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The ordered γ′-(Ni, Cu)3Al is a crucial strengthening phase that improves the high-temperature resistance of Cu-based alloys, so it is important to predict the kinetic evolution of the composition and microstructure of the phase for high-temperature applications. Herein, this paper discusses the temporal evolution of the composition and coarsening of the γ′ phase in a model ternary Cu50Ni37.5Al12.5 (at%) alloy during isothermal aging at 600, 700, 800, and 900 °C for 1–36 h. It is found that the γ′ phase composition evolves linearly toward a binary γ′ phase as the aging time increases during the process of aging at 800 and 900 °C, which cannot be predicted by the ternary phase diagrams alone. Meanwhile, through the utilization of the aforementioned linear law, the γ phase composition can be predicted at a given temperature within the alloy by determining the volume fraction of the γ′ phase. Additionally, the activation energy for coarsening decreases, and the coarsening rate of the γ′ phase increases owing to the higher diffusion rate of Cu at high temperatures. The addition of microalloying elements with strong enthalpic interactions is beneficial for reinforcing the structural stability of the γ′ phase. This work provides a simple method for the compositional analysis and performance prediction of Cu–Ni–Al alloys at elevated temperatures and sheds light on the subsequent compositional design and optimization of Cu-based high-temperature alloys. [ABSTRACT FROM AUTHOR]

Methods of economical alloying of high pipe steels were considered in the paper. Due to the large environmental, energy, and economic issues in the destruction of the pipeline, the quality of steel pipes is very important. The method described in this article is considered to be relevant not only for pipe steels but also for high-strength steels used in shipbuilding, bridge construction, etc. Review mechanisms of strengthening microalloyed steels were carried out in this work. Schema evolution of the microstructure of microalloyed steels was discussed. The influence of alloying elements in steel by means of optimal process parameters of thermomechanical rolling was analyzed. There are two methods of mathematical modeling used in the study: artificial neural networks (ANNs) which are based on the multilayered perceptron to select the optimal chemical composition and finite element analysis to optimize the process parameters. An experimental dataset was used to train multilayer perceptron (MLP) networks to allow for prediction of the yield strength, tensile strength, and elongation of steel. Due to large availability, low cost, and high accuracy of the results, these methods are considered to be the most promising ones. The mathematical model for calculating mechanical properties of a rolling pipe has been developed. Two ways to reduce the cost of a hot-rolled plate made of microalloyed steels were developed. There has been developed the complex of replacement technological impact which can make it possible to replace or reduce the amount of expensive chemical elements (vanadium, nickel, copper, manganese, chromium, and niobium) without loss of quality. [ABSTRACT FROM AUTHOR]

In this paper, a new explicit state variable was introduced which describes the AgSn intermetallic morphology inside of lead-free solder joints at different cooling rates. In the experiment, samples were prepared by melting standard Ag-content (4 % in wt%) and low Ag-content (0.3 % in wt%) solder alloys, and solidifying them at five different cooling rates between 0.8 and 3 K/s. Images were taken about the cross-section of solder joints by brightfield light-microscope to calculate the explicit state variables, which describe the morphology of precipitating AgSn intermetallic compounds. The captured images were processed then with an in-house developed automatic image processing algorithm. It was found that the area of AgSn intermetallic compounds followed exponential distribution, so a new state variable could be introduced, such as the amplitude of a certain exponential curve fitted to the area histogram of the AgSn IMCs. It was proven that our new variable described the different AgSn IMC morphologies obtained at different cooling rates better; it was more sensitive at both aforementioned solder alloys (4 and 0.3 % Ag content) than the widely applied parameters, like the mean-intercept length or the average area of particles. [ABSTRACT FROM AUTHOR]

