cu alloys were measured using the technique of electromagnetic levitation. This technique involves producing shadow images of the sample from which the volume is calculated by an image processing algorithm. Data was obtained at temperatures above the melting point. The concentration dependence of density and thermal expansion was studied for both systems. It was found for Al–Ag and Al–Cu that both density and thermal expansion can be related to a negative excess volume and its temperature coefficient.
68 citations
TL;DR: In this paper, heat transfer and visco-plastic flow during friction stir welding of Ti-6Al-4V alloy were modeled in three dimensions by numerically solving the equations of conservation of mass, momentum and energy using temperature dependent thermo-physical properties and temperature and strain-rate dependent viscosity values.
Abstract: Heat transfer and visco-plastic flow during friction stir welding of Ti-6Al-4V alloy have been modeled in three dimensions by numerically solving the equations of conservation of mass, momentum and energy using temperature dependent thermo-physical properties and temperature and strain-rate dependent viscosity values. The computed results showed that five important model parameters, i. e., the spatially variable friction coefficient, the spatially variable slip between the tool and the workpiece, the extent of viscous dissipation, the mechanical efficiency and the spatially variable heat transfer rate from the bottom surface of the workpiece significantly affected both the temperature fields and the computed torque on the tool. An important problem in the modeling of friction stir welding is that the values of these five parameters cannot be specified from fundamental principles and, and as a result, computed results are not always accurate. Here we show that by combining the heat transfer and pl...
66 citations
TL;DR: In this article, the Gibbs energy of formation of these associates determines the amount of Al 3+ that takes on the same structural role as Si 4+, thereby participating in the formation of the silica network.
Abstract: Our recently developed model to describe the viscosity of binary silicate melts is extended to describe and predict the viscosities of multicomponent silicate melts. The viscosity of multicomponent melts containing no AlO 1. 5 is modeled to vary linearly as a function of the mole fractions of the basic oxides at constant SiO 2 mole fraction. Systems containing AlO1.5 show a more or less pronounced viscosity maximum close to the charge compensating composition. This maximum is caused by some of the Al 3+ taking on the same structural role as Si 4+ , thereby participating in the formation of the silica network. The network-forming Al 3+ must remain associated with either one Na + , or two Al 3+ ions must remain associated with one Mg 2+ or Ca 2+ , in order to assure charge neutrality. To take this into account we introduce the associates NaAlO 2 , CaAl 2 O 4 and MgAl 2 O 4 that correspond to charge compensated network-forming Al 3+ . The Gibbs energy of formation of these associates determines the amount of Al 3+ that takes on the network-forming role. We assume the effect on viscosity of network-forming Al 3+ to be the same as Si 4+ and optimize the Gibbs energies of the associates to reproduce the experimental viscosity data. Viscosities in ternary silicate systems without AlO 1.5 are quantitatively predicted with no additional ternary model parameters. Ternary systems MeO x -SiO 2 -AlO 1.5 are modeled with only two temperature-independent ternary parameters per system. The model not only reproduces the magnitude of the observed viscosity maximum, but also its complex shape, asymmetry and temperature dependence.
64 citations
TL;DR: The serrations observed on the stress-strain curves of a Fe-22Mn-0.6C wt.% steel presented all the phenomenological features associated with dynamic strain ageing, including negative strain this article.
Abstract: The serrations observed on the stress–strain curves of a Fe-22Mn-0.6C wt.% steel present all the phenomenological features associated with dynamic strain ageing, including negative strain ...
64 citations
TL;DR: In this paper, the stress versus strain curve of ASME grade P92/T92 steels was analyzed and the stress dependence of the creep deformation behavior was investigated and a good correspondence between 50% of 0.2% offset yield stress and a proportional limit was observed over a range of temperatures from 550 to 700°C.
Abstract: The stress versus strain curve of ASME Grade P92/T92 steels was analysed and the stress dependence of the creep deformation behavior was investigated. Good correspondence between 50% of 0.2% offset yield stress and a proportional limit was observed over a range of temperatures from 550 to 700°C. Stress dependence of the minimum creep rate was divided into two groups of high and low stress regimes with a boundary condition of 0% offset yield stress. Creep deformation in the low stress regime was considered to be controlled by dislocation climb. Large stress dependence of the minimum creep rate in the high stress regime was equivalent to the strain rate dependence of flow stress observed in the tensile test. Creep strength in the high stress regime is assumed to be influenced by plastic deformation, and should be excluded for a long-term creep strength evaluation.
