bluuebunny/crossref_metadata_2025 huggingface dataset:
A Model of the Evolution of the Au/Si Droplet Ensembles during Rapid Thermal Annealing at High Temperatures
Authors: Sarikov Andrey V. , Klimovskaya A.I. , Oberemok O. , Lytvyn O. , Stadnik O.
Published: July 2011

Formation of the patterns of catalytically active metal containing droplets on substrates is an important process for the growing Si wire-like crystals because it predetermines the main crystal parameters. Understanding physical mechanisms of droplet evolution during thermal treatments and derivation of associated parameters are the clue to the controlled formation of droplet ensembles and thus to the predicted growing Si wire-like crystals. In this work, the kinetics of the evolution of droplet ensembles on the surface of substrate as a result of coalescence and atom evaporation is studied theoretically. Obtained theoretical results are compared to the experimental data on the evolution of the ensembles of Au/Si droplets on Si substrate formed by rapid thermal anneals of thin gold film in the temperature range from 900 to 1050°C. The activation energy of droplet diffusion on the surface of substrates is estimated.
Gate Control of Junction Impact Ionization Avalanche in SOI MISFETs: Theoretical Model
Authors: Dobrovolsky V. , Sizov Fedir , Cristoloveanu S.
Published: July 2011

Theoretical model of thin film SOI MISFET based on the gate control of impact ionization avalanche in the drain induced p-n+ junction is developed. Such operation principle opens a way of the creation of transistors with high transconductance and operation frequency, and switching between the ON and OFF states by low gate voltage variation.
Local Structure and Magnetic Properties of FeMnAl Nanocrystalline and Amorphous Alloys
Authors: Tarigan Kontan , Yang D. S. , Yu S. C.
Published: July 2011

The structural and the magnetic properties of nanocrystalline and amorphous Fe55Mn10Al35 alloys prepared by the mechanical alloying process are studied as functions of the milling time varying from 1 hr to 48 hrs. Structural analyses based on X-ray diffraction (XRD) and extended X-ray absorption fine structure spectroscopy (EXAFS) reveal that the alloying process took place after 12-hr milling. Nanocrystalline alloys are found until 24-hrs milling, and an amorphous phase afterward. Concerning the magnetic behavior, the data obtained from a vibrating sample magnetometer show that both the magnetization saturation (Ms) and the coercivity (Hc) are dependent strongly on the milling time and the crystallite size. By adjusting the milling time, both appropriate structural transformation and magnetization values are obtained.
Preparation of Porous Ceramic with Controllable Additive and Firing Temperature
Authors: Aripin Haji , Lestari L. , Agusu L. , Sudiana I.N. , Jumsiah N. , Rahmatia I. , Purwasasmita Bambang Sunendar , Nurdiwijayanto L. , Mitsudo S. , Sabchevski S.
Published: July 2011

P
orous ceramics were produced by mixing clay and ash of sago waste from the sago processing industry in Indonesia. The composition was prepared by adding an amount from 0 to 40 wt% of ash into the clay, and then the samples were milled for 6 h. The samples were dry pressed and sintered in the temperature range between 900°C and 1300°C. The influence of the ash content and the sintering temperature on the bulk density, firing shrinkage, and porosity was studied in detail. The results show that an amount of 10 wt% ash can be incorporated into the clay material without any appreciable effect on the bulk density and porosity of the samples sintered at 1000°C. It was found that if the amount of ashes is greater than 20 wt% and the sintering temperatures are lower than 1100°C, then the percentage of the porosity is greater than 30%. These results are important for optimization of the parameters of the technological processes for production of porous ceramics for various applications, each of which requires a specific porosity.
Al-Si/SiC Metal Matrix Composites Produced by Spontaneous Infiltration
Authors: Zulfia Anne
Published: July 2011

Aluminium Silicon reinforced with 50Vf% SiC has been produced by spontaneous infiltration at 900°C for 1 hour. Aluminium infiltrated preforms containing 1%wt Mg mixed with various of Si between 2 and 14wt%, as external dopant. However Al did not infiltrate a preform containing 1wt%Mg but if mixed with Si in the preform generated in more extensive infiltration. Effect of Si on characterisation of pure Al composites by spontaneous infiltration were studied and compared to Al-Si based matrix. Microstructural analysis of MMC as well as mechanical properties were also observed. It was found that increasing of Si content generated lower porosity thus increasing hardness due to aluminium could wet SiC preform well. Although the dopant was uniformly distributed throughout the perform but microstructural analysis and hardness measurements indicate that the resultant composite may not be uniform as infiltration inwards from the top to the bottom of preform.The hardness of Al-Si composites is significantly increased with increasing of Si for both externally and internally doped system. This is associated with decreasing porosity with higher Si in composites.
Electroless Deposition of Metal Oxide on SiC Particles Reinforced for Producing Al-Si /SiC Metal Matrix Composites
Authors: Zulfia Anne , Mas’udah Tatu , Lutfi Syukron
Published: July 2011

