Effects of Zr and Y on the Mechanical Properties and the Microstructure of Ti-Al-Sn-Nb-Mo-Si Alloy

In the present paper the effects of additions of Zr and Y on the microstructure and mechanical properties for Ti-(6.06.5)Al-(2.0～3.0)Sn-(1.5～6.0)Zr-(0.8～1.0)Mo-1.0Nb-0.25Si alloys are reported,The experimental results show that: with in-creasing of Zr content,tensile strength and creep resistance of the alloys increase,and reduction in area and thermal stability ofthe alloys decrease.Decrease in thermal stabiIity of the alloys mainly caused by surface thermal unstability.After heat treatmentY addition can make grain size of the alloys refine.The reduction in area and thermal stability of the alloys with Y addition areimproved,and tensile strength slightly decreases and creep resistance is essentially the same as the alloy without Y addition.Thesephenomena are explained in brief.     

Evaluation of the corrosion and oxide microstructural characteristics of pure Zr and the Zr−1.5Nb alloy

The corrosion behavior and the oxide microstructural characteristics of pure Zr and the Zr-1.5Nb alloy were investigated. The crystalline structure and morphology of zirconium oxide formed in a water at 360°C and 18.9 MPa was analyzed using a High Voltage Electron Microscope (HVEM). The corrosion rate increased more in pure Zr than in the Zr-1.5Nb alloy after the transition of the corrosion rate. From a HVEM oxide analysis and an imaging process using the DigitalMicrograph^™ program for both oxides formed on pure Zr and the Zr−1.5Nb alloy, it was found that most of the oxide amorphology consisted of both equiaxed and columnar grains. They formed in the outer and middle region of the oxide layer and were identified as a monoclinic phase. However, a complex oxide structure formed near the metal/oxide interface in the Zr−1.5Nb alloy, which showed good corrosion resistance. Thus, this implies that the Nb affected the oxide characteristics of the crystal structure and changed the corrosion behavior.     

The Influence of Method of Carburizing and Nitrocarburizing on the Microstructure and Properties of Tool Steels

The paper presents the results of wear and metallography tests of tool steel grades: ASTM A681, ChI2M and Ch12FS per GOST, AMS 6437E i BS X46Cr13, all surface hardened by the Carbo process (carburizing) and by the NiCar process (nitrocarburizing). The therrno-chemical treatment was conducted in powder pack for a duration of 6 h (carburizing) and for 4 h in the case of nitrocarburizing. Factors investigated were: morphology, depth and microhardness of the cases obtained, their microstructure, as well as phase composition. Wear tests were conducted by the three cylinder-cone method.Wear velocity was 0.58 m/s, unit load was 50 MPa and 400Mpa, wear path was 3470 m. Oil SAE30 was applied at the rate of 30 drops per minute.     

Recrystallization and the possibility of the realization of the α-γ diffusionless transformation during the ultrarapid laser heating of steels

Analysis is given of phase and structural transformations occurring upon ultrarapid laser heating in steels with different initial structures, namely, after annealing, after preliminary quenching, quenching and tempering, and after quenching with subsequent deformation and tempering. It is shown that a significant suppression of diffusion processes occurs during laser heating; this circumstance substantially affects the nature of the phase and structural transformations proceeding during laser processing. Special attention is given to studying the process of recrystallization and to the phenomenon of structural heredity during laser heating. The process of recrystallization during laser heating is considered as consisting of two stages, namely, an ordered lattice rearrangement (α-γ transformation) and the recrystallization of austenite that suffered phase-transformation-induced hardening (“phase naklep”). The effect of tempering and plastic deformation on the recrystallization of a preliminarily quenched steel consists in the intensification of the second stage, i.e., of the recrystallization of the transformation-hardened austenite. It is shown that the α-γ transformation during the laser heating of steels with the initial structure of lath martensite occurs by the “mechanism of recovery,” i.e., via the formation and growth of austenite nuclei. In steels with the initial structure of pearlite, the nucleation of austenite during laser heating can occur by a shear martensite-like diffusionless mechanism with the observance of characteristic orientation relationships between the initial ferrite and the newly formed austenite.     

