Direct observation of corrosion fatigue cracks in aluminum alloy using ultra-bright synchrotron radiation

Refraction contrast X-ray imaging using synchrotron source with ultra-bright light and highly directional beam is a unique method to diagnose non-destructively cracks or voids formed in materials, providing us in principle completely different information from conventional methods such as absorption contrast X-ray imaging. The authors have applied this imaging technique in SPring-8 to materials fracture study. We have also introduced home-made, in-situ observation facility system of crack formation and propagation in materials and the originally-designed 3D X-ray imaging systems to the experimental Hutch C of BL24XU (Hyogo BL) of SPring-8. Using these 3D X-ray imaging technique, in-situ observations of initiation and propagation of corrosion fatigue crack of Al-10%Mg alloy were conducted. The absorption contrast X-ray images were also obtained for comparison. It is concluded that the X-ray imaging method using ultra-bright synchrotron radiation is very useful for fracture research of materials and 3D X-ray contrast images are much more distinct than the conventional X-ray images to obtain information of the crack initiation and propagation behavior in the alloy.     

Computation of Eutectic Concentrations and Temperature in Two-Component and Multicomponent Systems

The initial data for computation of eutectic temperature in two-component and multicomponent systems are the form of the binary phase diagrams and the melting temperatures of the components of the eutectic. The eutectic components can be pure elements, chemical compounds, or solid solutions with ultimate solubility. In salt systems these are oxides, salts, or their complexes. Statistical analysis of some phase diagrams of binary, ternary, and other multicomponent systems makes it possible to formalize the interrelation between the eutectic temperature and the melting temperature of eutectic components. The dependences obtained have been used for developing methods of direct and successive computation of eutectic temperature and concentration in two-component and multicomponent systems. In order to reduce the error the elements and their compounds have been classified according to the electron structure and physicochemical properties in accordance with the Periodic System. The methods developed have been used for determining the temperature and concentration conditions of a boronizing process ensuring a liquid crystal state of treated surfaces at saturation temperatures with the aim of formation of pseudoeutectic structures of boronized layers on nickel alloys and high-speed steels.     

X-ray absorption studies of phase formation in a Ti/TiN coating on cubic boron nitride

We report on the use of X-ray absorption spectroscopy as a tool for the identification of the phases formed in the technological process of composite preparation. A composite is a mixture of several compounds and, in many cases, the use of traditional X-ray diffraction to determine the phases can be difficult because of the small amount of phases present. X-ray absorption studies (XANES and EXAFS) of the c-BN Ti/TiN layered system are presented. These materials are models of the powdered composites used in industry for tool production. XANES and EXAFS analyses showed that, after annealing up to 1300 °C, a TiB₂ phase is formed, but the chemical bonding of the Ti atoms differs slightly from that of standard TiB₂ powder, showing the presence of defects in site occupancy. Assuming that the X-ray absorption spectral shape is a linear combination of the spectra of all the components, we estimated the kind and limits of other phase inclusions.     

Computer simulation of the growth of intermediate phases in a complex metallic system

The technique and results of computational experiment on the contact melting in a two-component system with an intermetallic compound have been considered. The possibility of existence of metastable states in the liquid interlayer has been assumed. The conditions under which the parabolic law of growth of the liquid-interlayer extension is obeyed and the liquid-interlayer concentration field fits the equilibrium phase diagram have been clarified. Results of the simulation and real experiment have been compared.     

Phase equilibria in the AlVO4-Al2(MoO4)3 system

The phase equilibria established in the AlVO₄-Al₂(MoO₄)₃ system over the whole component concentration range up to 1000 °C have been investigated. A phase diagram has been constructed using the results of DTA and XRD methods. The AlVO₄-Al₂(MoO₄)₃ system is not a true two-component system, even in the subsolidus area.     

Phase equilibria in the AlVO4-Al2(MoO4)3 system

The phase equilibria established in the AlVO₄-Al₂(MoO₄)₃ system over the whole component concentration range up to 1000 °C have been investigated. A phase diagram has been constructed using the results of DTA and XRD methods. The AlVO₄-Al₂(MoO₄)₃ system is not a true two-component system, even in the subsolidus area.     