Metallization techniques based on electroless coating are used to coat SiC particles reinforced to make Al-Si/SiC metal matrix composites. Nitric Acid (HNO3), aluminum powder and different percentage of magnesium addition were used in solutions as electroless coating medium to coat the surface of SiC particles. Five different percentage of Mg was used from 0.1 to 0.5 wt% in electrolyte solution. Metal oxide coating was characterised by scanning electron microscope (SEM), energy dispersion spectroscopy (EDS), X-ray diffraction (XRD) as well as Transmission Electron Microscope (TEM). It is obtained that metal oxide layer formed on the SiC surface was MgAl2O4or spinel which was analysed by XRD and confirmed by EDS. Spinel (MgAl2O4) layer was found at all composition of Mg, and such layer improved wettability between SiC and Al-Si. It also is found that the solution with 0.2%wt Mg content generated more homogeneous metal oxide layer on SiC particles therefore the solution with 0.2wt% Mg was selected as electroless coating medium to coat SiC particles reinforced to produce Al-Si/SiC metal matrix composites by stir casting route. The phases present in Al-Si/SiC composites was spinel (MgAl2O4), Si eutectic and Mg2Si which was analysed by XRD.
Precipitates in Biomedical Co-Cr-Mo-C-Si-Mn Alloys
Authors: Narushima T. , Alfirano  , Mineta S. , Namba Shigenobu , Yoneda Takashi , Ueda Kyosuke
Published: July 2011

The phase and dissolution behavior of precipitates in biomedical ASTM F75 Co-Cr-Mo-C-Si-Mn alloys were investigated. Alloys of five different compositions, Co-28Cr-6Mo-0.25C-1Si, Co-28Cr-6Mo-0.25C-1Mn, Co-28Cr-6Mo-0.25C-1Si-1Mn, Co-28Cr-6Mo-0.15C-1Si, and Co-28Cr-6Mo-0.35C-1Si, were heat-treated from 1448 to 1548 K. The precipitates observed in the as-cast and heat-treated alloys were carbides (M23C6type, h-phase, and p-phase) and an intermetallic compound (c-phase). The main precipitates observed after heat treatment at high temperatures such as 1548 K were p-phase and M23C6type carbide. At these high temperatures, two types of starlike precipitates—dense and stripe-patterned—were observed. The starlike-dense precipitate was the p-phase, and the starlike precipitate with a stripe pattern was identified as the M23C6type carbide and metallic fcc g-phase. In the alloys heat-treated at 1448 to 1498 K, blocky-dense M23C6type carbide was primarily observed. c-phase was detected in the Co-28Cr-6Mo-0.15C-1Si alloy under as-cast condition and after heat treatment at 1448–1523 K for a short holding time. The addition of Si seemed to increase the holding time for complete precipitate dissolution because of the effects of Si on the promotion of p-phase formation at high temperatures and the increased carbon activity in the metallic matrix.
Analytical and Experimental Models of Porosity Formation of Duralumin Cast in Vacuum Casting System
Authors: Suprapto Wahyono , Suharno Bambang , Soedarsono Johny Wahyuadi , Priadi Dedi
Published: July 2011

Porosity in cast metals often leads to cracking of components due to stress concentration and leakage, and as the result, the castings need be repaired or rejected. Disharmony in casting process was resulting in porosity. Prediction of porosity in the casting is necessary as a step to avoid the waste products and reduce costs. But to ensure whether these predictions are accurate and precise, it is still necessary to validate the test trials and testing. This paper aims to provide early information when, where, and how large a defect occurs in particular foundry casting porosity on duralumin. The analytical study of porosity formation based analytic equilibrium wt% of element, the behavior of the thermodynamic, hydrodynamic, and rules of metallurgical on vacuum casting of duralumin. Experiments as a validation study are conducted by duralumin remelting on stainless-steel bowl in a vacuum casting furnace. Analytical simulation and experiments of the casting that has been vacuumed by melting 10 cmHg pressures higher than the pressure solidification, and duralumin melt is poured automatically into permanent mold carbon steel. In the study cast duralumin created five different thicknesses. Both these studies assume the addition of copper (2.5%, 3.0%, 3.5 %, 4.0%, and 4.5% Cu) and vacuum pressure (76, 50, 40, cmHg), as independent variables, while dependent variable in the studies is porosity characteristics, which includes morphology, number and dimensions of the porosity. Optical emission spectrometry test, Reynold's and Niyama numbers, Sievert's law, Archimedes' principle (Pycnometry and Straube-Pfeiffer tests), and Eichenauer equation are instruments which are used to determine the characterization of duralumin casting porosity. Duralumin ingots remelting process was performed by the control pressure (p1) and temperature (T1). Vacuuming process performed after the smelting room temperature reaches 600 °C. Once melted, it followed by duralumin into a permanent mold (p2, T2). As a control parameter is the height of pouring (7 cm), pour temperature and mold temperature respectively at 750 °C and 300 °C. The porosity characteristics studies of two models produce two types of porosity (gas and shrinkage), the quantity dimension and porosity, and distribution of porosity in the cast duralumin.
Effect of Elastic Driving Force on the Evolution of Microstructures in the Secondary Creep Stage
Authors: Tanaka Katsushi , Hashimoto Wataro , Inoue Toru , Inui Haruyuki
Published: July 2011

The effect of elastic driving force on the microstructural change of superalloys in the secondary creep stage is evaluated by elastic energy calculations with the concept of effective eigen strain where both lattice mismatch and creep strain are taken into account The elastic energy calculations indicates that the elastic state in the secondary creep stage is totally different to that in the initial one where the lattice misfit between γ and γ' phases is over accommodated along the [100] and [010] directions by creep deformation in the γ phase. The excess creep dislocations for the over accommodation are required so as to develop an internal stress field to prevent further creep deformations. The planer raft structure with the plane normal oriented to the [001] direction is unstable in the over accommodated state. The γ/γ' lamellar interfaces will be inclined to make a wavy raft structure of which elastic energy is lower than the ideal 001 planer raft structure.
Modeling of Precipitation Kinetics of TCP-Phases in Single Crystal Nickel-Base Superalloys
Authors: Rettig Ralf , Heckl Astrid , Singer Robert F.
Published: July 2011