60 citations
TL;DR: In this article, two different nano-structured samples of the FeTi compound were prepared by mechanical alloying and mechanical grinding, and the kinetics of the initial rate of hydrogen absorption and the equilibrium hydrogen pressure as a function of hydrogen concentration were measured.
Abstract: In this study, two different nano-structured samples of the FeTi compound were prepared by mechanical alloying and mechanical grinding. For these samples, kinetics of the initial rate of hydrogen absorption, and the equilibrium hydrogen pressure as a function of hydrogen concentration were measured. Mechanical alloying of Fe and Ti atoms produced the FeTi compound powder samples with microstructures of a mixture of nano-structured FeTi grains and amorphous phases. This sample exhibited a high initial rate of hydrogen absorption even at 298 K, however, a strongly reduced hydrogen storage capacity. Mechanical grinding of the FeTi produced samples of particles with a particular microstructure: surface layers with a mixture of nano-structured FeTi grains and amorphous phases, and a single crystalline phase of FeTi below the surface layers for each particle. This sample exhibited a high initial rate of hydrogen absorption without a significant reduction of the hydrogen storage capacity compared with t...
54 citations
TL;DR: In this paper, the effect of the pre-structure process on the magnetorheological elastomer performance was investigated. But, the authors focused on the effect on the microstructure.
Abstract: On fabricating magnetorheolgoical elastomer, the mixture of iron particles and un-vulcanized rubber is placed under a curing magnetic field for some time so that iron particles are driven by the magnetic force to form a columnar structure; this process is called the pre-structure process. The microstructure of a magnetorheological elastomer sample is influenced by the pre-structure process, however, few reports address this problem in detail. This paper aims to study the effect of the pre-structure process on the magnetorheological elastomer performance. The pre-structure process is dominated by three influencing factors: magnetic field, curing time and temperature. A variety of magnetorheological elastomer samples were fabricated under different pre-structure conditions and their shear moduli were measured by using a dynamic mechanics analyzer machine. Scanning electron microscope images of these samples were also taken. The results demonstrated the magnetic field-induced modulus shows an increasing trend with magnetic strength before the magnetorheological elastomer samples reach magnetic saturation. The relative magnetorheological effect has an optimal value when the pre-structure field is 110 mT. The effects of the pre-structure time and temperature on the magnetorheological effect were also addressed by using the optimal pre-structure field. These three pre-structure conditions also affect each other. Thus, to fabricate higher-performance magnetorheological elastomer, these pre-structure conditions should be optimized. These results were also explained by study of the particle motion within the matrix.
TL;DR: In this article, the influence of equal channel angular pressing on the microstructure and texture of the magnesium alloy AZ31, electron backscattering diffraction and well as neutron diffraction experiments were carried out.
Abstract: To investigate the influence of equal channel angular pressing on the microstructure and texture of the magnesium alloy AZ31, electron backscattering diffraction and well as neutron diffraction experiments were carried out Through these experiments it was possible to trace the microstructure and texture evolution with strain accumulated with the increasing number of equal channel angular pressing passes It was further demonstrated by subsequent compression tests that the microstructural changes produced by equal channel angular pressing have a beneficial effect on both the compressive strength and ductility of AZ31
TL;DR: In this article, the influence of Cr and V on the melting temperature of the binder phase in Co-based hardmetals was investigated and it was shown that both of them can affect the melting temperatures significantly.
Abstract: New measurements of the influence of Cr and V on the melting temperature of the binder phase in Co-based hardmetals are presented. It was shown that both Cr and V affect the melting temperature significantly. Cr decreases the melting temperature by over 100°C, and V by approximately 40°C. This is due to the high solubility of Cr and V in liquid Co, and this solubility was determined by experiments and calculations. The solubility of Cr in solid fcc-Co is also discussed, as well as the composition of the MC, M7C3 and the M6C carbides in alloys with Cr and V. The new experimental information is used to obtain a reliable thermodynamic description of the binder phase (Co-rich) in C – Co – Cr – W and C – Co – V – W alloys. Calculated equilibria are compared with experiments.
