Investigation of the microstructure and oxidation behavior of Cr-modified aluminide coatings on γ-TiAL alloys

The microstructure and oxidation behavior of aluminide coatings are investigated. The layers are examined by the optical microscopy, scanning electron microscopy (SEM) equipped with EDS, and the X-ray diffraction method. The isothermal oxidation behaviors of samples are investigated at 950°C for 200 h. The results show that TiAl₃ is formed on the substrate. In addition, the aluminide coating improves the oxidation resistance of γ-TiAl alloys by forming a protective alumina scale. Moreover, during oxidation treatment, the interdiffusion of the TiAl₃ layer with γ-TiAl substrate results in the depletion of aluminum in the TiAl₃ layer and the growth of the TiAl₂ layer. After the oxidation treatment, the coating layer preserves a microstructure with phases including TiAl₃, TiAl₂, and Al₂O₃.     

Effect of W content on the compression properties and abrasive wear behavior of the (TiB2–TiCxNy)/(Ni + W) composites

The (TiB₂–TiC_xN_y)/(Ni + W) composites were fabricated successfully by the method of combustion synthesis and hot press consolidation in the Ni–W–Ti–B₄C–BN system. The effect of the content of W on the hardness, compression properties and abrasive wear behavior of the composites was investigated. The results indicate that with increasing W content from 0 to 8 wt.%, the average sizes of the TiB₂ and TiC_xN_y particles decrease firstly and then keep almost constant, while the hardness and the compression strength increase firstly and then change a little. The abrasive wear resistance of the composites increases firstly and then decreases with the increase in the W content.     

Investigation of solidification behavior and associate microstructures of Co–Cr–W and Co–Cr–Mo alloy systems using DSC technique

This article presents a study of solidification behavior and the corresponding microstructure of Co–Cr–W and Co–Cr–Mo alloy systems using the differential scanning calorimetry technique. The influence of main constituents on the solidification behavior and associate microstructures of these alloys are investigated. It is found that chemical composition influences significantly the solidification behavior of cobalt-based alloys. Solution-strengthened alloy has the highest solidification temperature and narrowest solidification range. Presence of carbon decreases the solidification temperature and increases the solidification range. Addition of boron greatly decreases the solidification temperature. Carbon content dominates the solidification behavior of cobalt-based alloys when the contents of the solution-strengthening elements Mo and Ni are within their saturation in the solution matrix. However, as these contents reach a certain level, formation of intermetallic compounds changes the solidification behavior of these alloys remarkably. Increase in the contents of solution-strengthening elements reduces the solid solution transformation temperature and the eutectic temperature when carbon content is constant.     

Investigation of the Microstructure of Rolled Semi—Solid Steel

In this paper,spring steel-60Si2Mn and stainless steel-1Cr18Ni9Ti were rolled one pass in semi-solid state.The microstructural evolution during rolling of the steels with different solid fraction was investigated.The experimental results showed that the manner of liquid and solid phases flowing and deforming was different.During rolling,most of solid phases remained in the center of the rolled specimens,while liquid phase flowed to the edge,which resulted in the macrosegregation of liquid and solid phases.Only the amount of solid fraction reached a certain value,were the solid phases deformed and flattened.     

Characterization of the tableting properties of β-cyclodextrin and the effects of processing variables on inclusion complex formation,compactibility and dissolution

Abstract

The tableting properties of a number of commercially available β-cyclodextrins were characterized. Fluidity was insufficient for routine direct compression. Compactibility varied by source but was excellent. Lubrication requirements were minimal. An inclusion complex of β-cyclodextrin/Progesterone was formed and the tableting properties of the complex were compared to those of a physical mixture in both directly compressed and wet granulated products. Inclusion complexes spontaneously formed during wet granulation processing. Substantial differences in tableting properties were found as processing variables were changed. β-cyclodextrin exhibits considerable promise as a standard filler binder in tableting.     

Investigation the effect of sintering temperature on Young’s modulus evaluation and thermal shock behavior of a cordierite–mullite based composite

A marked mismatch between CTE of cordierite and mullite in composition develops internal stress, which causes significant growth of cracks and subsequent damages which confer them a very good ability to thermal shock resistance. To investigate the effect of sintering temperature on the thermal shock resistance, the samples sintered at four different temperatures and evaluation of Young’s modulus monitored during 25 shock cycles. The results showed that densification behavior, thermomechanical properties and thermal shock resistance of this refractory was closely related to sintering temperature. Furthermore, during specific (5th to 10th) thermal-shock cycles a notable increase occurs in the Young’s modulus of the samples, this attributed to the formation of viscose bridges, which shield the tip of growing cracks.     