The precipitation of brittle so-called TCP-phases is critical for the application of Re-containing single crystal superalloys. In this work a fully multicomponent precipitation model is presented, which is capable of simulating the precipitation process of the TCP-phases in superalloys considering complex precipitation sequences with several metastable phases. The model is coupled to multicomponent thermodynamic CALPHAD calculations and relies on multicomponent diffusion models based on the TC-API interface of the software DICTRA. The required mobility database has been newly developed and covers all relevant alloying elements of the Ni-base superalloys including rhenium (Re) and ruthenium (Ru). It is well known that adding Ru strongly reduces TCP-phase precipitation. Based on the developed precipitation model, possible mechanisms are investigated to explain this effect and it is concluded that Ru mostly influences the nucleation rate by a combined influence on interface energy, “reverse partitioning” and γ’-phase fraction.
Analysis of the Alloying System in Ni-Base Superalloys Based on Ab Initio Study of Impurity Segregation to Ni Grain Boundary
Authors: Razumovskiy Vsevolod I. , Lozovoi A.Y. , Razumovskii Igor M. , Ruban Andrei V.
Published: July 2011

A new approach to the design of Ni-based polycrystalline superalloys is proposed. It is based on a concept that under given structural conditions, the performance of superalloys is determined by the strength of interatomic bonding both in the bulk and at grain boundaries of material. We characterize the former by the cohesive energy of the bulk alloy, whereas for the latter we employ the work of separation of a representative high angle grain boundary. On the basis of our first principle calculations we suggest Hf and Zr as “minor alloying additions” to Ni-based alloys. Re, on the other hand, appears to be of little importance in polycrystalline alloys.
Modelling of Phase Evolution during Aluminizing Processes
Authors: Gariboldi Elisabetta , Verani Marco , Riva Christian
Published: July 2011

Aluminizing processes are a well-known set of techniques industrially adopted to enrich in aluminum the surface layers of Ni-based alloys, thus improving their resistance to environmental interactions at high temperature. The results of aluminizing are described in terms of the presence, compositions and thickness of the sequence of the resulting surface diffusion layers. A combination of difficulties arising both from the mathematical and the material side restricted the number of available user-friendly models and their applicability to specific alloys or process conditions. The aim of the research work here presented is to overcome part of these difficulties. A synthesis of some well-established models was implemented in a robust numerical algorithm, that automatically prevents instabilities and convergence problems. Such numerical algorithm has been experimentally validated by comparing the results to the experimentally measured composition of profiles obtained for a set of vapor-phase aluminized samples of commercially pure Ni. The model was then applied to predict the effects of the process temperature and of the chemical composition of the surface.
Continuum Damage Mechanics Modeling of Creep in DS GTD-111TM Superalloy
Authors: Sondhi Sanjay Kumar , Singh Gaurav , Mastromatteo Francesco
Published: July 2011

Safe extrapolation of short-term creep data requires development of creep models where (a) the constitutive laws are physics based, and (b) majority of model parameters are calculated rather than empirically fitted. This paper details the structure of such a physics-based creep model and its application to DS GTD-111TM superalloy. The constitutive creep law is derived from the kinetics of dislocation-particle interactions in the presence of thermal activation. This constitutive creep law is further coupled with the evolution kinetics of controlling microstructural parameters and associated damages. The model is expected to provide vital inputs for component design as well as remaining life assessment. (GTD-111TM is a trademark of the General Electric Company).
Dislocation Structures in the Gamma Prime-Phase of CMSX-4 and TMS75 after Degradation under Service Conditions
Authors: Link Thomas , Epishin Alexander , Nawrath Nils , Michel Catrina , Nazmy Mohamed
Published: July 2011

The single crystal superalloys CMSX-4 and TMS75 were tested for very long times at high temperatures in laboratory creep tests and in service. The microstructure was investigated in TEM and SEM. It was found, that the ’-phase is cut at stresses much below the threshold given in literature. Cutting takes place by <110> screw dislocations. These mobile dislocations can be locked locally by a Giamei-lock. Thus a stacking fault dipole forms between the locked segment and the preceding ones. The dipole consists of two supershockley dislocations with 30° character, which are also stabilized by Giamei locks. The dipole formation is analyzed and discussed in detail.
Dissolution of Fine γ’ Precipitates of MC2 Ni-Based Single-Crystal Superalloy in Creep-Fatigue Regime
Authors: Le Graverend Jean Briac , Cormier Jonathan , Gallerneau Franck , Paulmier Pascal
Published: July 2011