Effect of the structure of the oxidized titanium surface on the particle size and properties of the deposited copper–molybdate catalyst

The parameters of wetting of oxide coatings on titanium formed by the method of plasma electrolytic oxidation (PEO) in an aqueous silicate electrolyte with subsequent deposition of a layer of TiO₂ nanoparticles and ultrasonic treatment by a polymer–salt gel including copper and molybdenum compounds have been investigated. The effect of the oxidized surface microrelief, TiO₂ nanoparticle layer, and pore shape and size on impregnation solution spreading and the structure of the copper–molybdenum catalytic coating formed at further thermal treatment has been demonstrated. Complex oxide composites with ultradispersed catalyst particle sizes characterized with high activity in oxidation of carbon black particles have been obtained.     

An analysis of the dynamic resistance and the instantaneous energy of the CO2 arc welding process

A self-developed welding dynamic arc wavelet analyzer was adopted to analyze and assess the welding process of two CO2 arc welding machines. The experimental results indicate that the instantaneous energy can reflect the influence of the welding current and voltage on dynamic arc characteristic synthetically. Through calculating and analyzing the instantaneous energy, the energy during arc ignition and short circuit in CO2 welding process can be confirmed rationally, thus the foundation for the accurate design and control of the welding current and voltage can be provided. By reducing the ripple disturbance of the dynamic resistance, avoiding peak current and voltage waveform,and enhancing the transition frequency of short circuit suitably, the stability of the welding arc and the weld appearance can be improved.     

Relationship between the types of binary alloy phase diagrams of Ⅷ and IB group elements and the Mendeleev numbers

The relationship between the types of binary alloy phase diagrams of VIII and IB group elements and the Mendeleev numbers was discussed for the first time using the VIII and IB group elements as solvent metals (A) and the other elements as solute metals (B), basesd on their alloy phase diagram types. The Mendeleev numbers of the solvent metals and the solute metals were expressed as MA and MB, respectively. A two-dimension map of MA/MB was drawn. It is indi-cated that there is an oblique line in the map, which divides the binary alloy phase diagram types of solvent metals intotwo symmetry parts, the phase diagram types of the other elements with solvent metals located at the above or down ofthe line respectively, while on the line, ΔM= 0. The phase diagrams between the solvent metals basically are simple systems, mainly belong to the types of continues solid solution and the peritectic (about 40% for each type). The solvent metals can be divided into three groups: Co, lr, Rh, Ni, Pt, and Pd as the first group; Ag, Au, and Cu as the second group;and Fe, Os, and Ru as the third group. The characteristics of the phase diagrams formed between the elements in each group were discussed. About 80% phase diagrams belong to complex systems and less than 20% belong to the simple systems. The regular variation of the chemical scale, the metallic radii of the atoms, the number of valence electrons, and the first ionization energy with the Mendeleev numbers and the crystal structure were introduced as well.     

Determination of isothermal sections of the Co-Nb-Ni and Ni-Mo-Re ternary systems

The isothermal sections of the Co-Nb-Ni ternary system at 1373 K and the Ni-Mo-Re ternary system at 1473 K were determined by means of diffusion triple and electron probe microanalysis (EPMA).The results indicate that there are three three-phase regions found in the Co-Nb-Ni ternary system at 1373 K:(Ni,Co) NbCo3 Ni3Nb,NbCo3 NbCo2 Ni3Nb,and NbCo2 μ Ni3Nb;and four three-phase regions found in the Ni-Mo-Re ternary system at 1473 K:Re Ni χ,Ni NiMo σ,σ χ Ni,and σ Mo NiMo.No ternary eompoond is observed in the two isothermal sections.The isothermal sections arc contrasted with the previous study.     

Influence of cations and anions on the formation of β-FeOOH

In the presence of cations such as Cr³⁺, Cu²⁺ and Ni²⁺, and anions such as and , precipitation of β-FeOOH from Fe³⁺-solution containing Cl⁻ by hydrolysis have been investigated by means of X-ray diffraction technique (XRD), Mössbauer spectroscopy (MS) and transmission electron microscopy (TEM). XRD peaks of β-FeOOH were broadened when the cations were added as sulfates, and this tendency for Cr³⁺ was significantly observed. When the cations were added as nitrates, there was no significant change in XRD peaks. Inductively coupled plasma (ICP) analysis showed that only Cr added as sulfate was contained in β-FeOOH. Ni and Cu added as sulfates, and any cations added as nitrates were not contained in it. When β-FeOOH was synthesized with Na₂SO₄, the XRD peaks were broadened. XRD-peak broadening was mainly caused by the coexistence of ion. The incorporation of cations in β-FeOOH is affected by coexistent anions, and the XRD-peak broadening is caused by not only cations but also anions. This behavior has been discussed in association with the stability of Fe³⁺-complexes in the solution.     