Small angle x-ray scattering studies of Cu-Cd alloys obtained using electrodeposition

Small angle X-ray scattering (SAXS) studies have been performed on Cu-Cd alloys obtained using electrodeposition from an ethylenediamine electrolyte in the cathode potential range from -500 mV to -800 mV. SAXS results confirm the existence of at least two phases in these alloys (a solid solution of cadmium in copper and a phase enriched in cadmium) and also indicate that the phase enriched in cadmium has a complex structure which is independent of cathode potential.     

Boundary slope interrelation method for determination of tie lines in ternary isothermal sections

A new method for interpolation of tie lines in ternary isothermal sections has been developed. This method and a previously reported method have been analyzed for a ternary isothermal section of the Al-Mg-Zn system. The technique is well suited for use in computer-based phase diagram storage and retrieval systems. An application of the present interpolation method for equilibrium crystallization path determination is discussed.     

Shift of the transition temperature and the change in the free energy upon directional solidification of solutions at a given rate

Conditions of equilibrium at the interface between the solid and liquid phases in the course of directional solidification of a two-component melt and the rate of the decrease in the free energy of such a system in the case where diffusion in the solid phase can be neglected have been investigated. Using the previously suggested new boundary conditions for the diffusion equation, analytical expressions have been obtained for the shifts of the values of the concentrations in the liquid and solid phases at their interface, as well as for the solidification temperature as compared to the initial equilibrium values corresponding to a zero growth rate. It is shown that the magnitudes of these shifts are directly proportional to the solidification rate and are inversely proportional to the coefficients that describe the transport of atoms of various sorts through the interface. Using the above-mentioned boundary conditions, we have found an expression for the rate of the decrease in the free energy of the system under consideration and have shown that it can be divided into two parts, one of which is determined by the processes at the interface between the phases and the other is controlled by diffusion processes that occur inside the volume of the phases. The results are compared with those obtained in terms of a different approach, which is based on the determination of the balance between the changes in the free energy in the solid and liquid phases far from the solidification front. It is shown that both approaches yield similar results, so that in some cases they can be used as mutually complementary.     

X-ray diffraction study of the effect of annealing temperature on the phase and structural states of Fe79Zr10N11 films produced by magnetron sputtering

Fe₇₉Zr₁₀N₁₁ films 0.7 μm thick deposited on glass substrates have been produced by rf reactive magnetron sputtering. The films are a soft magnetic material, which can exhibit a combination of a high saturation inductance and a low coercive force and, therefore, shows promise as magnetic recording cores for the high-density magnetic recording. The results of X-ray diffraction studies of the phase and structural states of the films and the effect of annealing on these states are considered.     

MOLTEN SALT PHASE DIAGRAMS CALCULATION USING ARTIFICIAL NEURAL NETWORK OR PATTERN RECOGNITION-BOND PARAMETERS PART 3.ESTIMATION OF LIQUIDUS TEMPERATURE AND EXPERT SYSTEM

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Ordering,disordering and segregation at binary interfaces: model system Cu3Au(001)

In this article we discuss surface and subsurface thermodynamic phenomena as they emerge when the bulk of the system undergoes a discontinuous order–disorder phase transition. We have chosen Cu₃Au(001) as a model system and demonstrate that pronounced order, disorder and composition profiles are found at the Cu₃Au(001) surface. Surface-sensitive X-ray scattering techniques that exploit the high brilliance of modern synchrotron radiation sources are ideally suited to unravel this novel thermodynamics between two and three dimensions.     

Exposure values for a 300 kV halfwave X-ray unit using three X-ray films of different film classes Part 1. Welded steel plates over 10 mm thick

As a result of a large test series performed over many years, the parameters for exposing various X-ray films with different X-ray units were described. As relatively new parameters the dose rate values of the X-ray units, the doses for the X-ray films and the contrast values between various densities were applied. In the future, if the manufacturers of X-ray units publish the dose rate results, we will have more exact imformation on the properties of the units. The dose values for the X-ray films are also important. This information enables the X-ray staff to calculate the exposure values and determine the radiographic contrast between unequal densities. This article aims at shedding more light on these parameters with the aid of a 300 kV halfwave unit and three X-ray films of different film classes. The values are presented in combination with X-ray exposure tables.     