TL;DR: In this article, the diffusion coefficient of expanded austenite was determined from the rate of retracting nitrogen from thin initially N-saturated coupons, and the concentration depen-dent diffusion coefficient was approximated in the composition range where nitrogen can be extracted by hydrogen gas at the diffusion temperature.
Abstract: The concentration dependent diffusion coefficient of nitrogen in expanded austenite was determined from the rate of retracting nitrogen from thin initially N-saturated coupons. Nitrogen saturated homogeneous foils of expanded austenite were obtained by nitriding AISI 304 and AISI 316 in pure ammonia at 693 K and 718 K. Denitriding experiments were performed by equilibrating the foils with a successively lower nitrogen activity, as imposed by a gas mixture of ammonia and hydrogen. The concentration depen-dent diffusion coefficient of nitrogen in expanded austenite was approximated in the composition range where nitrogen can be extracted by hydrogen gas at the diffusion temperature. Numerical simulation of the denitriding experiments shows that the thus determined concentration dependent diffusion coefficients are an accurate approximation of the actual diffusivity of nitrogen in expanded austenite.
TL;DR: In this paper, the European reduced activation reference steel EUROFER was developed to provide materials design data for short-term needs of the ITER Test Blanket Modules and for a Fusion Demonstration Reactor.
Abstract: High performance materials are indispensable for economical and environmentally acceptable operation of fusion power and innovative fission reactor systems. In order to provide materials design data for short term needs of the ITER Test Blanket Modules and for a Fusion Demonstration Reactor, the international fusion materials community is concentrating their R&D work mainly on the four reduced-activation structural materials 8 – 9 CrWTa ferritic/martensitic steels, V – Ti – Cr alloys, W alloys and SiCf/SiC composites as well as on functional materials such as CVD diamond windows. Besides the development of the European reduced activation reference steel EUROFER, emphasis will be placed on synergies between fusion and fission materials R&D, namely the development of ductile oxide dispersion strengthened ferritic/martensitic steels with nano-scaled Y2O3 or Y2Ti2O7 particles that increase not only high temperature strength but also substantially the microstructural stability against irradiation embr...
TL;DR: In this article, the effect of boron on creep deformation behavior and microstructure evolution during creep has been investigated for a tempered martensitic 9Cr-3W-3Co-VNb steel with borons up to 140 ppm at 650°C (923 K).
Abstract: The effect of boron on creep deformation behavior and microstructure evolution during creep has been investigated for a tempered martensitic 9Cr-3W-3Co-VNb steel containing boron up to 140 ppm at 650°C (923 K) with the emphasis on long term behavior. Creep tests were carried out at 650°C for up to about 70 000 h. The base steel without boron exhibits degradation in creep rupture strength after times above about 1000 h. The addition of boron retards the onset of tertiary or acceleration creep, where the creep rate increases with time after reaching a minimum creep rate, at low stresses and long times. This effectively decreases the minimum creep rate and increases the time to rupture. The addition of boron reduces the coarsening rate of Ostwald ripening of M23C6 carbides near prior austenite grain boundaries during creep, which retards the onset of acceleration creep. It is considered that boron atoms occupy vacancies in the vicinity of growing carbide interfaces near prior austenite grain boundar...
TL;DR: The ternary phases τ1 and τ2 are confirmed and their crystal structures and solid state phase equilibria are corroborated in this paper, where the composition of Al-Si-Ti is reinvestigated over the entire composition range using X-ray diffraction, energy dispersive Xray analysis, differential thermal analysis up to 1500 °C and metallography.