The dissolution kinetics of an ultra-fine γ’ precipitation occurring in the γ matrix between the standard secondary precipitates of MC2 Ni-based single crystal superalloy was investigated. Creep-fatigue experiments at 1050°C including an overheating at 1200°C were performed on <111> oriented specimens to study the effects of fine γ’ particles on the plastic deformation. During these experiments, a decrease of the plastic deformation rate was observed just after the temperature peak. This hardening effect disappears once the fine γ’ precipitates had been dissolved. A mean time for this hyperfine precipitation dissolution could then be highlighted. Based on both simple binary diffusion and complex diffusion analysis, the mean time for the dissolution of the fine γ’ precipitates is analyzed and compared to the experimental ones. It is shown that considering only a simple binary diffusion is not sufficient and it should be considered a more complex diffusive analysis involving additional interplays.
The Relaxation Behavior of High Chromium- Ni Base Superalloys
Authors: Nazmy Mohamed , Gerdes Claus
Published: July 2011

The relaxation behavior of wrought high chromium Ni-base alloys Nimonic 80A, Nimonic 101 and Nimonic 105 was studied at different temperatures. All of these alloys exhibited increase in the residual stress during the relaxation tests e.g. at 450°C for Nimonic 80A and 650°C for Nimonic 105. The observed increase in the residual stress is a manifestation of the known phenomenon of “negative creep”. The stress free aging of specimens of these alloys exhibited dimensional contraction at different temperatures ranging from 450°C to 650°C. The abnormal relaxation behavior of these alloys and the observed contraction were attributed to the precipitation and ordering of the intermetallic phase Ni2(Cr,Mo) at the test temperature. The differential thermal analysis i.e. DTA results, demonstrated endothermic peaks to correspond with the order–disorder reaction of Ni2(Cr,Mo).
Influence of Grain Boundaries on Short Fatigue Crack Growth in “Polycrystalline CMSX-4”
Authors: Marx Michael , Schäf Wolfgang , Vehoff Horst
Published: July 2011

Increasing the resistance of a material to fatigue crack growth by optimizing the microstructure is a major task of materials science. In this regard, grain boundaries and precipitates are well known to decelerate short cracks. Thereby the strength of the interaction is influenced by the crack parameters crack length and distance to the obstacles, the grain boundary parameters like orientation of the adjacent grains and the precipitate parameters like size and distance. A comprehensive understanding of the underlying physical principles is missing. The focused ion beam (FIB) microscope offers new possibilities for systematic experiments and three dimensional investigations to quantify the microstructural impact. The ion beam is used to cut micro-notches as initiation sites for cracks. Contrary to natural cracks the influencing parameters can be varied independently for a systematic investigation of the mechanisms. Additionally, the ion beam is used to make a 3D image of the crack path and the surrounding microstructural elements. The commonly single crystalline nickel base superalloy CMSX-4 served as a model material in a polycrystalline modification. Thereby it was possible for the first time to reveal quantitative data of the effect of microstructural barriers on short fatigue crack growth.
A1-L12 Structures in the Al-Co-Ni-Ti Quaternary Phase System
Authors: Minshull James P. , Neumeier Steffen , Tucker Mattew G. , Stone Howard James
Published: July 2011

The phase constituents of alloys from the (Ni,Co)85(Al,Ti)15 plane of the Ni-Co-Al-Ti quaternary system were investigated following prolonged exposure at 750°C. Microstructural investigations confirmed the existence of a continuous A1-L12 two-phase region in the Ni-Co-Al-Ti quaternary system between Ni-Ni3Al and Co-Co3Ti. The lattice misfits of alloys from this quaternary system were determined using neutron diffraction. With increasing contents of Ti the positive lattice misfit increases up to +0.79% in the Ti-containing alloys, which leads to an increasing tetragonal distortion of the  matrix phase due to the increasing coherency stresses.
In Situ Investigation with Neutrons on the Evolution of γ ' Precipitates at High Temperatures in a Single Crystal Ni-Base Superalloy
Authors: Gilles Ralph , Mukherji Debashis , Eckerlebe H. , Strunz Pavel , Rösler Joachim
Published: July 2011

Single crystal Ni-base superalloys based on the  /  system are widely used in gas turbine applications. To understand the formation of  precipitates, including size distribution and growth, we performed in situ small-angle neutron scattering (SANS) measurements at elevated temperatures and - together with TEM as well as , SEM imaging - studied changes in the precipitates in short and long time scale. In the early stages, a bimodal precipitate size distribution of precipitate is observed, which (depending on the annealing temperature) changes to a cuboidal or nearly spherical morphology with almostmore or less uniform ( unimodal) size distribution. [Note: The term "more or less" is several times repeated in the text. I cannot imagine what it in fact means. Could you change it or explain in a more clear way]
Crack-Free Welding of IN 738 by Linear Friction Welding
Authors: Ola Oyedele T. , Ojo Olanrewaju A. , Wanjara Priti , Chaturvedi Mahesh C.
Published: July 2011

Inconel 738 (IN 738), like other precipitation-hardened nickel-base superalloys that contain a substantial amount of Al and Ti, is very difficult to weld due to its high susceptibility to heat-affected zone (HAZ) cracking during conventional fusion welding processes. The cause of this cracking, which is usually intergranular in nature, has been attributed to the liquation of various phases in the alloy, subsequent wetting of the grain boundaries by the liquid and decohesion across one of the solid-liquid interfaces due to on-cooling tensile stresses. In the present work, crack-free welding of the alloy was obtained by linear friction welding (LFW), notwithstanding the high susceptibility of the material to HAZ cracking. Gleeble thermomechanical simulation of the LFW process was carefully performed to study the microstructural response of IN 738 to the welding thermal cycle. Correlation between the simulated microstructure and that of the weldments was obtained, in that, a significant grain boundary liquation was observed in both the simulated specimens and actual weldments due to non-equilibrium reaction of second phase particles, including the strengthening gamma prime phase. These results show that in contrast to the general assumption of LFW being an exclusively solid-state joining process, intergranular liquation is possible during LFW. However, despite a significant occurrence of liquation in the alloy, no HAZ cracking was observed, which can be partly related to the nature of the imposed stress during LFW
Chip Formation and Machinability of Nickel-Base Superalloys
Authors: Siemers Carsten , Zahra Badya , Ksiezyk Dawid , Rokicki Pawel , Spotz Zdeněk , Fusova Lenka , Rösler Joachim , Saksl Karel
Published: July 2011