Investigation of the Dynamics of Evaporation of Condensed Bodies on the Basis of the Law of Spectral‐Radiation Intensity of Particles

The fundamentals of radiation theory and the mechanism of evaporation of condensed bodies are presented. The distribution functions of particles of a body by energies and by the intensity of their transition from one energy level to another in the process of evaporation have been obtained based on the law of spectralradiation intensity of the body particles. The temperature dependence of the resulting vapor flow on the outer surface of a massive condensed body and a thin layer in equilibrium and nonequilibrium states, which, in the limit, transforms to the known Hertz–Knudsen formula, has been found.     

Investigation of the Thermostability of Glass‐Ceramics of a Lithium Alumosilicate Composition

This paper presents the results of investigations of the thermostability of the glassceramics obtained by ceramic technology with the use of the method of casting blanks from highdensity aqueous suspensions of lithium alumosilicate glass with their subsequent sintering and crystallization under combined conditions of treatment. It is shown that the basic factors influencing the thermostability of materials are the values of the elastic modulus, CTLE, and porosity. Experiments and calculations indicate that the glassceramics exceeds the known radiotechnicalpurpose pyroceramics in thermostability and can be used in articles designed to operate under hard conditions.     

Speeding for fun? Exploring the speeding behavior of riders of heavy motorcycles using the theory of planned behavior and psychological flow theory

This paper focuses on a special segment of motorcyclists in Taiwan – riders of heavy motorcycles – and investigates their speeding behavior and its affecting factors. It extends the theory of planned behavior (TPB) to explore motorcyclist speeding behavior by including the variables of psychological flow theory. The levels of sensation-seeking and riding experience are also used as grouping variables to investigate group differences from the influences of their affecting factors on speeding behavior. The results reveal that the psychological flow variables have greater predictive power in explaining speeding behavior than the TPB variables, providing useful insights into the unique nature of this group of motorcyclists, who are more prone to engage in speeding. Group differences with regard to both sensation-seeking and rider experience in speeding behavior are highlighted, and the implications of the findings are discussed.     

Thermal,electrical and wear behavior of sintered Cu–W nanocomposite

High-energy mechanical milling was used to prepare Cu and W nanopowders. Cylindrical preforms with initial theoretical density of 86% were prepared using a die and punch assembly. The preforms were sintered in a muffle furnace and subsequently furnace cooled and then the hot specimens were extruded to attain 93% theoretical density. Differential Scanning Calorimetry and Thermal Gravimetric Analyzer, four point probe tester, Scanning Electron Microscope and pin on-disc system were used to evaluate the thermal, electrical conductivity, characterization and tribological property of Cu–W composite respectively and using curve fitting method the respective polynomial and power law model were developed. The results indicated that the wear rate decreased with increasing applied load and sliding distance. The composites were tested at high sliding speed which exhibited high value of coefficient of friction.     

Investigation of the Ice–Water Vapor Equilibrium Along the Sublimation Line

An accurate knowledge of the thermodynamic properties of water at low temperature plays an important role in atmospheric processes, chemical physics, and metrological applications. Preliminary investigations of the water vapor?Cice equilibrium along the sublimation line have been carried out at Istituto Nazionale di Ricerca Metrologica (INRIM). The measurements covered the temperature range from ?50?°C to 0?°C, corresponding to a saturation vapor pressure from about 4?Pa to 611?Pa. The measurements were performed using a small gold-plated cell kept in a liquid bath at a constant temperature with millikelvin stability. The sample cell was connected to a manifold where the pressure was measured using two capacitive diaphragm pressure gauges. The paper reports the water sample preparation, measuring method, and measurement corrections. Measurement results are discussed and uncertainty sources estimated. The resulting expanded relative uncertainty (k = 2) varies from 0.038 % at 0?°C to 0.70 % at ?50?°C.     

Critical behavior of the free surface of liquid 4He near the λ point

The noncriticality of the free surface of liquid ⁴He near the point and the finite-size scaling postulate are combined to show that the surface tension can have two singularities, one due to rounding and another due to shifting. The rounding singularity can be reduced, via a further scaling assumption, to that previously suggested by Sobyanin and Hohenberg. Results from calculations based on continuous symmetry models and experiments on topologically 2D ⁴He films are used to argue that the shift singularity is ¦t¦^1–, which is consistent with the leading singularity observed by Magerlein and Sanders.     

Investigation of the heat conductivity of niobium in the temperature range 0.05–23 K

We report thermal conductivity measurements on a single-crystal niobium specimen of resistivity ratio 33,000 over the temperature range 0.05–23 K in the superconducting state and above 9.1 K in the normal state. The axis of the niobium rod was [110] oriented. The surface roughness was varied by sandblasting of the sample. The values of the thermal conductivity in the range from the lowest temperatures up to the maximal value covered a range of six orders of magnitude (=2×10^–5 W cm^–1 K^–1 at 50 mK to =22 W cm^–1 K^–1 at 9 K). Above 2 K the results for the untreated and the sandblasted sample are in accord, whereas below 2 K the influence of the sample surface is discernible. The various conduction and scattering mechanisms are discussed.     