Determination of the effective zero-point and the extraction of spherical nanoindentation stress–strain curves

In this paper, we present a novel approach to converting the load–displacement data measured in spherical nanoindentation into indentation stress–strain curves. This new method entails a new definition of the indentation strain, a new procedure for establishing the effective zero-load and zero-displacement point in the raw dataset, and the use of the continuous stiffness measurement (CSM) data. The concepts presented in this paper have been validated by finite element models as well as by the analysis of experimental measurements obtained on aluminum and tungsten samples. It is demonstrated that the new method presented in this paper produces indentation stress–strain curves that accurately capture the loading and unloading elastic moduli, the indentation yield points and the post-yield characteristics in the tested samples.     

Atomistic modeling of the γ and γ′-phases of the Ni–Al system

A new embedded-atom potential has been developed for Ni₃Al by fitting to experimental and first-principles data. The potential describes lattice properties of Ni₃Al, point defects, planar faults, as well as the γ and γ^′ fields on the Ni–Al phase diagram. The potential is applied to calculate the energies of coherent Ni/Ni₃Al interphase boundaries with three different crystallographic orientations. Depending on the orientation, the interface energy varies between 12 and 46 mJ/m². Coherent γ/γ^′ interfaces existing at high temperatures are shown to be more diffuse and are likely to have a lower energy than Ni/Ni₃Al interfaces.     

Dependency of the thermal and electrical conductivity on temperatures and compositions of Zn in the Al−Zn alloys

The variations of thermal conductivity (K) with temperature for Al–xZn (x = 5, 10, 20, 30, 50 and 60 wt. %) alloys were measured by using a radial heat flow furnace. The variations of electrical conductivity (σ) of solid phases with temperature for the studied alloys were determined from the Wiedemann-Franz and Smith-Palmer equations by using the measured values of K from the plots of K. The thermal temperature coefficient (α_TTC) and the electrical temperature coefficient (α_ETC) were obtained. Dependency of the α_TTC and α_ETC on the composition of Zn in the Al?Zn alloys was also investigated. According to the present experimental results, K of Al–Zn alloys linearly decrease with increasing temperatures up to the melting temperature for each composition and exponentially decrease with the increasing Zn content. On the other hand, the σ of Al based Al-Zn alloys exponentially decrease with increasing temperature and Zn content.     

Improvement of the matrix and the interface quality of a Cu/Al composite by the MARB process

The matrix accumulative roll bonding technology （MARB） can improve the matrix performance of metal composite and strengthen the bonding quality of the interface./n this research, for the fwst time, the technology of MARB was proposed. A sound Cu/AI bonding composite was obtained using the MARB process and the bonding characteristic of the interface was studied using scanning electricity microscope （SEM） and energy-dispersive spectroscopy （EDS）. The result indicated that accumulation cycles and diffusion annealing temperature were the most important factors for fabricating a Cu/AI composite material. The substrate aluminum was strengthened by MARB, and a high quality Cu/AI composite with sound interface was obtained as well.     

Influence of the Anion Nature and the Metal-to-Additive Ratio on the Effectiveness of ε-Caprolactam during Cadmium Electrodeposition

The rate and mechanism of cadmium(II) electroreduction from electrolytes containing -caprolactam were found to significantly depend on the metal-to-additive ratio. Whatever the anion nature, the process sharply accelerates in the presence of an excess of cadmium cations, which form activated surface complexes with adsorbed -caprolactam molecules as bridging ligands. With an excess of the additive, metal depolarization due to the "-effect still persists in perchlorate media; in iodide solutions, -caprolactam inhibits this process. The formation of a dense adsorbed film composed of -caprolactam molecules and I^– anions at the electrode ensures a high throwing power of the electrolyte and makes it possible to obtain uniform elastic organocadmium plating.     