Abstract: The constitution of the ternary system Al–Si–Ti is reinvestigated over the entire composition range using X-ray diffraction, energy dispersive X-ray analysis, differential thermal analysis up to 1500 °C and metallography The ternary phases τ1 and τ2 are confirmed and their crystal structures and solid state phase equilibria are corroborated The compositions observed confirm previous literature The phase τ1 (I41/amd, Zr3Al4Si5-type) melts incongruently at 953 °C < T < 1000 °C into L + τ2 + TiSi2 The phase τ2 (Cmcm, ZrSi2-type) melts incongruently at 1338 °C into L + TiSi + TiSi2 The liquidus surface is characterized by a eutectic trough, which descends monotonically from the pseudobinary maximum emax1 L = βTi + Ti5Si3 at 1540 ± 5 °C through a series of transition reactions and ends in the ternary eutectic L = τ1 + (Si) + (Al) at 573 °C
TL;DR: The trend goes to better and more efficient gas turbine engines with lower emissions, greater durability and lower cycle costs as mentioned in this paper, and new materials such as Allvac 718PlusT...
Abstract: Nowadays, the trend goes to better and more efficient gas turbine engines with lower emissions, greater durability and lower cycle costs. To this end, new materials such as Allvac 718PlusT...
TL;DR: In this paper, the reaction path and effects of initial composition on the purity of dense bulk Ta(2)AlC ceramic was investigated and the lattice parameter and a new set of X-ray diffraction data were obtained.
Abstract: Dense bulk Ta(2)AlC ceramic was fabricated by in-situ reaction/hot pressing of Ta, Al and C powders. The reaction path and effects of initial composition on the purity were investigated. It was found that Ta(2)AlC formed through the reactions between AlTa(2) and graphite, or between Ta(5)Al(3)C, TaC and graphite at 1500-1550 degrees C. By modifying the molar ratio of the initial Ta, Al, and C powders, single-phase Ta(2)AlC was prepared at 1550 degrees C under an Ar atmosphere with an optimized composition of Ta: Al: C = 2: 1.2: 0.9. The lattice parameter and a new set of X-ray diffraction data of Ta(2)AlC were obtained. In addition, Ta(2)AlC was reported unstable above 1600 degrees C and decomposed to Ta(4)AlC(3), and then to TaC(x).
TL;DR: In this paper, the total energy and elastic properties of the L12-based Al3RE (RE = Sc, Y, Lanthanide) at T = 0 K are performed by using the projector augmented-wave method within the generalized gradient approximation.
Abstract: First-principles calculations of the total energy and elastic properties of the L12-based Al3RE (RE = Sc, Y, Lanthanide) at T = 0 K are performed by using the projector augmented-wave method within the generalized gradient approximation. The lattice constants, formation enthalpies, elastic constants and bulk modulus of the L12-based Al3RE are obtained. Young's modulus, shear modulus and Poisson's ratios are also estimated in the present work. By using the Debye – Gruneisen model, the Debye temperatures, Gruneisen constants and the sound velocity are obtained for the L12-based Al3RE. All the calculated results are in good agreement with experimental values and other theoretical calculations available.
TL;DR: In this article, the authors measured the stress and strain response of hairlike gecko setae and found that the setae have diameters in the micron range and are part of the attachment organs that enable lizards to cling to surfaces.
Abstract: Measurements of the stress – strain response of hairlike gecko setae are presented. These setae have diameters in the micron range and are part of the attachment organs that enable lizards to cling to surfaces. Three test methods were employed: (a) applying tension with a piezoresistive cantilever inside a focused ion beam microscope under vacuum conditions, (b) three-point bending in air using an atomic force microscope, and (c) nanoindentation tests on the circumference of the seta. Elastic moduli were found to depend strongly on the method of testing: Tensile testing in vacuum yielded an elastic modulus of 7.3 ± 1.0 GPa which was roughly five to six times higher than in bending and in nanoindentation tests at ambient conditions. The results are discussed in terms of the anisotropic nanostructure of the setae and humidity effects. They constitute valuable input parameters for optimizing the performance of artificial attachment devices.
TL;DR: In this article, the nucleation, growth, and coarsening kinetics of Cu-rich precipitates in a multicomponent Fe-Cu based steel, aged at 500 °C for up to 1024 h are investigated.