Mg-Zn-Zr wrought alloys have been widely developed for lightweight applications. Zr microalloying contributes to remarkable grain refinement during solidification and bimodal microstructure via forging. To obtain an optimum Zr content for a balance between cost and mechanical property, it is necessary to understand the influence of varied Zr addition levels on the microstructure and mechanical property of the final forged product. In the present study, two levels of Zr addition (nominally 0.40 wt.% and 0.60 wt.%) were added to a Mg-3 wt.% Zn alloy to investigate the effect of varied Zr contents on the microstructures under as-cast, as-forged and tensile-strained conditions, as well as the uniaxial tensile properties of the as-forged alloy. The as-forged microstructures comprise fine dynamic recrystallized (DRXed) grains and coarse deformed (unDRXed) domains, which become more refined with the Zr content increasing from ~ 0.43 wt.% to ~ 0.67 wt.%. The microstructural change caused by the increased Zr addition has minor impact on 0.2% proof stress but remarkably improves both uniform and post-uniform elongations, for which the underlying mechanisms have been discussed. [ABSTRACT FROM AUTHOR]

This work presents the results of research conducted by the authors over the past years in Nippon Light Metal Co., ltd. In the first stage, highly durable ceramic sonotrodes were designed and manufactured to introduce ultrasonic vibrations into molten metal in a launder or in a hot top during DC casting. It was shown that ultrasound can greatly refine the crystals of primary silicon in 75 to 178-mm billets, if vibration amplitude exceeds 40 μm (p-p). The structure uniformity was insufficient in launder treatment and fairly good in hot-top treatment. Care must be taken in controlling the passage of melt through the cavitation zone in order to fully exploit the refining potential of ultrasonic vibrations. The results suggest that if the treatment conditions are controlled properly, up to 20 kg/min of molten metal can be effectively treated using a 2-kW ultrasonic installation equipped with one ceramic sonotrode of 40 to 60 mm in diameter. [ABSTRACT FROM AUTHOR]

An effective alloying system for providing improved mechanical and technological properties of model cast Al–Cu alloys (Al-4.6%Cu-0.4%Mn-0.2%Ti), using magnetohydrodynamic (MHD) melt mixing, has been chosen in this research. It was shown that MHD treatment provides a non-dendritic (globular) ingot structure and can be applied to ensure thixotropy in the mass production of high-precision cast parts. Small additives of alloying elements that modify both grain structure (Mn, Zr) and reinforcing phases (Sn, In, Sc) were used. It is shown that the most effective alloying elements which improved the strength characteristics of the alloy are Sn and In. The introduction of 0.1–0.2% Sn or In followed by heat treatment led to a 50% increase in its yield strength, a 15% increase in the tensile strength. Sn and In modified the decomposition kinetics, providing a high density of precipitate and slow coalescence of nano-sized particles of the strengthening θ′-phase, which resulted in higher strength characteristics of the alloy. [ABSTRACT FROM AUTHOR]

The article presents a survey of articles that focus on age-hardenable microalloying in magnesium. Articles presented include the precipitation hardening and microalloying of high-strength magnesium alloys and the creation of an integrated density functional theory and electron work function study on solid-solution hardening. A research on microstructure evolution and hardness variation is also mentioned.

Metal sulfide grain boundary precipitates of a ferrous model alloy with 13 wt.% chromium formed at 650°C under a gas atmosphere containing 0.5% SO2 and 99.5% Ar were investigated after ageing for 3 h, 6 h, and 12 h. The precipitates formed along grain boundaries were identified as Cr5S6 using energy-dispersive x-ray spectroscopy in transmission electron microscopy and electron backscatter diffraction analysis. Serial focused ion beam slicing was conducted followed by three-dimensional reconstruction to determine the number, size, and penetration depth of the precipitates evolved at the different time steps. There was a linear increase in the number of precipitates with time, while their average size increased only for the initial aging time but became constant after 6 h. Based on these results, a model for grain boundary sulfidation of ferritic alloys is discussed. [ABSTRACT FROM AUTHOR]

The effect of Si and Y2O3 additions on the oxidation behavior of Ni-xAl (x = 5 or 10 wt%) alloys at 1150 °C was studied. The addition of Y2O3 accelerates oxidation rate of alloys, especially growth rate of NiO, but improves adherence of the scale to the substrate. The addition of Si facilitates the selective oxidation of Al, suppresses the formation of NiO and therefore reduces the critical Al content to form continuous layer of alumina scale. Higher Al content decreases the oxidation rate of alloys in binary Ni-Al alloys and increases the oxidation rate of alloys in ternary Ni-Al-Si alloys. The effect of third-element Si is more significant and beneficial than that of Al content in ternary Ni-Al-Si alloys. [ABSTRACT FROM AUTHOR]