Chemical transport reactions as a new variant of the phase composition control

It is shown that the composition of low-volatility two-component compounds in the Ga-Se system can be controlled using chemical transport reactions (CTR). For long-term heat treatment of a low-volatility phase in the presence of a transport agent, the annealed phase composition was found to be determined only by the temperature conditions and the chemical nature of the sample. In the case of a two-temperature anneal of gallium selenides with added iodine, the sample stability domains are presented as a function of the cold and hot zones temperatures. The role of the transport agent is discussed. The possibility of applying this technique to other binary systems with low-volatility phases is also considered.     

Chemical transport reactions as a new variant of the phase composition control

It is shown that the composition of low-volatility two-component compounds in the Ga-Se system can be controlled using chemical transport reactions (CTR). For long-term heat treatment of a low-volatility phase in the presence of a transport agent, the annealed phase composition was found to be determined only by the temperature conditions and the chemical nature of the sample. In the case of a two-temperature anneal of gallium selenides with added iodine, the sample stability domains are presented as a function of the cold and hot zones temperatures. The role of the transport agent is discussed. The possibility of applying this technique to other binary systems with low-volatility phases is also considered.     

Al-matrix composite based on Al-Ca-Ni-La system additionally reinforced by L12 type nanoparticles

The structure of the quaternary Al-(2−4)wt.%Ca-Ni-La system near the aluminum corner has been studied using computational analysis in the Thermo-Calc program and experimental studies (electron microscopy, microprobe analysis and X-ray diffraction). Based on the phase equilibria data obtained, the experimental projection of the liquidus surface and solid state phase-field distribution of the Al-Ca-Ni-La system have been proposed. Microstructure studies reveal that the alloys with the 2-4 wt.% Ca, 2−4 wt.% Ni and 1-3 wt.% La ranges have an ultra-fine hypoeutectic structure with 30% volume fraction of eutectic intermetallics, which allows one to classify these alloys as natural Al-matrix composites. The ultra-fine eutectic structure produces significant strengthening, the magnitude of which can be well described using the modified Orowan looping mechanism model. Small additives of Zr and Sc (0.2 and 0.1 wt.%, respectively) lead to significant strengthening (by ~25%) due to the formation of L1₂ type phase (Al₃(Zr, Sc)) nanoparticles during annealing of the alloy at 350-400 °C. Due to the high volume fraction of eutectic intermetallics, the new alloys have low coefficients of thermal expansion and high thermal stability of the structure and mechanical properties.     

Metastable Ti---Ni---Fe---Si alloys prepared by mechanical alloying

The phase formation and physical properties of mechanically alloyed Ti₅₆Ni₁₈Fe₁₀Si₁₆ have been investigated. The as-milled samples are amorphous and undergo a transition to the icosahedral quasi-crystalline phase on annealing at about 1025 K. Mechanical alloying in the presence of an additive of 1% quasi-crystalline phase yielded the same phase directly. Alloys have been studied by X-ray diffraction. Mössbauer spectroscopy and magnetic susceptibility methods. These results may be compared with those in the literature for amorphous and quasi-crystalline alloys of similar composition prepared by rapid solidification from the melt. In all cases the alloys produced by mechanical alloying show a greater concentration of open volume defects and in the icosahedral phase, a greater degree of disorder and largerphason strains. Hydrogen diffusion studies of these alloys have shown that the mean interatomic distance increases for short hydrogenation times, but that for longer hydrogenation times the hydrogen increases local atomic order which results in a reduction of mean interatomic distances.     

Columbium-vanadium alloy system

On the basis of microscopic studies, melting-point observations, and X-ray analyses, a phase diagram is proposed for the Cb-V system. A complete series of solid solutions is formed with a minimum in the solidus at 1810°C near 35 wt pct Cb. No compounds or intermediate phases were found in the system above 650°C.     

Effects of alloying elements on phase stability in Nb–Si system intermetallics materials

The effects of alloying elements, such as Ti, Cr, Al and Hf on phase stability in Nb–Si system intermetallics materials have been investigated by scanning electron microscopy (SEM), X-ray energy dispersive spectrum (EDS) and X-ray diffraction (XRD). The binary, ternary and multicomponent alloys have been fabricated by vacuum non-consumable arc melting method. The results showed that Ti and Hf tend to stabilize Nb₃Si phase to lower temperatures, while Cr and Al promote the direct formation of Nb₅Si₃ phase. The coordinate effects of alloying elements on microstructures of Nb–Si system intermetallics materials have also been examined.