Effects of Ce and Ti on the microstructures and mechanical properties of an Al-Cu-Mg-Ag ahoy

The effects of Ce and Ti additions on the microstructures and mechanical properties of an Al-Cu-Mg-Ag alloy have been studied, It has been shown that either Ce or Ti can decrease the as-cast grain size of the Al-Cu-Mg-Ag alloy, increase the nucleation ratio for Ω phase as heterogeneous nucleation centers, inhibit the growth of Ω phase during aging, and thus increase the volume fraction and decrease the spacing of Ω phase. These microstructures increase the yield strength and tensile strength. However, if both Ce and Ti are added to the alloy, they form （Ce,Ti）-contained compounds and increase the grain size during casting, but have no effects on the nucleation and the growth of Ω phase during aging. The alloy containing both Ce and Ti has a relatively lower Vicks hardness and strength compared to the alloy containing either Ce or Ti.     

Effects of Ce and Ti on the microstructures and mechanical properties of an Al-Cu-Mg-Ag alloy

1. Introduction Heat-treated aluminum alloys are required for several structural applications. Several efforts have been made to improve the mechanical properties of the alloys that are currently in use and also to de-velop a novel series of alloys. The approaches used are: alloy modification, or processing modification, or both. The strength of aging-hardenable alloys such as Al–Cu–Mg series relies upon the strength-ening precipitates that are formed during aging after quenching. The agin…     

Application of the annexation principle to the study of thermodynamic properties of ternary metallic melts In-Pb-Ag and In-Bi-Sb

Based on the phase diagrams, measured activities and the annexation principle, the calculating models of mass action concentrations for In-Pb-Ag and In-Bi-Sb ternary metallic melts have been formulated. The results of calculation both agree with practice, and obey the law of mass action, showing that the models formulated can reflect the structural reality of the corresponding melts and the annexation principle is applicable to the them.     

Description and Prediction of the Solid Solubilities of Binary Alloys Based on the Actinide Metals

The solid solubilities of 207 binary alloys based on the three actinide metals (Th, U and Pu) at room tem-perature are studied with the two theoretical schemes suggested by one of the present authors (ZBW).The re-sults show that the soluble elements can be distinguished from the insoluble ones by a parabola y_1=a--bx~2 oran ellipse (x_2,-m)~2/c~2+(y_2-n)~2/d~2=l with the total reliabilities of 87.9% and 92.3% respectively for the 207binary alloys. The contants a and b in the parabola equation, and c, d, m and n in the ellipse equation can berelated to some appropriate parameters for each host metal respectively. The reasons are discussed. From thetheories the soluble elements in these actinide host metals that have not been measured yet can be predicted inthe accuracies of the schemes.     

Mechanism and kinetics of discontinuous precipitation of the η phase in the 36NKhTYu alloy

A new mechanism of nucleation and growth of cells of the η phase in the deformed 36NKhTYu austenitic alloy has been found. The recrystallization nuclei are formed at the η-phase particles, which were precipitated according to the continuous mechanism. Simultaneously, they are nuclei of cells of discontinuous decomposition. Unlike the known growth mechanism, the η-phase cell grows in all directions until it collides with other cells. The Peterman-Hornbogen theory of discontinuous precipitation has been modified to describe the kinetics of the complex reaction of discontinuous precipitation of the η phase and recrystallization and also the kinetics of complex reaction of discontinuous coalescence of grains and phases. The theoretical dependences of the cell size on the aging time for these reactions are proportional to t ^1/3 and t ^1/4, respectively. A comparison of the theoretical and experimental results has been performed.     

Modelling the thermal oxidation of ternary alloys—compositional changes in the alloy and the development of oxide phases

A coupled thermodynamic–kinetic oxidation model is presented that describes the thermal oxidation of a single-phase ternary alloy. For given oxide-layer growth kinetics, the model computes composition–depth profiles in the alloy, as well as the amount of each oxide phase developed as a function of oxidation time, including the formation of multiple oxide phases during the initial stage of fast oxidation. Application of the model to the thermal oxidation of a γ-Ni–27Cr–9Al (at.%) alloy at 1373 K and a partial oxygen pressure (p_O2) of 2×10⁴ Pa showed that the phase constitution of the developing oxide layer is predominantly governed by the growth rate and duration of the initial oxidation stage, whereas the eventual, steady-state interface composition of the alloy is mainly determined by the parabolic oxide-layer growth rate.