Abstract: The nucleation, growth, and coarsening kinetics of Cu-rich precipitates in a multicomponent Fe – Cu based steel, containing 1.17 at.% Cu, aged at 500 °C for up to 1024 h are investigated. The temporal evolution of the precipitate, heterophase interface, matrix compositions and precipitate morphology are presented. Coarsening temporal exponents are determined for mean radius, number density, and supersaturations, and are compared to the Lifshitz – Slyzov – Wagner model for coarsening, modified for multicomponent alloys by Umantsev and Olson. The experimental results indicate that the alloy does not strictly follow Umantsev – Olson model behavior. Additionally, we compare the results to an investigation of a similar multicomponent steel containing 1.82 at.% Cu and to results in the literature. Furthermore, we present a Thermo-Calc determined phase diagram.
TL;DR: In this paper, the influence of the gauge length, wire diameter and grain size on the tensile properties of polycrystalline copper wires was analyzed using a recently developed fiber tensile module capable of high accuracy and flexibility.
Abstract: Tensile experiments on micro-sized polycrystalline copper wires with diameters ranging from 14 μm to 50 μm were performed using a recently developed fibre tensile module capable of high accuracy and flexibility. This module is able to fit into a scanning electron microscope for in-situ deformation studies. In this study the influence of the gauge length, wire diameter and grain size on the tensile properties is analysed. In-situ experiments performed in a scanning electron microscope revealed clearly that the occurrence of “pop-in” events in the load-displacement curves are related to slip. The results are compared to deformation studies of micro-sized copper samples in the literature and discussed taking in-situ scanning electron microscope observations into account.
TL;DR: In this article, a plasma assisted chemical vapour deposition process for a-C: H films has been studied experimentally by reciprocating sliding of an a-c: h-coated Si3N4 ball on an aC: hcoated 100Cr6 steel substrate and subsequent micro Raman spectroscopy of the wear track.
Abstract: Amorphous hydrocarbon (a-C: H) films have enormous potential as low friction, wear resistant coatings. Here, we present a plasma assisted chemical vapour deposition process for a-C: H that exhibits growth rates of 100 nm min– 1 and higher. The tribological performance of the resulting a-C: H films has been studied experimentally by reciprocating sliding of an a-C: H-coated Si3N4 ball on an a-C: H-coated 100Cr6 steel substrate and by subsequent micro Raman spectroscopy of the wear track. Running-in of the coatings is observed and characterised by a rapid decrease in the friction coefficient accompanied by a significant increase in sp2 hybridisation in the wear track. In order to gain a deeper understanding of the underlying running-in mechanisms, the sliding of two a-C: H films under a load of 5 GPa has been studied by classical molecular dynamics employing a range-corrected Brenner bond-order potential. The simulations reproduce the experimental trends and explain the running-in by a combination ...
TL;DR: In this article, the influence of different σ-phase morphologies on the mechanical, wear and corrosive behaviour of the duplex stainless steel 1.4462 (X2CrNiMoN 22 5 3) was investigated.
Abstract: The aim of the presented study is to investigate the influence of the different σ-phase morphologies on the mechanical, wear and corrosive behaviour of the duplex stainless steel 1.4462 (X2CrNiMoN 22 5 3). Different amounts of σ-phase were precipitated in tensile, impact strength, wear and corrosion samples by annealing at 750 °C, 850 °C and 938 °C. σ-phase shows a detrimental influence on the impact strength and the corrosion behaviour. To a very limited extent it can be used to slightly raise the strength under quasi-static load and to improve the wear resistance. Finally, it can be concluded that σ-phase has more unfavourable influences on the material' behaviour than advantageous ones. Therefore, it should be avoided in duplex stainless steels.
TL;DR: In this article, the precipitation behavior of Fe-25% Co-15% Mo (wt.%) alloys has been studied applying non-isothermal ageing and high sensitivity differential scanning calorimetry and atom probe tomography have been used to characterise the precipitation sequence.
Abstract: Fe – Co – Mo alloys show hardening behaviour comparable to that of precipitation hardened Al-alloys, which is characterised by a low hardness after solution annealing and a significant increase in the hardness during subsequent ageing at higher temperatures. In this study, the precipitation behaviour of Fe-25% Co-15% Mo (wt.%) has been studied applying non-isothermal ageing. High sensitivity differential scanning calorimetry and atom probe tomography have been used to characterise the precipitation sequence. Three overlapping exothermic reactions, which are related to precipitation reactions, are observed in the temperature range of 400 to 700°C. The investigations have shown that precipitation starts with diffusion of Mo, followed by the formation of the intermetallic μ-phase which reaches its equilibrium composition at a temperature of about 615°C.