The α(hcp)/β(bcc) phase equilibria of Ti-based multi-component alloys can be described by a Schaeffler-type diagram, where Al and Mo equivalents (Aleq and Moeq) are used. Aleq is thermodynamically defined by the ratio of partial molar free energy changes transfer of one mole of each α forming element and Al from a dilute solution of α to β phases, while Moeq is also deduced by similar thermodynamic quantities of β forming element and Mo. Aleq and Moeq for 40 alloying elements are estimated from the thermodynamic parameters assessed by Kaufman and Murray. It is shown that three types of Ti alloys, i.e., α and near α, α+β, and β alloys, can be exactly classified using Aleq and Moeq. The Ms and β transus temperatures can also be predicted by Aleq and Moeq. The proposed Aleq and Moeq are very useful for alloy design, heat treatment, and microstructural evolution of Ti-based alloys. [ABSTRACT FROM AUTHOR]

A new Fe-Cr-Al (FCA) alloy system has been developed with good oxidation resistance and creep strength at high temperature. The alloy system is a candidate for use in future fossil-fueled power plants. The creep strength of these alloys at 973 K (700 °C) was found to be comparable with traditional 9 pct Cr ferritic-martensitic steels. A few FCA alloys with general composition of Fe-30Cr-3Al-.2Si- xNb ( x = 0, 1, or 2) with a ferrite matrix and FeNb-type Laves precipitates were prepared. The detailed microstructural characterization of samples, before and after creep rupture testing, indicated precipitation of the Laves phase within the matrix, Laves phase at the grain boundaries, and a 0.5 to 1.5 μm wide precipitate-free zone (PFZ) parallel to all the grain boundaries. In these alloys, the areal fraction of grain boundary Laves phase and the width of the PFZ controlled the cavitation nucleation and eventual grain boundary ductile failure. A phenomenological model was used to compare the creep strain rates controlled by the effects of the particles on the dislocations within the grain and at grain boundaries. (The research sponsored by US-DOE, Office of Fossil Energy, the Crosscutting Research Program). [ABSTRACT FROM AUTHOR]

The evolution of microstructure and crystallographic texture has been investigated in double-sided friction stir welded microalloyed steel, using electron backscatter diffraction (EBSD). The microstructure analyses show that the center of stirred zone reached a temperature between Ac and Ac during FSW, resulting in a dual-phase austenitic/ ferritic microstructure. The temperatures in the thermo-mechanically affected zone and the overlapped area between the first and second weld pass did not exceed the Ac. The shear generated by the rotation probe occurs in austenitic/ferritic phase field where the austenite portion of the microstructure is transformed to a bainitic ferrite, on cooling. Analysis of crystallographic textures with regard to shear flow lines generated by the probe tool shows the dominance of simple shear components across the whole weld. The austenite texture at Ac - Ac is dominated by the B $$ \left\{ {1\bar{1}2} \right\}\langle 110\rangle $$ and $$ \bar{B} $$ $$ \left\{ {\bar{1}1\bar{2}} \right\}\langle \bar{1}\bar{1}0\rangle $$ simple shear texture components, where the bainite phase textures formed on cooling were inherited from the shear textures of the austenite phase with relatively strong variant selection. The ferrite portion of the stirred zone and the ferrites in the thermo-mechanically affected zones and the overlapped area underwent shear deformation with textures dominated by the D $$ \left\{ {\bar{1}\bar{1}2} \right\}\langle 111\rangle $$ and D $$ \left\{ {11\bar{2}} \right\}\langle 111\rangle $$ simple shear texture components. The formation of ultrafine equiaxed ferrite with submicron grain size has been observed in the overlapped area between the first and second weld pass. This is due to continuous dynamic strain-induced recrystallization as a result of simultaneous severe shear deformation and drastic undercooling. [ABSTRACT FROM AUTHOR]