Nickel-base superalloys like Alloy 625 are widely used in power generation applications and in the oil and gas industry due to their unique properties especially at elevated temperatures. The chip formation process of Alloy 625 is not yet well understood. Therefore, the cutting process of this alloy has been studied in detail by means of orthogonal cutting experiments at conventional cutting speeds and in the high-speed cutting regime. Alloy 625 shows a cutting parameter dependent change in the chip formation process from continuous to segmented chips. Silver has been added to Alloy 625 to improve the machinability. During machining of these modified alloys short breaking chips develop so that cutting processes are eased and can be automated.
In Situ Measurement of Internal Stresses and Strain Rates by High Energy X-Ray Diffraction during High Temperature Mechanical Testing
Authors: Jacques Alain , Dirand Laura , Chateau Jean Philippe , Schenk Thomas , Ferry Olivier , Bastie Pierre
Published: July 2011

The combination of high temperature (1050°C -1150°C) testing and in situ high energy X-Ray diffraction measurements using synchrotron Three Crystal Diffractometry may give various insights into the mechanical behaviour of superalloys: measurement of the lattice mismatch, order within the ' phase, elastic constants, and dynamic response to changes in the experimental conditions. Several examples are given on the rafted AM1 superalloy, resulting from experiments at the ID15A (ESRF) and BW5 (DESY) high energy beamlines.
Development of Chromium and Aluminum Coatings on Superalloys by Pack-Cementation Technique
Authors: Ledoux Xiaver , Vilasi Michel , Mathieu Stéphane , Pantiex Pierre Jean , Del-Gallo Pascal , Wanger Marc
Published: July 2011

Austenitic nickel-iron-chromium based superalloys are materials of choice for high temperature applications as they provide high temperature creep resistance associated with a suitable oxidation behavior in the temperature range of 600-1100°C. However, these properties are not sufficient for applications as Steam Methane Reformer (SMR). As a consequence, aluminum and chromium coatings are developed by the pack-cementation technique to improve their corrosion resistance. The oxidation behavior of the coated samples has been carried out in air at 1050°C. Chromium deposition leads to a layer of bcc chromium-iron solid solution. Oxidation tests indicated that a too high chromium concentration induces a too rapid growth of the chromia layer. In the case of aluminum coatings, a layer of -NiAl is formed at the surface of the alloy. It permits a significant decrease of the oxidation rate.
A Study of the Effects of Alloying Additions on TCP Phase Formation in 4th Generation Nickel-Base Single-Crystal Superalloys
Authors: Pang H.T. , Hobbs R.A. , Stone Howard James , Rae Catherine M.F.
Published: July 2011

The demand for higher engine operating temperatures to improve aeroengine efficiency has meant that increasing levels of alloying additions are being added to single-crystal nickel-base superalloys for turbine blades applications. Whilst better mechanical and environmental performance may be obtained with these alloying additions, they also destabilise the alloys forming topologically closed-packed (TCP) phases. In this study, the formation of TCP phases has been studied in a series of four alloys designated LDSX1-4 which have a systematic variation in the levels of Co, Mo and W. The alloys were exposed to elevated temperatures between 900-1100°C for up to 1000 hours. This was followed by detailed analysis of the microstructures in the SEM. Identification of the TCP phases in selected alloys was also carried out. The effects of each alloying addition on TCP phase formation is discussed in light of these results.
Light-Weight Intermetallic Titanium Aluminides – Status of Research and Development
Authors: Clemens Helmut , Smarsly Wilfried
Published: July 2011

Development and processing of high-temperature materials is the key to technological progress in engineering areas where materials have to meet extreme requirements. Examples for such areas are the aerospace and automotive industries. New structural materials have to be stronger, stiffer and lighter to withstand the extremely demanding conditions in the next generation of aero- and automotive engines. Intermetallic -TiAl based alloys exhibit numerous attractive properties which meet these demands. These properties include high melting point, low density, high specific elastic modulus, good oxidation and burn resistance, and high specific strength up to application temperatures of 700 to 800°C. Thus, current -TiAl based alloys outperform advanced Ti-based alloys and have the potential to replace heavy Ni-based superalloys.
Some New Aspects in Developing TiAl Based Alloys as Competitive High Temperature Materials
Authors: Zhang Ji , Feng Di , Yin Fa Jie
Published: July 2011