TL;DR: In this paper, the authors synthesize LiCoO2 targets in pure Ar plasma and prove the crystal structure by X-ray diffraction and Raman spectroscopy, which is suitable for large-scale implementation in foil coating set-ups.
Abstract: Cathode material for Li-ion batteries can be synthesised by r.f. magnetron sputtering of LiCoO2 targets in a pure Ar plasma. This technique is suitable for large-scale implementation in foil coating set-ups. By choosing the process parameters and by employing post heat treatment nanocrystalline, stoichiometrical LiCoO2 films can be fabricated which exhibit the desired high temperature phase. The determination of the elementary composition is possible by optical emission spectroscopy including plasma stimulation and carrier gas temperature extraction. The proof of crystal structure is carried out by X-ray diffraction and Raman spectroscopy. Heat treatment can be conventionally realised in a furnace or by laser impact. With regard to increasing the power density, the surface of the cathode material can be enhanced six-fold by laser-assisted surface patterning.
TL;DR: In this paper, a wide angle tomographic atom probe (WaTAP) was designed for femtosecond laser evaporation pulses rather than of high-voltage pulses.
Abstract: A laser assisted tomographic atom probe has recently been designed. The use of femtosecond laser evaporation pulses rather than of high-voltage pulses has opened the field of application of the technique to new materials such as semi-conductors and oxides. These classes of materials are of utmost importance in microelectronics for the design of nano-chips and nano-transistors in integrated devices. This type of instrument is the only 3D analytical microscope capable of mapping out the distribution of elements in a small volume (50 × 50 × 100 nm3) on a nearly atomic scale. In addition, the tomographic atom probe enables us to get quantitative composition measurements. This review illustrates the potential of this new instrument (laser assisted wide angle tomographic atom probe LaWaTAP) when applied to study scientific topics in nano-sciences. As an example, both the distribution of addition elements (Pt) during inter-diffusive reaction in NiSi contacts of nano-transistors and the investigation of ...
TL;DR: In this paper, a critical assessment of the methods for the estimation of crystallographic textures during the displacive transformation of austenite into martensite, bainite or Widmanstatten ferrite in steels is presented.
Abstract: Displacive transformations involve the disciplined motion of atoms. As a result, there are clearly defined relationships between all aspects of the parent and product lattices. The theory for this is well established but has not been exploited in the calculation of transformation textures. This paper is a critical assessment of the methods for the estimation of crystallographic textures during the displacive transformation of austenite into martensite, bainite or Widmanstatten ferrite in steels. The discussion is limited to the case where austenite is not in a plastically deformed state prior to its transformation.
TL;DR: In this article, it was shown that the competition between the precipitation of nitrogen gas (dissociation of nitrogen supersaturated ferrite into pure ferrite and nitrogen gas) at the grain boundaries and precipitation of hexagonal (wurzite) AlN led, via the coalescence of pores filled with nitrogen gas, to the emergence of microcracks along the grain boundary and the formation of nitride-precipitate free zones near the grain perimeter of the recrystallised specimens.
Abstract: Nitriding of recrystallised and cold-rolled Fe-4.65 at.% Al alloy at 550 °C in an ammonia – hydrogen gas mixture of nitriding potential 0.104 atm− 1/2 indicated that nucleation of the thermodynamically (most) stable hexagonal (wurzite) AlN in the ferrite matrix of recrystallised specimen is difficult. The competition between the precipitation of nitrogen gas (dissociation of nitrogen supersaturated ferrite into pure ferrite and nitrogen gas) at the grain boundaries and the precipitation of hexagonal (wurzite) AlN led, via the coalescence of pores filled with nitrogen gas, to the emergence of microcracks along the grain boundaries and the formation of nitride-precipitate free zones near the grain boundaries of the recrystallised specimens. Upon continued nitriding the initially partially nitrided grains became fully nitrided and the microcracks disappeared.