We present a process of semantic meta-model development for data management in an adaptable multiscale modeling framework. The main problems in ontology design are discussed, and a solution achieved as a result of the research is presented. The main concepts concerning the application and data management background for multiscale modeling were derived from the AM3 approach-object-oriented Agile multiscale modeling methodology. The ontological description of multiscale models enables validation of semantic correctness of data interchange between submodels. We also present a possibility of using the ontological model as a supervisor in conjunction with a multiscale model controller and a knowledge base system. Multiscale modeling formal ontology (MMFO), designed for describing multiscale models' data and structures, is presented. A need for applying meta-ontology in the MMFO development process is discussed. Examples of MMFO application in describing thermo-mechanical treatment of metal alloys are discussed. Present and future applications of MMFO are described. [ABSTRACT FROM AUTHOR]

Ni-base superalloy films were deposited on single-crystal (SC) Ni-base superalloy substrates from a target with the same alloy composition by pulsed laser deposition (PLD) technique. Microstructure and growth behavior of the films deposited were investigated by X-ray diffraction and scanning electron microscopy, and atomic force microscope. The homoepitaxial growth of the SC Ni-base superalloy film occurred at the 1123 K (850 °C) substrate temperature and 2 J/cm pulse energy. Films generally exhibited a strong polycrystalline characteristic as the substrate temperature and pulse energy increased. The SC film had a smooth surface. The measured root mean square roughness of the SC film surface was ~6 nm. Based on the Taguchi analysis, the substrate temperature and pulse energy were the most significant process parameters influencing the structural characteristics of the films. Also, the influence of the pulse repletion rate and deposition time was not found to be significant. [ABSTRACT FROM AUTHOR]

The influence of a transverse magnetic field on the microstructures in unmodified and Sr-modified Al-7wtpctSi alloys during directional solidification was investigated. Experimental results indicated that the magnetic field caused the channel and freckle macrosegregations during directional solidification. Comparison of the microstructures in unmodified and Sr-modified Al-7wtpctSi alloys showed that the Sr-addition enhanced the convection effects. Moreover, the EBSD analysis revealed that the magnetic field changed the alignment of the α-Al dendrite and modified the distribution of dendrite fragments in both unmodified and Sr-modified Al-7wtpctSi alloys. Indeed, the application of the magnetic field caused the 〈001〉-crystal direction of the α-Al dendrite to deflect from the solidification direction and induced the formation of dendrite fragments on one side of the sample. Further, the Seebeck signal ( E) at the liquid/solid interface was measured in situ during directional solidification of Al-7wtpct Si alloy and the results indicated that the value of the E was of the order of 10 μV and decreased with the increase of the growth speed. The above results may be attributed to the thermoelectric magnetic convection and its effect on the distribution of the solute Si. It is proven that solute effects are primarily responsible for dendrite fragmentation. [ABSTRACT FROM AUTHOR]

Fine precipitation was observed in the channel region of the Ni-based, two-phase NiAl and NiV intermetallic alloys containing Mo and W, which are soluble in the A1 phase at high temperatures but less soluble in the two intermetallic phases at low temperatures. The fine precipitates were identified as Mo- or W-rich phases (Mo solid solution with a body-centered-cubic (bcc) structure or NiW with a tetragonal structure) accompanied by a rigid orientation relationship and a habit plane with the constituent phases in the channel region. Fine precipitation was induced when added elements were substituted for Ni, thus, stabilizing the two intermetallic phases; however, it was not induced when the two intermetallic phases were destabilized by the addition of elements to substitute for Al and V. Fine precipitation was induced to a greater extent when Nb was concomitantly added to the alloys with Mo or W and when the two intermetallic phases were stabilized. Annealing at temperatures below the eutectoid temperature was necessary to induce fine precipitation in the alloys containing W. Accordingly, age hardening by annealing did not occur in the alloys containing Mo but did occur in the alloys containing W, whose behavior was correlated with the difference in the diffusivity of the Mo and W elements in the two-phase eutectoid microstructures (phases). [ABSTRACT FROM AUTHOR]