In order to make the TiAl Intermetallics-based materials more competitive with conventional superalloys, further work on microstructure modification and alloying process has been carried out specific to the cast and wrought process, respectively. It is proved that directional lamellar microstructures can be formed in the cast TiAl. Those microstructures have demonstrated preponderant mechanical properties under unidirectional load after the cast porosity being removed by HIP at proper temperatures. This microstructure design specific to the rotating parts has benefited the endurance capacity of cast TiAl turbochargers. On the other hand, the additions of Gd have shown significant effect in refining the lamellar microstructures of forged TiAl alloys but do not bring out the detrimental influence to the tensile ductility. The reason is that the Gd-containing precipitates can greatly impede the growth of  grains while themselves dispersing during the thermal process. Upon those technology advances, the further success of TiAl alloys’ applications is prospected.
Qualification of a Casting Technology for Production of Titanium Aluminide Components for Aero-Engine Applications
Authors: Aguilar Julio , Schievenbusch Andre , Kättlitz Oliver
Published: July 2011

Actual alloy and process development for high temperature turbine applications in the aerospace sector is strongly aimed at reaching the high demands on reduction of CO2 emissions responsible for the green house effect. Based on weight reduction the main objective resides in improving engine performance and efficiency. Last generation intermetallic titanium aluminides (γ TiAl) have a big potential to reach this goals. γ TiAl is nevertheless a very demanding material requiring very sophisticated processing routes. Access has developed a casting route for production of high quality γ TiAl components based on skull induction melting (SIM) and centrifugal investment casting. Although the feasibility of the technology has been already proven in earlier projects, it is still necessary to improve the process for series production of parts with the high quality standards required by the aerospace industry. With aid of a new developed centrifugal casting facility Access and its partners are conducting a comprehensive qualification process for the production of aerospace components, e.g. low pressure turbine blades. Basic issues comprising casting cluster design based on numerical simulation, process control and quality management are being addressed.
Chromium-Based Alloys Strengthened by Ordered Phase Precipitation for Gas Turbine Applications
Authors: Locq Didier , Caron Pierre , Ramusat Catherine , Mévrel Rémy
Published: July 2011

Chromium-based alloys are considered as potential candidates for applications in hot sections of aero engine turbines due to their high melting point and their moderate density. Some ternary (Cr-Ni-Al) and quaternary (Cr-Ni-Al-Ti) alloys have been designed with the aim to induce precipitation of ordered strengthening precipitates and to promote the formation of a protective alumina scale. These alloys were cast using various techniques in order to assess their microstructural and mechanical properties and their oxidation resistance.
Secondary Reaction Zone Formations in Pt-Aluminised Fourth Generation Ni-Base Single Crystal Superalloys
Authors: Suzuki Aya S. , Rae Catherine M.F. , Hobbs R.A. , Murakami Hideyuki
Published: July 2011

Fourth generation superalloys are characterised by the addition of Ru which contributes to improved creep resistance whilst improving the microstructural stability. However, Ru additions have a negative effect on coated Ni-base superalloys, promoting Secondary Reaction Zone (SRZ) formation. Formation of a layer of SRZ beneath an aluminised or Pt-aluminised coating has the potential to reduce the effective cross section of a blade by in excess of 100 μm or 10% of the wall thickness. In this paper the effects of alloy composition on the formation of the SRZ in Pt-Aluminised fourth generation alloys were investigated systematically. A series of experimental fourth generation alloys was used having two distinct compositions of Co, Mo, W and Ru and conforming to a four factorial 'Design of Experiments' model. These alloys showed significant and consistent changes in the SRZ depending on alloy composition. These were in distinct contrast to the effects of these elements on stability in the bulk. Mo was demonstrated to be by far the most effective element suppressing SRZ formation, followed by Co. In contrast, both W and Ru enhance SRZ formation.
Some Deformation Micromechanisms in Ni-Based Superalloys Evidenced Using TEM In Situ Experiments
Authors: Pettinari-Sturmel Florence , Benyoucef Mustafa , Douin Joël , Caron Pierre , Locq Didier , Clément Nicole , Coujou Armand
Published: July 2011

In situ straining of microsamples have been carried out at different temperatures in a transmission electron microscope (TEM) to provide information about the elementary micromechanisms, which control the deformation in Ni-based superalloys at the nano and microscopic scales. The obstacles to the propagation of the dislocations have been identified and quantified when possible. The strengthening effect in the -matrix channels and the shearing of ' precipitates have been chosen to illustrate some results deduced from moving dislocation analysis. A quantitative evaluation of the stresses acting on dislocations has been performed. The shearing process of the ' precipitates at 850°C has been precisely analysed.
Preparation and Properties of Recycled Polypropylene /Carbon Nanotube Composites
Authors: Gao Jing Long , Liu Yan Hui , Li Dong Ming
Published: July 2011

Recycled polypropylene (PP)/carbon nanotube (CNTs) composites with different CNTs fraction were prepared by the melting blend method. The effects of CNTs content on the thermal properties and mechanical properties were mainly investigated. The results show that the thermal degradation of the composites shifts towards higher temperatures as the concentration of CNTs is increased. With increasing CNTs content, tensile strength and elongation at break increase firstly and then decrease. When CNTs content is 3 %, tensile strength and elongation at break are 34.71 and 27.00, respectively. Moreover, a unique tensile rupture characteristic was found by SEM observations, which explained the critical broken theory of the PP/CNTs composites.
Preparation and Properties of High-Density Polyethylene/Silica Composites
Authors: Gao Jing Long , Liu Yan Hui , Wei Shou Dong
Published: July 2011