Investigation of the microstructure and toughness of 550 MPa grade pipeline after the hot-bending process

In this work, the effects of the hot-bending process on the microstructure and low temperature (?40°C) toughness of weld metal of pipeline K65 (the highest grade of the Russian natural gas pipeline) were studied. The weld metal from the longitudinally submerged arc welding (LSAW) pipe making process was compared with that subsequently treated by the hot-bending process. It was found that the latter process led to serious deterioration in toughness, which obviously degraded the sound properties achieved in the original weld metal of LSAW pipes. Microstructural characterisation revealed that the weld metal, which originally consisted mainly of acicular ferrite in the as-deposited condition, became predominantly composed of bainitic ferrite after hot bending. It is clear that reaustenisation caused a smaller austenite grain-sized matrix, which brought about a very high volume fraction of bainite. Consequently, the low temperature toughness was deteriorated, in contrast to the excellent toughness achieved in the as-deposited weld metal.     

Investigation on preparation and mechanical properties of W–Cu–Zn alloy with low W–W contiguity and high ductility

In order to improve the mechanical properties of the W–Cu alloy, the W–Cu–Zn alloys with low W–W contiguity were fabricated by three different preparation methods. For the first method, the mixed powder of copper-coated tungsten powder and Zn powder was sintered by SPS (Spark Plasma Sintering) process. For the second method, the mixed powder was processed by CIP (Cold Isostatic Pressing) before SPS. For the third method, a skeleton of the copper-coated tungsten powder was prepared by CIP, and then the skeleton was infiltrated with H70 brass. The microstructure, mechanical properties and failure mechanism of the prepared W–Cu–Zn alloys were investigated. The results show that the W–Cu–Zn alloy fabricated by the third method achieves a high relative density of 98.4% and a low W–W contiguity of 10%. The alloy exhibits a high dynamic compressive strength of 1000 MPa, with a high critical failure strain of 0.7. The Cu-Zn matrix of the alloy fabricated by the third method is composed of α-phase Cu–Zn alloy and Cu₃Zn particles. The homogeneous distribution of Zn in the matrix manifests good solution strengthening effect and the uniformly distributed Cu₃Zn particles has a strong precipitation strengthening effect, which are both responsible for the evidently enhanced mechanical properties.     

Investigation on the Initial Stage of Film Growth in Situ

The initial stage of Ag film growth on Cu(100). Ta(100) and Ta(110) single crystals as well as YBaCuO on Si single crystal covered by Pd was investigated in situ by means of LAS 600 surface analysis system with a sputtering source in sample preparation chamber. The results show that the initial state for Ag / Cu(100) film growth is typical S-K model, for Ag / Ta(100) and Ag / Ta(110)they have the same S-K characteristics, but due to the different surface energies of two crystalline planes. there is some difference for Ag / Ta (100) and Ag / Ta(110). YBCO sputterjng process is rather complex and Cu is the first element appearing in the film.     

The viscoelastic behavior of β-In3Sn and the nature of the high-temperature background

The damping behavior in torsion of single phase -In₃Sn has been evaluated at room temperature over a broad range of frequencies (10^–4 to 10³ Hz) and as a function of various mechanical and thermal treatments. The results are consistent with a model for the power-law (tan f ^–n), high-temperature-background absorption being effected by diffusional processes on grain and, particularly, on subgrain boundaries. The results are compared/contrasted with those for damping in single-phase -InSn₄ and in the two-phase - eutectic. Failure of the eutectic material to follow a composite model for damping, combined with a thermal aging effect that lowers damping only for certain frequencies, shows that the boundary-based absorption model for the high-temperature background applies, too, to phase boundaries.     

Investigation of the Serviceability of the Heat Shield of the Orbital Aircraft “Buran” under the Conditions of Radiant Heating on Solar Plants

We have investigated the serviceability of the heatinsulating tiles of the orbital aircraft Buran under radiant heating on an SGU7 solar plant with a mirror concentrator 5 m in diameter. Cycles of aerodynamic heating with a duration of 20 min were simulated. For the total number of cycles for different materials from 20 to 85, the efficiency and serviceability of TZMKtype materials with different coats have been corroborated. The results obtained agree with the test data obtained on gasdynamic (power consumption 1 MW) and radiation (250 kW) test beds, which enables such tests to be recommended for use at preliminary stages in powersaving and ecologically harmless solar furnaces.