In the present article, the intermixing and clustering of U/Nd, O, and vacancies were studied by both laboratory and synchrotron-based x-ray diffraction in U1−yNdyO2−x alloys. It was found that an increased holding time at the high experimental temperature during initial alloy preparation results in a lower disorder of the Nd distribution in the alloys. Adjustment of the oxygen concentration in the U1−yNdyO2−x alloys with different Nd concentrations was accompanied by the formation of vacancies on the oxygen sublattice and a nanocrystalline component. The lattice parameters in the U1−yNdyO2−x alloys were also found to deviate significantly from Vegard's law when the Nd concentration was high (53%) and decreased with increasing oxygen concentration. Such changes indicate the formation of large vacancy concentrations during oxygen adjustment at these high temperatures. The change in the vacancy concentration after the oxygen adjustment was estimated relative to Nd concentration and oxygen stoichiometry. [ABSTRACT FROM AUTHOR]

The precipitates of biomedical Co-28Cr-6Mo-(0.5 to 2)Si-(0.05 to 0.35)C alloys (mass pct) have been investigated before and after heat treatment, focusing on the formation of the χ-phase precipitate. The precipitates were precisely and directly analyzed after using electrolytic extraction to separate the precipitates from the alloys. Heat treatment was performed at 1523 K (1250 °C) for a holding time of 0.6 ks. The χ-phase precipitate was detected with Si content of 1.3 to 2 mass pct and C content of 0.05 to 0.15 mass pct in both the as-cast and heat-treated alloys. The higher Si content and the mid-level C content of about 0.15 mass pct favored the formation of the χ-phase precipitate. Moreover, the χ-phase precipitate was not observed in the compositional range of the ASTM F 75 standard: Si content ≤1.0 mass pct and C content ≤0.35 mass pct. In the as-cast Co-28Cr-6Mo-1.3Si-0.15C alloy, which is outside of the ASTM F 75 standard, the content of the χ-phase precipitate was around 6 pct in area percent; the decrease in the ductility was detected in the tensile test of this alloy. The amount of precipitates decreased due to heat treatment at 1523 K (1250 °C), where the dissolution of precipitates occurred. After the heat treatment, a single χ-phase precipitate region was detected. [ABSTRACT FROM AUTHOR]

Background: One of the main concerns for archaeo-metallurgists and archaeologists is to determine to what extent ancient craftsmen understood the effect of metal alloy composition and were able to control it in order to produce objects with the most suitable features. This problem can be investigated by combining compositional analyses of a high number of ancient artefacts with correlation analyses of the objects' age, production site, destination of usage etc. - and thus chemometric data treatment is carried out. In this study, multivariate analyses were performed on a matrix composed of elemental compositional data from 134 archaeological bronze objects, obtained by XRF analyses. Analysed objects have been dated back from the Eneolithic Period to the end of the Bronze Age including the early Iron Age and were excavated in Central Italy (mainly Abruzzo Region). Results: Chemometric analysis was performed attempting to visualise clouds of objects through PCA. In parallel and independently, object grouping was attempted using several different approaches, based on object characteristics (e.g. shape, weight, type of use - cutting or hitting and age) following indications given by archaeologists (or derived from the archaeological context). Furthermore, case-tailored data pretreatment (logratio-centred scaling) was used, but no homogeneous groups could be identified. Conclusions: By using chemometric data analysis, homogeneous groups of objects could not be detected, meaning that compositional data of alloys is not correlated with the considered objects' characteristics. This favours the conclusion that - without discussing the ascertained ability of ancient foundry-men - they had also already discovered the convenience of recycling broken objects thus producing a more or less similar bronze alloy each time, depending on materials' availability; necessary mechanical characteristics could then be obtained by post processing. [ABSTRACT FROM AUTHOR]

Nucleation is a critically important process as the rate of nucleation determines the number density of new phase particles and thus microstructures of a material during phase transformations. Predicting and controlling nucleation rates in solids is one of the grand challenges in materials science because the spatial scale involved in nucleation is at the atomic/nanoscale, the rate of nucleation process is extremely temperature sensitive, and the morphology of a critical nucleus can be highly nonspherical and complex. In this article, we briefly review the recent advances in modeling and predicting nucleation during solid-phase transformations based on the diffuse-interface or nonclassical description of critical nucleus profiles. The focus is on predicting the critical nucleus morphology and nucleation free energy barrier under the influence of anisotropic interfacial energy and elastic interactions. Incorporation of nucleation events in phase-field modeling of solid-to-solid phase transformations and microstructure evolution is also discussed. [ABSTRACT FROM AUTHOR]