High-density polyethylene (HDPE)/silica composites with different silicon dioxide fraction were prepared by the melting blend method. The effects of silicon dioxide content on the thermal properties and mechanical properties were mainly investigated. The results show that the thermal degradation of the composites shifts towards higher temperatures as the concentration of silicon dioxide is increased. With increasing silica dioxide content, the tension yield strength of HDPE/silicon composites increased, but its breaking elongation decreased. When silicon dioxide content is 5 %, the tension yield strength and its breaking elongation are 29.33 MPa and 102.82 %, respectively.
Synthesis and Crystal Structure of a Novel Copper Complex Cu(Phen)(C8H7O2) 2
Authors: Xia Ping
Published: July 2011

Reactions of a freshly prepared Cu(OH)2×yH2O precipitate, 2-methyl benzoic acid with 1,10’-phenanthroline in C2H5OH/H2O afforded Cu(phen)(C8H7O2)2. The title compound was structurally characterized by X-ray diffraction methods. The unit of complex molecule was proposed 4+2 coordination sphere. In the crystal, molecules are connected by aryl π-π packing forming chains along [010] direction, the supramolecular double chains are further constructed two-dimension layers which parallel to (011) by π-π packing interactions.
Influence of Melt Holding Time on Microstructure and Mechanical Properties of Ductile Iron
Authors: Liu Zhe , Chen Wei Ping , Deng Yu
Published: July 2011

Six groups of castings which solidified at different cooling rates with or without addition of 0.03%Sb were fabricated. The effects of the melt holding time, cooling rate, and Sb on the microstructure of ductile iron were studied. Results show that as for the other three blocks with addition of 0.03%Sb, reducing the length of eutectic plateau could improve the graphite morphology, and sufficient residual contents of spheroidizing elements REE and Magnesium could also lead to small and diffuse globular graphite particles no matter what the cooling rate is. As for the other three blocks with addition of 0.03%Sb, no matter what the cooling rate is, the nodularity index values are all about 90%. The main difference among the three blocks is just the size of nodular graphite. And even if two of the blocks solidified at different cooling rates, they own nearly identical NI value and globular graphite average diameter value, which is because they both possess the tolerated rare-earth elements/antimony ratio for spheroidal graphite formation.
Finite Element Analysis and Optimization of Electric Field Structure of New-Type Electrospinning Machine
Authors: Duan Hong Wei , Jiang Jin Gang
Published: July 2011

Electrospinning technique is currently one of the most important methods for preparing nanofiber. Aiming to the fact that the electric field at the receiver is relatively weak, the electric field’s distribution in the typical electrospinning device was calculated and analyzed by ANSYS. It put forward the method of optimizing electric field’s distribution by using an assistant electric field device. At the same boundary conditions, the electric field’s distribution in the original device and improved binode device are compared. The simulation analysis provides an effective reference for the optimization design of electric field’s distribution in the electro-spinning device. The experimentation results show that the distribution of fiber diameter of polyimide non-woven fabric is equal and has a certain directivity after adding assistant electric field.
Principle and Experiment of Ultrasonic Subtle Atomization in CMP
Authors: Liu Xiao Peng , Chen Xiao Chun , Li Qing Zhong
Published: July 2011

The method of chemical mechanical polishing (CMP) using slurry which was ultrasonic subtle atomized was researched, and the system of Ultrasonic Subtle Atomization—Chemical Mechanical Polishing was established. The effects of polish parameters on polishing were also investigated. The results show that the experimental system can fully realize the expected function of polishing, the use of slurry is about one-tenth of the amount of traditional CMP, material removal rate can reach 113.734nm/min and the surface roughness is similar to the surface roughness in the traditional way.
Studies on Methacryloyl Guar Gum: Surface Morphology, Crystallinity, Biodegradability and Viscosity Behavior of Semi-Dilute Solutions
Authors: Xiao Wen Fa , Dong Li Tao
Published: July 2011

Methacryloyl guar gum was investigated with respect to crystallinity, surface morphology, biodegradability and viscosity of semi-dilute solutions. It was studied that the shear-dependent viscosity behaviour could be well described by the Cross viscosity model, under various methacryloyl guar gum concentrations, salts addition and temperature. The zero-shear-rate viscosity was observed to change with different methacryloyl guar gum concentration and decease with the increase of temperature.
Parameters’ Optimized Allocation of Spiral Feeder of RP953 Paver
Authors: Yang Yin Wei , Liu Xu
Published: July 2011

Paver is a kind of equipment used for high quality road alignment. As an important system of the paver, spiral feeder system consumes power accounted for about half the total power of the engine. Based on RP953 paver as an example, this paper analyzes the spiral feeder of the parameters of the points and optimizes configuration design basis, which can provide valuable information for the designing of the spiral feeder.
Hydrodynamics of Coarse Coal Slime and Quartz Particles in a Liquid-Solid Fluidized Bed Separator
Authors: Sha Jie , Xie Guang Yuan , Peng Yao Li , Shi Ben Xuan
Published: July 2011

The hydrodynamics of particles of coarse coal slime and quartz of different sizes in a liquid-solid fluidized bed separator were investigated experimentally, including minimum fluidization velocities, bed expansion ratios, and segregation of mixed particles with two methods. Experimental parameters studied included density and size of particle, superficial water velocity and initial static bed height. The results provide a reference for choice of size scope on coarse coal slime separation by liquid-solid fluidized bed separators.
The Analysis and Control of Noise on Steam Header of Heat Exchange Station
Authors: Wang Chang Tian , Bao Huai Qian , Zhang Wen Hao
Published: July 2011

Based on the noise characteristics of heat exchange station, the reasons of the high noise are investigated by analyzing the mechanism of noise of steam header, simulating and calculating the internal flow field. Then the comprehensive noise abatement measures are proposed according to the characteristics of the equipment operating and laws of the noise spectrum. As a result, the working environment of staff was improved, and noise pollution to surrounding environment was reduced. In a word, there were a lot of good results by adopting the measures of noise control.
In Situ SEM Investigation of Tensile Fracture Process of Fe-25Cr-35Ni Based Superalloy
Authors: Guo Jing Feng , Xu Ren Gen , Zhao Li , Shao Wen Zhu , Qin Lian Jie
Published: July 2011

Initiation and propagation of micro cracks in the Fe-25Cr-35Ni based superalloy were observed and investigated through in situ tensile test in SEM using a single-edge notched specimen. The results show that the micro crack sources may easily occur with one of those, the second phase particles and matrix interface, and the stress concentration region. The micro-cracks which propagated at first for those that are perpendicular to the tensile load would be growing up and connected mutual with the increase of external stress until forming the main crack. While the length of the mail crack enlarged enough in the specimen, it become instable for the main cracks and the fracture occurred rapidly.
Sequencing Mixed Model Assembly Lines Based on Genetic Algorithm Optimization
Authors: Huang Yin Di , Bian Rong Hua , Xu Zhen
Published: July 2011

Firstly, genetic algorithm optimization method was put forward to solve optimization problems of sequencing in actual mixed model passenger car factory assembly line. Then genetic algorithm optimization methods and procedures of mixed model total assembly line production sequencing were studied. Finally, according to the characteristics of the mixed production line, the least total waiting time of vehicle was set to complete assembly as a sequencing optimization objective, the AutoMod simulation software was used to balance the allocation of resources and optimize the sequence by way of genetic algorithm, and the optimal sequencing solution was obtained. After optimization and balance, the total waiting time of mixed model vehicles in complete assembly line was reduced by 69.5%, which improves production efficiency greatly. This also proves the effectiveness of genetic algorithm optimization.
A Study on the Vision-Based Flexible Vibratory Feeding System
Authors: Han Liang , Li Chao Biao , Hu Guo Ping
Published: July 2011

This paper describes a vision-based flexible vibratory feeding system (VBFVFS) for agile manufacturing, which mainly consists of a decupled vibratory feeder, a machine vision system, displacement sensors, power amplifiers and a computer system. Its major feeding parameters such as the vibration angle, frequency, acceleration amplitude, and phase difference all can be easily adjusted online by software means. Consequently, the system not only can feed a wide range of parts without any retooling of the feeder, but also can feed various parts made of different material in a way close to the optimal state. The VBFVFS also has intelligence. It can find out the natural frequencies of the decoupled vibratory feeder by means of automatic frequency response analysis and hence determine the best frequency for the driving signals. It can also find out any parts jamming and eliminate it by making the parts move in reverse directions. Prototypes of the decoupled vibratory feeder have been successfully developed. Experimental investigation is carried out based on the prototypes and the results agree well with the simulation results. Moreover low-cost vision technique is also discussed for the commercialization of the vision-based flexible vibratory feeding system.
Synthesis and Electrochemical Properties of Li4Ti5O12/CuO Anode Material for Li-Ion Batteries
Authors: Zhu Ji Ping , Yang Guang , Zhao Jun Jie , Wang Qing Song , Yang Hong Wei
Published: July 2011

Spinel-type electrode material Li4Ti5O12/CuO was synthesized by a two-step solid state reaction method. Cupric acetate (Cu(Ac)2) was used as raw material mixed into Li4Ti5O12 to coat the surface of Li4Ti5O12 with CuO in order to improve the electrochemical and cycle performances. The samples were characterized by XRD and the grain size analysis was researched by laser particle-size analyzer. The curves of charge/discharge and cycles Li4Ti5O12/CuO were researched. The results showed that the electrochemical properties of the material were improved. Among the three samples investigated, it was found that the Li4Ti5O12/CuO (coating amount was 4wt%) possesses the best electrochemical performance, and the first discharge specific capacity was 224, 173, 165 and 162mAh/g at 0.5C, 1C, 5C and 10C rate, respectively.
Preparation and Properties of Cement Bricks Based Paraffin for Thermal Energy Storage by Phase Change
Authors: Chen Hai Feng , Tang Pei Song , Cao Feng , Xu Min Hong
Published: July 2011

Using paraffin as phase change material, expanded perlite (EP) as porous materials, the EP/paraffin was prepared by vacuum impregnation treatment and tested by scanning electron microscopy (SEM). Adding other building materials, cement bricks based paraffin (CBBP) for thermal energy storage were molded and tested by means of water absorption, compressive strength and actual working of thermal energy storage. The testing results showed that paraffin was absorbed into the holes and cracks of EP, and CBBP had not linear change of various properties versus amount of cement or paraffin. Its mechanical strength was full compliance with national standard GB 21144-2007-T. At last, by phase change material exothermic or endothermic, CBBP effectively regulated outdoor surface temperature in summer: in temperature rising stage, CBBP was 4.63 °C lower than general cement bricks (GCB, no paraffin); in the cooling stage, CBBP was 2.30 °C higher than GCB.